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Wire and Wireless Communication Applications Chap. 8
the Intelsat IV satellite, assume that a (G AR T syst ) of 40 dB is needed. Using a 30-m antenna, give
the required antenna efficiency if the system noise temperature is 85 K. How does the required
antenna efficiency change if a 25-m antenna is used?
8–33 Evaluate the performance of a TVRO system. Assume that the TVRO terminal is located in
Miami, Florida (26.8° N latitude, 80.2° W longitude). A 10-ft-diameter parabolic receiving
antenna is used and is pointed toward the satellite with parameters as described in Table 8–5,
Fig. 8–25, and Fig. 8–27.
(a) Find the TVRO antenna look angles to the satellite and find the slant range.
(b) Find the overall receiver system temperature.
(c) Find the (CN) dB into the receiver detector.
(d) Find the (SN) dB out of the receiver.
8–34 Repeat Prob. 8–33 for the case when the TVRO terminal is located at Anchorage, Alaska
(61.2° N latitude, 149.8° W longitude), and a 8-m-diameter parabolic antenna is used.
8–35 A TVRO receive system consists of an 8-ft-diameter parabolic antenna that feeds a 50-dB, 25K
LNA. The sky noise temperature (with feed) is 32 K. The system is designed to receive signals
from a satellite. This satellite system is described in Table 8-5, Fig. 8-25, and Fig. 8-27.The
LNA has a post-mixer circuit that down-converts the satellite signal to 70 MHz. The 70-MHz
signal is fed to the TVRO receiver via a 120-ft length of 75-Ω coaxial cable. The cable
has a loss of 3 dB100 ft. The receiver has a bandwidth of 36 MHz and a noise temperature of
3800 K. Assume that the TVRO site is located in Los Angeles, California (34° N latitude,
118.3° W longitude), and vertical polarization is of interest.
(a) Find the TVRO antenna look angles to the satellite and find the slant range.
(b) Find the overall system temperature.
(c) Find the (CN) dB into the receiver detector.
★ 8–36 An Earth station receiving system operates at 11.95 GHz and consists of a 20-m antenna with a
gain of 65.53 dB and T AR = 60 K, a waveguide with a loss of 1.28 dB and a physical temperature
of 290 K, a LNA with T e = 50 K and 60 dB gain, and a down converter with T e = 11,000 K.
Using MATLAB, find (GT) dB for the receiving system evaluated at
(a) The input to the LNA.
(b) The input to the waveguide.
(c) The input to the down converter.
8–37 Rework Ex. 8-4 for the case of reception of TV signals from a direct broadcast satellite (DBS).
Assume that the system parameters are similar to those given in Table 8–5, except that
the satellite power is 316 kW EIRP radiated in the 12-GHz band. Furthermore, assume that a
0.5-m parabolic receiving antenna is used and that the LNA has a 50-K noise temperature.
★ 8–38 A distant object from our sun is Pluto, which is located at a distance from the Earth of 7.5 × 10 9 km.
Assume that an unmanned spacecraft with a 2-GHz, 10-W transponder is in the vicinity of Pluto.
A receiving Earth station with a 64-m antenna is available that has a system noise temperature of
16 K at 2 GHz. Calculate the size of a spacecraft antenna that is required for a 300-bs BPSK data
link to Earth that has a 10 -3 BER (corresponding to E b N 0 of 9.88 dB). Allow 2 dB for incidental
losses.
8–39 Using MATLAB, or some spreadsheet program that will run on a personal computer (PC), design
a spreadsheet that will solve Prob. 8–35. Run the spreadsheet on your PC, and verify that it gives
the correct answers. Print out your results. Also, try other parameters, such as those appropriate
for your location, and print out the results.
8–40 Assume that you want to analyze the overall performance of a satellite relay system that uses a “bent
pipe” transponder. Let (CN) up denote the carrier-to-noise ratio for the transponder as evaluated in