High Sensitivity Radio Design

7/28/2019 High Sensitivity Radio Design

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High Sensitivity RadioReceiver Design

Webinar

2009 National Semiconductor Corporation


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Panelists

Bobby Matinpour Marketing Manager, Wireless Infrastructure Solutions

Scott Kulchycki Marketing Manager, High Speed Signal Path



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Objectives

Discuss Base Station Market Trends & NeedsReview Radio Receiver BasicsDescribe Receiver Architectures & Trade-OffsDescribe the High-IF Receiver Requirements

RF & IF blocks, anti-aliasing filter, and the ADCDemonstrate an Example Using Nationals Portfolio

ADC16DV160, LMH6517, and LMK04000Call to Action



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Base Station Market Trends & Needs

Network Efficiency More user channels in a given radio

Lower Total Cost of Ownership Infrastructure hardware, deployment and operation



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Base Station Market Trends & Needs

Flexible & High Capacity Base Stations Multi-Carrier

Enable higher capacity per radio Multi-Standard

Flexible deployment along with legacy infrastructure Streamlined development & maintenance

Wideband Enable higher capacity per radio Flexible deployment along with legacy infrastructure Streamlined development & maintenance



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Radio Receiver Basics



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Radio Receiver Overview

Function Translate RF signal to lower frequency digital bits

Wireless Markets & Applications Cellular Base Stations & Repeaters Point-to-Point RF & Microwave Links Microwave Backhaul



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Radio Receiver Figure of Merit

Receiver Sensitivity Normal (non-Blocking) Condition

How small of a signal can the receiver detect and process Most critical receiver performance metric is Noise Figure

Blocking Condition How small of a signal can the receiver detect and process in the

presence of a strong interferer (source closer to antenna)

Most critical receiver performance metric is Linearity

Strong

Interferer

Signal



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Receiver Architectures

Homodyne (Direct Conversion) Directly converting RF to baseband quadrature signals

Simple but difficult to get high performance

Heterodyne Converting RF to low-frequency IF using single or multipledown-conversion stages

Complex but yields the best performance



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Homodyne (Direct Conversion) Receiver

AdvantagesAll IF filtering in baseband No image rejection filters

Disadvantages Needs stringent I & Q channel phase & amplitude balance LO is in-band and can radiate through antenna DC offsets and 2nd order intermodulation are now in-band

DVGAAnti-Aliasing

FilterQuadrature

Mixer

RF FilterLNA

LO

90

ADC

AntennaFilter

Q-channel

I-channel



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Heterodyne Receiver

Advantages Multiple stages of filtering allows for high performance DC offsets and 2nd order intermodulation are now out of band

Disadvantages Requires multiple filtering stages (more complex) Frequency planning is much more complex

IF Filter Chain DVGAAnti-Aliasing

FilterMixerRF FilterLNA

LO

ADCAntenna

Filter



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Filtering in Heterodyne Receivers

signal

RFLO

interfererimage

in-band

blocker

RF Filtering Image band Mixer two-two spurs (2xLO 2xRF) Out-of-band blockers & interferers

High-IF Example

mixer 2-2 spur



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signal

RFLO

interfererimage

IF

in-band

blocker2nd harmonic of

In-band blocker

signal

in-band blocker

interferer

RF Filtering Image band Mixer two-two spurs (2xLO 2xRF) Out-of-band blockers & interferers

IF Filtering (no more filtering on 2-2 spur & image)

Remaining out-of-band blockers & interferers

Harmonics of the in-band blocker Wide-band noise High-IF Example

mixer 2-2 spur



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signal

RF

interfererimage

in-band

blocker

RF Filtering Image band Out-of-band blockers & interferers Mixer two-two spurs (2xLO 2xRF)



Harmonics of the in-band blocker Wide-band noise Low-IF Example

LOmixer 2-2 spur



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signal

RF

interferer

IF

in-band

blocker2nd harmonic of

In-band blocker

signal

in-band blocker

interferer

RF Filtering Image band Out-of-band blockers & interferers Mixer two-two spurs (2xLO 2xRF)



Harmonics of the in-band blocker Wide-band noise Low-IF Example

image

mixer 2-2 spurLO



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Frequency Planning for a High-IF Receiver

Filtering RF filtering simplifies with higher IF

Image & Mixer 2-2 spurs are further away from the desired signal IF filtering simplifies with higher sample rate & IF

Lower-order filter required

Amps & Converters Data converters perform better at lower IF & sample rates

Better SNR & SFDR Amplifiers perform better at lower IF frequency

Lower Noise & Better Linearity



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IF Filtering Selecting a Sampling Rate

Desired signal

fS/2 fS 3fS/2 2fS

fS/2 fS 3fS/2

Signal will alias

in-band on sampling

Increase

Sampling RateDecreased slope

Relaxed filter requirements



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IF Filtering Selecting an IF

Amplifier HD2 Distortion

Amplifier HD2 Distortion

Increase IF

Decreased slope

Relaxed filter requirements

Desired signal

In-band blocker

Signal will alias

in-band on sampling

fS 3fS/2 2fS

fS2fS 3fSfS/2



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Multi-Carrier Multi-Standard

20-MHz Receiver Example



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Multi-Carrier Receiver Design Example

Requirements (including Multi-Carrier GSM) Sensitivity in 200-kHz bandwidth

-104 dBm under normal condition (no margin) -92 dBm under blocking condition

-16 dBm in-band & out-of band blockers Require 9-dB Carrier-to-Noise-and-Interference Ratio

