the application of dsp technology in hf/vhf/uhf radio systems

July 23, 1998 1

Advanced Technology CenterAdvanced Subsystems & Signal Processing DepartmentDSP, Photonics, Digital Radio, Frequency Control, and Power Conversion

1998 Int’l Symposium on Advanced Radio Technologies

THE APPLICATION OF DSPTHE APPLICATION OF DSPTECHNOLOGY IN HF/VHF/UHFTECHNOLOGY IN HF/VHF/UHF

RADIO SYSTEMSRADIO SYSTEMS

September 10, 1998September 10, 1998

Presented By Rich GroshongPresented By Rich Groshong

RockwellCollins

July 23, 1998 2



• Superheterodyne Radio Technology

• Direct Conversion Radio (DCR)Technology

• Critical DSP Radio Performance Issues

• Tricks of the DSP Trade

• Future DSP Radio Technology

PRESENTATION AGENDA

July 23, 1998 3



SUPERHETERODYNE RADIO TECHNOLOGY

July 23, 1998 4



DIRECT CONVERSION RADIO TECHNOLOGY

MULTI-BAND, MULTI-MODE DIRECT CONVERSIONRECEIVER

DSP

Preselector& LNA

ADC

COS(ωRFt)

SIN(ωRFt)

LO

I

Q

FRONT-ENDGAIN CTL

TO DSPBASEBANDPROCESSING

LPF

LPF ADC

QUADRATURENETWORK

LPF

LPF

PROGRAMMABLELPF

July 23, 1998 5



Waveform Frequency BWSINCGARS 30-88MHz 25KHz

VOR 108-118MHz 18KHz

ILS (MB,LOC,GS) 75,108-112,329-335MHz 36KHz

VHF/UHF (Clear Voice Com & Data) 30-400MHz 8.33KHz, 18KHz

HAVE QUICK, HAVE QUICK II 225-400MHz 25KHz,36KHz

SATURN 225-400MHz 36KHz

Link 4 225-400MHz 70KHz

Link 11 225-400MHz 70KHz

SATCOM (DAMA) 240-317MHz 8KHz, 36KHz

Constant Source (T-A/B, TIBS, TRAP) 240-270MHz 8KHz, 36KHz

IFF / TCAS (XPND / INT) 1030,1090MHz 10.0MHz

Link 16 / JTIDS 969-1206MHz 3.0MHz

TACAN 962-1213MHz 400KHz

Weapons Data Link 1500-1900MHz 10.0MHz

HF 2-30MHz 3, 6KHz

MODULAR AVIONICS RADIO WAVEFORMS

July 23, 1998 6



• DCR Offers Lower Cost / Size / Power for a WideFrequency Coverage Radio

– How do you build a 2 to 3000 MHz Superheterodyne?

– Single Synthesizer DCR, 1-Loop at RF Carrier Frequency

– Single Frequency Translator DCR, RF to BB & BB to RF

– All DCR components are suitable for integration

• MMIC’s & ASIC’s

– Spurious Responses are well behaved (No Crossovers)

• DCR May be the only “practical” near-term technology forlow-power PCMCIA Radio

• DCR REQUIRES DSP Calibration of Analog Circuits– Phase & Gain error, Rcvr DC Offset, Xmtr LO Leakage

– DCR DSP is more complex but can be digital VLSI

DCR PRO’S AND CON’S

July 23, 1998 7



Receiver Spurious Responses225-500MHz, IF=27MHz, Hi-Side Injection

-100

-80

-60

-40

-20

0

20

40

60

80

100

225 275 325 375 425 475

Input Signal Range

-1 1

1 -1

-2 2

2 -2

3 -3

-3 3

-4 4

4 -4

5 -4

-5 4

4 -3

-4 3

3 -2

-3 -2

-1 -2

1 -2

DeltaawayfromInput

Signal

4th order Spur (-2,2)(half-IF spur)

is always 13.5MHzabove Tune Frequency

Image Spur (-1, 1)is always 54MHz

above Tune Frequency

UHF SUPERHET SPURS

July 23, 1998 8



Direct Conversion Receiver225-500MHz, 9th Order (& lower) Spurs

-100

-80

-60

-40

-20

0

20

40

60

80

100

225 275 325 375 425 475

Input Signal Range

1 -2

2 -3

3 -4

4 -5

-5 4

-4 3

-3 2

-2 1

DeltaawayfromInput

Signal

9th order Spur (4,-5)is always 1.2 X

Tune Frequency

9th order (-5,4) Spur is always 0.8 X

Tune Frequency

7th order (-4,3) Spuris always 0.75 XTune Frequency

UHF DCR SPURS

7th order Spur (3,-4)is always 1.33 XTune Frequency

July 23, 1998 9



DCR Spur Chart, 29th Order (and lower)

