An investigation into the principles of signal detection using multiple simultaneous waveforms

The Doppler resolution of a radar is determined by the total coherent integration time, which in turn is constrained by the target decorrelation time. When target or platform speed is very high, as is the case in spaceborne applications, the decorrelation time may be very short, and Doppler resolution poor. In addition, the shape of the radar´s response in the range/Doppler plane is determined by the ambiguity function of the waveform transmitted. Linear FM has been much studied and gives a tapered ridge across the ambiguity function, however this ridge makes detection of multiple targets with differing Doppler and range uncertain. To improve upon this, zigzag/non-linear FM, frequency hops or phase codes may be used. However the Doppler resolution is still limited to 1/pulse length. This paper aims to investigate the possibility of improving the nominal Doppler resolution, i.e. reducing the width of the main lobe on the Doppler axis, by taking the product, instead of the sum, of the outputs of correlator banks when the inputs to each are separately (but coherently) correlated FM sweeps