Suppression of higher-order modes in subsidiary resonance waveguide limiters

One shortcoming of the simple ferrite subsidiary resonance waveguide limiter is that its bandwidth is restricted by the onset of higher-order modes in its small-signal insertion-loss characteristic. The letter describes a simple mode suppressor consisting of a thin film wire metallisation along the length of the ferrite section. It includes the description of an 8.5¿9.6GHz low-loss limiter in WR90 waveguide.