PROXIMITY FUZESTHEORY AND TECHNIQUES

DRDO Monographs/Special Publications Series

Introduction to Camouflage and Deception: JV Ramana Rao

Solid Propellant Chemistry: Prof K Kishore and K Sridhara

Environment in Submarines: MVR Koteswara Rao

An Introduction to Night Vision Technology: Dr R Hradaynath

Photonics in Warfare: Dr VV Rampal

Aerodynamic Predictive Methods and their Validation in Hypersonic Flows:

Dr AK Sreekanth

Modelling Radar ECCM: A System Approach: AK Subramanian

Microwave Circuits and Components: Prof GP Srivastava

Inverse Gas Chromatography: Dr AK Sen

Environmental Conservation and Security: Dr AK Datta and Dr Ram Kumar

Defence Research & Development Organisation: 1958-1982: Dr RP Shenoy

Infrared Detectors: Materials and Technology: AK Sreedhar and Prof KSRKoteswara Rao

Reminiscences of a Defence Scientist: A Quest for Self-reliance: V Narayana Rao

Acousto-optic Devices and their Defence Applications: Dr JC Joshi

Military Bridging: MR Joshi

IGMDP: Lt Gen (Retd.) VJ Sundaram, et al.

Microwave Remote Sensing: Prof OPN Calla

Defence Against Chemical and Biological Agents: AK Sen

PROXIMITY FUZESTHEORY AND TECHNIQUES

VK ARORA Former Director

Defence Science CentreDelhi

DEFENCE RESEARCH AND DEVELOPMENT ORGANISATIONMINISTRY OF DEFENCE

NEW DELHI 110 105

2010

DRDO MONOGRAPHS/SPECIAL PUBLICATIONS SERIES

PROXIMITY FUZES: THEORY AND TECHNIQUES

VK ARORA

Series EditorsEditor-in-Chief Asso. Editor-in-Chief Sr. Editor EditorDr AL Moorthy Shashi Tyagi Vinod Kumari A Saravanan

Asst. Editor Editorial Asst Printing MarketingKavita Narwal Gunjan Bakshi SK Gupta Rajpal Singh

Cataloguing in PublicationArora, VK

Proximity fuzes: Theory and Techniques

DRDO monographs/special publications series.

1. Proximity fuze 2. Oscillators 3. Photodetectors 4. AntennasI. Title II. Series623:614.8.086.4

2010, Defence Research & Development Organisation, New Delhi 110 105.

ISBN: 978-81-86514-29-0

All rights reserved. Except as permitted under the Indian Copyright Act 1957, no partof this publication may be reproduced, distributed or transmitted, stored in a databaseor a retrieval system, in any form or by any means, electronic, mechanical,photocopying, recording, or otherwise, without the prior written permission of thePublisher.

The views expressed in the book are those of the author only. Theeditors or Publisherdo not assume responsibility for the statements/opinions expressed by the author.

Designed, produced and printed by Director, DESIDOC, Metcalfe House, Delhi110 054.

ContentsPreface xi

CHAPTER 1: HISTORY OF PROXIMITY FUZES1.1 Significance and Background of the Radio Proximity Fuze in World

War II 11.2 Development Work in the Department of Terrestrial Magnetism 21.3 Research and Development Work at Applied Physics Laboratory 41.4 Development Work at National Bureau of Standards 41.5 Tests 51.6 Production Scale-up 51.7 A Striking Combat Success 61.8 Electronic Countermeasures 61.9 Development of Proximity Fuzes 71.10 Post-War Developments 71.11 Brief History of Development of Proximity Fuzes in India (1966-1975) 8

CHAPTER 2: PROXIMITY FUZES: AN OVERVIEW2.1 Introduction 112.2 Basics of Proximity Fuzes 122.3 Radar Proximity Fuzes 142.4 Laser Proximity Fuzes 242.5 Pulsed Time of Flight Method 262.6 Beam Modulation Telemetry 262.7 Electronic Countermeasures 272.8 Electronic Counter Countermeasures 282.9 Antennas 302.10 Fuze Nose Cones 342.11 Oscillators 352.12 Power Sources/Reserve Battery of Proximity Fuzes 362.13 Safety and Arming 382.14 Shock and Acceleration 402.15 Fuze Classification 422.16 Evolution of Fuze Technology 472.17 Military Standards 48

vi

CHAPTER 3: FUZE RANGE EQUATIONS3.1 Introduction 493.2 Range Equations for Point Targets in Noise 503.3 Fuze Range Equation for CW and FMCW Radar 533.4 Range Equation for an Area Target 543.5 Fuze Equation for Self-Protection Jammers 563.6 Range Equation for Pulsed Laser Proximity Fuzes 58

CHAPTER 4: RESERVE BATTERY4.1 Introduction 634.2 Basic Power Sources 634.3 Applications 70

CHAPTER 5: OSCILLATORS5.1 Introduction 735.2 Specifications of Fuze Oscillators 735.3 Basics of Oscillators 755.4 Design Approach 765.5 Oscillator Limiting 835.6 Power Output of the Oscillators 835.7 Resonators 845.8 Active Devices 865.9 Voltage Controlled Oscillators 875.10 Phase Noise 89

