MICROWAVE REPEATER RESEARCH 



221 



2 IF = nAf + 



A/ 



or 



IF = Y i2n + 1) 



where A/ is the frequency spacing and n is any integer greater than zero. 



In general, better noise figures and circuit stabihty are obtained with 



low intermediate frequencies, while high intermediate frequencies lead to 



f,,f3,f5 :: RECEIVED SIGNAL 



FREQUENCIES 



^2.^41^6--* = TRANSMITTED SIGNAL 



FREQUENCIES 

 0t.03i05-- = RECEIVING BEATING 



OSCILLATORS 

 02,04,06"- = TRANSMITTING BEATING 

 OSCILLATORS 



Il.l3tl5 = RECEIVING IMAGE 



FREQUENCIES 



biUJs = TRANSMITTING IMAGE 



FREQUENCIES 

 IF = INTERMEDIATE FREQUENCY 



Af - SPACING OF SIGNAL 

 FREQUENCIES 



RECEIVING 



Fig. V-2. — Frequency spectrum of a multichannel microwave repeater circuit. 



more symmetrical amplitude and phase characteristics. The research on 

 the intermediate frequency components described below was conducted in 

 the 60 to 70-megacycle range. 



Frequency Stability — If all receiving and transmitting beating oscillators 

 are independently controlled in a multichannel relay circuit of this kind, 

 there is a possibility that small variations will add to produce large variations 

 at the distant end of the system. This difficulty can be overcome by the 

 frequency control system shown schematically in Fig. V-3. The transmit- 

 ting and receiving beating frequencies are both derived from an oscillator 



