August 2004 MONITORING TIMES 23

the 21st century will change radio communica-tions more than it has changed since the inven-tion of radio over 100 years ago.

We all have many questions and concernsabout the radio communications in the 21st cen-tury. What type of radio signals will be invadingthe 21st century airwaves? How high is high fre-quency in the 21st century? How will the radioreceivers of the 21st century look? What is a Digi-tal Radio, Configurable Radio, DSP Radio, Soft-ware Definable Radio? Cognitive Radio? Howare they different? Will we ever see one on themarket? How and why did all this technologyget developed? What’s the driving force behindall of these changes? ... Important questions, es-pecially to anyone who began their interest inradio communications in the last century … inother words, all of us!

Over the next few issues we will try to givesome insight into the answers to these questionsand more. Clues to the future can be found bylooking at major developments in radio commu-nications during the past few years. How thesedevelopments have been implemented in today’sradio products is another indicator of the futuretechnologies. The purpose of this series of ar-ticles is to introduce new radio and technologyconcepts, to stimulate thought as to how ourradio world is evolving, and to make some pre-dictions for the next five to twenty years.

We will cover just enough of the theory togive you some idea of the new technological meth-ods. These discussions are not meant to be rigor-ously complete. Instead they are presented ingeneral concept form as an introduction. Websites will be included throughout the series forthose of you (and I hope it is many) who wish tofully understand the science behind the conceptsand perhaps join the development efforts as acareer.

We’ll start at the beginning of the digitalradio revolution, which took place in the lastquarter of the 20th century.

From a Spark to an ExplosionThe historical beginnings of radio, from

early spark gap communications tomodern times was the topic of a 2001Monitoring Times series feature ar-ticles entitled “The History and Fu-ture of Radio.” I direct you to thisseries if you are interested in the howradio developed from its beginningthrough most of the 20th century.Also included in these articles is abrief overview and comparisons ofanalog and digital methods.

Software Every-wareI’m sure most of you have heard the term

“software radio,” or something similar. Todaythe dream of radio designers for the past twentyyears is becoming a reality. The Holy Grail ofradio design is SDR, Software Defined Radio.SDR is as important to 21st century radio com-munications as superheterodyne once was tothe 20th century radio. Simply put, SDR movesradio design from dedicated analog-based circuithardware to software configurable digital dataprocessing. The SDR will revolutionize radiocommunication. Clearly the words “software”and “digital” go hand-in-hand in SDR.

A quick review of the basic analog and digi-tal worlds might be a good place to start ourjourney toward the SDR radio.

Analog and Digital ConceptsThis is going to be a very quick and dirty

overview of a complex subject. In the analogworld, signals are modulated, or converted, in amanner analogous to the input signal. For ex-ample, let’s look at recording of sound, which isa varying air pressure wave. In order to record iton an analog tape recorder, the sound is con-verted into a varying magnetic field and appliedto the iron particles on the tape. To play backthe analog recording, magnetic variations are con-verted into electrical variations. Detection ofthese small signal variations, which can be verysmall and difficult to detect, is the limiting fac-tor of analog communications.

The digital world is quite different. Here,by using a circuit called an analog to digital con-verter (ADC), a sound wave is converted in aseries of rapid “on” or “off” pulses. In the digi-tal world these pulses are read as binary basednumbers of “ones” and “zeros” respectively. Theresulting on/off magnetic field is applied to thetape.

True, this digital conversion process is muchmore complex than in the analog world. Also thedigital process of encoding must be fast enoughso that little or no delay is noticeable.

To play back the digital recording, the pro-cess is reversed and the magnetic digital signal of“ons” and “offs” are converted into the originalhigh fidelity analog sounds with crystal clarity.

Only two variations, on and off, need be de-tected, instead of an almost infinite number ofvariations of an analog signal. Further, the signalamplitude between the two levels is relativelylarge. Clearly (pun intended) digital methodsprovide cleaner, clearer signals. Just look at thequality of a VHS tape and compare it to its bigbrother, DVD!

You can imagine that the digital processingspeeds and computer power to accomplish theseprocesses require some complex high-speed hard-ware. But the results can’t be beat!

That’s enough of background. What wecovered we’ll need later. Now let’s get on with21st century radio technology story.

Enter the Digital (Audio) RadioWhat is a Digital Radio? Well, this term is

evolving almost as fast as radio technology it-self! In the last quarter of the 20th century themilitary communications market demanded digi-tal radio systems for maximum receive-abilityunder adverse conditions and to provide a mea-sure of security. Back then, the “digital” referredto a digitizing of the audio. This was accom-plished via traditional analog circuitry with somenew circuit twists called Analog to Digital (ADC)and Digital to Analog Converters (DAC), seeFigure 1-1. These simple circuits, together withthe semiconductor electronics technology of theday, were fast enough to cope with the audiofrequency spectrum of 100 to 20,000 Hz.

In 1992, Collins Radio introduced into theconsumer/professional markets the revolution-ary model 926 communications receiver, whichwas PC controlled and utilized DSP in the audiosection. See Figure 1-2. The performance of theDSP audio filtering really wowed the communi-cations world with adjacent signal heterodynesbecoming things of the past. The 926 was de-rived from a Collins receiver supplied to themilitary market, but the DSP audio concept wassoon to become a feature on many ham and SWLreceivers.

Perhaps it was about this time that radiodesigners began to dream of moving the digitali-zation from just the audio section to more of theradio circuits. But with limitations in speed andcomplexity of semiconductor technology of the

early 1990s, it was just a dream.

Cell Phones Hit TheAirwaves

The staggeringly hugecellphone market was exactly what thesemiconductor companies needed toget out of the slump they found them-selves in, in the closing years of the20th century. The thought of everyonecarrying around an analog two-way

21st Century Radio Communications – Part 1By Dr. John F. Catalano

T he dawning of the new century has ush-ered us into a revolutionary era of radiocommunications. The first ten years of

Figure 1-1 – Simple Analog to Digital (ADC) and Digital to Ana-log Converter (DAC) Circuits

24 MONITORING TIMES August 2004

high frequency radio made the semiconductorindustry’s financial mouths water. Integrated cir-cuit companies turned their massive and power-ful attentions to the design of micro-miniature,silicon circuit, 800MHz radio blocks.

Once just the realm of high cost, low vol-ume, military and professional markets, thesecompanies used all their technical and manufac-turing muscle to create low cost, commodity,circuit blocks to enable the introduction of a con-sumer priced 800 MHz portable transceiver –i.e., cellphone.

The NEED for Digital Grows!Today, electronic technological advances are

usually motivated by market need. The largerthe market potential the more aggressively theelectronics industry works to fulfilling the seem-ingly impossible market requirement. This wasthe case with digital audio as Philips Electronicswas leading the charge to make their digitallyencoded optical Compact Disk invention thereplacement of the LP record. Digital encoding,and of course decoding, of audio was springingup in communication and entertainment marketsand becoming the norm as the 20th century wasending.

At the same time, satellite TV was plan-ning to grow from its hobby status to a full-fledged high volume consumer product. But theindustry was demanding something better andmore efficient than the analog signals that it hadendured from birth. That meant a move to digi-tally encoded signals.

Cellphones Go DigitalAs the demand for cellphones grew, the 800

MHz band was becoming very crowded, possi-bly limiting the cellphone companies’ business.This fact, plus some issues of privacy frommonitoring, gave the initial motivation to moveto digitally modulated cellphones.

