Analysis and design of a frequency-hopped spread spectrum transceiver for wireless personal communications

Personal Communications Services (PCS) require low-power radio technologies. One such transceiver architecture employing frequency-hopped spread spectrum techniques is described. Low power and robustness are two keys to a wireless personal communications device. A frequency-hopped code-division multiple access (CDMA) scheme is chosen over other multiple access methods because it provides an inherent immunity to multipath fading and the signal processing is performed at the hop rate, which is much lower than the chip rate encountered either in a direct-sequence CDMA or time-division multiple access (TDMA) system. This potentially results in much lower receiver power consumption. Other features such as antenna diversity with equal-gain combining and sequential hop combining are also incorporated into the transceiver design to achieve robust wireless digital data transmission over fading channels. A direct-conversion architecture from radio frequency (RF) to baseband reduces the overall power consumption by eliminating intermediate frequency (IF) components. High-rate frequency hopping with frequency-shift keying (FSK) modulation is implemented using a direct digital frequency synthesis technique. A multiplierless correlation FSK detector, suitable for direct-conversion receivers, has been designed for quadrature noncoherent detection. Robust acquisition algorithms based on energy detection and pattern matching and tracking architectures using digital phase-locked loops are also developed for system synchronization. The proposed transceiver is well-suited for PCS applications and other portable wireless communications.