On nonlinear beamforming for interference cancellation

Nonlinear beamforming based on the method of radial basis functions (RBF) is proposed to combine with constant modulus algorithm (CAM) for interference cancellation. First, a signal space is constructed from the input array data vectors utilizing RBF. In our case, a set of exponential functions are used to transform the Euclidean norm of the input array data vectors into the signal space. Then, CMA is employed to eliminate the interference. Both Gaussian and non-Gaussian noise are considered in the experiment. The simulation results indicate that this scheme is effective and robust in terms of interference cancellation. A deep null can be formed to the direction of interference. Furthermore, these results are compared with that of digital beamforming (DBF) with CMA based on FFT technique. The comparison shows that a DBF array antenna with CMA based on the method of RBF outperforms its counterpart based on FFT technique, a widely used linear beamforming technique