Ferrite-Tunable Microwave Cavities and the Introduction of a New Reflectionless, Tunable Microwave Filter

Large ferrite samples are placed in microwave cavities with the object of achieving tunable microwave cavities. Experimental data, at X band frequencies, on ferrite tuning of conventional band-pass and band elimination cavities are presented. Curves of applied dc magnetic field vs cavity resonant frequency, bandwidth, loss, cavity Q, and window coupling coefficients are included. Of particular interest are the results obtained with a new type cavity filter. With a single circularly polarized cavity, a reflectionless filter is achieved which couples nearly 100 per cent of the energy from the main waveguide at the cavity resonant frequency. Experimental results, on the ferrite loading of these circularly polarized cavities, are presented, and a number of practical microwave applications are discussed.