A receiver system with a pitch synchronized interpolator

Abstract

AbstractIn mobile communications (e.g., vehicular telephony) instantaneous interruption is caused by rapid fading while passing through a downtown area where buildings are dense. The interference caused by this fading markedly deteriorates the quality of communication. To improve the quality of communication, the authors propose a method called pitch synchronized interpolation which interpolates the transient signal by employing the time intervals between speech signals. This paper deals with a receiver system which incorporates this pitch synchronized interpolator. In the pitch synchronized detection or interpolation process of this system, the received speech signal, after undergoing A/D conversion, is fed to a sequential delay memory. This delay memory speech signal is processed by a digital signal processor. Various methods and parameters used here are discussed (e.g., the pitch period detecting method, the frequency of execution of pitch period detection, coding methods, maximum interpolation time, the damping coefficient for damping the interpolation output level to zero when the interruption period exceeds the interpolation time and the design parameters for the speech specimen period). Further, the necessary condition for these parameters are clearly defined. Also, based on the studies of these parameters, a prototype model of pitch synchronized interpolator is designed and fabricated with a reduced pitch period detection cycle of 4 ms and the desired decrease in interruption noise is confirmed.