-500

-400

-300

-200

-100

0

100

200

300

400

500

0 500 1000 1500 2000 2500

Input Signal Frequency

1 -2

2 -3

3 -4

4 -5

5 -6

6 -7

7 -8

8 -9

9 -10

10 -11

11 -12

12 -13

13 -14

14 -15

-15 14

-14 13

-13 12

-12 11

-11 10

-10 9

-9 8

-8 7

DeltafromInput

Signal

Well-Behaved Spurious Performance

HF/VHF/UHF DCR SPURS

July 23, 1998 10



– Direct Conversion Receiver / Direct Conversion Exciter• Multi-Band Receiver and Exciter: 30 MHz to 2000 MHz

• Multiple Channel Bandwidths: 5 KHz to 10 MHz

• 3-Pitch SEM-E Form Factor (5” x 6” x 1.8” ), reducing to 1-Pitch (5” x 6” x 0.6” )

• Custom MMICs and ASICs and FPGAs

– 30-2000MHz Synthesizer:• Single-Loop PLL, utilizing Fractional Division Technology

• Continuous Freq. Coverage 30-2000MHz / 10 Hz resolution.• Fast Tune (15uS), Medium Tune (80uS), and Slow Tune (1mS) modes.

• Eliminates need for Synthesizer in PA

– Digital Signal Processing:• Phase, Gain, and DC Offset Correction Algorithms

• Exciter Phase, Gain, and Carrier Leak Correction Algorithms

• Decimation/Interpolation, Channel Selectivity, & Baseband Selectivity Filtering

• Automatic & Manual Gain Control Algorithms

• I/Q and AM/FM Modulation and Demodulation Algorithms

• Squelch Algorithms

• Digital Baseband I/Q or AM/FM Interface for both Tx and Rcv

MODULAR AVIONICS RADIO CAPABILITIES

July 23, 1998 11



DIRECT CONVERSION RADIO ARCHITECTURE

RF TO BASEBAND

BASEBAND TO RF

LNAAGC/SW &Blank

RX 0 DegHybrid

5 MHzWBLPF

5 MHzWBLPF

SWITCHEDNB LPF

SWITCHEDNB LPF

AMP

AMP

A/D

A/D

DigitalFilter

DigitalFilter

0 DegHybrid

5 MHzWBLPF

5 MHzWBLPF

D/A

D/A

AMPCPLR

DigitalFilter

DigitalFilter

DIVIDE/4

LPF(80uS)

LPF(1mS)

VCOQUADRATURENETWORK

PROMD/A

LPF(15uS)

1X3SW

GAINADJ

DIVIDE32+N

FRACTIONALDIVIDER

TX

100 MHz

GainPhase

&DC OffsetCorrection

OverloadDetector

OverloadDetector

DitherNoise

Generator

GainPhase

&CarrierLeak

Correction

HI-SPEEDDSP

ReceiverAlgorithms

HI-SPEEDDSP

ExciterAlgorithms

SWDSP

LO-SPEEDDSP

Algorithms

RCVR CORRECTION

XMTR CORRECTION

DSPINFCFLASH

MEM

EXT.INFC

ControlBUS

DataBUS

PHASEDET

1-2 GHzI

Q

SWITCHEDNB LPF

Frequency

HWDSP (VHDL)

SWITCHEDNB LPF

ATTN

AMP

RCVR GAINCONTROL

July 23, 1998 12



TYPICAL RECEIVER DSP ALGORITHMSINPUT FILTER

Filter

I QIn Pre-Detection

BW

SquelchAlgorithm

AM/FMDemod

DCReceiver

CalibrationAlgorithm

AGCAlgorithm

GainMultiplier

RADIOCNTLINFC

LOCALSYNTHCNTLINFC

CNTLSTATUS

INFC

Analog Gain

Gain

ReceiverGain

FM

ADCINFC

DC Receiver Correction

I

Q

AM

SAMPLE RATE CHANGER

ADC Overload

Analog BW

C

Filter

OUTPUT FILTER

I or AM Audio or ?Q or FM Audio or ?

