MILLIMETRE-WAVE RADIO ASTRONOMY RECEIVERS

SOLID-STATE LOCAL OSCILLATOR SYSTEMS FOR

MILLIMETRE-WAVE RADIO ASTRONOMY RECEIVERS

A Thesis

Submitted for the Degree

of

in the Faculty of Engineering

RADHE SHYAM ARORA

Department of Electrical Communication Engineering INDIAN INSTITUTE OF SCIENCE

BANGALORE-560 0 1 2 JULY 1984

A man should n o t abandon h i s work, 0 Son of Kunti (Arjuna), even i f he cannot achieve it i n f u l l p e r f e c t i o n ;

because i n a l l work t h e r e may be imperfection, even a s i n a l l f i r e t h e r e i s smoke.

ACKNOWLEDGEMENTS

The work presented i n t h i s t h e s i s was c a r r i e d out a t t h e Rman Research I n s t i t u t e

(RRI),

~ a n ~ a l b r e i n connection with t h e millimetre-wave r a d i ~ ~ t e l e s c o p e p r o j e c t . I m g r a t e f u l t o

Prof. V. Radhakrishnan, D i r e c t o r , R . R . I . , f o r h i s encouragement and support during t h e course o f t h i s work.

I would l i k e t o express my deep sense of g r a t i t u d e t o ⁱ Prof. N.V.G. Sarma, my r e s e a r c h s u p e r v i s o r a t R . R . I . , who f i r s t suggested t h e r e s e a r c h t o p i c t o me and has s i n c e been a c o n s t a n t guide and f r i e n d . I thank my r e s e a r c h s u p e r v i s o r s a t t h e E . C . E . Department o f I . I.Sc., Prof. (Mrs.) R. Chatt'erjee f o r h e r kind h e l p and advice and Prof. A. Kwnar f o r h i s i n v a l u a b l e guidance and a c t i v e i n t e r e s t i n my work.

I have b e n e f i t e d considerably from t h e t e c h n i c a l d i s c u s s i o n s with s e v e r a l o f my colleagues; M r . K. Smiles Mascarenhas,

c M r . M. Vivekanand, D r . Rajaram Nityananda, D r . D.K. Ravindra, M r . K.R. h a n t h a r a m a i a h and M r . K.T. Balakrishnan, and it i s a p l e a s u r e t o acknowledge t h e i r help.

I thank Mr. V. K. Valsan and Mr. M. Achankunju f o r h e l p i n t h e f a b r i c a t i o n of o s c i l l a t o r mounts, My thanks a r e due t o M r . G. Rengarajan and M r . h t o n y Joseph f o r h e l p i n t h e wiring and t e s t i n g o f t h e phase-lock system, and M r . R. Ganesan and M r . K. Sukumaran f o r h e l p i n computations.

I thank M r . S. Narasimha Rao f o r t h e e x c e l l e n t job i n t y p i n g t h e manuscript, Mr. P.S..Somasundaram f o r t h e t r a c i n g s , and

M r . C. Ramachandra Rao and Mr. P. S. S a s i Kumar f o r t h e photographs.

F i n a l l y , I would l i k e t o thank my wife, Sushma, and my ^two l i t t l e c h i l d r e n , Sanjay and Sanjana, f o r t h e i r p a t i e n c e and under- standing while 'Papa1 was away t o work.

SOLID-STATE LEAL OSCILLATOR SYSTEIG FOR MlLLIMETM-WAVE RADIO ASTRCNM RECEIVERS

R.D. Thesis

Presented i n t h i s t h e s i s i s the work on t h e development of s o l i d - s t a t e sources f o r l o c a l o s c i l l a t o r a p p l i c a t i o n i n ~ i l l i - metre-wave r a d i o r s t r m q receivers f o r t h e two widely used atnospheric trllinsmission windows, 33-50 @iz and 75-110 GMz.

Such sources a r e required t o provide a , r e l i a b l e a l t e r n a t i v e t o t h e highly expensive and s h o r t - l i v e d k l y s t r s n s which have been t r a d i t i o n a l l y employed a s l o c a l o s c i l l a t o r s .

Post-coupled Guan o s c i l l a t o r s have been developed f o r t h e 33-50 Gnz frequency band i n various c i r c u i t configurations using a standard rectangular waveguide, a reduced-height waveguide m d a c i r c u l a r waveguide. E f f e c t s of t h e p o s t d i m t e r m d t h e backshort p o s i t i o n on t h e o s c i l l a t i a n f r q u s n c y and power output of t h e s e o s c i l l a t o r s have been i n v e s t i g a t e d .

