THE DESIGN OF BAND SEPARATION FILTERS
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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A band separation filter is a network with one input and m outputs, each corresponding to a different portion of the frequency spectrum. When a voltage is applied to the input terminal, it will appear at one of the output terminals only slightly attenuated. The filter considered here is a lossless network with each output terminal terminated in a one ohm resistance. The further condition that the input impedance of this network equals 1 j0 for all frequencies is imposed. In this thesis a sufficient condition for realizability on the m transfer impedances is derived. It is shown that Butterworth characteristics for each of the m transfer impedances can be achieved with networks synthesizable in ladder form. It is also shown that L filter characteristics are also realizable but that the synthesis procedure is more complicated and necessitates coupled coils. Normalized curves of the attenuation characteristics for each type are presented. The extension of this method to transmission line networks is discussed, and it is shown that the Butterworth characteristic can be achieved with this type of element.
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