Analysis and modelling of adaptive antennas for a handheld terminal in the presence of a person

摘要

Multipath fading and human body influence affect the performance of a Low Earth Orbit Satellite (LEOS) handheld terminal. In this research, the effectiveness of optimum combining is compared with selection diversity and omni-directional antenna systems. By using the electric field and magnetic field antennas, zero correlation can be provided. In the presence of interference, adaptive antennas can nullify the interference. In the absence of interference, adaptive antennas can maximise the final Signal to Noise Ratio (SNR). In this case, an adaptive antenna is the same as a maximum ratio combiner. An adaptive antenna system provides a 2.0dB gain on average when its performance is compared with the selection diversity system. The adaptive antenna system also provides a 9.5dB gain on average when its performance is compared with the omni-directional antenna system. Finally, adaptive antennas can automatically resolve the phase ambiguity effect, so that differential coding is not required. Therefore, an extra 3dB gain can be obtained.