Agenda - materias.fi.uba.armaterias.fi.uba.ar/6644/info/anespec/basico/spectrum analysis... ·...

Spectrum Analyzer Basics Copyright 2000

Agenda

● Overview:● What is spectrum analysis? ● What measurements do we make?

● Theory of Operation:● Spectrum analyzer hardware

● Specifications:● Which are important and why?

● Features● Making the analyzer more effective

● Summary● Appendix


Agenda

● Overview● Theory of Operation● Specifications● Features● Summary● Appendix


OverviewWhat is Spectrum Analysis?

8563ASPECTRU M ANALYZER 9 kHz - 26.5 GHz


OverviewTypes of Tests Made .

ModulationModulation

DistortionDistortion

NoiseNoise


OverviewFrequency versus Time Domain

time

Amplitude(power) freq

uency

Time domainMeasurements

Frequency DomainMeasurements


OverviewDifferent Types of Analyzers

Parallel filters measured simultaneously

LCD shows full spectral display

A

ff1 f2

Fourier Analyzer


OverviewDifferent Types of Analyzers

A

ff1 f2

Filter 'sweeps' over range of interest

LCD shows full spectral display

Swept Analyzer


Agenda



Theory of OperationSpectrum Analyzer Block Diagram

Pre-SelectorOr Low Pass

Filter

CrystalReference

LogAmp

RF inputattenuator

mixerIF filter

detector

videofilter

localoscillator

sweepgenerator

IF gain

Inputsignal

CRT display


Theory of OperationMixer

MIXER

fsig

LOf

fsig LOf

LOf fsig-

LOf fsig+RF

LOIF

input


IF FILTER

Display

InputSpectrum

IF Bandwidth(RB W)

Theory of OperationIF Filter


Theory of OperationDetector DETECTOR

Negative detection: smallest valuein bin displayed

Positive detection: largest valuein bin displayed

Sample detection: last value in bin displayed

"bins"

amplitude


Theory of OperationVideo Filter

VIDEO FILTER


Theory of OperationOther Components

LCD DISPLAY

S WEEP GEN

LO

IF GAIN

frequency

RF INPUT ATTENUATOR


Theory of OperationHow it all works together

3.6(GHz)

(GHz)

0 3 61 2 4 5

0 31 2

3 64 5

3.6

(GHz)0 31 2

fIF

Signal Range LO Range

fs

sweep generator

LO

LCD display

input

mixer

IF filter

detector

A

f

fLO

fs

fs

fs

fLO-

fs

fLO+

fLO

3.6 6.5

6.5


Theory of OperationFront Panel Operation


RF Input Numerickeypad

Control functions(RBW, sweep time, VBW)

Primary functions(Frequency, Amplitude,

Span)Softkeys


Agenda



Specifications


➤ Frequency Range➤ Accuracy: Frequency & Amplitude➤ Resolution➤ Sensitivity➤ Distortion➤ Dynamic Range


SpecificationsFrequency Range

Measuring harmonics50 GHz and beyond!Measuring harmonics50 GHz and beyond!

Low frequenciesfor baseband and IFLow frequencies

for baseband and IF


SpecificationsAccuracy

AbsoluteAmplitude

in dBm

RelativeAmplitudein dB

RelativeFrequency

Frequency


SpecificationsAccuracy: Frequency Readout Accuracy

Typical datasheet specification:

Spans < 2 MHz: (freq. readout xfreq. ref. accuracy+ 1% of frequency span+ 15% of resolution bandwidth+ 10 Hz "residual error")

+_

Frequency


SpecificationsAccuracy: Frequency Readout Accuracy Example

Single Marker Example:

1% of 400 kHz span15% of 3 kHz RBW10 Hz residual error

+_

2 GHz400 kHz span3 kHz RBW

Calculation: (2x10 Hz) x (1.3x10 /yr.ref.error) 9 -7 ====

260 Hz4000 Hz450 Hz10 Hz

4720 HzTotal =


● Display fidelity● Frequency response● RF Input attenuator● Reference level● Resolution bandwidth ● Display scaling

SpecificationsAccuracy: Relative Amplitude Accuracy



● Applies when signals are not placed at the same reference amplitude

● Display fidelity includes–Log amplifier or linear fidelity–Detector linearity–Digitizing circuit linearity

● Technique for best accuracy

SpecificationsAccuracy: Relative Amplitude Accuracy - Display Fidelity



SpecificationsAccuracy: Relative Amplitude Accuracy - Freq. Response

-1 dB

+1 dB

0

BAND 1

Specification: ± 1 dB

Signals in the Same Harmonic Band


● RF Input attenuator● Reference level● Resolution bandwidth ● Display scaling

SpecificationsAccuracy: Relative Amplitude Accuracy



SpecificationsAccuracy: Absolute Amplitude Accuracy

AbsoluteAmplitud

ein dBm

● Calibrator accuracy

● Frequency response

● Reference level uncertainty


SpecificationsResolution

Resolution Bandwidth

Residual FM

Noise Sidebands

What Determines Resolution?

