multipath propagation; signal strength; interference; personal wireless communication systems
In personal wireless communications systems, multipath propagation has a significant effect on system design and performance. Signal strength fading caused by destructive interference between multiple replicas of the signal of interest arriving at the receiver over different paths often is the limiting factor in system range/fidelity. Antenna diversity is one technique that can be used to help overcome multipath fading. This paper presents a description of experiments, data processing, and results used to evaluate the diversity performance of three candidate dual-antenna handset configurations: two side-mounted planar-inverted F antennas (PIFAs), a back-mounted PIFA with a top-mounted helix, a top-mounted PIFA, and a "flip" monopole. In particular, the indoor industrial, scientific, and medical (ISM) band (902-928 MHz) propagation channel was of interest. These experiments did not include operator proximity effects, and in these tests, the dual-antenna handset remained stationary while the transmitter was moved along predetermined indoor paths. The issue of data normalization for extraction of fast fading behavior from measured data is addressed, with results showing its effect on observed correlation presented. Also, measured indoor fading distributions are presented and seen to fit the Rician and Rayleigh models well. From the diversity results presented, it is seen that the three proposed dual-antenna handsets yield sufficient decorrelation to warrant consideration for use in diversity systems.
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