Interdisciplinary Theory & Technology

Systems, algorithms, circuits, and methods for pattern detection of signature events in a type of signal dynamics defined by instantaneous states of multiple pulse-waveform signals. Selected patterns may be recognized individually or in equivalence classes. A variety of conditions can be detected in parallel, including course degrees of phase detection, ambiguity states, types of asymmetry, and current or last-determined frequency comparison. One application provides a real-time frequency comparator operation on asynchronous square-wave or pulse signals over an extremely large frequency range. Under certain conditions it may be used on phase-locked signals with frequencies that are relatively prime. Implementation may employ either state or transition analysis, may be event-driven or periodically sampled, and may be realized in hardware, as physical processes, or as algorithms. The approach may be expanded to more than two signals. Implementation can be feedback-free, and no signal is required in quadrature form. An example transition-oriented circuit implementation involves a few flip-flops and logic gates, depending upon features. An example state-oriented circuit implementation involves two to four flip-flops, or two-stage two-bit shift registers and modest combinational logic. Either resulting system may be readily implemented as a utility integrated circuit of modest "MSI" scale or as a small-scale "IP-core" within larger-scale system-on-a-chip (SoIC) realizations. As a dedicated chip or IP core, circuit implementations also find application in expandable "last to cycle" switch and detector interfaces.