Resonant-cap Gmn o s c i l l a t o r s have been developed f o r t h e 75-110 GHz frequency bmd. These o s c i l l a t o r s have been ~ e a l i z e d i n a new c i r c u i t configuration using c i r c u l a r waveguide a s well

PIS i n t h e s t m d a r d rectangular waveguide c i r c u i t . The e f f e c t of t h e resonant-cap d i m n s i o n s on t h e o s c i l l a t i a n frequency has been studied. An e a p i r i c a l r e l a t i o n between t h e o s c i l l a t i o n frequency and t h e r e s e n a t - c a p d i m n s i m s has been obtained f o r t h e c i r c u l a r waveguide configuration. The p r f o

c i r c u l a r waveguide o s c i l l a t o r which is s i q l e r i n construction i s found t o be comparable t o t h a t of t h e r e c t a n g u l a r waveguide design.

AM s i d e b a d noise, which i s a c r i t i c a l parameter f o r l o c a l o s c i l l a t o r a p p l i c a t i o n , has been measured f o r a number of

millimetre-wave G u m o s c i l l a t o r s amd L l y s t m s i n t h e 75-110 CiWz frequency bmd. The noise performance of t h e Gum o s c i l l a t o r s i s found t o be b e t t e r than t h a t of t h e k l y s t r o n s ,

ia

A phase- lock loop c , i r c u i t has been d e v e l q e d f o r t h e frequency s t a b i l i z ~ t i o n of millimtre-wave o s c i l l a t o r s . The c i r c u i t has been used t o phase-lock s e v e r a l millimtre-wave Gunn o s c i l l a t o r s t o a highly s t a b l e s i g n a l derived from a WF frequency synthesizer.

LIST OF FIGURES

PAGE

NO

v

LIST OF\ TABLES

XI

CHAPTER 1

CHAPTER 2

d

CHAPTER 3

INTRODUCTION

1.1 Historical Background.

1.2 Millimetre-wave radio astronomy receivers.

1.3 Scope of present work.

THE

GUNN

DIODE 13

2.1 Introduction. 13

2.2 Principle of operation of Gunn diodes. 13 2.3 ,Modes of oscillation of Gunn diodes. 16 2.3.1 Transit-time mode. 16 2.3.2 Quenched and delayed-domain modes. 19 2.3.3 Limited space-charge accwnula-

tion (LSA) mode. 20

2.3.4 Hybrid mode. 2 1

2.3.5 Harmonic mode operation of Gunn

diodes. 2 1

2.4 Gunn diode structure and packaging. 2 2 2.5 Oscillator design considerations. 26

2.6 Oscillator circuits. 2 8

POST-COUPLED GUNN OSCILLATORS FOR 33-50 GHz BAND.

Cii)

3.1 Introduction.

3.2 Post-coupled Guhn oscillator in a standard rectangular waveguide.

3.2.1 Design and construction.

3.2.2 Oscillator performance.

3.2.3 Effect of the post diameter.

3.3 Reduced-height waveguide Gunn oscillator.

3.3.1 Design and construction.

3.3.2 Oscillator performance.

3.4 Post-coupled Gunn oscillator in a circular waveguide.

3.4.1 Design and construction.

3.4.2 Oscillator performance.

CHAPTER 4

3.5 Discussion. 5 1

RESONANT-CAP GUNN OSCILLATORS FOR 75-110 GHz

BAND.

57

4.1 Introduction. 5 7

4.2 Resonant-cap Gunn oscillator in a circular

waveguide. 5 8

4.2.1 Design and construction. 5 8 4.2.2 Oscillator performance. 6 1 4.2.3 Effect of cap parameters on the

oscillation frequency. 6 7 4.2.3.1 Effect of cap diameter

D.

6 7 4.2.3.2 Effect of cap. thickness t

.

^{6 9}

4 . 2 . 3 . 3

Effect of post dia d.

₆₉

4 . 2 . 3 . 4

Effect of post length

R. 6 9

4 . 2 . 4 An

empirical relation for deter-

,

mining the oscillation frequency.

_{7 3}

4 . 2 . 5

Effect of cap parameters on the

oscillator power output.

74

4 . 3

Resonant-cap Gunn oscillator in a rec-

tangular waveguide. .

76

4 . 4

Discussion.

