Patent ID: 7483684
Filing Date: 2009-01-27
Classification: H03D

Abstract:
1. A mixer for producing a base band signal by demodulating an input signal which is a carrier modulated with the base band signal, the mixer comprising: a current source for generating a current in proportion to a voltage of the input signal; a charge subsampling circuit to which the current generated by the current source is supplied; and a control circuit for generating a signal controlling sampling of the current by the charge subsampling circuit, wherein the charge subsampling circuit, under control of the sampling by the control circuit, generates a discrete time signal in a bandwidth 1/N times a frequency of the carrier from the input signal (N is an integer greater than 1), and the mixer performing filtering by means of an FIR filter realized by a charge integrating process of forming current which accompanies the generation of the discrete time signal, wherein the charge subsampling circuit carries out: the sampling at the same sampling frequency as the frequency of the carrier; and in the integrating process, weighting of terms in a transfer function of the FIR filter with weights selected from a set of weights.