As the digital market has matured, a num-ber of different digital encoding cellphone stan-dards have been adopted by different countriesand phone companies. This has become increas-ingly costly to cellphone companies who sellinto many different encoding markets. Todaythey find it difficult and costly to balance theirinventories of different types of cellphones us-ing different digital standards.

One Radio – ManyUses

The thinking goes like this.Every radio receiver has thesame basic block functions.However, manufacturers haveto make changes to some cir-cuits depending upon their fre-quency, digital encoding/decod-ing method, application, etc.

The military’s “one radio”requirement came about as aresult of a number of deadlyincidents. Since each one of theUSA’s armed services aretasked with different missionobjectives, their communica-tions needs are also different.

However, in joint operations, this leads to Armytroops not being able to easily communicate with,say, Air Force aircraft. This inability to commu-nicate has been the cause of an alarming, andgrowing, number of friendly fire casualties.

The military first experienced these com-munications problems in 1983 in Grenada andthen in 1991 during the first Persian Gulf War.But the military’s need would escalate withworld events of the 21st century, and they knewit.

The Configurable RadioAlthough their motivation was profit,

cellphone manufacturers also had the need for aradio that could change itself to fit the situation,just like the US military.

Now, assuming all the required hardwarebuilding blocks for all different requirements werebuilt-in to a radio. Then the signal path could bedirected to the required circuit blocks and aroundother blocks by a programmable series of simplelogic switches or gates. In this way, the radio’shardware circuits could be configured to the de-sired functions. This concept probably camefrom a radio designer who remembered his youthspent with Heathkit, Lafayette and Radio Shackelectronic experimenter’s labs.

Simple BeginningsThese “labs” consisted of a piece of wood

or cardboard upon which a number of compo-nents, transistors, light bulbs, resistors etc, weremounted. On each connection of each compo-nent was a spring. The lab, with a fixed set ofhardware components, could be rewired by con-necting wires to the springs in different configu-rations to make many different electronic de-vices. Does that bring back childhood memo-ries?

Imagine that instead of boards with largecomponents we have a piece of silicon, or a num-ber of pieces, with a much larger number of totalmicro-components. Instead of manually connect-ing, the connections are routed via logic gates, orswitches, which can be programmed to be open(no connection) or closed (connected). You havejust constructed a programmable array.

Let’s take this one step further by makingthe micro-components into groups of compo-nents wired into circuits used in communica-tions receivers, such as AM, FM, and digital

audio decoders, stages of IF, RF and audio filtersand amplifiers. Now, using user one-time con-trolled switches or gates we can “configure” theradio to whatever our need requires. And withthat, we have a configurable function radio. Ofcourse, all the added unused circuitry makes thishardware-intensive, programmable switched ar-ray approach very expensive, limiting its use tomilitary and professional markets.

Wishful Thinking?With the advent of commonly available digi-

tized audio integrated circuits, radio designersbegan again to dream. The dream of making allsignal manipulation from the antenna to thespeaker into digital data and therefore control-lable by mathematical algorithms was near. Thiswould be the truly digital radio.

Let’s go back to ones and zeros and seeexactly what this means to users.

Digital’s Real Edge!As we saw earlier with digital audio radios,

once we digitize a signal it is reduced to a math-ematical representation of the signal in the formof ones and zeros. These binary words can bemanipulated using mathematical formula, or, assoftware engineers like to call them, algorithmsand transforms.

Let’s look at an over-simplified example.During most of the 20th century, in order to de-modulate a FM signal we would have to build anFM demodulator using hardware componentssuch as diodes, resistors, and inductors.

Instead, in the digital world we can calcu-late what effect these components have on thesignal using circuit theory. For example, a resis-tor-capacitor-inductor (RLC) combination wouldtransform the signal using a time constant deter-mined by their relative values. A transistor act-ing as a gain stage would impart a characteristicamplification to the signal. These very simpleexamples can be applied to complex multi-cir-cuit functions.

In the digital world we can cause the sameeffects as the hardware by subjecting the digi-tized signal to the same set of signal condition-ing mathematical transforms. The effect of thehardware LRC circuit can be defined mathemati-cally by the same set of equations we used above,dependent on their component values. To de-modulate a digitized FM signal all we need is afaster microprocessor that can take the formulaequivalent of the RLC and run our input signalthrough it.

Flexible HardwareThe hardware required in the digital case is

a complex, fast running processor and its equallyfast “A to D” and “D to A” converters. In fact,in component count the digital circuit wouldtake more than one hundred thousand more com-ponents to decode FM than its analog equiva-lent! However, in the 21st century, integratedcircuit technology is routinely capable of pro-ducing circuits having a million devices on asmall piece of silicon. So circuit complexity isnot necessarily a limiting issue. But still, whereis the savings?

The savings is that hardware – the digital

Figure 1-2 – DSP Audio Radio Collins 926 circa 1993

August 2004 MONITORING TIMES 25

signal-processing integrated circuit – need onlybe designed once and then can be mass-pro-duced. These production stages are the mostexpensive and time-consuming steps requiredto bring a new integrated circuit-based productto market.

If we were designing a traditional analogcircuit-based integrated circuit radio, a new de-sign and manufacturing run would be neededeach time we wanted to change a function, verycostly in time and money.

With our digital signal-processing chip(within some limitations) the same integratedcircuit can produce many different manipula-tions on the incoming signal just by program-ming the processor with different software al-gorithms. Meet the Software Definable Radioconcept.

“Within Limitations”Let’s not forget that the frequencies which

we can digitize, and the complexity of the pro-grammed functions, are limited by the speed ofour digital electronics, among other factors. Thehigher the speed of our input signals and themore complex signal manipulations we desire,the faster the required digital electronics mustbe.

If the direct conversion radio, which digi-tizes the signal right from the antenna, were pos-sible, we could say goodbye to messy analog!Then all control, functions, and operating modeswould be configuration via software. But in or-der to realize this dream, complex, inexpensivechips having low power consumption and veryhigh speed processors (at least 1 GHz) wouldbe needed. A very tall technical order during mostof the 20th century. In fact, to some it seemed toborder on science fiction.

A Piece of the PuzzleWe can now begin to answer the first ques-

tion we posed: What’s the driving force behindthese radical changes in radio communication?In part, it is the rapid development of high-speed digital integrated circuits and micropro-cessors for the huge and competitive personalcomputer market.

Wake Up, Silicon Guys!Silicon manufacturers began to see the need

to design and manufacture off-the-shelf, complexintegrated circuits aimed squarely at communica-tions applications. By combining fast processors,digital encoding/decoding control and digitallyconfigurable filtering all on a single chip, the Digi-tal Signal Processor, DSP, was born in the facto-ries of Texas Instruments (TI) in the late 20th cen-tury. See Figure 1-3 for a block diagram of a TIDSP chip, vintage 1999.

DSP technology was a step in the directiontoward the SDR, but the technology of the daylacked the microprocessor muscle required tohandle the number of complex computations re-quired to function as a complete receiver. And, ofcourse, there was the processor’s speed, whichfurther limited the functions as well as the fre-quency of the input signal. DSP began to appearin communications products, replacing some func-tions of the receiver, usually in the audio section.

By the mid 1990s, DSP had proven theconcept of a digital processor being able to con-figure and control signal processing methods,albeit in limited manner. Today, DSPs are socommon that just about every PC sound cardis built around one.

As faster digital electronics were devel-oped, the digitized portion took a larger partof the radio receiver. The goal to convert theRF signal to digital form right from the antennawas moving from dream to reality. See Figure1-4, the all digital radio.

