Radar apparatus with directional discrimination and increased radar sensitivity

Claim 1

A radar apparatus for use with a monostatic radar to determine target motion toward or away from the radar by determining the direction of doppler frequency shift imposed upon the reflected target pulse from a target of interest comprising first mixer means receiving an intermediate frequency output signal representative of said reflected target pulse, the intermediate frequency carrier frequency being fc, first local oscillator means generating a first signal with a frequency of fc, said first mixer heterodyning said intermediate frequency output signal and said first signal, first filter means to remove from the output of said first mixer means image components of frequencies near 2fc, second local oscillator means generating a second signal of a frequency fl, second mixing means heterodyning said second signal and the output signal of said first filter means, first means to phase shift said first signal a predetermined magnitude to provide a first phase shifted signal, third mixing means heterodyning said intermediate frequency output signal and said first phase shifted sigNal, second means to phase shift said second signal a predetermined magnitude to provide a second phase shifted signal, second filter means for the output signal from said third mixer means, fourth mixer means heterodyning the output signal from said second filter means and said second phase shifted signal, first summing means to add the output signals from said second and fourth mixing means to provide a third signal representative of a negative doppler shift, and second summing means to subtract the output signals from said second and fourth mixer means to provide a fourth signal representative of a positive doppler shift.