Fm multiplex broadcasting receiver

Abstract

A receiver for FM Multiplex broadcast packet communications is provided that includes a block identifying code (BIC) detection circuit which determines whether a received packet is a data packet type or a parity packet type based on predetermined BIC patterns. The receiver further includes block counter circuitry that counts blocks in a synchronized frame and determines whether a received packet is a data type or a parity type (D/P) based on the count value. An abnormality detection circuit detects discrepancies between these two D/P determinations and indicates a synchronization abnormality. In another embodiment, the BIC detection circuit provides an indication of a received BIC type (BIC1-BIC4) based on predetermined BIC patterns while the block counter circuitry determines the BIC type based on the counted number of the block in a synchronized frame. In this case, the abnormality detection circuit detects discrepancies between the two BIC type determinations and indicates a synchronization abnormality. A history of detected abnormalities is stored in an abnormal history memory circuit. If the number of abnormalities detected exceeds a predetermined threshold within a predetermined period, a packet offset determining circuit then generates a signal for canceling the frame-in-synchronism state and initiates a resynchronization process.