Electron Speed LimitsIn the 21st century, with 2.8 GHz personal

computers being sold at under $800, gigahertz-processing speeds are common and relativelyinexpensive. Where has all this processing speedcome from?

To find the speed-limiting factor of circuitswe have to take a little detour into semiconduc-

tor device physics. In order to make this a de-tour and not an odyssey, we’ll take some liter-ary liberties and keep it simple.

Electronics is all about moving electrons.The basic circuit element of a modern-day inte-grated circuit is the MOS (metal-oxide-semicon-ductor) field effect transistor. This device con-sists of two “electrodes,” the source and drain,separated by a third. The electric field on the“separating electrode,” called the gate, controlsthe flow of electrons from the drain to the source.

One factor that controls the transfer speedof the electrons is the gate width. The smallerthe gate width, the faster the field can propagateand the shorter the distance the electrons haveto traverse. The speed to gate width relation-ship is not linear but logarithmic. This meansthat speeds increase by a large amount with asmall decrease in width.

Advances being made by the semiconduc-tor companies are constantly reducing the mini-mum size structure that can be reliably manu-factured in high volume. This minimum struc-ture has been reduced from 5 microns (1 micron= 0.000000000001 meters) in 1985 to 0.1 mi-crons in 2004.

Simultaneously, the size of the silicon areathat can be reliably manufactured and the num-ber of on-chip components have also been in-creasing at a rapid rate. In the 1980s the compo-nent count was in the hundred thousands. To-day it is approaching tens of millions. This meansthat more devices can be placed on a single “chip,”allowing for whole “Systems on Chip” (SoC) tobe designed and manufactured.

Pieces In Place - AlmostAs we have seen, required technological

“pieces” to make a full digital software definableradio a reality are in place. Planning for the thirdgeneration of SDRs are in progress. Will it be anall software radio using a PC-type platform?What is a “cognitive” radio?

Remember, in order for a technology to tran-sition from prototype development to produc-tion, it requires industrial “Godfathers” in a num-ber of industries who are willing to risk theirown career on the product’s success. Next timewe’ll answer these questions and more. We’llalso see if the industrial climate is right for SDRto become a real, high volume, commodity, 21st

century product.Figure 1-3 – Block Diagram of TI DSP ChipTMS320vc5420

Figure 1-4 – Full Digital RadioUsing DSP– Digital CircuitsFrom Antenna to Audio. SourceTexas Instruments

22 MONITORING TIMES September 2004

radio over 100 years ago. In Part 1 last month,we tried to make sense of the various definitionsand acronyms associated with radio develop-ment.

JTRS (Joint Tactical Radio System), Uni-versal Radio, SDR (Software Definable Radio),Project X – regardless of what it’s called, basicrequirements for the ultimate digital radio aretwo-fold:1. To digitize the signal right from the antenna

to the speaker, and2. To have all functions of the transceiver – in-

cluding frequency range, frequency agility,mode of operation, modulation methods, en-cryption (if any) and display – to be totallysoftware controllable.When these two conditions are met, we have

achieved the ultimate goal of one radio that doesit all: military, cellphone, professional, emer-gency, law enforcement, aircraft and ham com-munications. Of course, it must be capable of alltypes and modes of operations for any existingradio communications system and programmablefor just about any future system.

For 20th century technology such a dreamwas an impossibility, bordering on science fic-tion. Is it close to a reality for the first decade ofthe 21st century?

Quick Tech ReviewToday, in 2004, we have the major techno-

logical pieces in place that did not exist in the20th century:a. Gigahertz speed digital integrated circuits,

microprocessors and high levels of complexcircuit integration on a chip which allow forwhole systems on a chip (SOC). Many ofthese advances have been gleaned from thehuge, and competitive, personal computermarket which has developed at a dizzyingpace.

b. Inexpensive high radio frequency integratedcircuit design and manufacturing capabili-ties.

c. System level programming methodologieswhich is hardware independent, providinggreater commonality. Although we have nottouched on this topic, it is a crucial require-ment to the complete implementation of theSDR concept.

Therefore, in 2004 we now have gigahertzprocessing speeds, low power semiconductortechnologies, large chips allowing systems-on-chip, and inexpensive processing methods de-veloped for the consumer PC market.

Mind Your BusinesBut one factor that we have not yet cov-

ered is the business climate for SDR. In orderfor a new radio technology to transition from

prototype development to real production, itrequires industrial “Godfathers” in a number ofindustries, such as communications, semicon-ductors, software and production. These peoplemust be willing to risk their own careers on theSDR product’s success.

Let’s review some companies in variousmarket sectors, their efforts in SDR develop-ment, and the results.

Where Do We Stand Today?With the turbulent world events of the past

few years it should come as no surprise that themilitary is “leading the charge.” However, theroots of SDR actually trace back to the 1990SPEAKeasy DOD program. The SPEAKeasyconcept is a 2 MHz to 2 GHz, softwareconfigurable radio. The second phase was suc-cessfully demonstrated in March of 1997 afteralmost seven years in development. It was aproof of concept for SDR and set the stage forthe next phase, JTRS.

In 1997 DOD issued a request for a JointTactical Radio System (JTRS) that could handlevoice, data and video in a digital format across awide frequency spectrum. The request require-ments includes communication capabilities be-tween all elements of the military as well as civilauthorities. The request also included the terms

21st Century Radio Communications – Part 2By Dr. John F. Catalano

I n the first ten years of the 21st century,radio communications will change morethan it has changed since the invention of

Figure 2-1 EchoTek ECDR-4814 Digital Receiver BlockDiagram

September 2004 MONITORING TIMES 23

“software programmable and hardwareconfigurable digital radio system.”

Everything is “almost” in place for the com-plete digital software definable radio, althoughin 2002, a director of one of the major contrac-tors predicted that “an actual physical JTRS ra-dio is some years away.” Let’s look elsewherefor some real product activity and developmentefforts.

Digital Modular Radio - DMRThe US Navy’s requirement for one radio

to provide all fleet communications, which isessentially based on four different communica-tions structures, was a prime candidate for earlySDR designs. General Dynamics and Motorolaboth provided DMR four-channel product tothe US Navy beginning in 2000 and are commit-ted to the JTRS/SDR concept in future designs.

The Falcon Flies In 2002, Harris Corporation’s (http://

www.harris.com) software-defined Falcon IIradio was one of the first to demonstrate “voicewaveform on a fielded, software-defined radioplatform and successfully conducted on-airinteroperability demonstrations of its capabili-ties.” That mouthful says they have a workingmodel SDR.

The RF-5800 series of software definableradios covers 30 to 512 MHz. It includes fre-quency bands and modulation modes for combatnet, close air support, military and civilian air-to-ground, long-range patrol and government landmobile radio (LMR). Falcon II radios come invarious configurations, including man-packs,portables, fixed station and tactical mobile. Sig-nal encryption is, of course, a standard feature.

Harris’ advertising slogan for the Falcon IIradio is “Multiple bands. Multiple missions. Onesolution.” That’s pretty close to the fully Soft-ware Definable Radio, but not quite. A total SDRmission statement should read, “All Missions.One Radio.” It is toward this end that manycompanies are diligently working.

SDR Developer’s KitDRS Technologies claims to be the first

company to offer a software definable receiverwith a software developer’s kit. The kit enablesusers to download DSP algorithms that employIQ filtering, special demodulation, signal pre-processing, or signal post-processingtechniques.

