Direct-sequence spread spectrum system

The authors discuss the construction and evaluation of the performance of a direct-sequence spread spectrum (DSSS) system. The system uses a special type of injection-locked oscillator called a synchronous oscillator for code synchronization. The DSSS system was constructed in a manner that provides a test-bed for demonstrating SS principles and allows researchers to evaluate their own subsystem design concepts. The DSSS system, designed as a one-way link in the 420-450-MHz band, is constructed to operate in accordance with FCC rules and regulations pertaining to the Amateur Radio Service (Part 97). The system directly modulates an FM modulated carrier with the PN code sequence. The criteria used for evaluation are synchronization time, processing gains, and probability of bit-error rate. The receiver lacks good sensitivity. The fundamental concepts of DSSS were evaluated and the measurements agreed favorably with theoretical values