08 ELEC5101 Antennas and Propagation.
Issued 30 September 2008. Question 1.
Tutorial 3.
Using lecture material confirm that the following graph does indeed apply for a single wire traveling wave antenna.
Design a Rhombic antenna with sides of length 5 to provide the optimum boresight pattern. What height above the ground would you arrange this antenna so that the main beam is elevated at approximately 300 to the horizontal?
Question 2. The inner 5 meter radius of the Parks radiotelescope has been made to be extremely accurate and will operate satisfactorily at 94 GHz. Estimate the Gain and beamwidth at this frequency. Also estimate the near/far field transition distance in this case. Question 3. Two aeroplanes 10 km apart are in radio communication. The transmitting aeroplane radiates 500 Watts of power and its antenna gain in the direction of the receiving aeroplane is 10 the power into the receiver is 2Watts. Find the effective area of the receiving antenna. Assume that any ground and ionosphere reflections can be ignored. Question 4. Four vertical transmitting antennas are uniformly spaced along a straight line running from North to South with the distance between adjacent antennas being 5 metres. The antennas carry equal amplitude currents but with progressively different phase the The antenna is operating at current in any one lagging its northern neighbour by 300 .
15 MHz. Determine the angle of the beam maximum from the East West direction. If the progressive phase change is now doubled to 600 determine the angle the of new beam maximum to the East West direction. Question 5. In Lecture 5 page 14 I introduced you to the Redlich glidepath antenna which used an array of 7 radiating elements to create an unusual radiation pattern. Evaluate the far field pattern of this 7 element array (assuming that it is in free space with no ground imaging involved) from the drives which are quoted and separately using the Schelkunoff unit circle on the complex plane. (These should give the same answer). See if you can calculate the field that you would receive if you measured on a vertical line 100 in front of the array as shown in the following sketch:
Question 6. Satellite Communications 1. Briefly describe the processes which are involved in setting up and pointing a Ku off set parabolic dish designed to receive TV satellite signals from the Optus C1 domestic satellite. Note in your explanation the equipment that is required to accurate...