NOVEL MICROWAVE FILTER DESIGN TECHNIQUES

Abstract
Results of a mathematical study of a proposed multiplexer design technique are presented. Using this technique a separate channel unit is used for each channel that is to be separated out. Each channel unit consists of a band-pass filter and a band-stop filter. At the frequencies to be separated by a given channel unit, the band-pass filter will pass the signal to be separated, while the band-stop filter blocks any energy from escaping down the main transmission line. At frequencies outside the band to be separated, the energy flows through the channel unit without attenuation. It is shown that such units can be designed to have a constant-resistance input impedance. Techniques for the design of magnetically tunable band-stop filters using ferrimagnetic garnet resonators (such as yttrium-iron garnet spheres) are presented. A study of the use of varactor diodes for tuning transmission line resonators for a proposed form of band-pass filter phase shifter is discussed. Results obtained from a trial interdigital filter with capacitively loaded resonators are presented.

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