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The paper analyses the performance of quasi-coherent combining of signals from a small circular antenna array in a Rician fading indoor multipath channel at microwave or millimetre wave frequencies. Instead of maximum ratio combining, where the complex weighting of signals results in an optimum for a single frequency, the proposed concept is based on quasi-coherent combining of the dominant component of the multipath signal of each antenna. The resulting channel impulse response, shows less delay spread and a higher signal to noise ratio. A scheme for this combining technique is given for a coherent binary phase shift keying receiver and evaluated by simulation. Cumulative BER results for the Rician channel and normalised bit rates are presented for circular arrays of 1, 2 and 4 antennae with a diameter of one wavelength. It is shown that this combining technique results in a significant improvement of the BER or application of higher bit rates,.

The paper analyses the performance of a dual-signal receiver in a Rician fading channel. The receiver is designed for simultaneous reception of two narrowband binary phase shift keying (BPSK) modulated co-channel signals, e.g. two desired signals, of different strength. The dual signal receiver consists of two demodulators. The principle of operation is based on separation of both signals using the data signal of the large signal which is estimated by the first demodulator. After cancellation of the large signal, the small signal is demodulated. The bit error rate (BER) and receiver outage performance in the Rician fading channel with additive white gaussian noise are derived for both signals. Numerical results are presented for two receiver structures with different second demodulator: (i) the coherent BPSK demodulator; (ii) the differentially coherent (DPSK) demodulator. It is shown that the dual-signal receiver outperforms the conventional receiver significantly, especially in the interference limited channel with high signal-to-noise ratio.