The DRS WJ-9104B multi-channel digital tuner is a software-de-fined receiver that allows the user tomonitor up to eight RF channels, witha frequency range of 20 to 3000 MHz.It has some impressive operatingspecs:• 20 to 3000 MHz frequency cov-

erage• 10-MHz instantaneous BW (2 MHz

or 25 MHz also available)• 80-dB Spur-Free Dynamic Range

(SFDR) digital, 85-dB SFDR ana-log

• 60 millisecond tuning speed• Up to 8 phase-coherent or inde-

pendently tunable channels• Digitized IF outputs from each

channel at 14 bits of precision• Supported by Spectrum Signal Processing’s

SDR Development SystemDRS Technologies products, which are not

priced for the consumer market, can be seen ontheir website at http://www.drs.com

EchotekThe Echotek Company (http://

www.echotek.com) has a range of “receivers”which use high speed and high resolution A to DConverters and digital receiver processing. Theresult, ECDR-4814’s block diagram, is seen inFigure 2-1. The ECDR is not a stand-alone fullreceiver. The input can be as high as 100 MHz;however, a relatively high level input signal of100 mV (millivolts) is required, as compared toa modern receiver input which is around .001µV (microvolts). The ECDR-4814 is actually amulti-input IF (intermediate frequency) blockor down converter, that can then be defined bysoftware to do just about anything.

Another Echotek product, ECDR-GC314-PCI, is a PCI card for use in a personal com-puter. It has three analog IF inputs that can beused up to 200 MHz and 12 digital channelsthat can be combined for wide band use. It alsohas impressive dynamic range specs. However,it also requires a high input level of 100 mV,since it is designed as an SDR function block,not an entire SDR.

Gray Who?If you look at Figure 2-1 you will see that

a large part of the functionality of the Echotekproduct is performed by GrayChip’s GC4016Quad Multi-Standard Digital Down converter.This device has some very impressive digitalperformance capabilities. In fact, it is critical tothe receiver’s operation. Figure 2-2 shows howthe GC4016 fits into a receiver.

If you are wondering who GrayChip is,think back to the first producer of DSP chips –Texas Instruments (TI). In 2001, TI purchasedGrayChip, a small fourteen-person companyfounded in 1989, to design reconfigurable digitaldown converters (DDC) and digital up convert-ers (DUC) for high-speed communications. TI’sacquisition of GrayChip clearly shows that it iscommitted to expanding the DSP concept to theentire radio.

“It’s Only a Software Glitch”In the 1980s a NASA spokesman used these

ill-chosen words to explain a shuttle lunch de-lay. As a result of his glib, over-simplified com-ment, technical people around the world deridedhim. Anyone who has been involved in the de-velopment of a hardware/software productknows never to minimize the software’s criticalimportance or to underestimate the required de-velopment resources.

Major software efforts directed towardSDR by a number of companies have producedthe first generation of “middleware.”Middleware has the difficult task of making op-erational software independent of the hardware.Hardware manufacturers have been co-operat-ing with the SDR effort by producing hardwareplatforms which can accessed using this “com-mon” language. This is another major step alongthe road to realizing the one radio SDR concept.

Where is SDR Today?In January 2004 Cubic Corporation (http:/

/www.cubic.com), a noted military communica-tions systems company, and Spectrum SignalProcessing (http://www.spectrumsignal.com),an SDR software company, joined forces. To-gether they have won an ambitious contract fromthe US Army. Under the 18-month contract,Cubic will develop waveform software that willhelp all branches of the military and multiplepublic agencies communicate with one another.

The software will be based on commonSoftware Communications Architecture (SCA)that will guarantee interoperability, compatibil-ity with current communications systems in-cluding APCO-25, and provide voice, data andvideo communications. This is a major step, ormaybe even a leap, closer to the complete SDRconcept.

One interesting fact is that although manycompanies are working on a true JTRS software,Cubic found that only Spectrum Signal’sflexComm package could perform to JTRS sig-nal processing requirements as laid out in the1997 JTRS Request. Looks like the marketingmouth of some companies outpaces their tech-nical capabilities! (SOS - Same Old Stuff!)

Other major international companies areproceeding along the development path to SDR.One interesting product providing a develop-ment link along the path to SDR is coming from

Thales Communications Inc. Theyare working on defining an enhancedversion of the JTRS radio calledJTRS-JEM. JEM will provide en-hanced multi-band inter/intra teamcommunications, including ciphertext. Version 2.2 of the JTRS soft-ware will be used on their currentlittle SDR, AN/PRC-148, whichweighs under two pounds.

As we have seen above, the soft-ware radios currently deployed in thefield are really software configurableradios. They are the first step to-ward Software Definable Radios andthe complete interoperability of the1992 JTRS requirement.

When a radio is manufacturedFigure 2-2 How GrayChip’s GC-4016 Digital Down Converter “Fits”Into a Digital Receiver

24 MONITORING TIMES September 2004

which is capable of morphing itself, via down-loads or internal programming, to communicatein any and all communications situations whethermilitary or civilian, then we will have a full JTRSand an advanced software definable radio, SDR.Some are now defining this as the Universal Ra-dio.

Strength in NumbersA group called the SDR Forum (http://

www.sdrforum.org) is steadily gaining member-ship among the hundred plus companies work-ing on SDR. The forum’s members include mili-tary communications, cellphone and professionalcommunications companies. These include es-tablished companies with market muscle suchas Harris, BAE Systems, General Dynamics, L-3 Communications, Intel and Motorola, as wellas young companies such as Vanu Inc.

All are working to break down radio com-munications paradigms of the 20th century. Theprograms of interest have different names – JTRSfor the military boys, SDR for the cellphonepeople, or Project25 for the public safety crowd– but the goals are the same: TotalInteroperability.

3rd Generation SDRAlthough the military applications for SDR

are pretty tough, many feel that the cellphoneindustry presents the greater design challenge.First, they have to be backwards compatiblewith all existing formats: CDMA, CDMA-2000,GSM, D-AMPS, to name a few.

Then there is the issue of cost; very lowcost is a prerequisite.

And, finally, the operational issues are farfrom easy to accomplish: 330 MHz to 2 GHZfrequency range, bandwidth in excess of 75MHz, and dynamic range greater than 75 dB!Not easy operational parameters to achieve evenwithout the economic constraints. To see thedirection of SDR in the next five years, I suggestyou carefully watch the cellphone industry forthe real advances.

The Next Leap - CognitiveRadioCognition is defined by dictionary.com as,

“The mental process of knowing, including as-pects such as awareness, perception, reasoning,and judgment.” The idea of the cognitive radio isa stretch of the SDR’s downloadablereconfiguring capabilities.

Key to the SDR concept is its ability to bereconfigured through user initiated downloads.Okay, now let’s say we build into the radio theability to receive and then analyze any signal.Then, in theory, with this information and somevery fancy internal software, the radio could learnhow to reconfigure itself to communicate withany received signal. See Figure 2-3. Talk aboutartificial intelligence!

Cognitive Radio could handle all of today’smodes: FDMA, TDMA, CDMA, TDD, AM,FM, MFSK, MPSK, MQAM, CPM, SSB,DSSS, DES, 3DES, AES, MeXe, Trunked Ra-dio, APCO-25, GSM, Iridium, 802.11X, tonecoded squelch, CVSD, LPC, VSELP, AMBE…and the list goes on. Let cognitive radio hearit, and it becomes it.

The potential is huge. It has been hypoth-esized that cognitive radios could perform manymore tricks such as selecting the optimum fre-quency spectrum, mode and power levels forgiven use, propagation and radio traffic condi-tions. The possibilities are limitless. The mili-tary has funded a cognitive project called XG,Next Generation Communications.

