A multifunction FIR filter for delta modulated signals

The purpose of this paper is to show that a lowpass DM FIR filter, which has been implemented with reduced hardware due to the special relationship among its coefficients, can be easily modified in practice to operate also as a highpass, a bandpass or a bandstop filter. This is achieved by means of a binary logic circuit, while the desired filter function can be selected by suitable binary signals applied to the circuit externally. The multifunction filter has been simulated on the computer and also built using discrete CMOS ICs. Its frequency response in all four operations is also given