Impedance Transformations in Four-Element Band-Pass Filters

In a recent paper by Belevitch it was shown how a four-element band-pass filter with all its frequencies of peak attenuation located on the same side of the pass band, could be transformed into a structure having, with the exception of the terminating half sections, the configuration of a high- or low-pass filter, with a consequential saving in components. Although this was proved possible for particular cases, it was assumed to hold for the general case. In the present paper it will be shown that, by using a different type of basic section for constructing the filter, a similar result may be obtained with slightly greater economy, and it will be proved that this can be achieved in the general case.