For an SDR to perform as a cognitive radioit must have some “self worth.” It must knowits own capabilities and how to reconfigure them.In 2004 this is pure concept since no radio existswith this ability. There are many licensing, con-trol, and interaction issues which must be con-sidered However, many heavyweights such asMicrosoft and Intel, are diligently working oncognitive radio. I have no doubt that it will be atechnical reality by the end of the decade.

Currently there is lobbying going on to al-low cognitive radio in the UHF TV band. A num-ber of groups have expressed their oppositionto the cognitive concept. They point out thatdue to cognitive radio’s auto adaptability it couldmonitor almost any radio communications, in-cluding voice, video, trunked system, satelliteand data such as wireless LANs and Bluetoothnetworks. Wow! And the 20th century thoughtit had a privacy problems with scan-ners!

SDR for the HobbyistThe military, professional and

cellphone industries are not theonly ones interested in SDR com-munications. In their own words,“GNU Radio is a collection of soft-ware that when combined withminimal hardware, allows the con-struction of radios where the ac-tual waveforms transmitted andreceived are defined by software.”

The GNU radio’s goal istransceiver operation in all hambands – HF, VHF and UHF up to2.4 GHz. Currently the hardware’smaximum bandwidth is 6 MHz andit has a capability of extracting upto four separate channels simulta-neously.

The minimal hardware re-ferred to is not exactly a simple

onechip printed circuit board. It is, as expected,a sophisticated collection of high speed Analogto Digital and Digital to Analog converters(ADCs and DACs) and programmable logic. SeeFigure 2-4.

The large chip in the center is the program-mable array for math functions and control. TheRF front ends (receiver antenna input) are noton the board. They are “daughter” circuit boards(nearing availability when this was written) whichplug into the two connectors on the top of theboard. Software downloads and hardware infoand purchase details are available on the websitehttp://www.gnu.org/software/gnuradio. It ap-pears to be in the early beta-testing phase of thehardware/software interfacing of the main board.The RF modules are either being prototyped orare under development.

Since the SDR technology is evolving at arapid pace and the available chips are trying tokeep up, designing and making a piece of hard-ware at this time is like trying to hit a movingtarget. But the GNU project is a great SDRground floor learning experience open to any one.

The Essential AntennaAlthough we have only concentrated on the

Figure 2-3 Cognitive Radio –A “Thinking” Radio

Figure 2-4 GNU’s Universal Receiver Project PC Board. NoteFour Horizontal Slots for Daughter Boards.

September 2004 MONITORING TIMES 25

receiver of the 21st century an-other element in the receivinghardware chain will requireequally revolutionary develop-ment. When we have thesewildly frequency agile radiosrunning all around the radiospectrum, fixed-tuned antennasare going to be as useless as aspark gap sphere!

The 21st century antennamust be capable of tuning itselfon the fly as the radio runsaround 2000 MHz of spectrumin different modes. Tuning andbeam forming must be per-formed at very high speeds bythe “antenna.”

Watch for an explosion ofadaptive antenna technology.This technology is not trivial.Although it has already beenused in military applications,commercializing for consumeruse it will be a major technicaland manufacturing challenge.

Other Radio Systems UnderDevelopment

Although SDR promises to affect everyfacet of radio communications in the future, thereare developments in other radio systems as well.Let’s leave SDR and look at a few other majorradio developments occurring in the 21st century

Digital Audio AM/FM RadioThe commercial radio bands are going

through a new phase with the introduction ofdigital satellite and terrestrial radio services.Admittedly, satellite radio has not proven to bea commercial success as yet. And, after a num-ber of false starts, digital terrestrial radio is try-ing to get off the ground again.

Texas Instruments, Philips Electronics,STMicroelectronics, and others are about to rollout their chips for demodulating commercialbroadcast AM/FM digital audio. These are basedon a software configurable approach.

Market predictions say that 2006-2007 willbe the year that the digital radio makes itsbreakout and sells tens of millions of units. Ipredict that, without great pressure from thegovernment to go digital, the acceptance periodcould be far greater.

Don’t Discount AnalogIf Motorola has its way, analog radio has a

life yet! For the past few years Motorola hasbeen working on improving analog radio usingdigital methods. Their latest chip effort is calledSymphony™. According to a press announce-ment, Symphony is to the AM/FM radio whatCompact Disk is to a cassette.

In actuality, it is a three chip set which is acomplete digital Intermediate Frequency (IF)radio. See Figure 2-5. It is composed of combin-ing a Digital Signal Processor (DSP) with a Ra-dio Frequency (RF) front-end and IF analog in-terface.

Symphony was designed to improve radiostatic, fading, pops and hisses, tuning, adjacent

station interference, limited listening range fromexisting signals, and audio clarity and volume.The digital methods that Motorola is employingshould make a big difference in signal detection,bandwidth, distortion and resulting audio qual-ity. The chipset is capable of AM/FM andweather band. I’m looking forward to hearingoff air commercial radio using a Symphony basedreceiver. Will a wideband-monitoring receiver benext? Let’s hope so.

Voice Activated Wireless ControlA low cost one-chip receiver and matching

transmitter which uses FSK (frequency shiftkeying) promises to be the foundation of 21st

century wireless applications. EZRadio by In-tegration Associates (http://www.integration.com) features user program-mable frequencies in the ISM (Industrial Scien-tific and Medical) band of 315, 433, 868 and 915MHz. Remote sensing, toy, vehicle monitoring,and control applications are immediately obvi-ous. It has a range of between 100 and 40 metersand is capable of data rates of 256 kbps. It uti-lizes a patented antenna tuning method that istotally controlled on chip. All it requires for ex-ternal parts is a 10 MHz crystal! Everythingelse is on-chip.

When EZRadio is coupled to the speechrecognition technology of a company called RSC,via an EEPROM, we have a complete speechcontrolled remote system. Two chips and notmuch more which make a two-way wirelessspeech-controlled link.

21st Century Sat ComAs we saw in the first part of this series,

digital satellite TV played a major part in thedevelopment of the digital signal technology andproduct base. But no industry can stand stilland expect to survive. Broadband connectivityvia satellite is the product being developed to-day. It is currently estimated that, using eitherwired T1 or DSL, only 60% of the business inthe USA can be served. That translates to over40% of broadband providers’ potential business

customers being lost due to their remote loca-tion. That is a lot of lost revenue. Satellite broad-band may be the answer.

The technical challenges required to make asatellite broadband act like terrestrial broadbandare not simple modifications. Both hardware andsoftware are being developed to fit the role. Sat-ellite links have lots of signal path variations.For TCP/IP the satellite link’s unpredictable pathtiming events and signal strength variations re-quire taming.

Whatever coding method is used, it has tobe smarter and more robust than its constantpropagation environment land-based brother.

Hughes Gives it a TryHughes has developed a whole new proto-

col for its Ka broadband satellite system,SPACEWAY. In Hughes’ words, “Operating inglobally assigned Ka-band spectrum,SPACEWAY employs high-performance, on-board digital processing, packet switching andspot-beam technology to offer single-hop con-nectivity, regardless of location.” The move tothe Ka band results in a higher bandwidth and,therefore, higher density data structure is pos-sible.

It had better work as advertised if it is go-ing to feel and act like a landline connection.Others trying to compete in this untapped, butrisky market are iDirect and Aloha Networks.

What’s NextWe have inhabited about the same 1000 or

so MHz of frequency spectrum for the past 100years. To what frequencies can the 21st centurysemiconductor technology take us?

