Resolução Eletromagnetis...o para Engenheiros Ulaby - 45795 - ulabyismch10

Resolução Eletromagnetis...o para Engenheiros Ulaby - 45795 - ulabyismch10

Chapter 10: Satellite Communication Systems and Radar Sensors

Lesson #70 and 71 Chapter — Section: 10-1 to 10-4 Topics: Communication systems

Highlights:

Lesson #72 and 73

Chapter — Section: 10-5 to 10-8 Topics: Radar systems

Highlights:

• Acronym for RADAR • Range and azimuth resolutions

Chapter 10

Sections 10-1 to 10-4: Satellite Communication Systems

Problem 10.1 A remote sensing satellite is in circular orbit around the earth at an altitude of 1,100 km above the earth’s surface. What is its orbital period?

Solution: The orbit’s radius is R0 Re

GMe

Problem 10.2 A transponder with a bandwidth of 400 MHz uses polarization diversity. If the bandwidth allocated to transmit a single telephone channel is 4 kHz, how many telephone channels can be carried by the transponder?

Solution: Number of telephone channels 2 400 MHz

channels.

Problem 10.3 Repeat Problem 10.2 for TV channels, each requiring a bandwidth of 6 MHz.

Solution: Number of telephone channels

We need to round down becasue we cannot have a partial channel.

Problem 10.4 A geostationary satellite is at a distance of 40,0 km from a ground receiving station. The satellite transmitting antenna is a circular aperture with a 1-m diameter and the ground station uses a parabolic dish antenna with an effective diameter of 20 cm. If the satellite transmits 1 kW of power at 12 GHz and the ground receiver is characterized by a system noise temperature of 1,0 K, what would be the signal-to-noise ratio of a received TV signal with a bandwidth of 6 MHz? The antennas and the atmosphere may be assumed lossless.

Solution: We are given f 12 GHz Tsys 1

Gt Dt 4piAt

4pi pi 1

Gr Dr 4piAr

Sn PtGtGr

KTsysB λ 4piR

Sections 10-5 to 10-8: Radar Sensors

Problem 10.5 A collision avoidance automotive radar is designed to detect the presence of vehicles up to a range of 0.5 km. What is the maximum usable PRF? fp c

Problem 10.6 A 10-GHz weather radar uses a 15-cm-diameter lossless antenna. At a distance of 1 km, what are the dimensions of the volume resolvable by the radar if the pulse length is 1 µs?

Solution: Resolvable volume has dimensions ∆x ∆y, and ∆R.

∆x ∆y βR λ dR

∆R cτ

Problem 10.7 A radar system is characterized by the following parameters:

Pt 1 kW, τ 0 1 µs, G 30 dB, λ 3 cm, and Tsys 1 500 K. The radar cross section of a car is typically 5 m2. How far can the car be and remain detectable by the radar with a minimum signal-to-noise ratio of 13 dB?

Rmax PtτG2λ2σt

4pi 3KTsysSmin

Problem 10.8 A 3-cm-wavelength radar is located at the origin of an x–y coordinate system. A car located at x 100 m and y 200 m is heading east (x-direction) at a speed of 120 km/hr. What is the Doppler frequency measured by the radar? θ u = 120 km/hr200 m

100 m x

Figure P10.8: Geometry of Problem 10.8.

Solution:

θ tan

fd 2u

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