Page 370 - Fundamentals of Radar Signal Processing

2πF T. Equation (3.20) gave the M-pulse discrete-time Fourier transform of this
D
signal; converting to analog frequency gives

(5.74)

7
Y(F) is an asinc function with its peak at F = F as expected and a peak
D
magnitude of MA. Its magnitude is illustrated in Fig. 5.17a for the case where F D
= PRF/4, M = 20 samples, and A = 1. So long as M ≥ 4, the Rayleigh (peak-to-
null) mainlobe bandwidth is 1/MT Hz; this is also the 4-dB bandwidth. The
width of the mainlobe at the –3 dB points is 0.89/MT Hz. The first sidelobe is
13.2 dB below the response peak. These mainlobe width measures determine
the Doppler resolution of the radar system. They are all inversely proportional

to MT, which is the total elapsed time of the set of pulses used to make the
spectral measurement. Thus, Doppler resolution is determined by the
observation time of the measurement as first discussed in Chap. 1. Longer
observation allows finer Doppler resolution.