Patent ID: 7227477

Claim:
An apparatus for performing sample rate conversion comprising: an upsampling filter stage having an interpolation filter stage for performing upsampling interpolation on an input signal to the upsampling filter stage, the interpolation filter stage interpolating the input signal with a cumulative interpolation ratio product of N M to produce an upsampled signal, the input signal to the upsampling filter stage having a sample rate of F SYM , the upsampled signal produced by the interpolation filter stage having a sample rate of F IN , wherein F IN =N M ×F SYM ; and an output sampling rate stage having a sample rate converter, the output sampling rate stage receiving the upsampled signal having the sample rate of F IN , the sample rate converter converting the upsampled signal into an output signal having a sample rate of F OUT , wherein a ratio of F OUT to F IN is less than two, wherein the sample rate converter comprises: a numerically controlled oscillator (NCO) having an accumulator, a register and a divider, the accumulator receiving a frequency control word (FCW) and adding the FCW with a previous accumulated value to produce a current accumulated value, the current accumulated value including a current carry out value, the register temporarily storing the previous accumulated value, the previous accumulated value including a previous carry out value, and wherein the divider receives the previous carry out value from the register, the divider dividing the previous carry out value by N M to produce a control signal having a frequency equal to F SYM , the control signal being output to the upsampling filter stage, the upsampling filter stage using the control signal to control timing of inputting the input signal to the upsampling filter stage.