29:106/186 RADIO ASTRONOMY
Seventh Homework Set...March 29, 2000
Due: April 5, 2000
(1) Consider a rectangular antenna with a horizontal width b. The feed has a taper such that the aperture excitation function in the x (horizontal) direction is
Compare the beamwidth in the horizontal direction and the forward gain
to that of a uniformly illuminated antenna.
(2) Repeat (1) for the case of the following aperture function
(3) An interferometer has a baseline of 2.0 kilometers in the
East-West direction. It is observing a radio source at an azimuth angle
of 120 
and an elevation angle of 50 . What is the
geometric delay between the antennas?
(4) A circular antenna (like the real ones) is uniformly illuminated. What
is the beamwidth 
in terms of 
and D. Calculate
a number for an antenna with a diameter of 32 meters and an observing
wavelength of 3.4 centimeters. What is the level of the first sidelobe
relative to the main beam? I want engineering-quality numbers for this,
not back-of-the-envelope estimates!
(5) For the case of Problem 3, the interferometer is observing with a
bandwidth of 50 MHz. How precisely must the delay be adjusted to get the
proper value of 
?