Low-Complexity Digital Tone Detector for Telecommunications Switching Systems

An improved structure for an envelope detection multifrequency receiver based on digital nonrecursive quadrature filters is proposed. The receiver utilizes a property of digital nonrecursive quadrature filters to reduce the required computational complexity by a nominal factor of 2 with a negligible hardware increase. The application to the tone detector implementation for two CCITT standard signaling systems is considered, showing the low computational and structural complexity required by the proposed technique. The required multiplication rate is reduced by more than twice with respect to other conventional approaches.