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312ps8

# 312ps8 - PROBLEM SET 8 ECE 312 Autumn Quarter 2010 Assigned...

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PROBLEM SET 8 ECE 312 Autumn Quarter 2010 Assigned: November 24th Due: December 3rd in class Instructor: Joel Johnson Problem 1 An antenna operated in free space has an input impedance of 75 j 10 ohms at 3 GHz, and has a loss resistance of 1 Ohm. (a) Find the efficiency of the antenna. (b) Find the total time averaged power radiated by this antenna if a current of amplitude 0.5 A flows from a circuit into the antenna terminals. (c) Find the length (in meters) of a Hertzian dipole antenna that would produce the power radiated (i.e. the same radiation resistance) in part (b). Problem 2 An AM broadcast antenna operating at 820 kHz is 2.5 m long and is placed on the ground with the current flowing upwards (i.e. toward the sky) from the ground. Define the “z” direction in this problem as pointing directly upwards from the ground, while the “x” direction is pointing North along the ground and the “y” direction is pointing West. A transmitting circuit drives a current of amplitude 8 Amps into the antenna, and the antenna is 100% efficient. We will neglect any effects

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