CHAPTER 6: MIXERS6.1 Introduction 956.2 Basics of Mixers 956.3 Mixer Archtecture 966.4 Mixer Properties 996.5 Mixer Non-Linearity 996.6 Self-Mixing in Mixers 1036.7 Fuze Mixer Requirements 1036.8 Mixers for Fuze Receiver 1046.9 General Consideration in Optimisation of Mixer Performance 1126.10 FET Resistive Mixers 113

CHAPTER 7: ANTENNAS7.1 Introduction 1217.2 Basic Charactristics of Microstrip Antenna 1217.3 Feed Techniques 1227.4 Bandwidth Enhancement Techniques 124

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7.5 Characteristics of Patch Antennas 1307.6 Basic Characteristics 1317.7 Design Examples 135

CHAPTER 8: FMCW PROXIMITY FUZES8.1 Introduction 1398.2 Basic Structure of FMCW Fuzes 1408.3 Attributes of FMCW System 1408.4 Basic Aspects of FMCW System 1428.5 Range Resolution 1478.6 Range Accuracy 1488.7 Bandwidth Requirement 1518.8 Transmitter/Receiver Leakage 1518.9 ECM Systems 1558.10 ECCM Systems 157

CHAPTER 9: LASER SOURCES AND PHOTODETECTORS9.1 Introduction 1599.2 Diode Laser 1599.3 Characteristics of Laser Diodes 1619.4 Microchip Solid State Lasers 1639.5 Q-Switched Microchip Lasers 1649.6 Photodiodes for the Laser Range Finders 1659.7 Broad Features of Avalanche Photodiodes 1659.8 Structure of APD 1669.9 APD Parameters 1679.10 Choice between Pin Diode and APD for LRF 172

CHAPTER 10: NANOSECOND PULSE GENERATOR10.1 Introduction 17310.2 Requirements of Laser Diode Driver 17310.3 Avalanche Transister Pulse Generator 17410.4 MOSFETS 18010.5 Techniques for Achieving Fast Switching 186

CHAPTER 11: LASER PROXIMITY FUZES11.1 Introduction 18911.2 The Basic Principle and Structure of a Pulsed Laser Range Finder 19011.3 Transmitter 19111.4 Receiver 19211.5 Subsystems of Proximity Fuze Receivers 19411.6 System Considerations 203

viii

11.7 Solar Background Radiation 20611.8 Range Equation for Anti-aircraft Fuze 20911.9 Laser Radar Equation for the Clutter due to Fog and Clouds 212

Index 215

Preface

This monograph deals with theory and design aspects of RF-FMCW and Laserproximity fuzes. The book begins with a short history of development of proximityfuzes. The successful development of the fuze by the US during the Second WorldWar was an outstanding technical achievement. Though the Radar, a more complexsystem had been developed and used during the war, there were unique features ofthe proximity fuzes which made its development extremely difficult. The ability ofthe fuzes using vacuum tubes to withstand g shocks of ten of thousands when firedfrom the gun, was considered a formidable task. The development of the fuzes wasso significant that many experts consider this to be next only to the development ofatomic bomb. The history of development in India from 1966 to 1975 is also brieflycovered.

Lack of technical literature on the proximity fuzes was the key motivation towrite this monograph. The book will be useful at many levels: Professionals whospecialise in allied/areas such as a missiles, young engineers who are entering thefuze development programmes, military personnel who use these fuzes andelectrical/ electronics engineers for general reading.

The book is divided into three main subject areas. The first section considersthe basics of proximity fuzes. The second section deals with FMCW fuzes. The lastsection covers the latest Laser Proximity Fuzes.

Chapter 2 gives an overview of Proximity Fuzes. This chapter contains materialeveryone associated with proximity fuzes should know, in particular, the users andthe decision makers. This chapter covers the evolution of CW proximity fuzes fromfuzes developed during the second World War to the FMCW fuzes which becamethe workhorse fuze after the 1980s and continues to be most effective proximity-sensor till today. This chapter gives an overview of all of the subsystems of FMCWand the recent Laser proximity fuzes. The chapter also addresses the problem of g- several tens of thousands which the fuzes for high speed artillery and anti aircraftshells have to withstand.

Chapter 3 on the fuze range equations is a standard material available in Radartexts but is included for the basic orientation and for the sake of completeness.

Chapter 4 deals with reserve battery and power sources required by all types offuzes - FMCW, their variants and Laser proximity fuzes.

x

Chapters 5, 6 and 7 deal with of FMCW fuzes and their sub-systems.

Chapter 5 deals with voltage controlled oscillators. In particular the importanceof phase and amplitude noise of oscillator is addressed because low phase andamplitude noise are a fundamental requirement of fuzes. The active devices whichachieve the objective of low noise are considered and compared.

Chapter 6 on the mixers deals with highly linear mixers - Gilbert cell mixers andFET resistive mixers. High degree of linearity is a basic prerequisite of mixers sincethe modern fuzes operate in an intense environment of Electronic Counter Measure(ECM). ECM signals can penetrate into the receiver through the mixer non-linearity.

Chapter 7 deals with microstrip antennas for fuzes. These antennas can be usedwith a wide range of fuzes which requires a radiation pattern along the projectile axissuch as fuzes for bombs, mortars and high angle artillery shells. Fuze an