Patent ID: 7860913

Claim:
An FIR filter for processing a digital input signal to generate a digital output signal, the FIR filter having a tap amount N and a decimation ratio D, the FIR filter comprising: a first memory for storing a plurality of tap coefficients, wherein for an input sample of the digital input signal, the first memory provides N/D corresponding tap coefficients from the plurality of tap coefficients in turn; a multiplier, coupled to the first memory, for multiplying the input sample with the N/D corresponding tap coefficients provided by the first memory in turn to generate N/D product values; and an accumulation module, coupled to the multiplier, for adding the N/D product values to N/D previous accumulation values in turn to generate N/D renewed accumulation values, wherein for a renewed accumulation value of the N/D renewed accumulation values, if the renewed accumulation value has already accumulated N product values, the accumulation module outputs the renewed accumulation value as an output sample of the digital output signal.