Question

Waveguides

Consider a rectangular waveguide, with transverse dimensions a = 10.668 mm and b = 4.318 mm. The waveguide is uniformly filled with a non-magnetic dielectric with????=2.

We wish to use this waveguide to propagate a wave at frequency ??=13 GHz.

(i)Which propagation modes can be sustained by this waveguide at 13 GHz? Explain in detail how you arrive at the answer. (ii)Calculate the propagation constant ? for the allowed modes at f = 13 GHz.(iii)Assume that the 13 GHz signal along this waveguide is used to transmit data. Calculate at what speed the information travels along this waveguide? Clearly explain the reasoning used to arrive at your answer.

(iv)Now assume that the dielectric has broken perpendicularly to the length of thewaveguide, and that the two resulting pieces of dielectric have been pulled out slightly,leaving a 1 mm gap (see figure below). Calculate the insertion loss (in dB) resulting from thisfault. The insertion loss is defined as: ? 10 Log(P2 / P1) where P1 is the incident power andP2 is the transmitted power. Explain the physical origin of this loss.

Answer 1