S.N. Kulinich, A.N. Fomin

The article is devoted to the research and determination of the maximum possible retuning range of discretetunable matrix type-s microstrip filters which discretetuning frequency is performed by the switching the elements of the weighting matrix. If the minimum set of discrete elements n is available, one can get 2n discrete frequency state. It is shown that the maximum tuning range is limited, on the whole, by the oscillation third-order mode and depends on the electromagnetic interaction between disconnected matrixes-s microstrip lines with basic resonators is stipulated by the type of applicable weight matrix unit. Score limiting valuation of discretely tunable band with ideal keys shows, that the maximum adjustment range for sequent matrix type equals to about two octaves, depending on the specific requirements. In the weight matrix units of parallel type adjacent modes first and third are brining together and make narrow the tuning filter range of the filter up to one octave. It is established that during retuning within frequency range of current type of filter the equidistance between restructuring discrete frequency states is disturbed, and can be saved by the introduction of the weight matrix with redundant digit capacity to the structure of the filter.