RB W Type and Selectivity


SpecificationsResolution: Resolution Bandwidth

3 dB3 dB BW

LO

Mixer

IF Filter/Resolution Bandwidth Filter

(RBW)Sweep

Detector

InputSpectrum

Display

RB W


Demo -Theory: IF filter

One signal -change RB W to see how display traces out shape of IF

filter

FilterESG-D4000A Sigl Gen

Spec An

8447F Amplifier

Power Splitter(used as combine)

inout

ESG-D4000A Sigl Gen

On

Off

Bandpass filter(center frequency = 170 MHz)

f=170 MHz, A=-25 dBm

fc=170 MhzRB W=1 MHzVB W=300 kHzspan=10 MHz

Spectrum Analyzer Setup

Signal Generator Setup


SpecificationsResolution: Resolution Bandwidth

3 dB

10 kHz

10 kHz RB W


Demo #4 - Resolution: RB W


Spec An

8447F Amplifier

Power Splitter(used as combiner)

inout

ESG-D4000A Sigl Gen

On

On

Two equal-amplitude signals spaced 10 kHz apart -change RB W to 10 kHz to see 3 dB

'dip'


fc=170 MhzRB W=30 kHzVB W=1 kHzspan=100 kHz


1 Signal Generator Setup

f=170.01 MHz, A=-25 dBm



SpecificationsResolution: RB W Type and Selectivity

3 dB

60 dB

60 dBB W

60 dB BW

3 dB BW

3 dB BW

Selectivity =


SpecificationsResolution: RB W Type and Selectivity

10 kHz

RB W = 10 kHzRB W = 1 kHzSelectivity 15:1

10 kHz

distortion products

60 dB BW = 15 kHz

7.5 kHz

3 dB

60 dB


SpecificationsResolution: Residual FM

Residual FM"Smears" the Signal


SpecificationsResolution: Noise Sidebands

Noise Sidebands can prevent resolution of unequal signals

Phase Noise


SpecificationsResolution: RB W Determines Measurement Time

Penalty For Sweeping Too FastIs An Uncalibrated Display

Swept too fast


Demo - Specs: Resolution: RBW Determines Measurement Time


Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Two equal-amplitude signals spaced 10 kHz

apart -change sweep time to show 'uncalibrated'

message, & signal shifted down and to the right

On





f=170.01 MHz, A=-25 dBm



SpecificationsResolution: Digital Resolution Bandwidths

DIGITAL FILTER

ANALOG FILTER

SPAN 3 kHzRES BW 100 Hz

Typical Selectivity

Analog 15:1

Digital 5:1


SpecificationsSensitivity/DANL

Sweep

LO

MixerRFInput

RES BWFilter

Detector

A Spectrum Analyzer Generates and Amplifies Noise Just Like Any Active Circuit

A Spectrum Analyzer Generates and Amplifies Noise Just Like Any Active Circuit



10 dB

Attenuation = 10 dB Attenuation = 20 dB

signal level

Effective Level of Displayed Noise is a Function of RF Input Attenuation

Effective Level of Displayed Noise is a Function of RF Input Attenuation

Signal-To-Noise Ratio Decreases as RF Input Attenuation is Increased


Demo #6 - Sensitivity/DANL - SNR decreases as RF input attn increases

Small signal -change Input attenuation to see

SNR decrease

Filter

ESG-D4000A Sigl Gen

Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off


fc=170 MhzRB W=100 kHzVB W=10 kHzspan=10 MHz




SpecificationsSensitivity/DANL: IF Filter (RBW)

Decreased B W = Decreased Noise

100 kHz RB W

10 kHz RBW

1 kHz RBW

10 dB

10 dB

Displayed Noise is a Function of IF Filter Bandwidth

Displayed Noise is a Function of IF Filter Bandwidth


Demo -Specs: Sensitivity/DANL: IF Filter

Small signal -change RB W to see Noise level decrease


Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off


fc=170 MhzRB W=100 kHzVB W=10 kHzspan=10 MHz




SpecificationsSensitivity/DANL: VBW

Video BW Smoothes Noise for Easier Identification of Low Level Signals

Video BW Smoothes Noise for Easier Identification of Low Level Signals


Demo -Theory: Video FilterSmall signal in noise -change VBW to see

smooth out


Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off

f=170 MHz, A=-100 dBm



fc=170 MhzRB W=100 kHzVB W=100 kHzspan=10 MHzDetector=SP



SignalEqualsNoise

Sensitivity is the Smallest Signal That Can Be Measured

Sensitivity is the Smallest Signal That Can Be Measured

2.2 dB



★ Narrowest Resolution BW

★ Minimum RF Input Attenuation

★ Sufficient Video Filtering(Video BW < .01 Res BW)

