Introduction to Radar Basics - MATLAB Simulations for Radar Systems Design - page 17

Symbol Description Units Status

b bandwidth Hz input

nf noise figure dB input

loss radar losses dB input

range target range (can be either a sin-

gle value or a vector)

meters input

snr SNR (single value or a vector,

depending on the input range)

dB output

The function Ðradar_eq.mÑ is designed such that it can accept a single value
for the input ÐrangeÑ , or a vector containing many range values. Figure 1.12
shows some typical plots generated using MATLAB program Ðfig1_12.mÑ
which is listed in Listing 1.2 in Section 1.10. This program uses the function
Ðradar_eq.mÑ, with the following default inputs: Peak power

,

P t = 1.5 MW

operating frequency , antenna gain , effective tempera- f 0 = 5.6 GHz G = 45 dB

ture , radar losses , noise figure . The radar band- T e = 290 K L = 6 dB F = 3 dB

width is . The radar minimum and maximum detection range are B = 5 MHz

0.1 m 2

and . Assume target cross section .

R min = 25 Km R max = 165 Km σ =

Note that one can easily modify the MATLAB function Ðradar_eq.mÑ so
that it solves Eq. (1.54) for the maximum detection range as a function of the
minimum required SNR for a given set of radar parameters. Alternatively, the
radar equation can be modified to compute the pulsewidth required to achieve
a certain SNR for a given detection range. In this case the radar equation can be
written as

4( 3 kT e FLR 4 SNR
P t G 2 λ 2 σ

τ = -------------------------------------------------

(1.57)

Figure 1.13 shows an implementation of Eq. (1.57) for three different detection
range values, using the radar parameters used in MATLAB program
Ðfig1_13.mÑ . It is given in Listing 1.3 in Section 1.10.

When developing radar simulations, Eq. (1.57) can be very useful in the fol-
lowing sense. Radar systems often utilize a finite number of pulsewidths
(waveforms) to accomplish all designated modes of operations. Some of these
waveforms are used for search and detection, others may be used for tracking,
while a limited number of wideband waveforms may be used for discrimina-
tion purposes. During the search mode of operation, for example, detection of a
certain target with a specific RCS value is established based on a pre-deter-
mined probability of detection . The probability of detection, , is used to
calculate the required detection SNR (this will be addressed in Chapter 2).

P D P D