Frequency change arrangement and radio frequency tuner

摘要

A frequency changer arrangement is provided for a radio frequency tuner. The arrangement comprises a first quadrature frequency changer for converting a desired input channel to zero or near-zero intermediate frequency in-phase and quadrature signals. These signals are filtered by low pass filters, whose turnover frequencies may be varied so as to vary the intermediate frequency bandwidth. A second quadrature frequency changer upconverts the filtered signals and supplies these to a summer. The resulting output intermediate frequency is determined by the frequency of commutation signals in the second frequency changer so that the output intermediate frequency may be continuously varied to allow any desired frequency to be selected.