Design of high-speed digital bandpass filters without multipliers

Using a special case of the frequency-sampling design approach with N=6, it is possible to design FIR (finite impulse response) bandpass filters without the need for multipliers. The technique is highly modular and thus lends itself to VLSI implementation and, since it only uses adders and registers (delays), it can be implemented with a very high sampling frequency (e.g. 100 MHz). The basic bandpass filters are limited to center frequencies at multiples of π/3, and thus are somewhat restrictive. However, by applying a multirate technique and adding an additional low-sampling-rate filter, it is possible to place center frequencies at any multiple of π/18. Further stages can refine the center frequency to any multiple of 2π/(6ⁿ), where n is the number of stages. The low-sampling-rate filters may be time-multiplexed but they do create undesirable image spectra unless they are centered at one of the original π/3 multiples. Adjustment of the sampling frequency can place these bandpass filters at any desired center frequency