Equalizer and detector performance in digital VCRs

Various equalization and detection techniques are considered for the digital video cassette recorder (DVCR) application. Bit error rate (BER) performances are evaluated based on computer simulation. The equalization/detection schemes considered are class IV partial response equalisation followed by Viterbi algorithm detection (PR4/VA), extended class IV combined with VA detection (EPR4/VA), decision feedback equalization (DFE) and fixed-delay tree search with decision feedback (FDTS/DF). For all cases, the rate 24/25 modulation DC-controlled channel code is used. The BER simulations are performed at different channel SNR values and in the presence of off-track, head-tape space variations and sampling phase error. The results show that the FDTS/DF with a search depth of 3 has significant performance advantage and improved robustness over other schemes under various channel conditions.