Spin echo matched filter ECM detector

DETAILED DESCRIPTION Having described what is at present considered to be the preferred embodiment of the subject invention, we claim: 1.
An intermodulation product frequency detector of a received RF signal comprising in combination: a first and second RF source respectively generating transmitted pulses of a first and second instantaneous carrier frequency simultaneously and having a predetermined frequency difference therebetween; means coupled to said first and second RF source for sampling a portion of said pulses transmitted and providing a composite RF pulse therefrom having intermodulation product frequencies substantially the same as those to be detected; a spin echo system operable as a matched filter coupled to said above recited means and having a microwave cavity with a paramagnetic sample located therein tuned to a paramagnetic resonance center frequency in the region of said intermodulation product frequencies, said spin echo system receiving as a first input signal said composite RF pulse; another RF source generating a RF pulse having a bandwidth substantially covering the frequency spectrum of said intermodulation product frequencies after a predetermined time delay and including means coupling said RF pulse as a second input to said spin echo system for setting the spin system of the paramagnetic sample to said composite RF pulse; and relatively highly linear circuit means coupling said received RF signal to said spin echo system, said RF signal causing a spin echo signal to be produced after said predetermined time delay in the event that intermodulation product frequencies to be detected are present.
2.
The apparatus as defined by claim 1 whereby said first and second RF source generate the pulses of frequencies f.
sub.
1 and f.
sub.
2, respectively, and having a frequency difference .
DELTA.
f, where .
DELTA.
f << f.
sub.
1 and f.
sub.
2.
3.
The apparatus as defined by claim 2 wherein said first and said second RF source comprise radar RF pulse signal generators and additionally including linear power combiner means coupled to said generators for providing a bi-frequency composite radar pulse, and antenna means coupled to said power combiner means for radiating said radar pulse