Page 283 - Fundamentals of Radar Signal Processing

Stretch processing and especially Eq. (4.110) will be revisited and

extended in Chap. 8, where the technique is central to the polar format algorithm
for spotlight synthetic aperture radar imaging. Additional details of stretch
processing are given in Keel and Baden (2012).

4.7 Range Sidelobe Control for FM Waveforms
It was seen in the previous section that the output of the LFM matched filter
exhibits sidelobes in range (equivalently, delay). These are a consequence of
the approximately rectangular LFM matched filter output spectrum, which

produces a sinc-like range response. The first range sidelobe is approximately
13 dB below the output peak for moderate-to-high BT products, and about –15
dB for small BT products. Sidelobes this large are unacceptable in many
systems that will encounter multiple targets in range due to target masking. This
phenomenon is shown in Fig. 4.33a, where the smaller target is barely visible
above the sidelobes of the stronger target despite being separated by

approximately sixteen times the Rayleigh resolution. The smaller target could
not be reliably detected in this scenario. If the sidelobes could be reduced, this
masking effect could be greatly reduced as shown in part b of the figure.