The Bell System Technical Journal 



Vol. XXVI Ja72uary, 1947 No. i 



Development of Silicon Crystal Rectifiers for 

 Microwave Radar Receivers 



By J. H. SCAFF and R. S. OHL 



Introduction 



TO THOSE not familiar with the design of microwave radars the exten- 

 sive war use of recently developed crystal rectifiers^ in radar receiver 

 frequency converters may be surprising. In the renaissance of this once 

 familiar component of early radio receiving sets there have been develop- 

 ments in materials, processes, and structural design leading to vastly 

 improved converters through greater sensitivity, stability, and ruggedness 

 of the rectifier unit. As a result of these developments a series of crystal 

 rectifiers was engineered for production in large quantities to the exacting 

 electrical specifications demanded by advanced microwave techniques and 

 to the mechanical requirements demanded of combat equipment. 



The work on crystal rectifiers at Bell Telephone Laboratories during 

 the war was a part of an extensive cooperative research and development 

 program on microwave weapons. The Office of Scientific Research and 

 Development, through the Radiation Laboratory at the Massachusetts 

 Institute of Technology, served as the coordinating agency for work con- 

 ducted at various university, government, and industrial laboratories in 

 this country and as a liaison agency with British and other Allied organiza- 

 tions. However, prior to the inception of this cooperative program, basic 

 studies on the use of crystal rectifiers had been conducted in Bell Telephone 

 Laboratories. The series of crystal rectifiers now available may thus be 

 considered to be the outgrowth of work conducted in three distinct periods. 

 First, in the interval from 1934 to the end of 1940, devices incorporating 

 point contact rectifiers came into general use in the researches in ultra- 

 high-frequency and microwave communications techniques then under 

 way at the Holmdel Radio Laboratories of Bell Telephone Laboratories. 



' A crystal rectifier is an assymmetrical, non-linear circuit element in which the seat of 

 rectification is immediately underneath a point contact applied to the surface of a semi- 

 conductor. This element is frequently called "point contact rectifier" and "crystal de 

 tector" also. In this paper these terms are considered to be S3'nonymous. 



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