Once there, it is unlikely that we will useradio in the same manner. What form will radiotransmissions take? How will we use the ex-panded radio spectrum? When does a radio notact like radio? We’ll attempt to gaze into thecrystal ball to answer these questions and morein the next and final installment of radio in the21st century.

Figure 2-5 Motorola’s Symphony Device: A Digital Treatment of Analog Broadcast Signals

October 2004 MONITORING TIMES 17

ating frequencies and methods. A businessaxiom says that applying new technologiesto old applications and methods is not thething to do. The logic goes that old applica-tions do not fully utilize the capabilities ofnew technologies. Instead they impose arti-ficial limits on the use of the new technology.

These limitations are no longer neces-sary, efficient or cost-effective, but they areinherited by trying to use the new technolo-gies in the old manner. Simply put, 21st cen-tury radio will use communications methodsthat did not exist, or were not even consid-ered in the 21st century.

The Radio-ComputerConnection

Last time, in Part 2, we gazed into thefuture of the radio communications in the 21stcentury. In doing so we became pretty adroitwith acronyms such as ADC, DAC, DSP,SDR, JTRS and a few others. The bottomline is that radios will become extensions ofour computer-intensive society. We have seenit happen with home entertainment, wherethe VCR has been replaced by the DVD,which is little more than a purpose-built com-puter with digital optical input. The softwaredefinable radio, SDR, is the evolutionaryjump to radio communications becoming acomputer appliance.

Silicon Goes Higher and HigherWhen silicon based semiconductor technol-

ogy first replaced tubes (called valves in the UK)a 1 MHz silicon device was considered “hot.” Inthe past, experts thought that silicon had beenpushed to its maximum speed. This “limit” wasreached at 50 MHz, 100 MHz, 500 MHz andagain, most recently, 1 GHz. Each time, siliconhas surprised the “experts” and provided higherspeeds. In the 21st century 4 GHz processors arefound in home PCs, and radio communicationsystems using a 7.5 GHz wide spectrum are be-ing vigorously developed.

Ultra Wide Band – UWBFirst worked on with vigor in the last

years of the 20th century, ultra wide bandcommunications, or UWB, is close to becom-ing an everyday reality for data. Surprisingly,the spark gap method, which started all thisradio technology, was a type of UWB signal.A spark discharge is inherently rich in har-monics, which means it does not transmit ona single narrow frequency. Instead the sparkproduces a wide band of signals whichstretched quite high up and down the radiospectrum. In the case of spark gap this “side”energy was lost. In contrast, UWB is verypower efficient. Today, UWB methods areutilizing all of its energy (frequencies) fortransmitting data in the 3 to 10 GHz fre-quency band with bandwidths of 500 MHz!

UWB’s Initial TargetsIn 2000, an explosion of new companies

were formed in an attempt to meet the de-mand for PC wireless data communications.Interest in UWB took off as the market de-

mand for wireless PC communications, localarea networks (LAN), and wireless home en-tertainment distribution grew. The IEEE, In-stitute of Electronic and Electrical Engineers,formed committees to define wireless datacommunications standards.

In 2001, it seemed that every day a newstartup company introduced a new wirelessdata method. Today, in 2004, many of thesecompanies no longer exist because they couldnot keep pace with the costly, ever-changingtechnology developments and “standards.”You may have heard of wireless standardssuch as 802.11, 802.15.3, 802.15.4 and802.whatever.

A Moving TargetCurrently these systems are designed

for data transfer applications over relativelyshort ranges. No DX here yet. You can checkthe IEEE web site for various wireless stan-dards details at http://standards.ieee.org/wireless/ .

Summarizing, different standards are

T he new semiconductor and electronictechnologies of the 21st century willprovide vastly expanded radio oper-

21st Century Radio CommunicationsPart 3: An Unimaginable Future

By Dr. John F. Catalano

Figure 3-1 UltraWide Band(UWB) RadioBlock Diagramfrom PicosecondPulse Labs Inc.

18 MONITORING TIMES October 2004

being developed for different applications.Data rates range from 1 to 500 Mbits persecond and distances from 1 to 50 meters.Clearly, equipment interconnects and LANsare the first target markets.

In one UWB method there is no carriersignal, no radio signal as we have become ac-customed to in the 20th century. UWB uses aunique very short pulse ”modulation”method. UWB pulse widths are on the orderof 10 to 500 picoseconds. That’s really short!

Instead, data encoding is performed uti-lizing three pulse parameters: amplitude,shape and timing. Decoding is performed bydetecting these pulses of varying width acrossa spectrum of about 7.5 Ghz. The pulse sig-nal is the data. Another UWB method beingproposed cuts the 3 to 10 GHz band into 528MHz sub-bands.

No Need For DSPAlthough we have previously discussed

how digital signal processing chips, DSP, arebecoming the “heart” of digital mode radios,UWB technology is already looking to theday when digital data radio communicationswill not require a DSP! See Figure 3-1

The key to decoding one form of UWBis its pulse’s three parameters, relative to eachother. Hence, no traditional radio conversionstages are required. Gone is the whole down-conversion chain from RF stage to intermedi-ate frequency (IF), and then to demodula-tion. This approach to UWB radio does notrequire digital processing, thereby eliminat-ing the need for an expensive and power hun-gry DSP chip.

Huge Bandwidth, Tiny PowerDue to the pulse nature of UWB signals,

power levels can be in the tens of nano-watts.The UWB signal, sounding like backgroundnoise, will have data rates projected to be ashigh as 1000 Mbits per second. Initial UWBdesigns call for 300 Mbits per second rateswhich will suit the initial local area data andmultimedia home networks.

Providing video, audio and PC datathroughout a home is UWB’s first productgoal. Be assured, however, that if UWB works

close to its theoretical plan, it will be expandedto long range communications. In late 2003the 3.1 to 10.6 GHz band was designated forUWB applications. Recently, Wisair Ltd,working with Intel, produced a UWB trans-ceiver chip, UB501, which requires just acrystal and some resistors and capacitors.

Standards Face-Off for aFightThe standards battle took place when

VCRs were being introduced: VHS vs Beta.Currently, DVDs are still trying to decide ifits standard format is R+ or R-. It happenswhenever an important new technology isemerging. A number of standard methods areproposed by “teaming” companies.

Many times the competing“sides” are notdetermined by the best technical capabilities.Instead, it comes down to what technologypatents are held by which companies. An-other consideration can be which new stan-dard can be easily applied to a company’sexisting product lines. The UWB world iscurrently spli t between the MultibandOFDM Alliance (MBOA) and the CDMAteam, now known as the UBW Forum.

The MBOA TeamMBOA members include some heavy hit-

ters: Intel, TI, Microsoft and Philips to namea few. Smaller companies such as Wisair Ltd.,with its first generation UB501 UWB chip,are also members. The foundation technol-ogy of this method is OFDM, OrthogonalFrequency Division Multiplexing. OFDM hasbeen employed by cellphones, wired datatransmission such as ADSL, Europe’s DigitalAudio Broadcast (DAB), and other commu-nications system for the past 40 years.

MBOA’s current UWB proposal utilizesa 528 MHz multi-sub-band method. This ap-proach should provide data rates of near 1000Mbits per second for links up to 2 metersapart. Although greater distances are possible,the reliable data rate decreases as the distanceincreases. For more information and addi-tional proposed UWB standards you cancheck the MBOA website at http://www.multibandofdm.org.

The UWB ForumMotorola and a Motorola backed start-

up XtremeSpectrum (http://www.xtremespectrum.com) led the DS-CDMA team, which included OKI semicon-ductor and others. Code Division MultipleAccess (CDMA) had its origins in the early1990s, tailored to the needs of the cellphoneindustry by its developer Qualcomm. DSstands for the latest twist, Direct Sequence(spread spectrum).

