From special analogous crystal filters to digital impacting filters

The implementation of high-speed and high-efficiency wireless communications, or Ultra Narrow Band (UNB) modulation, depends on the design of a special digital filter, which needs to not only maintain or even enlarge the minute differences in modulated waveforms, but also weaken noise or interference. This paper proposes a novel but simple digital impacting filter produced by exploiting the mechanism of zero group delay crystal filters. The proposed filter can cooperate with the usual small-angle modulation of UNB modulation, especially with Extended Binary Phase Shift Keying (EBPSK) modulation, which can convert the signal characteristics in noise into high-amplitude impacting at the phase jump points, such that the UNB signal is easy to detect. A computer simulation illustrates the validity of the proposed filter.