A high-speed FIR digital filter with CSD coefficients implemented on FPGA

A very fast and low-complexity FIR digital filter on FPGA is presented. Multipliers in the filter whose coefficients are expressed as canonic signed digit (CSD) code are realized with wired-shifters, adders and subtracters. The critical path is minimized by insertion of pipeline registers and is equal to the propagation delay of an adder. The number of pipeline registers is limited by using an equivalent transformation on a signal flow graph. The price paid for the 100% speedup is 5% increase in the area. The maximum sampling frequency is 78.6 MHz.