Optimization of the RC matching network in adaptive active hybrids for high-speed data communications

The feasibility of an automated adjustment of the four components of the matching circuit for the active hybrid termination of digital subscriber loops is demonstrated. The loops are used for primary rate ISDN data transmission using a 65-point constellation with QAM modulation. The band of investigation lies between 20 kHz to 270 kHz. The results indicate that, compared to conventional hybrid networks, the proposed active hybrid circuit offers the capability of increasing the near-end transhybrid loss by an amount ranging from approximately 8 to 26 dB