Array Noise Matching—Generalization, Proof and Analogy to Power Matching

In array antennas with residual coupling, the signal-to-noise ratio (SNR) can suffer from noise coupling from the inputs of the low noise amplifiers (LNAs) to the other channels. As shown recently, the lost SNR can be retrieved by changing the individual matching circuits. This paper explains the theory behind array noise matching and generalizes it for non-equal LNAs and non-reciprocal sources. It also shows an analogy between noise matching of an array and power matching into the complex conjugate of the optimum noise impedances of the individual LNAs. This turns out to be useful for practical noise matching of mutually coupled arrays. In some cases it becomes impossible to reach the theoretical optimum matching with passive matching networks. Therefore an additional boundary condition will be introduced and investigated.