In contrast to the MBOA method, theXtremeSpectrum method uses only one fre-quency band. The CDMA-DS team is aheadon silicon development, with their third gen-eration silicon chips about to be produced.Since the beginning of 2004, Motorola hasused a second-generation chip set to producecustomized UWB products. See http://e-www.motorola.com/files/wireless_comm/doc/fact_sheet/UWBFACT.pdf

Samsung, originally an MBOA member,recently jumped ship and used a MotorolaUWB system to send multiple HDTV streamsto their flat panel HDTV product at the 2004Consumer Electronics Show. Freescale Semi-conductor has recently joined the UWB Fo-rum.

King Kong vs GodzillaAs of May 2004, after five voting at-

tempts, no UWB standard has been decidedupon. This is going to be a world-class battlewhich will not be decided for several morerounds.

Today, to say that UWB is in a state offlux is an understatement. As we have seen,the protocols being considered includeTDMA, CDMA and OFDM. Further, a num-ber of different combinations have been de-veloped: TM-UWB (time-modulated UWB),MB-OFDM (multi-band OFDM), and DS-UWB (direct sequence UWB), to name a few.Each has its own strengths and weaknesses.

If you’re feeling a bit confused you’renot alone. There is a lot of market, moneyand ego riding on the choice of the UWB stan-dard, so watch for a battle royal during thenext twelve months. The standards war hastaken a major casualty with XtremeSpectrumfiling Chapter 11 bankruptcy in March 2004.

Overlooking the “situation” that existsin the UWB community today, and using abit of positive thinking, we can expect to seea highly evolved UWB technology providinglong range radio communications some timearound 2012.

To 60 GHz and Beyond!As we have just seen, the 3.1 to 10.6

GHz band has been defined for ultra wideband (UWB) communications systems. In2003 the Federal Communications Commis-sion (FCC) opened the 5 GHz U-NII bandfor new communications methods, includingbut not limited to Cognitive Radio (CR).

CR, which was covered in Part 2 of thisseries, is an intelligent software definable ra-dio (SDR) which can learn on its own how toreconfigure itself to communicate with anyFigure 3-2 The Electromagnetic Spectrum Shows That Radio, Light, X-rays & Gamma Rays Are

The Same Animal. (Courtesy of Lawrence Berkeley National Laboratory)

October 2004 MONITORING TIMES 19

signal that it receives. In addition, after “lis-tening” to band conditions – such as propa-gation, traffic density and interference level/type – it decides the optimum band for a givencommunications requirement at a given time.Artificial intelligence comes to radio commu-nications, and the 5 GHz band may be whereit is first tried.

In 2004, the FCC opened the 60 to 90GHz band to future broadband services. Atthese frequencies the whole concept of a ra-dio transceiver changes paradigm yet again.At these high frequencies (high for the firstdecade of the 21st century, that is) the electri-cal characteristics of material properties, suchas dielectric constants and magnetic perme-

ability, do not behave in a strictly Ohm’s lawmanner.

At these frequencies electrical designmethodologies and materials choices must beradically changed from today’s. Interestingly,in theory these short wavelengths do allowtotal on-chip system integration, includingadaptive antenna arrays. Now the questionis, can these concepts be turned into low-cost manufacturable realities? A whole newfamily of semiconductor materials may needto be developed.

Interdisciplinary, InternationalChallenges

Operating at frequencies of 60 GHz re-quires not just faster, but more accuratelydefinable data pulses. By accuracy, we meanvariations in pulse locations in time fromwhere it is supposed to be to where it actu-ally appears.

The position of data pulses in time is afunction of many system factors includingtime base stability, delays introduced by go-ing through transistors, chip interconnectmetalization, and other process-related fac-tors. As the frequency goes up, so must ourunderstanding and control of each of these.Pulses must “behave” as expected in order tofor a digital system to work at all.

Also, using traditional electronic designmethods, as the frequency increases so doesthe power required. Not a happy thought at90 GHz. Add to this, the fact that 21st cen-

tury portable equipment is still tied to 19th

century battery technology, and a whole newset of problems loom.

Solving these problems will not be easy.It is almost like re-inventing solid state de-vice technology and electronics. It will take alarge team of dedicated innovative people withexperience and knowledge in device physics,material science, mathematics, communica-tions systems, digital design, analog design,chemistry and manufacturing. Equally impor-tant will be the group of dedicated, deep-pocketed companies needed to support theexpensive commercialization effort.

As is usually the case for emerging tech-nologies, much of the current work is beingperformed at universities around the world.Berkeley (CA) Wireless Research Center hasrecently shown that, using current 0.13 mi-cron CMOS processes, 60 GHz operation ispossible. National Taiwan University is in-vestigating system on chip (SoC) for the 60GHz band. In addition, all companies thatproduce ADC/DAC, a key component, areconstantly working to make them faster.

This is only the beginning for 60 GHzcommunications. Just consider the amount offrequency spectrum that will available to us.For most of the 20th century, over ninety per-cent of radio communications took place inthree gigahertz of spectrum. When (not if) 60GHz communications become a reality, it willincrease our radio spectrum by 20 times.

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Waves of the FutureWatch for 60 GHz digital com-

munications to become a widely usedcommercial reality by 2012 and thenbe extended to around 100 GHz. Also,keep an eye on developing SDR, CRand UWB technologies which will allbe showing off their strengths in wayswe cannot yet imagine.

With the seemingly ever-increas-ing maximum frequency that radio ispushed to, let’s review the electromag-netic spectrum and see where radiowaves fit. We may get an insight tothe future of radio by considering whatother types of electromagnetic wavesborder the radio spectrum of frequen-cies and what their properties are.

The Electromagnetic SpectrumThe full electromagnetic spec-

trum, shown in Figure 3-2 on page 18,shows that radio waves, light (infra-red/visible/ultraviolet), X-rays, andgamma radiation are all the same ani-mal. Their relative frequency rangescause them to interact with us differently andtherefore they have different properties, usesand effects. However, if we look at the bound-aries where one category of electromagneticwave ends and the next one begins, it is not aclean break.

Interfaces or boundaries between physi-cal phenomena are oftentimes the most inter-esting regions to explore, due to their hybridnature. Look at where 100 GHz communica-tions systems lie on the spectrum in the fig-ure. This corresponds to 1011 waves per sec-ond on the second line from the bottom (fre-quency) in Figure 3-2. We can also see fromthe figure that infrared light is centered at1013. In other words, the radio wave spec-trum goes all the way up to the 1000 GHzrange, or 1 terahertz (THz).

Properties of THz WavesSince at the bottom end terahertz waves

are relatively close in frequency to radarwaves, it should come as no surprise thatterahertz waves can be used for the samepurposes. However, terahertz waves can pro-duce enhancements over radar, such as muchgreater accuracy.

At terahertz frequencies, free ions in ma-terials cannot react as quickly, or strongly, tothe THz electromagnetic field. Material prop-erties such as dielectric constant, which is ameasure of ionic mobility and bonding, changedramatically at terahertz frequencies. There-fore, THz waves penetrate many materials,acting similar to x-rays, but without the depthof penetration or the damaging ionizing ef-fects of x-rays.

Therefore, a THz transceiver could beused to image objects behind thin or low tomedium density materials such as plastic,wood, paper, skin tissue or clothes. Clothes?Talk about violation of privacy!

