This paper describes a 256 kbit/s spread-spectrum system designed for indoor wireless applications with no direct path. The key element of the receiver is a differential phase shift keying (DPSK) surface acoustic wave (SAW) matched filter, and its design is described. The excellent performance of such a system is displayed using the case of mobile robotics inside a nuclear plant. Good agreement with theoretical results is also illustrated. Finally, we propose a bandlimited scheme allowing a very simple implementation of diversity with only one DPSK SAW demodulator.
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