Q1. In your own words, describe the following: a) affective aperture, b) array factor, c) Friis equation, d)Antenna H-plane and E-plane, e) radiation resistance
Q2. An antenna in free-space driven by current Io radiates far-field E as:
, for 0 ≤Φ ≤ π, here C = constant
= 0 everywhere else
a) Compute the power density, b) Compute the total radiated power, c) Compute the gain and directivity (D) of the antenna
Q3. Four Hertzian dipoles (oriented in the z-dir.) are placed on an x-y plane with spacing (d=λo/2) between them as shown in figure.
a) Derive the array factor for this setup
b) Determine the total far-field
Q4. A 90° perfectly conducting corner cube reflector has a shortdipole (oriented in the z-direction) placed at a distance d from the vertex. The antenna is fed by current Io.
a) Find the equivalent array of dipoles by determining a system of images
b) Derive the array factor
c) Determine the total far-field (E)
d) For a distance d=0.5λ, find out the directivity on y-axis
Q5. Design a rectangular patch antenna (substrate: εr = 3, tan-δ=0, h = 0.75 mm) operating at f0 = 2.5 GHz
a) Determine the dimensions W and L of the antenna, assume w/λo << 1
b) The antenna is to be matched to 100Ω using recessed feeding line. Design the recessed length (L1) to match the antenna to the feed line.
c) This antenna design is now used in an array of (2X1, side by side placement).
C1. In which direction does the main radiation beam points if the antennas are symmetrically fed.
C2. In which direction does the main radiation beam points if the antennas are fed with different length transmission lines that gives rise to a phase difference of 0.75 between them.