Page 63 - Fundamentals of Radar Signal Processing

that signal processing techniques can be used to improve resolution far beyond

the conventional Rθ limit and to make it independent of range as well.
The radar resolution cell volume V is approximately the product of the
total solid angle subtended by the 3-dB antenna mainlobe, converted to units of
area, and the range resolution. For an antenna having an elliptical beam with
azimuth and elevation beamwidths θ and ϕ , this is
3
3

(1.27)

The approximation in the second line of Eq. (1.27) is 27 percent larger than the

expression in the first line, but is widely used. Note that resolution cell volume
increases with the square of range because of the two-dimensional spreading of
the beam at longer ranges.

1.4.3 Data Integration and Phase History Modeling
A fundamental operation in radar signal processing is integration of samples to
improve the SIR. Both coherent integration and noncoherent integration are of

interest. The former refers to integration of complex (i.e., magnitude and phase)
data, while the latter refers to integration based only on the magnitude (or
possibly the squared or log magnitude) of the data.
Suppose a pulse is transmitted, reflects off a target, and at the appropriate
time the receiver output signal is measured, consisting of a complex echo
jϕ
amplitude Ae corrupted by additive noise w. The noise is assumed to be a
sample of a random process with power . The single-pulse SNR is

(1.28)

Now suppose the measurement is repeated N – 1 more times. One expects
to measure the same deterministic echo response, but with an independent noise
sample each time. Form a single measurement z by integrating (summing) the

individual measurements; this sum of complex samples, retaining the phase
information, is a coherent integration: