Frequency comparison circuit

摘要: A frequency comparison circuit for determining, at least within certain limits of accuracy, whether the a received signal is equal or not to F. Generating means produce first and second reference signals F, in phase quadrature. logic periodically compares signs m, p q two according results these comparisons (m, alike, m different from q, q) applies pulse plus minus input bidirectional counter counter, one counters overflowing when sufficiently close In variant embodiment has 2F.