System and method for multimode operation of a digital filter with shared resources

Abstract

There is disclosed a digital filter cell capable of processing in a first mode a first signal having real data components only and processing in a second mode a second signal having real data components and imaginary data components. The digital filter cell comprises: 1) a plurality of serially coupled coefficient registers for receiving a sequence of coefficients; 2) a plurality of serially coupled data registers for receiving a sequence of digital data samples, each register having a tap output; 3) a data multiplexer having a plurality of input channels for receiving the tap outputs from the plurality of serially coupled data registers; and 4) a product summation circuit having a first input coupled to an output of the data multiplexer and a second input coupled to an output of a selected one of the plurality of serially coupled coefficient registers. The product summation circuit generates a summation of a plurality of products formed by sequentially multiplying each coefficient received from the selected coefficient register by a corresponding digital data sample received from a selected one of the plurality of serially coupled data registers. The product summation circuit adds each of the plurality of products to the summation when the digital filter cell is operating in the first mode. In the second mode, the product summation circuit selectively adds ones of the plurality of products to the summation or selectively subtracts ones of the plurality of products from the summation.