Multiplier-free FIR filters based on multiple step-size delta modulation

FIR (finite impulse response) filter structures based on the multiple-step-size delta modulation (MSS-DM) technique are proposed. The purpose of MSS-DM is to counter the slope overload problem that plagues the ordinary DM systems. In the MSS-DM system, the quantization step-size is adjusted according to the slope of the waveform of the impulse response to reduce the slope overload noise. The resulting filter needs a lower oversampling ratio compared to the ordinary DM filters. Therefore, the length of the filter can be shortened, reducing the hardware cost. In addition, the structure retains the modular structure, with simple interconnection between modules, of binary and ternary DM filters. This allows the filter order to be increased simply by adding additional sections. Numerical results show that the MSS-DM structures offer a valid alternative to the conventional filter structures