A new approach of the intermediate sampling filter

Many signal processing algorithms aim at complex signals, so it is important to create a complex signal from the bandpass real signal. The IF (intermediate frequency) sampling technique samples the intermediate frequency signal directly and produces a complex signal by digital signal processing. Unlike the current IF sampling method, the bandwidth of the sampling filter proposed in this paper is variable, and the coefficients of the filter are given analytically. The new filter produces similar results when the sampling rate is 2b or 4b, and works much better when the band of the signal is narrow.