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ELEC5101 Antennas and Propagation
Assignment 2
1. A twin antenna system with a single feed is in operation. Each antenna has input
impedance of 73 Ohm are fed with coaxial cables with impedances and wavelength
specified below (assume lossless transmission lines for coaxial cables), and then
connected using a quarter wavelength impedance transformer to a 75 Ohm feed
cable, as shown in the figure below. Calculate the impedances as specified in the
figure. (2 points)
2. An antenna has a conical field pattern with uniform field for zenith angles (θ) from
0° to 60° and zero field from 60° to 180°. The pattern is independent of the azimuth
angle (φ). Find exactly
a) the beam solid angle
b) directivity (0.5 point)
3. A wave traveling normally out of the page (toward the reader) has two linearly
polarized components Ex = 2 cos (ωt) and Ey = 3 cos (ωt + 90)
a) What is the axial ratio of the resultant wave?
b) What is the tilt angle τ of the major axis of the polarization ellipse?
c) Does E rotate clockwise or counter clockwise? (0.5 point)
4. A right-handed monofilar helical antenna has 10 turns, 100 mm diameter and 70 mm
turn spacing. The frequency is 1 GHz.
a) What is the HPBW?
b) What is the gain?
c) What is the polarization state?
d) Repeat the problem for a frequency of 300 MHz.