Page 173 - Fundamentals of Radar Signal Processing

1.3 and assume operation near sea level to estimate atmospheric losses.

What is the ratio in decibels of the received power to the transmitted
power?

2. By how many dB will the received power be reduced (not the absolute
power received, but the reduction in power) in problem 1 if the weather
changes from clear to a heavy rain of 25 mm/h? Estimate the needed
parameters from Fig. 1.4.

3. Suppose the parameters of a radar are such that the power of the echo from
a particular target is just detectable at a range of 50 miles. If the target RCS
is reduced by 10 dB, what will be the new detection range? By how many

dB must the RCS be reduced to reduce the detection range to 5 miles?
4. According to the Smithsonian Air and Space Museum, the RCS of a B-52

2
–6
2
bomber is about 1000 m , while that of a B-2 stealth bomber is 10 m . If a
given radar system could detect the B-52 at a range of 100 km, at what
range could the same radar system detect the B-2 stealth bomber? Assume
that atmospheric losses are negligible. If the B-2 flies at 550 mph, how
much warning time would the radar give?

5. The example around Eq. (2.12) in the text calculated a received power P =
r
–9
3.07 × 10 W at a range of 10 km. If the radar noise figure is 10 dB and the
receiver noise equivalent bandwidth is 10 MHz, what is the expected
signal-to-noise ratio in dB for the same target and range? Assume the
receiver is at the standard temperature T = 290 K.
0
6. Consider a “millimeter wave (MMW) seeker,” which is a small radar
typically used on a small missile. The RF frequency is 95 GHz and the 3
dB beamwidth is 1º in both azimuth and elevation. The range resolution ΔR
is 5 m. The grazing angle of the antenna beam with respect to the ground is
20º, and the slant range to the ground, i.e., along the line of sight of the

0
antenna, is 5 km. The terrain has a reflectivity of σ = –10 dB. Is the range
resolution of this system beam limited or pulse limited? What is the
approximate area of the resolution cell on the ground? What is the total
RCS σ of the resolution cell?

7. A radar is attempting to detect a point target in the presence of ground
clutter. The parameters of the radar and its environment are such that the
SNR at a range of R = 10 km is 30 dB, while the clutter-to-noise ratio
(CNR) at the same range is 20 dB. The detection performance at this range

is “clutter limited” because the clutter is the dominant interference.
Assuming pulse-limited clutter interference, at what range will the SNR
and CNR be equal? Equivalently, at what range will the signal-to-clutter
ratio (SCR) equal 1 (0 dB)?

8. Consider the WSR-88D “NEXRAD” weather radar used by the U.S.