DETAILED DESCRIPTION This application is a continuation-in-part of Patent Application Ser.
No.
797,197, now abandoned, a continuation of which is pending as Application Ser.
No.
926,265, now abandoned.
That application covers means for enhancing target echo relative to clutter that compare signals resulting from the use of two or more polarizations and use various signal processing means.
This disclosure also includes the use of different polarizations, but it also includes comparisons of echoes caused by differences in transmit carrier frequency, pulse length, antenna beamwidth, and antenna pointing direction.
As is discussed in the section Use of Other Discriminants, there are useful polarization combinations possible when using two frequencies that were not previously disclosed.
In addition, this continuation-in-part discusses the use of frequency agility with the various embodiments of Patent Application Ser.
No.
797,197, now abandoned and with the embodiments disclosed herein.
The various embodiments of the present invention distinguish targets from clutter by using various discriminants.
A discriminant is a radar parameter for which two "values", called operatives, of the parameter will give different received video signals.
For example, received polarization and transmit carrier frequency are both discriminants.
Operatives include specific polarizations, transmit carrier frequencies, transmit pulse lengths, antenna pointing directions, and antenna beamwidths.
Some of the novel features of the present invention include: A.
a comparator means for comparing a first received video signal with a second received video signal and for providing an output only when both video signals are of substantial magnitude and when the relative magnitude of the first received video signal to the magnitude of the second received video signal is a ratio within a predetermined range of ratios.
It is noted that the prior art comparator of Nirasawa and Ota provides a radar signal output if one of the two received video signals is of substantial magnitude and the other received video signal is zero because gates in parallel are used
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