Patent ID: 7236110
Filing Date: 2007-06-26
Classification: H03H

Abstract:
1. A sample rate converter for reducing the sampling rate of a signal by a fractional number U/D, where U represents an up-sampling rate and D represents a down-sampling rate, the converter comprising: an input for receiving an input data stream at a first rate; an FIR filtering stage comprising a set of D polyphase filter branches, each branch including a set of filter coefficients for operating on a sample of the input signal; a commutative switch which is arranged to selectively connect a sample of the input data stream to one of the polyphase filter branches, the switch being arranged to skip every U−1 filter branches during a cycle through the filter branches and, an output for outputting an output data stream at a second data rate which is lower than the first data rate, wherein each polyphase filter branch comprises a set of coefficient multiplication stages where a coefficient is multiplied by an input sample, and the commutative switch comprises a counter which is arranged to selectively output indexes to filter coefficients for a required filter branch and a coefficient generator which generates the filter coefficients for use in the coefficient multiplication stages of the required filter branch.