DATAor

DACINFC

Post-DetectionBW

I or AM Audio or ?Q or FM Audio or ?

Output

Key Control Flow

Data Flow

ManualGain Control

SquelchThreshold

Decimateby C

(C=1,..,N)

Decimateby A

(A=1,..,N)

Interpolateby B

(B=1,..,N)

BA

Gain, Phase, DC OffsetCorrection

NOISEDither

Generator

CUSTOM?Demod

IQ

July 23, 1998 13



• Rapid & Accurate DCR Calibration Algorithms– Off-line/Factory/Pwr-up Calibration

• e.g.

– Calibrate entire Receiver and Exciter from 30 to 2000 MHz in lessthan 10 seconds

– Tuning Event Calibration• e.g.

– Calibrate DC Offset in 5 microseconds to support fast frequencyhopping

– Calibration Performance Requirements• e.g.

– Calibrate Phase & Gain to -60 dBc Distortion

– Phase error < 0.1 degree, Gain error < 0.01 dB

– Calibrate DC Offset to preserve 80 dB SFDR

DCR CALIBRATION TECHNOLOGY

July 23, 1998 14



• Random Noise due to Quantization– Know your Effective Number of Bits (ENOB) !

• Phase Noise due to Sampler Aperture Jitter

• Harmonic & Intermodulation Distortion due to :– Non-Uniform Quantizer Step Sizes

– Cubic & Quadratic Amplifier Transfer Curve

– Slew Rate Limiting

– Nonlinear Impedance

– ADC Overload

– Inadequate Quantizer Noise Dither

• Spurious Noise & Distortion due to :– Undesired Digital Noise Pickup

• The Sample Clock is a Local Oscillator & MUST BE CLEAN

– Aliasing (including Broadband Noise Aliasing in ADC!)

ADC & DAC NOISE & DISTORTION SOURCES

July 23, 1998 15



SP

EC

TR

AL

DE

NS

ITY

FREQUENCY2FS

FS/2

SIGNAL

QUANTIZING NOISE SPECTRUMFOR SAMPLING RATE FS

QUANTIZING NOISE SPECTRUMFOR SAMPLING RATE 4FS

1.0E-01 1.0E+00 1.0E+01 1.0E+02

SAMPLE FREQUENCY (MHz)

90.00

100.00

110.00

120.00

130.00

140.00

150.00

160.00

170.00

180.00

SN

R IN

dB

-Hz

MAX ADC SNR

16-Bit

15-Bit

14-Bit

13-Bit

12-Bit

11-Bit

10-Bit

9-Bit

8-Bit

MAX SNR IN dB-HzFOR 8 TO 16 BITENOB

ADC QUANTIZING NOISEQUANTIZER NOISE DENSITY

DECREASES 3 dBFOR EVERY DOUBLINGOF THE SAMPLE RATE

SNR INCREASES 6 dB PER BIT

July 23, 1998 16



ADC NOISE & DISTORTION SOURCES

July 23, 1998 17



• Set Analog Gain to meet sensitivity requirement– e.g. 10 dB SNR @ -113 dBm in 3 kHz BW

• Ensure ADC output noise has Uniform Density– Either amplify thermal noise or add out-of-band dither noise

• Keep analog gain high until Ultimate SNR is obtained– Control output level with DSP gain control

• Hold ADC level constant if Ultimate SNR is obtained– Reduce analog gain & hold DSP gain constant

• Detect out-of-band interference at ADC– Reduce analog gain & increase DSP gain to maintain output

• Use Spreadsheet to select ADC, set gain distribution, andanalyze noise & distortion performance

DSP RECEIVER DESIGN

July 23, 1998 18



DSP RECEIVER GAIN DISTRIBUTION AND NOISE PERFORMANCE VHF/UHF RCVR, 36 kHz BW

Analog RF/IF Front-End Noise Figure 8.00 dB

Max. Receiver Antenna Signal Level 20.00 dBm

A/D Converter Effective No. of Bits 11.00 bits 68.0 dB Max. A/D S/N in Nyquist BW

