METHOD AND APPARATUS FOR DETECTING SYNC. SIGNAL

摘要

PURPOSE: A frequency hopping synchronous device in asynchronous serial data communication is provided to easily extract a synchronous signal necessary for frequency hopping, as using an asynchronous data transmission system for data transmissions of a wireless section in a wireless data transmission system using a frequency hopping system. CONSTITUTION: An RF modulator/demodulator(501) outputs received serial data frames. If high-level signals having short constant times are inputted among the data frames, an integrator(502) accumulates the signals to integrate the signals. If the integrated signals are low-level signals, a low-level detector(503) discharges inputted signals. If a frequency hopping synchronous signal is inputted after high-level signals having long constant times are inputted, a comparator(504) compares an output value of the integrator(502) with a comparison voltage, and outputs a square wave pulse. A timer(506) is preset as the same time as one frequency frame length. If an elapsing time of the timer(506) is remarkably earlier than a synchronization expiring time, a deciding circuit(510) decides a wrong operation signal by using a timer completion signal. If the elapsing time is close to the synchronization expiring time, the deciding circuit(510) performs a frequency conversion to hop into a next step of communication frequency from a present communication frequency. If the elapsing time exceeds the expiring time, the deciding circuit(510) performs a frequency conversion by using a timer expiring signal as an additional synchronous signal. A PN generator(511) is driven by an output of the deciding circuit(510).