Mode propagation constants in hollow oversized circular waveguides with low-conductivity wall material

Using convenient parameters, the mode propagation constants in hollow circular waveguides with low-conductivity wall material are derived into practical formulas. The variations of these propagation constants versus electrical characteristics of the wall material are studied. The results allow the determination of optimal materials for low-loss mode transmission and the improvements achieved with these optimal materials compared to the usual dielectrical materials are pointed out. Application to the particular case of ordinary glass as a guide wall material is made. The condition to have the fundamental EH₁₁ mode the less attanuated is given.