ABSTRACT
The term “radar” stands for radio detection and ranging. As the name suggests, the primary function of most of the radars is to find the range of certain target objects. When two or more such targets are very close, it becomes difficult to identify them as individual targets. Radar that overcomes such a difficulty is said to have good range resolution capability. In radar applications, it is desirable to have high range resolution (HRR) [1], while maintaining adequate average transmitted power (ATP). This is accomplished by a technique called pulse compression, as a part of which, either the frequency modulation (FM) or the phase modulation (PM), is employed. FM can in turn have variants that use one of the following waveforms: linear FM (LFM) waveform, frequency-modulated continuous waveform, and stepped frequency waveform (SFW). One undesirable effect of pulse compression is that side lobes appear at the output. This problem can be solved by making use of window functions. It is known from the earlier chapters that a proper choice of a window can considerably reduce the side-lobe effect. LFM pulse compression can be implemented either by correlation processing (mainly used for narrow-band and some medium-band applications) or by stretch processing (used for wideband applications). The use of SFW is known to produce HRR target profiles. We will now proceed to see how exactly windowing is used in (i) obtaining HRR target profiles and (ii) stretch processing. Furthermore, we shall illustrate the effect of different windows on pulse compression using computer simulations for various scenarios.
