Switching Mode Optimisation for Channel Sounding with Switched Multiple-Element Tx and Rx Antennas

The capability of the ISI-SAGE algorithm in estimating high Doppler frequency (DF) has been investigated for channel sounding using switched multiple-element arrays at the Tx and the Rx. It is shown that with this setting it is possible to estimate DF with an absolute value equal to half the rate with which the pairs of Tx and Rx array elements are switched (switching rate), rather than half the rate with which any fixed pair is switched (cycle rate) as commonly believed. This implies that the maximal absolute DF that can be estimated with a channel sounder using switched antenna arrays is similar to that achievable with an equipment performing parallel sounding technique. Recent studies further reveal that when the DF estimation range is extended from minus to plus half the switching rate, so-called modulo-type switching modes applied to uniform linear and planar arrays lead to an ambiguity in the estimation of the DF and the directions. The switching mode of a switched array is the order with which the array elements are switched. Theoretical and experimental investigations show that the ambiguity problem can be easily avoided by appropriately selecting the switching modes and the Tx and Rx. (Xuefeng Yin, Bernard H. Fleury)