Waveguide propagation of microwave signals at frequencies less than cut-off.

Using transform techniques, a time dependent study has been made of the evanescent wave in a waveguide or similar dispersive medium, Firstly, the field created by the application of a unit step modulated carrier wave to an unterminated waveguide, cut-off with respect to the carrier frequency, has been investigated as a function of time and the distance from the point of application. The behaviour of the transverse electric and magnetic field components and the resulting Poynting vector has been presented graphically. Secondly, the interaction of nanosecond microwave carrier pulses with a terminated section of cut-off waveguide was investigated theoretically and experimentally. This waveguide was cut-off with respect to the carrier frequency and was interposed between two identical propagating guides. Under certain conditions it is possible to predict reflection and transmission times for the pulse on interaction with the cut-off guide. These reflection interaction times have been correlated with those measured experimentally. This time dependent study forms an extension of the steady state microwave analogue of the quantum mechanical tunnel effect