nn 



lUiLL SYSTEM TECIIMCM. J01R.\AL 



frequencies it is customary to employ vacuum tube radio-frequency ampli- 

 t'lers preceding the converter element, and in these cases, similar vacuum 

 tubes are employed as the nonlinear element. The output frequency of the 

 converter commonly ranges from 30 mc to 100 mc. Because of the com- 

 parative difficulties experienced in the transmission of microwave energy 

 over transmission lines or waveguides as contrasted with the problem at the 

 lower intermediate frequency region, it is standard practice to locate the 

 converter in close proximity to the antenna and transmitter portions of the 

 radar system. 



The intermediate frequency (IF) amplifier and associated second detector 

 unit following the converter in Fig. 4 is required to obtain the necessary 



Fig. 4. — Schematic diagram of principal C()mi)niu"iits ol" a military radar recei\-ei 



amplilication to the wanted signal, to sui)ply discrimination against un- 

 wanted signals, and to finally convert the desired signal to a video form for 

 presentation purposes. The usual gain required of a modern radar inter- 

 mediate amplifier is of the order of 100 db. The band width of the ll-' 

 ami)lirier is usually chosen between 1 mc and 10 mc depending on the specific 

 radar system requirements. The techniques of construction developed for 

 high gain radar IF amplifiers have resulted in compact component designs 

 which are complete units in themselves, caj)al)le of being integrated into 

 various radar systems. 



The video amplifier characteristics are dependent to a large degree on 

 llic parti( iilar type of display system associated with it. Its primary func- 



