THE RADAR RECEIVER 



731 



2.2 The Radar Inlermediate Frequency Amplifier 



The intermediate frequency (IF) amplifier component of the radar re- 

 ceiver has as its function the selection and amplification of the received 

 signal following its conversion to the intermediate frequency. The further 

 conversion of the IF signal to a video form suitable for use in the display 

 device is usually included as an integral part of the IF amplifier and will, 

 therefore, be considered here as an additional function of this component. 



2.21 IF Amplifier Requirements — Band Width 



The frequency-selectivity characteristic of the radar receiver is deter- 

 mined effectively by the IF amplifier, since the pieceding converter and 

 other microwave components offer little or no selectivity. The receiver 



FROM 

 fv<AGNETRON 



TUNING 

 PLUG 



TO l-F 

 AMPLIFIER 



Fig. 24. — Schematic diagram of 10,000-mc AN/APS-4 converter unit. 



band width required to adequately transmit the wanted signal, while restrict- 

 ing the noise contributions, is an extremely important factor in the radar 

 system design and represents, therefore, a basic consideration in the design 

 of the IF amplifier. 



The receiver band width required to adequately transmit the basic re- 

 ceived pulse information can be determined by a consideration of the fre- 

 quency-energy characteristics of a radar pulse. The microwave pulse is 

 created by the sudden application of a high-energy pulse to the magnetron 

 microwave generator. It has been found sufficient to treat this output 

 envelope as a simple rectangular pulse in band width computations. Fig- 

 ure 25 indicates the amplitude, time, and frequency relationships which 

 exist for an idealized rectangular radar pulse envelope. It may be observed 



