Question

Question 1

 The power radiated by a lossless antenna is 10 watts. The directional characteristics of the antenna are represented by the radiation intensity of U = 2cos³θ watts/unit solid angle. Find the

 (a) Maximum power density at a distance of 1000 m (assume far-field distance)

 (b) Maximum directivity

 (c) Maximum gain 

Question 2

 In target-search ground-mapping radars it is desirable to have echo power received from a target, of constant cross section, to be independent ofits range. For one such application, the desirable radiation intensity of the antenna is given by 

Find the directivity (in dB) 

Question 3 

The normalized radiation intensity of a given antenna is given by

The intensity exists only in the 0 ≤ θ ≤ π,0 ≤ ψ≤π region, and it is zero elsewhere. Find the 

(a) Exact directivity 

(b) Half-power beamwidths (in degrees) 

Question 4 

A λ/2 dipole, with a total loss resistance of 2 ohm. is connected to a generator whos internal impedance is 50 j25 ohms. Assuming that the peak voltage of the generator is 3 V and the impedance of the dipole, excluding the loss resistance, is 73+j42.5 ohms, find the power

 (a) Supplied by the source (real)

 (b) Radiated by the antenna

 (c) Dissipated by the antenna

Answer 1