A parallel-plate waveguide has plate separation d = 1 cm and is filled with Teflon having dielectric constant εr = 2.1. Determine the maximum operating frequency such that only the TEM mode will...

A parallel-plate waveguide has plate separation d = 1 cm and is filled with Teflon having dielectric constant εr = 2.1. Determine the maximum operating frequency such that only the TEM mode will propagate. Also find the range of frequencies over which the TE1 and TM1 (m = 1) modes, and no higher-order modes, will propagate.