Chaotic Pulse-Position Baseband Modulation for an Ultra-Wideband Transceiver in CMOS

Abstract

A CMOS impulse radio transceiver that uses chaotic pulse-position modulation for ultra-wideband (UWB) communications is designed. While the conventional direct-sequence spread-spectrum (DSSS) system dither the time delay between impulses by a pseudorandom number generator, chaotic modulation dithering uses a predictable but wideband nonlinear function, resulting in significant improvements in spectral spreading. The nonlinear functions implemented in the transmitter and receiver use a tent map, requiring only a voltage-to-time and time-to-voltage converter. A R-S latch enables the parallel implementation of two consecutive states of the tent map. Due to the predictable nature of the nonlinear mapping functions, receiver synchronization time is achieved in Order (0) time, as opposed to the conventional DSSS correlating receivers. Implemented in a 0.25 μm CMOS technology, the transceiver achieves an average data rate of 25 Mbps and a BER <; 10e-9, while sending 0.4-ns wide UWB baseband impulses.