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Abstract

A filter utilizing charge transfer devices and having resonant transfer characteristics is described. The filter includes a first charge transfer shift register including a plurality of stages to which a first sequence of packets of charge is serially applied and clocked from stage to stage. Charge division and collection means are provided at the various stages of the shift register to divide and collect fractions of charge appearing in the various stages thereof. The charge collection means of the various stages except the last are connected together to provide a first output representing the sum of the charges collected at the various stages thereof. These fractions represent the weighting coefficients of the various stages of the first shift register. A second charge transfer shift register identical to the first shift register is provided. A second sequence of packets of charge is serially applied to the second shift register and clocked from stage to stage. The charge collection means of the various stages except the last are connected together to provide a second output representing the sum of the charges collected at the various stages thereof. The output of the last stage of the first shift register is coupled to the input of the second shift register and the output of the last stage of the second shift register is coupled to the input of the first shift register so as to implement a recursive feedback of charge. A resultant output is obtained which is the difference of the first and second outputs.

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