A Simplified Two-Stage Equalizer with a Reduced Number of Multiplications for Data Transmission over Voiceband Telephone Links

The paper presents an equalization scheme based on the two-stage equalizer originally introduced by Proakis. Mostly additions are required for implementation of the equalizer structure and the adaptation algorithm. The equalizer can be applied to data transmission Systems which use four-phase modulation, especially in 1200/2400 bit/s modems, thus replacing the fixed equalizer recommended by CCITT. The results presented in the paper deal with the analog and digital implementation of the proposed equalizer. Its performance is compared to the performance of the conventional transversal equalizer, a decision-feedback equalizer, an ideal linear canceller, and an ideal QPSK system.