Using software-sectioning methods cur-rently in use with x-rays, three-dimensional

imaging applications by the medical, secu-rity and fault inspection fields are limitlessand without danger to humans.

In fact, it has been found that many ma-terials naturally emit terahertz waves. Thisphenomenon enables imaging of materialswithout the need of an illuminating transmit-ter and is called passive imaging. Figure 3-3shows a computer-enhanced terahertz pas-sive image of a human hand. For a technologyat such a early stage, this image shows theincredible potential of this technology.

Light on the SubjectScientists have long used the wave prop-

erties of light to determine the compositionof material. White light is composed of allwavelengths (colors) of light. Each elementon the periodic table emits or absorbs spe-cific wavelengths of light, not the entire spec-trum of light. For example, by carefully ana-lyzing the light that is emitted from a sourcewe can determine of what elements the sourceis composed. Using this emission spectramethod, astronomers can determine what el-ements are on distant stars.

When a chemical compound is illuminatedby a source, it absorbs specific wavelengthsdepending on its composition and structure.This is called the absorption spectra of thatcompound.

Remembering and utilizing the fact thatterahertz radio waves have light-like proper-ties, allows for a whole new tool that can beused with the imaging. Using a two-frequencymethod, terahertz waves can perform com-pound composition analysis …while imag-ing.

Not only will terahertz scans givemedical personnel three-dimensional imagesof even the thinnest growth, but it will alsogive a chemical analysis of the image. In thismanner medical technicians will be able toisolate cancerous tissue without the need forinvasive biopsies. (Images of De Forest

Kelly’s medical doctor character,Bones, on Star Trek come to mind.Waving a salt shaker-looking body ana-lyzer over a wounded colleague hewould say to Captain Kirk, “Damn it,Jim. I’m only a doctor!” Perhaps hissalt shaker instrument was actually aterahertz imager and composition ana-lyzer.)

Where is Terahertz Today?Scientists in the Soviet Union be-

gan to investigate the properties ofterahertz (THz) radio waves in the1950s. They used vacuum tube tech-nology to generate THz waves. Resur-gence in terahertz studies worldwideoccurred in 2000. Today, a collabora-tion that would have been unthinkablein the 1950s is working on solid stateTHz chips.

Russian and American scientists arecombining their knowledge and creativ-ity to develop THz chips based on asilicon-germanium semiconductor tech-nology. Transmitters producing 8 THz

emissions have been created.Europe is also developing THz tech-

nology with an announcement from the Eu-ropean Space Agency’s (ESA) Star Tiger Teamthat they had an operating terahertz imagingprototype. European universities are work-ing on silicon-germanium THz emitters. StarTiger’s website has a wealth of Terahertz in-formation for further study. Check it out athttp://www.startiger.org/index.htm

Terahertz pulsed imaging work isbeing carried out by Tochigi Nikon of Japan.You can view a number of terahertz images,as well as watch a Venus Flytrap plant atwork using THz imaging. Their website ishttp://www.tochigi-nikon.co.jp/technolo-gies/terahertz/eng/movies.html#03

You Know It’s Real When …Many technologies that are pursued

at research establishments never become prod-ucts. In fact, less than three out of ten makeit to production. However, when a number oflarge companies start backing the technologyby making it their own, you can be sure it hasa reasonable chance of making it to a product.

In addition to the companies wehave already mentioned, Intel is working hardon THz devices. The Toshiba company hasbeen working on THz devices in the lab for anumber of years and in 2001 created a com-pany called TeraView http://www.teraview.co.uk. They now have a wholerange of terahertz-based spectrometer prod-ucts starting at $450,000. So why is it thatmost people have not heard of Terahertzspectrum products?

Once again we have an example of a semi-conductor technology (or lack of it) being themajor limiting factor in the evolution of a newindustry. A number of THz emission meth-ods are being studied. Sometimes referred toas “quasi-optical,” some use a combinationof optical and radio methods. These includelasers, micro-electromechanical structures,

Figure 3-4 Artist’s Conception of an Integrated Terahertz Re-ceiver

October 2004 MONITORING TIMES 21

quantum transistors, carbon-nanotubes, andlaser pumped crystals, to name a few.

Since 2000 the number of teams workingon Terahertz components, methods and ap-plications has been steadily growing. Today,Terahertz research, development and prod-uct development is being performed by orga-nizations worldwide. The list includes manylarge international corporations, startup com-panies, government agencies and universities.If I compare Terahertz development to thatof the home PC, which was introduced byIBM in 1983, I predict that Terahertz prod-ucts will be a reality before the end of thenext decade.

THz CommunicationsWith all the possible uses for THz waves,

we have yet to consider terahertz communi-cations – the application of greatest interestto MT readers. Just think of the availablespectrum. Going to 60 GHz band gives us a20 times increase in available spectrum. Go-ing to 6 THz will enable a 2000 fold increase!

Figure 3-5, from ESA’s Star Tiger Team,is an artist’s impression of a simple terahertzradio receiver. The pyramidal horn is madefrom stacked layers of etched silicon. Thisfocuses the terahertz waves onto the Tshaped aerial at the bottom that carries thesignal to the detector. Again, this is only adrawing of a complex, futuristic receiver.

We are witnessing the birth of an entirelynew communication technology. It’s as if wehave been transported back to 1900, watch-

ing a sparking gap being operated for the firsttime. Now try to make the mental jump fromspark gap to cellular communications or Soft-ware Definable Radios.

There is no way this jump could havebeen made within the bounds of the 1900human intellect.

In generations to come, terms such ascoherent communications, CR, ambient intel-ligent networks and 100 THz operation willbe everyday terms. Gone will be vocabularysuch as co-signal interference, QRM, spec-trum crowding, AM, FM, SSB and even per-haps some illnesses – all as a result ofTerahertz technology.

As of 2004, a team of researchers atGermany’s Technical University atBraunschweig hold the Terahertz DX record.They claim to have broadcast audio from aCD player over a THz link of one meter,approx. 3.3 feet. The audio that was trans-mitted was the song “We Didn’t Start theFire” by Billy Joel – a 21st century version of“Watson, come here I need you.”

Use the Gifts WiselyThe constant, face-paced advances in

electronics, personal computing, digital meth-ods and semiconductor technologies havebrought about today’s revolution in radio andin all aspects of our life. As these technolo-gies continue to develop and converge at afrenetic pace, they hold the promise of com-munications systems, applications and tech-nologies unimaginable in the 20th century.

However, they will become commonplacetechnologies of the 21st century. It is trulyexciting times.

Today we live in a world of self-pow-ered radio transponders (RFID) sewn intoarticles of clothing, attached to our airline lug-gage and embedded into products that wepurchase … and the revolution is just begin-ning.

Imagine the explosion in the use of ra-dio when all products and manufacturers usethis RFID technology. Every factory, ware-house, distributor, trucking company, rail-road, airline, cargo ship, and retail store willhave a radio system to track products duringtheir trip through their supply and retail chain.

Hopefully, the tracking will end when theproduct leaves the store. Revolutionary tech-nological developments sometimes carry withthem intrinsic moral issues. The technologyis not at fault. Nor are the scientists whohave created it. It is the moral responsibilityof society to allow, reject or restrict atechnology’s uses.

History has shown that the problem isnot centered around scientific issues. Instead,it comes down to a dilemma of morality ver-sus economy. Let us all hope that the humanrace makes equally impressive advances inmorality as well as technology, in the 21st

century.I hope this series of articles has been

entertaining, stimulated your interests, andbroadened your thinking about the use of ra-dio waves. Welcome to the 21st Century!