Propagation and radiation behaviour of corrugated circular waveguide having dual depth combination

A study of the propagation and radiation behavior of a corrugated circular waveguide having dual depth combination is presented. The expressions for propagation equation and equivalent wall admittance are derived by using a space harmonics technique (SHT), and the formulae for expressing the radiation far fields are obtained by consideriing the higher space harmonics contribution. The calculated results show that this new type feed is a dual narrow bandwidth structure, and the values of lambda/p and d/p have a great influence on the propagation and radiation behavior. For a medium aperture feed, the relative frequency bandwidth for achieving cross polarization radiation less than -40dB is about 4 and 6 percent for the low and high frequency band respectively. It is necessary to choose the value lambda/p larger than 7 to obtain a better cross polarization behavior in dual frequency bands.