To decrease the Inter-Symbol Interference (ISI) for the frequency selective channel at low SNR, a spectrum combining technique based on average phase from the multiple sensors without synchronization is proposed. The combining signal's phase will converge to the average phase instead of the value of the fixed branch to meliorate adverse effect on the demodulation performance caused by the single nonlinear phase characteristic. Finally the simulations show that the spectrum combining technique

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... n achieve a substantial performance improvement without the symbol timing synchronization. Therefore it could be regarded as a useful combining technique in the frequency selective channels at low SNR, especially when synchronization is difficult to achieve.