Patent ID: 6198427
Filing Date: 2001-03-06
Classification: G01S

Abstract:
An apparatus comprising:a radar transmitter for transmitting radar waves said radar waves having the frequency of a local oscillator;a radar receiver for receiving reflected radar waves and generating RF signals therefrom, mixing said RF signals with a local oscillator signal to generate a first channel doppler signal and mixing said RF signals with the same local oscillator signal that was used to generate said first channel doppler signal but shifting either the local oscillator signal or said RF signals by an integer multiple of 90 degrees relative to the local oscillator signal used to generate said first channel doppler signal before mixing with said RF signals to generate a second channel doppler signal;means for converting said first and second channel doppler signals into digital samples;a display;a digital signal processor coupled to said display and programmed to receive a plurality of digital samples from each of said first and second channel doppler signals and perform a complex fast fourier transform using one of said first channel digital samples as the real magnitude of each input point and the corresponding paired sample point from the second channel digital samples as the imaginary magnitude of the input point so as to generate an approaching target spectrum of Fourier components and a receding target spectrum of Fourier components, and searching a predetermined one of said approaching or receding or both approaching and receding target spectra for a strongest target and calculating the speed thereof and displaying said speed.