a band pass filter for extracting a desired frequency band from an input signal that is represented in a sequence of data stream . breaking through a traditional infinite - duration impulse response or finite impulse response filter design technologies , by using a difference of an input signal and a delayed version of the input signal , the present invention provides another way to make a band pass filter that greatly reduces the complexity , the costs , the power consumption , the design area required of an iir or a fir based band pass filter .