7-19] 



ANGLE DEMODULATION 



389 



receiver. If the AGC demodulator is connected to the range error detector, 

 and the angle demodulator connected directly to the AGC demodulator 

 output, both range and angular error characteristics will be determined by 

 the AGC regulation. 



It is desirable, however, that the video signals applied to these demodu- 

 lators be as large as possible to minimize the bias errors resulting from 

 contact potential in the demodulators. Frequently separate filtering of the 

 range and angle video signals may be performed. A single AGC loop 

 operating from the angle channel controls the receiver gain. To obtain a 

 stable range-error detector characteristic, the video amplification between 

 the input to the range detector and the AGC demodulator must then be 

 stabilized by feedback. A typical arrangement is shown in Fig. 7-16. 



Local 

 Osc. 



AGC 



Amplifier 



Filter 



IF 

 Amplifier 



AGC Delay 

 Voltage 



Envelope 

 Detector 



Range Gate 



Pulse 

 Lengthener 



Cathode 

 Follower 



Video 

 Amplifier 



Range 



Error 



Detector 



Video 

 Amplifier 



Range 

 "Gate 



Noise Free Signal 

 at Lobing Frequency- 



Angular 



Error 



Demodulator 



A z. Error 



Angular 



Error 



Demodulator 



El. Error 



Noise Free Signal 

 •at Lobing Frequency 



Fig. 7-16 Connection of a Receiver Employed with Sequentially Lobed Antenna 

 to Related Circuits. 



7-19 ANGLE DEMODULATION 



The antenna tracking error signal can be considered to be proportional 

 to the magnitude of the fractional modulation of the signal resulting from 

 division of the difference signal by the sum signal. In monopulse radar sets 

 the sum and difference signals are separated at the receiver input, whereas 

 in a conical scanning radar the composite signal is passed through the 

 receiver. To obtain a tracking error signal from a monopulse radar, the 

 difference signal is heterodyned with the sum signal, which is effectively a 

 noisy carrier signal. In some cases carrier reconditioning may be performed 



