An analysis is presented of the performance of the optimum detection for NRZ magnetic recording. The error rate performance of the optimum detection is obtained by theoretical analysis. And the recording density with the optimum detection is compared with that with some other well-known detecting methods.

To improve picture quality of a color-under VCR, chrominance bandwidth expansion is studied using subsampling technique. It is concluded that line offset subsampling and field offset subsampling are effective methods of improving reproduced picture quality.

Quadrature amplitude modulation (QAM) was found to suitable for the bandpass type frequency characteristic of magnetic recording/reproducing channels. A method of 20 Mbps signal recording using 32 QAM coded modulation is described.

Recording and reproducing of quadrature amplitude-modulated (QAM) signals on magnetic recording channel of VCR is studied. While the frequency characteristics of QAM signal is nearly matched to that of the magnetic recording channel, the linearization of magnetic transmission channel associated with odd-order nonlinear transfer function is considered to be essential to record QAM signals, and the employment of bias recording method is experimented for this purpose. Simple 16 QAM and coded 32 QAM signals are recorded on an experimental VCR. It is found that the SNR required by coded 32 QAM signal is lower than that by 16 QAM signal for the channel SNR higher than 14 dB. Coded 32 QAM signals of 20 Mbps data rate are recorded and reproduced at a scanning speed of 3.5 m/s using a head of 50 µm track width, and the word error rate less than 10-5 is successfully accomplished.

To study lower sideband enhancement, three kinds of modulation methods are applied to recording. Compared with results of experiments using a VCR and simulations, it is concluded that the order of magnitude of lower sideband enhancement is AM, Dual-frequency, FM with lower modulation index.

The recording density 34 KFRPI was achieved by the use of transversal recording. A tape orientated transversal direction was employed and a ferrite head with 3.8 µm gap length and 15.5 µm track width was used. The frequency characteristics of transversal recording and its bitter patterns are described.