For Best Sensitivity Use:For Best Sensitivity Use:


SpecificationsDistortion

Frequency TranslatedSignals

Signal ToBe Measured

Resultant

Mixer GeneratedDistortion

Mixers Generate Distortion



Two-Tone Intermod Harmonic Distortion

Most Influential Distortion is the Second and Third Order

< -50 dBc < -50 dBc< -40 dBc



Distortion Products Increase as a Function of Fundamental's Power

Second Order: 2 dB/dB of FundamentalThird Order: 3 dB/dB of Fundamental

3

f 2f 3f

Powerin dB

2

f f2f -f1 2 1 2

Powerin dB

33

2 12f -f

Two-Tone Intermod

Harmonic Distortion

Third-order distortion

Second-order distortion


Demo - Specs: Distortion - Distortion products increase as a function of fundamental’s power

ESG-D4000A Sigl Gen

Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off

Signal to create harmonic distortion products -change fundamental's power level to see appropriate changes in

harmonics

Filter

f=170 MHz, A=+10 dBm



fc=340 MHzcf step=170 MHzRB W=1 MHzVB W=300 kHzspan=200 MHz



Relative Amplitude Distortion Changes with Input Power Level

f 2f 3f

1 dB

3 dB2 dB

21 dB

20 dB

1 dB



Distortion is a Function of Mixer Level

PO WER AT MIXER =INPUT - ATTENUATOR SETTING dBm

DISTORTION, dBc

0

-20

-40

-60

-80

-100

-60 -30 0 +30

.

TOI

SecondOrder

ThirdOrder



Distortion Test:Is it Internally or Externally Generated?

IF GAIN

➙ No change in amplitude = distortion is part of input signal (external)

Change Input Attn by 10 dB

1Watch Signal on

Screen:

2

➙ Change in amplitude = at least some of the distortion is being generated inside the analyzer (internal)

RF INPUT ATTENUATOR


SpecificationsDynamic Range

DynamicRange

DynamicRange




SIGNAL-TO-NOISE RATIO, dBc

0

-20

-40

-60

-80

-100

-60 -30 0 +30

.

Displayed Noise in a 1 kHz RB WDisplayed Noise in a 1 kHz RB W

Displayed Noise in a 100 Hz RBW

Displayed Noise in a 100 Hz RBW

Signal-to-Noise Ratio Can Be Graphed



Dynamic Range Can Be Presented Graphically


SIGNAL-TO-NOISE RATIO, dBc

-20

-40

-60

-80

-100

-60 -30 0 +30

..

TOI

Optimum Mixer Levels

Optimum Mixer Levels

Maximum 2nd Order Dynamic Range

Maximum 2nd Order Dynamic Range

DISPLAYED NOISE (1 kHz RB W)

THIRD ORDER

SECO

ND ORDER

Maximum 3rd Order Dynamic Range

Maximum 3rd Order Dynamic Range

SOI



Noise Sidebands

Dynamic Range Limited By Noise Sidebands

dBc/Hz

Displayed AverageNoise Level

Dynamic Range

Compression/NoiseLimited By

100 kHzto

1 MHz

Dynamic Range for Spur Search Depends on Closeness to Carrier



Actual Dynamic Range is the Minimum of:

Noise sidebands at the offset frequencyNoise sidebands at the offset frequency

Maximum dynamic range calculationMaximum dynamic range calculation

Calculated from:➙ distortion➙ sensitivity



+30 dBm

-115 dBm (1 kHz BW & 0 dB ATTENUATION)

MAXIMUM POW ER LEVEL

LCD-DISPLAY

RANGE80 dB

-10 dBm

-35 dBm

-45 dBm

INCREASINGBAND WIDTH ORATTENUATION

SECOND-ORDER DISTORTION

MIXER COMPRESSION

THIRD-ORDER DISTORTION

SIGNAL/NOISERANGE105 dB

RANGE145 dB

MEASUREMENT

MINIMUM NOISE FLOOR

70 dB RANGEDISTORTION

80 dB RANGEDISTORTION

0 dBcNOISE SIDEBANDS

60 dBc/1kHz

SIGNAL /3rd ORDER

SIGNAL/ 2nd ORDERSIGNAL/NOISE SIDEBANDS


Agenda



Features


➤ Basic Operation✓ remote operation✓ markers✓ limit lines

➤ Noise Measurements✓ noise marker✓ averaging

➤ Modulation Measurements✓ time domain✓ FFT✓ AM/FM detector✓ time-gating

➤ Stimulus Response Measurements✓ tracking generator


FeaturesBasic Operation: Remote Operation, Markers & Limit Lines


MARKER 1.025 MHz-54.04 dB


Demo #9 - Features: Basic OperationShow use of %AM markers under [Meas User] hardkey