Frequency Plan ADC Sample Rate = 76.8 or 153.6 Msps IF centered at middle of Nyquist zone

Chose 3rd Nyquist zone (192-MHz) to simplify anti-aliasing filter



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Noise & Gain Calculations Under Normal Condition

Noise Thermal Noise Floor = -174 dBm + 10 x log(200e+3) = -121 dBm Maximum Noise Figure = -121 dBm + 9 dB - 104 dBm = 8 dB

Gain No limitation; need to make sure to not saturate any stages

Under Blocking Condition Noise

Not a critical spec since limitation is the blocker Gain

Maximum gain is set by blocker & ADC full-scale (~4-dBm) Rx Gain = 0 dBm (4-dB back-off from FS) (-16 dBm) = 16 dB



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IF Filter Chain DVGAAnti-Aliasing

FilterMixerRF FilterLNA

LO

ADCAntenna

Filter

-16 dBm 0 dBm

-92 dBm -76 dBm

Gain = 16 dB

NF = ? dBSignal

Blocker



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Design Example: RF Front-End

IF Filter Chain DVGAMixerRF FilterLNA ADCAntenna

Filter

GNF

OP1dB

-1 dB1 dB

16 dB0.8 dB

14 dBm

-1 dB1 dB

-7.5 dB7.5 dB

8 dBm

Anti-AliasingFilter

LO

Cascaded Noise Factor:



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Design Example: Blocking Condition


Filter

0 dB9 dB

-5 dB5 dB

? dB? dB

? dBm

?

Anti-AliasingFilter


GNF

OP1dB

-1 dB1 dB

16 dB0.8 dB

14 dBm

-1 dB1 dB

-7.5 dB7.5 dB

8 dBm

LO

GNF

OP1dB

-20 dB20 dB

20 dB5.5 dB

20 dBm

-20 dB20 dB

20 dB5.5 dB

20 dBm

DVGA Gain RangeBlocking Condition = 16 - 1.5 = 14.5

Normal Condition = -1.5 + DVGA max gain



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Design Example: Blocking Condition


Filter

GNF

OP1dBOut

-1 dB1 dB

-17 dBm

16 dB0.8 dB

14 dBm-1 dBm

-1 dB1 dB

-2 dBm

-7.5 dB7.5 dB

8 dBm-9.5 dBm

0 dB9 dB

-9.5 dBm

-5 dB5 dB

0 dBm

14.5 dB12 dB

15 dBm5 dBm

?

Anti-AliasingFilter

4-dB back-offfrom fullscale

GNF

OP1dBOut

-20 dB20 dB

-9.5 dBm

20 dB5.5 dB

20 dBm10.5 dBm

-20 dB20 dB

-9.5 dBm

20 dB5.5 dB

20 dBm10.5 dBm

Tracing the BlockerStay 10-dB below P1dB at all times

LO



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Design Example: Normal Condition

IF Filter Chain DVGAMixerRF FilterLNA ADCAntennaFilter

22 dB5.5 dB ?

Anti-AliasingFilter


0 dB9 dB

-5 dB5 dB

GNF

-1 dB1 dB

16 dB0.8 dB

-1 dB1 dB

-7.5 dB7.5 dB

LO

Max Gain



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Design Example: Normal Condition

IF Filter Chain DVGAMixerRF FilterLNA ADCAntennaFilter

GNF

-1 dB1 dB

16 dB0.8 dB

-1 dB1 dB

-7.5 dB7.5 dB

0 dB9 dB

-4 dB4 dB

22 dB5.5 dB

Gain overall = 23.5 dB

NF overall < 8 dB ADC NF = 27.5

?

LMH651

7

Anti-AliasingFilter

ADC Noise Density = -174 dBm/Hz + 27.5 dB - 3.5-dB margin = -150 dBm/Hz

-150 + 79 = -71 dBm/76.8MHz (156.3 Msps) SNR = 75-dB FS

LOADC1

6DV160



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Design Summary

Review of the Numbers Sensitivity

Meet -104 dBm under normal condition (with 3.5-dB margin) Simulation confirms -107.2 dBm

Meet -92 dBm under blocking condition (with 4-dB margin) Simulation confirms -95.5 dBm

Nationals High-IF Receive Sub-System LMH6517, ADC16DV160, and LMK04000



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High IF Receiver Sub-System

Solution using LMH6517+ADC16DV160+LMK04000 Accelerate design of multi-carrier multi-standard receivers



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Call to Action

Go to Nationals website for more information ADC16DV160: http://www.national.com/pf/DC/ADC16DV160.html LMH6517: http://www.national.com/mpf/LM/LMH6517.html LMK04000: http://www.national.com/pf/LM/LMK04000.html

Check on High-IF Sub-System Board (Late Sept) View other webinars such as Clock & Timing Webinar on

PowerWise Design University

Download & examine Wireless Communications Brochure:http://www.national.com/vcm/NSC_Content/Files/en_US/

Documents/national_comms_infrastructure.pdf



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Contact Information

Bobby Matinpour Marketing Manager, Wireless Infrastructure Solutions Email: [email protected] Desk: (408) 721- 7235

Mobile: (408) 332 - 4321

Scott Kulchycki Marketing Manager, High Speed Signal Path Email: [email protected] Desk: (408) 721- 5851 Mobile: (408) 832 - 9391



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High Sensitivity Radio Design

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