FREQUENCY CONVERTING FILTER

摘要

Disclosed is a frequency converting filter comprised of a charge transfer device transversal filter and a non-sampling filter. The transversal filter has an output lead coupled to an input of the non-sampling filter, and has frequency passbands of width .DELTA.f centered at the fixed frequencies nfs ? fo where n is an integer multiple of the sampling frequency, fs is the sampling frequency, and fo is the center frequency removed from the sampling frequency of the desired frequency passband. The non-sampling filter has a single passband. The single passband has a width of less than fs - fo - .DELTA.f/2 and it is centered to include only a selected one of the passbands of the transversal filter. The invention provides an improved device for filtering having an abrupt transition from stopband to passband, no involved oscillator circuit, no mixing circuit, and is capable of being integrated on a single semiconductor chip.