A/D Converter Full-Scale Level 0.50 V-pk = 4.0 dBm (full-scale sinewave level) A/D Converter Sample Frequency 25,000.0 kHz -62.2 dBm Min. A/D Input Noise (reqmt)

A/D Converter Input Bandwidth (BW1) 5,000.0 kHz -68.0 dBm A/D Quant. Noise in BW1

DSP Pre-Detection (IF) Bandwidth (BW2) 36.0 kHz -89.4 dBm A/D Quant. Noise in BW2

DSP Post-Detection (Audio) Bandwidth (BW3) 3.0 kHz -100.2 dBm A/D Quant. Noise in BW3

Analog RF/IF Front-End AGC Threshold -80.00 dBm Analog RF/IF Front-End AGC Range 81.00 dB

Receiver AGC Threshold -115.00 dBm -16.00 dBm IQ Output Signal Level

Max. DSP Internal Gain 58.00 dB

AM Modulation Percentage 80.00 % -23.96 dBm AM Output Signal Level

FM Detector Sample Frequency 64.00 kHz FM Peak Deviation 8.00 kHz -8.06 dBm FM Output Signal Level

Synthesizer Noise Density -100.00 dBc-Hz 33.01 dB Max pre-A/D SNR in BW1

54.44 dB Max pre-A/D SNR in BW2

65.23 dB Max pre-A/D SNR in BW3---------------------------------------------------------------------------------

Antenna Analog A/D Noise at Noise at Noise at Total Total IQ IQ AM FM DSP IQ Total Antenna Antenna

Signal RF/IF Signal A/D InputA/D InputA/D Input Noise Noise SNR SNR SNR SNR Internal Output Noise Ovld Ovld/Sig

Level Gain Level in BW1 in BW2 in BW3 in BW2 in BW3 in BW2 in BW3 in BW3 in BW3 Gain Level Figure Level Ratio

(dBm) (dB) (dBm) (dBm) (dBm) (dBm) (dBm) (dBm) (dB) (dB) (dB) (dB) (dB) (dBm) (dB) (dBm) (dB)

-120.00 41.00 -79.00 -58.01 -79.44 -90.23 -79.02 -89.81 0.02 10.81 2.85 0.31 58.00 -21.00 8.42 -37.0 83.0

-110.00 41.00 -69.00 -58.01 -79.44 -90.23 -79.02 -89.81 10.02 20.81 12.85 30.85 53.00 -16.00 8.42 -37.0 73.0

-100.00 41.00 -59.00 -58.01 -79.44 -90.23 -79.02 -89.81 20.02 30.81 22.85 41.09 43.00 -16.00 8.42 -37.0 63.0

-90.00 41.00 -49.00 -57.99 -79.42 -90.21 -79.01 -89.80 30.01 40.80 32.84 51.08 33.00 -16.00 8.43 -37.0 53.0-80.00 41.00 -39.00 -57.84 -79.27 -90.06 -78.87 -89.66 39.87 50.66 42.70 60.94 23.00 -16.00 8.57 -37.0 43.0

-70.00 31.00 -39.00 -66.55 -87.98 -98.77 -85.63 -96.42 46.63 57.42 49.46 67.70 23.00 -16.00 11.81 -27.0 43.0

-60.00 21.00 -39.00 -71.04 -92.46 -103.26 -87.67 -98.46 48.67 59.46 51.50 69.74 23.00 -16.00 19.77 -17.0 43.0

-50.00 11.00 -39.00 -71.90 -93.33 -104.12 -87.93 -98.73 48.93 59.73 51.77 70.01 23.00 -16.00 29.50 -7.0 43.0

-40.00 1.00 -39.00 -72.00 -93.43 -104.22 -87.96 -98.75 48.96 59.75 51.80 70.03 23.00 -16.00 39.47 3.0 43.0-30.00 -9.00 -39.00 -72.01 -93.44 -104.23 -87.96 -98.76 48.96 59.76 51.80 70.04 23.00 -16.00 49.47 13.0 43.0

-20.00 -19.00 -39.00 -72.01 -93.44 -104.23 -87.97 -98.76 48.97 59.76 51.80 70.04 23.00 -16.00 59.47 20.0 40.0

