Band-pass effect in wave-filters terminated in negative resistances

Abstract

The paper relates to the "band-pass effect" obtained when symmetrical low-pass and high-pass filter sections of simple type are terminated by stable negative resistances of magnitude equal to their maximum characteristic impedances in the transmission band. The cut-off frequencies of the resulting band-pass arrangement depend upon the values of elements in the original filter section. Amplitude and non-linear distortions are inappreciable in the resulting band-pass arrangement. Effect of increasing the number of original filter sections on the resulting arrangement is to shift the position of the transmission band in the frequency spectrum, to reduce the band-width, and to increase gain in the band. Since, in addition, gain is obtained in the transmission band, this method of obtaining band-pass arrangement has distinct advantages on account of lower cost, better characteristics, and simpler design over a composite band-pass filter and an associated amplifier to give the same gain in the transmission band.