Reactance transformation to improve range resolution in pulse-compression detection systems

The presence of side-lobes in the impulse response retrieved after pulse compression is a limitation in the range resolution performance of detection systems; in order to limit this effect the signal is often shaped by means of windows. In this paper we analyse the causes that produce side-lobes and propose a technique for their reduction, based on time-domain constraints which, in the case of base-band signals, turn in the definition of a particular low-pass filter. In real world applications, the pulse compression is performed by using bandpass signals as excitation, and among these the chirp signals are largely adopted: the useful bandwidth is thus shifted from the base-band. We consequently modify the filtering procedure defined for processing base-band signals, and propose a reactance transformation of the frequency axis to define the filter for the reduction of side-lobes in the case of band-pass chirp excitations. The paper shows that the application of the proposed filtering technique to chirp signals is particularly simple. The effectiveness of the technique is validated on experimental test data.