Research On Wireless Communications Based On Surface Acoustic Wave Technology

The work is supported by the 863 National High Technology Programme, National Natural Science Fund, Tianjin scientific and technical development plan and key scientific and technological research of Science and Technology Division, the Tianjin Science and technology support key project plan.According to the target of the above projects, theoretical research and simulation experiments are carried out on Surface Acoustic Wave (SAW)-based wireless communications, inclusive of signal processing technology for SAW device, SAW-based Ultra-Wideband (UWB) system, SAW-based RFID meeting UWB regulations using chirp spread spectrum encoding, and SAW-based multi-channel gas detection system, respectively. Among all these studies, it is especially noticeable that the introduction of UWB regulations into SAW-based RFID leads to a realization of decreased loss compared with that of narrow-band SAW-based RFID and that of chirp spread spectrum encoding for SAW RFID offers a promising way in distinguishing a variety of multi-sensor system. Application of SAW technology in the field of wireless communications is efficiently studied. The achievements for the work done are due to be summarized as follows:1. The basic principle and current development with relevant standards of UWB wireless communications,RFID technology were demonstrated. An overview of application and prospects for RFID in the field of UWB spread spectrum system,RFID system were illustrated. The booming for SAW technology is in fine favor of the subsequent research from whatever theoretical perspectives or physical realizations.2. The fundamental block and working principle were depicted for SAW devices. Signal processing using SAW devices is studied. An overview and mathematical simulations were made focusing on varied types of integrity transducers and reflectors. Simulations based on signal processors algorithms using SAW were carried out for linear and nonlinear devices, respectively. Mathematical modeling was constructed for SAW signal processing, which renders a further research on the spread-time application using SAW device based on FFT theory. Contents for this section lays a foundation for chirp UWB,multi-user detection for chirp UWB,spread-time algorithms for UWB,UWB SAW RFID and gas detection systems.3. Profound research on linear spread spectrum UWB system using SAW device was dealt with. The parameters that affected the system including cross-correlation measurement, overlapping rate were studied using mathimatical deduction. Monto-Carlor simulations were carried out to specify system performance. Simulation results show that the results are in exact accordance with theoretical ones. This system is the fundament for spread-spectrum, spread-time and multi-frequency sampling rates UWB algorithms.4. Development of SAW technology in UWB wireless communications is illustrated. A novel multi-access UWB system is proposed based on multi-frequency rates chirp signals. This proposal outdoes in the practicability performance comparing with traditional multi-chirp UWB system, which allocates for each user randomly a specific chirp-rate filter, making it intensively difficult to be realized for analogy devices. Besides, a great deal of further and more profound theoretical analysis on BER performance are made in terms of overlapping for chirp signals, based on former contributions which focused on merely chirp-based narrowband wireless communications. Study in this chapter offers a solid foundation for SAW-based UWB system, which may take the place of Impulse Radio (IR) UWB in the foreseen years. Considering for narrow-band interference for UWB, spread-time algorithms constructed in section Two was applied. Various from the ever existed spread-time communications, multi-frequency rate chirp filters were proposed to mitigate MAI simultaneously. This chapter contributes to the mitigation of narrow-band interference and multi-access interference (MAI) parallelly using low-cost, simpler construction than the traditional multi-user detection UWB system.5. Current research on SAW-based RFID was generalized from the aspects of transmission waveforms, tag encoding and so on. It is very firstly proposed a SAW-based RFID meeting UWB regulations making use of multi-chirp spread spectrum to offer multi-access proposal. This system outdoes other narrow-band SAW RFID in the low-path-loss and inclined to separation for interfering tags. Exhaustive calculations were dealt with for signal processing of SAW-based RFID meeting UWB regulations system.6. Gas detection based on SAW technology is studied. It is practical to detect gas and temperature simultaneously consisted of a two-channel SAW block. This designation mitigates the inaccuracy during detection as a result of the sensitiveness to temperature for SAW equipment.7. Gas detection algorithms based on SAW UWB system was proposed. Parameter estimations modeling were constructed. Time-delay algorithm owing to domestic temperature change is employed and corresponding performance simulation results were given. Maximum likelihood algorithms were used.