Modified constant modulus algorithm for digital signal processing adaptive antennas with microwave analog beamforming

This paper proposes a novel algorithm, called modified constant modulus algorithm (M-CMA), which is able to give adaptability to microwave beamforming phased array antennas. Since microwave analog beamformers basically require much less RF devices than digital beamformers, microwave analog beamformers based on M-CMA, that is, adaptive microwave beamformers, can be cheaply fabricated. Therefore, they are much suitable for mobile communication systems where both miniaturization and lowcost are required for the mobile terminals. Actually, M-CMA obtains a gradient vector by combination of analytical calculation and perturbing the microwave beamforming control voltage. Though M-CMA is implemented with a digital signal processor, M-CMA controls the microwave analog beamformer by utilizing the gradient vector. The microwave analog beamformer based on M-CMA is analyzed to have the following characteristics: 1) The beamformer can point its main beam to the desired direction in additive white Gaussian noise (AWGN) channels and 2) although the beamformer may possibly fail in ill solutions in co-channel interference (CCI) channels, M-CMA can converge to the optimum solution when the desired direction is roughly a priori known.