THE RADAR RECEIVER 



717 



performance. The performance of two types of vacuum tubes are included 

 for comjmrison purposes. The development details of the silicon crystal 

 unit have been discussed elsewhere.*^ This development, together with the 

 corresponding magnetron and reflex oscillator studies, assumes a status of 

 major importance in the progress of the development of military radar equip- 

 ment during World War II, allowing the designers to extend the frequency 

 of operation upward with increased system performance resulting. 



It is sufficient to limit our attention to the frequency region 3000 mc and 

 above in the consideration of the silicon crystal converter. It is apparent 

 that the absence of suitable vacuum tube radio-frequency amplifiers in this 

 region imposes a strict requirement on the efficiency of conversion of this 

 component. 



Fig. 12.— 3000-mc Crystal Converter of an early design. 



Historically, one of the fiist of the microwave converters of the silicon 

 crystal type, operating at 3000 mc and which was employed in military radar 

 equipment, is shown in Fig. 12 together with an illustration of the mechanical 

 arrangement^ in Fig. 13. In this early model the silicon crystal element was 

 mounted in a cartridge type unit, a method which proved quite satisfactory 

 and was followed for the remainder of the war years. The input tuning 

 circuit of the converter here illustrated consists of a coaxial transmission 

 line element having a length of approximately three-quarters of a wave- 

 length and adjustable to enable fine control of tuning. The nonlinear ele- 



s'' Development of Silicon Crystal Rectifiers for Microwave Radar Receivers," 

 J. H. bcatf and R. S. Ohl, Bell System Technical Journal, Vol. XXVI, January 1947 



'"'Microwave Converters," C. F. Edwards, To be published in a forthcoming issue of 

 rroceedtngs I.R.E. 



