Tracing Distortion and its Correction in Carrier Quadraphonic Disc Records

Abstract

Carrier quadraphonic disc technology introduced in the early seventies, underscores the importance of tracing correction because of the paricular way in which base band signals interact with carrier signals. In a carrier disc, tracing distortion not only results in the familiar degradation of base band signals, but also allows the base band to modulate the carrier components directly (UP-talk). On the other hand, methods for dealing with tracing distortion through the generation of complementary functions based upon Hunt's analysis (Eq. (4)) were developed. But Hunt's analysis is insufficient in the present disc recording technology because of omitting the tilted cutting-tracing process (Figs. 2, 3, 4). In this paper, first an extended analysis is made and a generalized equation (8) is derived. Based upon (8), the UP-talk in a carrier quadraphonic disc is represented in the general equations (17), (18), and some numerical examples are shown (Figs. 8, 9, 10, 11, 12, 13). UP-talk has the basic characteristics of frequency dependent increase by 12 dB/oct, proportionality of playback stylus radius γand carrier frequency ω_c, and inverse proportionality to the square of the groove velocity V. Next, the effects of conventional predistortion are discussed and shown insufficient because of the existence of residual distortion or UP-talk (Eqs. (23), (25). Figs. 14, 15, 16, 17). Finally a new complementary function considering the effect of the tilt is derived (Eq. (33) and the functional diagram is shown (Fig. 19)). The new distortion compensation device results in satisfactory UP-talk reduction as shown in Fig. 20.