Standardizable low-pass voice band hybrid circuit filters for pulse code modulation (PCM) communication systems

A standardizable design approach to realize the voice band low-pass filters for a variety of pulse code modulation (PCM) communications systems is described. This design concept incorporates cascaded RC active filter sections, thick and thin film hybrid technologies, and functional tuning to allow the use of the same hybrid design for both transmit and receive filters, for a range of input and output requirements. Tuning, sensitivity analyses, and implementation tradeoffs are described. Thick film implementations, using NPO chip capacitors, with the new high stability resistor inks as well as thin film implementation, using the usual tantalum integrated thin film technology are presented. Very stringent requirements have been successfully met using state-of-the-art hybrid technologies.