364 



THE RADAR RECEIVER 



pole pairs in the 2 plane, so that a single pole cluster is obtained in the 2 

 plane. 



Placing the poles on a semicircle in the 2 plane produces a constant 

 potential in the s plane. When the poles in the s plane are placed at the 

 position given by transforming the equally spaced poles of the 2 plane to 

 the s plane, a maximally flat transfer characteristic is obtained. 



The desired transfer function for the amplifier could be realized by a 

 single four-terminal network followed by an extremely wide-band amplifier. 

 (The amplifier, of course, would have a particular pole-zero structure, 

 but the contribution to the selectivity in the frequency band of interest 

 is negligible.) Practically, however, the four-terminal network is limited 

 to a four-pole structure, and most commonly to a one or two-pole structure 

 because of the limitation of realizable unloaded ^'s for the network in- 

 ductors. The most commonly used network of the IF amplifier is shown in 

 Fig. 7-5. When k = I and Li = L2 the network reduces to a one-pole 

 structure as shown. 



C2 



= H- 



S'*+aS3+/3S2+ 7S+6 

 S 



(s-s,)(s-si)(s-s^)(s-s;) 



Where H 





7 = 



Qj Q2 



2 



COj 002 



Q2(l-K^j'^Qi(l-K2j 



Qi Q2 



4=^ 



w,R.C, 





■'2 '2'^2'-2 



When K=l and Li= L2the Single ■ Tuned Circuit With Bifilar Coil is Obtained. In This Case 

 Usually All of the Damping is Provided By R 2 -. ^ 



Then: 



H, 



= H, 



5^+ 7 S + X 

 S 



7 



X 



Fig. 7-5 Commonly Used IF Interstage Coupling Network. 