ESG-D4000A Sigl Gen

Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off

Filter


20%AM, 1kHz





FeaturesModulation Measurements: Time Domain

LIN

MARKER 10 msec1.000 X

CENTER 100 MHz SPAN 0 HzRES BW 1 MHz VBW 3 MHz SWP 50 msec


Demo #10 - Features: Mod Meas'ts: Time Domain

AM signal -look at in zero-span

ESG-D4000A Sigl Gen

Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off

Filter


20%AM, 1kHz



fc=170 MhzRB W=3 MHzVB W=1 MHzspan= zero


FeaturesModulation Measurements: FFT

LIN

CENTER 100 MHz SPAN 0 Hz

MARKER 1 kHz-26 dBc

10 dB/

CENTER 100 MHz SPAN 10 kHz

MARKER 1 kHz-26 dBc

Swept Frequency Domain FFT Frequency Domain


Demo #11 - Features: Mod meas: FFT

AM signal -look at in zero-span, turn on FFT with stop frequency = 4 kHz

ESG-D4000A Sigl Gen

Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

On

Off


20%AM, 1kHz


fc=170 MhzRB W=3 MHzVB W=1 MHzspan= zero

Filter



FeaturesModulation Measurements: FFT

SPAN 50 kHzCENTER 100 MHz


FeaturesModulation Measurements: AM/FM Detector with Speakers



FeaturesModulation Measurements: Time-Gating

1 2 3

45

01

3

4 5 60

12

Time

Frequency

A mplitude

Timeslot

Channel Number

Time Division Multiple Access (TDMA)

user #1


FeaturesModulation Measurements: Time-Gating

EnvelopeDetector

VideoFilter

GATE

Time-Gated Measurements in the Frequency Domain

Frequency

time

"time gating"


FeaturesNoise Measurements: Noise Marker & Video Averaging


1.025 MHzMKR -135.75 dBm/Hz

AVG10


FeaturesStimulus Response: Tracking Generator

DUT

SourceReceiver

IF

LO

CRTDisplay

Tracking Generator

Tracking

RF in

Spectrum Analyzer

TG out

Adjust

DUT


Agenda



Agilent Spectrum Analyzer Product Families

856XEC family● 30 Hz up to 50 GHz● high performance● color display● W-CDMA test set● fast, digital 1 Hz RBW

ESA-E Series● 30 Hz to 26.5 GHz● MID-Performance● Flexible Platform● Application Focused Solutions● Color Display● Fast and Accurate

ESA-L series● 9 kHz up to 26 GHz● low cost● general purpose● fully synthesized● rugged

89400 family● DC to 2.65 GHz● vector signal analyzers● digital modulation● complex, time-varying signals● spectrum and time waveform analysis


Agenda



SpecificationsAccuracy: Other Sources of Uncertainty

● Mismatch ● Compression due to overload ● Distortion products● A mplitudes below the log amplifier range● Signals near noise● Noise causing amplitude variations● Two signals incompletely resolved

(RF input port not exactly 50 ohms)

(high-level input signal)



Where TOI = Mixer Level -dBc/2

SOI = Mixer Level -dBc

Optimum Mixer Level = DANL - MDR

Attenuation = Signal - Optimu m Mixer Level

MDR = 2/3 (DANL - TOI)3

MDR = 1/2 (DANL - SOI)2

Calculated Maximum Dynamic Range



Where TOI = (-30) -(-70)/2

= + 5 dBm

3MDR = 2/3 [(-115) -(+5)]

= -80 dBc (1 kHz RB W)

Example Calculation

Optimum Mixer Level = (-115) -(-80)

= -35 dBm

Attenuation = (0) -(-35)

= +35 dBm


Demo -Theory: DetectorNo signal (just noise) -

change detector modes to see difference


Spec An

8447F Amplifier


inout

ESG-D4000A Sigl Gen

fc=170 MhzRB W=100 kHzVB W=100 kHzspan=10 MHzDetector=SP


Agenda - materias.fi.uba.armaterias.fi.uba.ar/6644/info/anespec/basico/spectrum analysis... ·...

Documents

Transcript of Agenda - materias.fi.uba.armaterias.fi.uba.ar/6644/info/anespec/basico/spectrum analysis... ·...