Comparison of two maximal ratio combining techniques in antenna arraying

When signals from a user (fixed or mobile) are received at multiple antennas, the signals can be arrayed to increase the signal-to-noise ratio (SNR) of the received signal. This article describes two maximal ratio combining techniques referred to as full spectrum combining (FSC) and complex symbol combining (CSC), and then compares them in terms of the achievable arraying gain. Although the performance of these techniques is derived for the case of binary phase shift keying (BPSK) signalling in an additive white Gaussian noise channel, the analytical techniques here are applicable to other modulations and channels. The paper also addresses the use of symbol SNR degradation and symbol SNR loss as system performance measures. It is shown that degradation and loss are equal at weak signal levels but degradation is a lower bound for loss when the signal is strong. The telemetry arraying techniques described are applicable to any phase modulated signal. We assess the deep space communication channel performance scenario where the weakest signals ever are detected.