HW2 - is total length of the wire. 3. Consider a plane wave...

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ECE 613 Antennas and Propagation for Wireless Systems Fall 2010 Homework Set 2 Problems: 1. Find the directivity gain and directivity of a dipole wire antenna which is 30 cm long at f = 1 GHz. Note that the antenna power pattern was obtained in the last HW and you can use that result. You must use numerical integration by writing a small computer code or by using Matlab, for example, to find P rad 2. Use the numerical integration program above to find the radiation efficiency of two different dipole wire antennas: The first having /4 length and the second having length, both operating at f = 10 MHz. Assume that the wire is made of copper ( = 5.7 x 10 7 S/m) with a radius of 10 -3 . Assume that the loss resistance of the dipole wire antennas is given by R loss =  2 / 0 P l where P is the perimeter of the of the wire cross section and l
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Unformatted text preview: is total length of the wire. 3. Consider a plane wave with the magnetic field given by H = e j z j x 4 / ˆ ) 1 ( ˆ e-jky (a) What is the polarization of the wave (LP, CP, or EP)? (b) What is the sense of rotation (left- or right-hand), if any? (c) Determine the associated electric field. 4. Show mathematically that any linearly polarized (LP) wave can be written as a linear superposition of two circularly polarized (CP) waves traveling in the same direction but with having opposite senses of rotation. 5. Discuss why an isotropic antenna (same radiation intensity in all directions) cannot be realized. Hints: (1) Recall that the radiated far-field has a polarization transverse to the direction of propagation. (2) Invoke the so-called “hairy-ball” theorem (search the literature on this)....
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This note was uploaded on 10/21/2010 for the course ECE 613 taught by Professor Teixeira during the Fall '10 term at Ohio State.

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