6-4] 



CORRELATION AND STORAGE RADAR TECHNIQUES 



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307 



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INPUT SIGNAL-TO-NOISE RATIO (db) 

 Fig. 6-9 Comparison of Autocorrelation and Cross Correlation. 



with those of the signal component in/i(/) and permitting a variable delay r 

 to match the echo delay, thereby indicating range. This would be a specific 

 application to the radar problem of echo ranging or the measurement of 

 delay. A simplified block diagram of a cross-correlation detector is shown 

 in Fig. 6-10. The output ^i2(t,T) could be used in the same manner as the 

 output from the second detector of a conventional radar. 



Echo ranging as a major application of the cross-correlation principle to 

 radar has been studied comprehensively by Woodward^ in the light of 

 information theory. Woodward shows that in order to extract the most 

 information about the exact target range from a received radar echo in 

 additive Gaussian noise, the optimum receiver is one which forms the 



^P. M. Woodward, Probability and Information Theory, with Applications to Radar, McGraw- 

 Hill Book Co., Inc., New York, 1953. 



