Novel method of decreasing influence of phase noise on FMCW radar

In the last decade, the frequency-modulated continues wave (FMCW) radar has been widely used both in military and civil (automotive) applications. Using low peak power it is possible to build reliable, low cost radar, which can measure target position, radial velocity and also the target radial acceleration. The radar sensitivity, accuracy and sub-clutter visibility (SCV) are limited by the transmitted power and the presence of phase noise in a transmitted signal. The influence of transmitter phase noise on FMCW radar performance has been investigated. The low-frequency 1/f type phase noise of FMCW radar free running oscillator degrades significantly the target velocity spectrum estimated by the 2-dimensional FFT of the video signal and thus limits the radar ability to detect moving targets against heavy ground clutter. To improve the radar performance the new method of low frequency phase noise compensation, based on the polynomial phase modeling concept has been worked out. On the basis of the received signal, assuming that ground clutter echoes are present in the signal, the low frequency phase noise polynomial model parameters are estimated. The estimated parameters are further used for digital correction of the video signal phase, which leads to a sharpened echo velocity spectrum and increased SCV and accuracy of velocity estimation. The presented concept can also be used for attenuation of synchronous interference in FMCW radar.