Broadband Adaptive Beamforming of Conformal Arrays for Wireless Communications Based on Generalized Sidelobe Canceller

Conformal arrays are increasingly used in recent wireless communication systems due to their flexibility in mounting on arbitrary surfaces. Many of such systems require working with broadband signals. However, designing conformal arrays has been limited mostly to pattern synthesis techniques due to the complexity imposed by the different contribution of individual antenna patterns to the overall array response. Such pattern synthesis techniques greatly confine the application of the beamformer in dynamic environments since they are fundamentally non-adaptive data independent methods. In this article, the conventional space-time broadband generalized sidelobe canceller (GSC) is used to develop an adaptive method for an arbitrarily-shaped conformal array. The constraint matrix assumed for the main beam of the conventional GSC structure is modified to incorporate the pattern of each individual element. This treatment allows the element responses to be directly involved in the weight adjustment algorithm and contribute to the array overall response without having any additional complexity. The proposed method can handle different types of the constraints, although the analysis presented here is based on the angle-frequency domain constraints which nevertheless eliminates the presence of the pre-steering delays and ensures a frequency invariant beampatterm required for wideband beamforming. The simulation results which are presented for a typical cylindrical array show that the proposed method can create the desired broadband beampattern with high performance and in an adaptive manner.