-10.00 -29.00 -39.00 -72.01 -93.44 -104.23 -87.97 -98.76 48.97 59.76 51.80 70.04 23.00 -16.00 69.47 20.0 30.0

0.00 -39.00 -39.00 -72.01 -93.44 -104.23 -87.97 -98.76 48.97 59.76 51.80 70.04 23.00 -16.00 79.47 20.0 20.010.00 -40.00 -30.00 -63.01 -84.44 -95.23 -83.24 -94.03 53.24 64.03 56.07 74.31 14.00 -16.00 85.20 20.0 10.0

20.00 -40.00 -20.00 -53.01 -74.44 -85.23 -74.30 -85.09 54.30 65.09 57.13 75.37 4.00 -16.00 94.14 20.0 0.0

DSP RECEIVER SPREADSHEET EXAMPLE

RECEIVER OPERATING CURVES

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

-120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20

RECEIVER INPUT LEVEL IN dBm

ADC

INPU

T LE

VEL

IN d

Bm

ADC OVERLOAD LEVEL

ADC INPUT LEVEL

3RD ORDER IMDFOR +30 dBm IP3FRONT-END

SYNTH NOISE LEVEL IN BW3

ADC QUANTIZING NOISE IN BW3

ADC DISTORTIONFOR 15-BIT LINEARITY(SFDR=90 dB)

ADC INPUT NOISE IN BW3

July 23, 1998 19



• Digital Generation of Out-of-Band Noise Dither– Dither May Be Required in NB Modes to Ensure Uniform Quantizing

Noise ( e.g. to Linearize ADC Model )

– Dither Reduces ADC Spurs & Distortion

PN SEQUENCE GENERATORSHIFT REGISTER LENGTH >= 7

EXTERNAL RESISTOR SUMMING NETWORKFOR NOISE SPECTRAL SHAPING

(ANALOG FIR FILTER)

P/O DSP

SAMPLECLOCK

OUT-OF-BANDDITHER NOISE

7-SHIFT REGISTER TAP OUTPUTS(NON-INVERTED OUTPUT FOR POS. COEF,

INVERTED OUTPUT FOR NEG. COEF)

NOISE DITHER GENERATION

0.00 0.10 0.20 0.30 0.40 0.50

Normalized Frequency

-110.00

-100.00

-90.00

-80.00

-70.00

-60.00

-50.00

-40.00

Lev

el R

elat

ive

to A

DC

Fu

ll S

cale

in d

B

FIR filter, 7 taps noise7b.cf

July 23, 1998 20



• Decimation & Interpolation– Cascade-Integrator-Comb (CIC) Digital Filters

• Linear Phase Response

• Variable Decimation / Interpolation Ratio

• Multiplier-less Design

OUTPUT@ Fs/R

CIC DECIMATOR (N=6, M=1, R=1,...,N) :

INTEGRATORS

REG REG REG REG REG REG

INPUT@ Fs

CIC INTERPOLATOR (N=6, M=1, R=1,...,N) :

OUTPUT@ Fs

COMB FILTERS


COMB FILTERS


INPUT@ Fs/R


INTEGRATORS

RESAMPLE AT Fs/R

RESAMPLE AT Fs, INSERT R-1 ZEROES

0

HI-SPEED (MULTIPLIER-LESS) DIGITAL FILTERING

July 23, 1998 21



• FIR Digital Filtering– Selectivity Filtering

– CIC Frequency Response Correction• CIC Passband Rolloff Compensation

• CIC Alias Suppresion (Selectivity Filtering)

– Multiplier-less Designs Possible

– e.g.


REGREG REG REG

REGX(n)

H(9) H(8) H(7) H(0)

Y(n-1)

H(1)

H(0) = H(9) = 0.001953125 = 2-9

H(1) = H(8) = -0.058593750 = 2-8 - 2-4

H(2) = H(7) = -0.093750000 = -2-5 - 2-4

H(3) = H(6) = 0.132812500 = 2-7 + 2-3

H(4) = H(5) = 0.500000000 = 2-1

OPTIONALINPUT REGISTER

10-TAPMULTIPLIER-LESSLINEAR PHASEFIR FILTER EXAMPLE

July 23, 1998 22




July 23, 1998 23




July 23, 1998 24



FUTURE DSP RADIO TECHNOLOGY

the application of dsp technology in hf/vhf/uhf radio systems

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