G. S. AXELBY • D. J. HEALEY III 

 D. D. HOWARD • R. S. RAVEN • C. F. WHITE 



CHAPTER 8 



REGULATORY CIRCUITS* 



8-1 THE NEED FOR REGULATORY CIRCUITS 



To determine the bearing, range, and velocity of a target with high 

 accuracy, three basic conditions must be fulfilled by the radar receiver and 

 its associated data processing system: (1) the desired target intelligence 

 components of the received signal must be faithfully reproduced at the 

 output of the receiver; (2) undesired input signals which tend to reduce the 

 S /N ratio of the desired target intelligence must be suppressed; (3) sources 

 of noise internal to the radar must be minimized. 



The desired target intelligence appears as amplitude, phase, and fre- 

 quency modulations of the received signals. The target information is 

 extracted by taking a cross product between the received signal and a 

 reference signal and filtering the resultant signal to remove extraneous cross 

 products (see Paragraph 1-5). In a practical radar receiver, there are 

 several potentially troublesome sources of degradation in these processes. 



An optimum demodulation process depends upon the accuracy with 

 which the receiver can be tuned to the incoming signal. Various environ- 

 mental and electrical factors will cause receiver tuning to vary or drift as a 

 function of time. Receiver tuning control or automatic frequency control 

 (AFC) is therefore required to reduce the effects of such variations. 



Receiver components must be operated under such conditions that the 

 linear dynamic range of the receiver is very limited. Unless some form of 

 automatic gain control (AGC) is utilized, signal distortion will take place in 

 the receiver. For example, saturation effects will tend to erase amplitude 

 modulation on the received signal; this in turn will cause poor tracking or 

 loss-of-track in a conically scanning system. 



A large number of vacuum tubes must be employed in the receiver to 

 amplify the noise level to the desired output level. Variations in the tube 

 characteristics occur when the voltages supplied to the tubes vary. The 

 desired output signals are then modulated with the undesired fluctuations 

 of the power supply voltages. Thus electronic power regulation is required. 



♦Paragraphs 8-1 and 8-3 through 8-13, and 8-21 are by D. J. Healey III. Paragraph 8-2 is 

 by D. D. Howard and C. F. White. Paragraphs 8-14 through 8-20 are by C. F. White and 

 R. S. Raven. Paragraphs 8-22 through 8-34 are by G. S. Axelby. 



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