AM SIDEBAND NOISE MEASUREMENT. .

5 . 1

Introduction.

5 . 2

Noise measurement setup.

5.3

System calibration.

90

5.4

Noise measurement.

5.5

'Discussion.

J

CHAPTER

6

FREQUENCY STABILIZATION.

9 7

6 . 1

Introduction.

9 7

6 . 2

Principles of operation of phase-lock

loop CPLL).

9 9

6 . 3

Phase-lock system for frequency stabi-

lization of millimetre-wave oscillators.

103

6 . 3 . 1

Harmonic mixer and the triplexer.

106

6 . 3 . 2

Frequency discriminator and phase

detector.

10 7

6.3.3 Error s i g n a l a m p l i f i e r . ^.

1 6.3.4 Driver k l i f i e r ( f o r Gunn

o s c i l l a t o r s ) . 113

6.3.5' High voltage t r a n s l a t o r ( f o r

k l y s t r o n s ) . 11 3

6.4 Performance of t h e phase-lock system. 118 6.5 E f f e c t of phase-lock loop on o s c i l l a t o r

noise.

6.6' Discussion.

CHAPTER 7 CONCLUSION

REFERENCES

FIG. NO.

LIST OF FIGURES

TITLE PAGE NO.

1.1 Atmospheric a b s o r p t i o n o f millimetre- waves. 7 ( a f t e r Penzias and Burrus, 1973).

2 . 1 Conduction band s t r u c t u r e o f GaAs and InP. 15 ( a f t e r Eastman, 1976)

.

2 . 2 V e l o c i t y - F i e l d c h a r a c t e r i s t i c s o f GaAs and InP. 17 [ a f t e r Kuno, 1981).

2 . 3 O s c i l l a t i o n modes of a Gunn di'ode..

( a f t e r Narayan and S t e r z e r , 1970).

2.4 S t r u c t u r e o f a t y p i c a l millimetre- wave Gunn device. 23

16 ( a f t e r Krames, 1976)

.

2.5 Millimetre- wave Gunn diode package.

2.6 S i m p l i f i e d lumped e q u i v a l e n t c i r c u i t of a packaged Gunn diode.

( a f t e r B i s c h o f f , 1979).

2.7 Typical Gunn diode o s c i l l a ' t o r c i r c u i t s . 29 ( a f t e r Kuno, 1981).

3.1 C r o s s - s e c t i o n a l view of t h e s t a n d a r d r e c t a n g u l a r waveguide Gunn o s c i l l a t o r f o r t h e 33-50 GHz

frequency band. 3 3

3.2 Photograph o f t h e r e c t a n g u l a r waveguide Gunn

\

o s c i l l a t o r f o r t h e 33-50 GHz frequency band.

Block diagram o f t h e measuring s e t u p f o r t h e

33-50 GHz frequency band Gunn o s c i l l a t o r s . 36 Photograph of t h e measuring s e t u p f o r t h e

33-50 GHz frequency band Gunn o s c i l l a t o r s , 37 O s c i l l a t i o n frequency v s . backshort p o s i t i o n f o r

t h e s t a n d a r d r e c t a n g u l a r waveguide Gunn o s c i l l a t o r . 38 O s c i l l a t i o n frequency v s . post- diameter f o r t h e

s t a n d a r d r e c t a n g u l a r waveguide Gunn o s c i l l a t o r f o r a f i x e d backshort p o s i t i o n .

Power vs. frequency c h a r a c t e r i s t i c s of t h e s t a n - dard r e c t a n g u l a r waveguide Gunn . o s c i l l a t o r . C r o s s - s e c t i o n a l view of t h e reduced- height wave- guide Gunn o s c i l l a t o r f o r t h e 33-50 GHz f r e - quency band.

O s c i l l a t i o n frequency v s . backshbrt p o s i t i o n f o r t h e reduced- height waveguide Gunn o s c i l l a t o r . Power v s . frequency c h a r a c t e r i s t i c s of t h e reduced- height waveguide Gunn o s c i l l a t o r ,

C r o s s - s e c t i o n a l view o f t h e c i r c u l a r waveguide

Gunn o s c i l l a t o r f o r t h e 33-50 GHz frequency band ⁴⁸

Photograph o f t h e c i r c u l a r waveguide Gunn o s c i - l l a t o r f o r t h e 33-50 GHz frequency band.

O s c i l l a t i o n frequency v s , backshort p o s i t i o n f o r t h e c i r c u l a r waveguide Gunn o s c i l l a t o r .

