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World War II Electronics and the Early History of Computers

IP.com Disclosure Number: IPCOM000129955D
Original Publication Date: 1996-Sep-30
Included in the Prior Art Database: 2005-Oct-07
Document File: 9 page(s) / 35K

Publishing Venue

Software Patent Institute

Related People

John M. Bennett: AUTHOR [+2]

Abstract

This text is based on a talk given in September 1994 on the occasion of a golden anniversary reunion held at the University of Sydney School of Physics to commemorate the six radiophysics courses conducted by the staff of the school for the Australian armed services in the years 1941-1944. The courses were designed as initial training for radar (then called radiolocation) technical officers. I will discuss interactions between World War II radar and other wartime developments (such as code-cracking devices) and the computer field. I am fortunate in that after almost four wartime years in RAAF ground radar, I have been able to spend most of my subsequent career in the computer field. Most of the first 15 years of that time was spent in the United Kingdom and Australia designing, building, or using computers with memory systems developed from techniques originally devised in a radar context. Also, I worked with a number of engineers and mathematicians who had come to computers from radar development and code-cracking centers.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

Copyright ©; 1996 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Used with permission.

World War II Electronics and the Early History of Computers

John M. Bennett

John M. Bennett

Introduction

This text is based on a talk given in September 1994 on the occasion of a golden anniversary reunion held at the University of Sydney School of Physics to commemorate the six radiophysics courses conducted by the staff of the school for the Australian armed services in the years 1941-1944. The courses were designed as initial training for radar (then called radiolocation) technical officers.

I will discuss interactions between World War II radar and other wartime developments (such as code-cracking devices) and the computer field. I am fortunate in that after almost four wartime years in RAAF ground radar, I have been able to spend most of my subsequent career in the computer field. Most of the first 15 years of that time was spent in the United Kingdom and Australia designing, building, or using computers with memory systems developed from techniques originally devised in a radar context. Also, I worked with a number of engineers and mathematicians who had come to computers from radar development and code-cracking centers.

Radar

Toward the end of World War II, major radar developments related to MTIs -- moving target indicators [8]. The movement of targets can be detected by storing reflections from successive pulses and subtracting them. Noncancellation indicates movement, and separation between two noncanceling signals is a measure of the movement of a target between successive transmitter pulses. What is needed is a means of storing echoes from successive pulses and subtracting them. Storage techniques so devised were later used (in modified form) to store digital information for computation, two-level (binary) representation being the most convenient.

In its simplest form, a radar transmitter outputs power only during the pulse modulation period. The Doppler effect, which changes the frequency of electromagnetic radiation reflected from a moving object, can be exploited by comparing the frequency of the reflected pulse with that of the transmitted pulse. To do this, some technique is needed for retaining information about the transmitted pulse carrier phase -- a process that is not possible if the transmitter oscillator operates only for the duration of the modulating pulse, as is the case, say, with a magnetron oscillator. However, if the transmitter pulse carrier is generated by amplifying the amplified output of a klystron during the pulse period, the Doppler effect will result in a frequency shift in the moving target echo that can be measured by the frequency differences between reflected echo and the transmitter pulse to give the target velocity with respect to the transmitter. Mixing with an intermediate frequency -- a long-establi...