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# ECET 425 Final Exam

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Author: Christine Farr
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1a) Explain the physical significance of the Standing Wave Ratio (SWR) and the implications of a SWR greater than unity
1b) Explain the physical significance of the reflection coefficient.
2) The output of a transmitter with an output voltage of 325 VRMS and a resistance of 300 ohms is connected through a transmission line to an antenna. Assume that the transmission line is terminated in its characteristic impedance. Determine (a) the input impedance of the line, (b) the RMS current flowing into the line, (c) the power accepted by the line, and (d) the load power if the line is considered lossless.
4) A coaxial cable has physical dimensions as follows:
5) Identify and explain the key characteristics of electromagnetic waves, including an explanation of vector relationships associated with the propagation of electromagnetic waves.
6) Compare and contrast the differences between the protocol formats and functionality of synchronous versus asynchronous communication protocols. Please use the format for the synchronous communications protocol that was discussed in the class lecture.
7) Determine the distance from a vertical antenna having a length of a quarter wavelength at 25 MHz to the boundary between the near field and the far field.
8) Explain the purpose of an antenna and identify two key performance metrics of an antenna.
9) A certain 8-GHz parabolic reflector antenna has a physical diameter of 10 m. The illumination efficiency is 75%. Determine the following parameters: (a) the effective area, (b) the gain in dB, and (c) the 3-dB beamwidth in degrees.
11) The lowest uplink frequency for the Ku-band Direct Broadcast Satellite service in America is 17.3 GHz. Consider a ground station transmitter operating at this frequency with a desired beamwidth of 1.5°. Assuming an illumination efficiency of 75%, determine the diameter and the gain of the ground station uplink antenna.
12) A FO communications link will be established between two locations that are 2000 m apart. Multimode fiber with an insertion loss of 2.5dB/km will be used. The connectors at the ends of the fiber have a loss of 0.7 dB each. A PIN photodiode receiver that requires an input of –25 dBm to achieve a BER of 1*10-10 will be used. Assume a dispersion penalty of 1 dB and a margin of at least 3dB. What is the minimum output required of the light source?
16) Determine (a) the magnitude of the magnetic field intensity, (b) the power density of the plane wave, and (c) the total power transmitted through a square surface in the x-y plane with sides of 10 m each. Assume that the power density is constant over the surface area.
17) The RMS values of the electric and magnetic fields in a certain medium are 300 mV/m and 150 μA/m, respectively. Determine (a) the intrinsic impedance, (b) the power density, and (c) the dielectric constant.

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