Power v s . frequency c h a r a c t e r i s t i c s o f t h e c i r - c u l a r waveguide Gunn o s c i l l a t o r .

C r o s s - s e c t i o n a l view o f t h e resonant- cap Gunn o s c i l l a t o r i n a c i r c u l a r waveguide f o r t h e 75-110 GHz frequency band.

Photograph o f t h e 75-110 GHz band Gunn o s c i l l a t o r ^' i n a c i r c u l a r waveguide, ( a ) Assembled view,

(b) Exploded view. 6 0

Photograph o f t h e measuring s e t u p f o r t h e

\

75-110 GHz frequency band Gunn o s c i l l a t o r s . 6 2 Dimensional parameters o f t h e resonant- cap Gunn

o s c i l l a t o r i n a c i r c u l a r waveguide. 6 3 O s c i l l a t i o n frequency vs. cap diameter D f o r t h e

c i r c u l a r waveguide resonant- cap Gunn o s c i l l a t o r . 6 8 O s c i l l a t i o n frequency v s . cap t h i c k n e s s t f o r t h e

-

c i r c u l a r waveguide resonant- cap Gunn o s c i l l a t o r . 70

O s c i l l a t i o n frequency v s . p o s t d i a d f o r t h e

c i r c u l a r waveguide resonant-cap Gunn o s c i l l a t o r . 7 1

O s c i l l a t i o n frequency vs. p o s t length R f o r t h e c i r c u l a r waveguide resonant-cap Gunn o s c i l l a t o r .

Power vs. frequency c h a r a c t e r i s t i c s of t h e c i r c u l a r

I

waveguide Gunn o s c i l l a t o r f o r s e v e r a l resonant caps. 75

4.10 Photograph of t h e resonant- cap Gunn o s c i l l a t o r i n a W-band (75-110 GHz) r e c t a n g u l a r waveguide.

4.11 O s c i l l a t i o n frequency v s . p o s t length R f o r t h e

r e c t a n g u l a r waveguide resonant- cap Gunn o s c i l l a t o r . 80

, 4 . 1 2 Power vs. frequency c h a r a c t e r i s t i c s of t h e r e c t a n - g u l a r waveguide Gunn o s c i l l a t o r f o r s e v e r a l

resonant-caps

.

Typical output power spectrum of a millimetre-wave o s c i l l a t o r .

AM sideband n o i s e measurement setup

-

^System

c a l i b r a t i o n .

AM sideband n o i s e measurement setup

-

Noise measurement.

An elementary phase-lock loop.

Loop filter.

Block diagram of the phase-lock system for fre- quency stabilization of millimetre-wave osci- llators.

Circuit diagram of the triplexer for the harmonic mixer.

6.5 Block diagram of the frequency discriminator/

phase detector.

6 . 6 Voltage-frequency characteristics of the frequency

discriminator for I.F. input frequencies between

275 to 525 MHz. HOR-25 MHz/div., VER-SOmV/div. 111

Circuit diagram of the error signal amplifier. 112

Circuit diagram of the driver amplifier. 114

Circuit diagram of the high voltage translator for

millimetre-wave reflex klystrons 116

Circuit diagram of the floating d.c. regulated

power supplies. 117

6.11 Output spectra of an 87 GHz Gunn oscillator

(a] Free-running, (b) Phase-1ocked.HOR-200 KHz/div.

,

6.12 Output s p e c t r a o f t h e 87 GHz phase-locked Gunn o s c i l l a t o r i l l u s t r a t i n g ' t h e e f f e c t of loop g a i n (a) Loop g a i n t o o h i g h , (b) Optimum loop g a i n and Ic) Loop g a i n t o o low. HOR-2 MHz/div.,

VER- 10dB/div. 120

TABLE NO.

LIST OF TABLES

TITLE PAGE NO.

4.1 O s c i l l a t i o n frequencies and output powers obtained with v a r i o u s resonant- caps f o r t h e 75-110 GHz Gunn o s c i l l a t o r i n a c i r c u l a r

waveguide. 6 4

O s c i l l a t i o n frequencies .and output powers obtained with various resonant-caps f o r t h e 75-110 GHz Gunn o s c i l l a t o r i n a W-band rec- t a n g u l a r waveguide.

5 . 1 Results o f AM sideband n o i s e measurements on v a r i o u s m i l limetre-wave o s c i l l a t o . r s

.