In this paper, we present an adaptive beamforming scheme for smart antenna arrays in the presence of several desired and interfering signals, and additive white Gaussian noise. As compared with standard schemes, the proposed algorithm minimizes the noise and interference contributions, but enforces magnitude-only constraints, and exploits the array-factor phases in the desired-signal directions as further optimization parameters. The arising nonlinearly-constrained optimization problem is recast, via the Lagrange method, in the unconstrained optimization of a non-quadratic cost function, for which an iterative technique is proposed. The implementation via artificial neural networks is addressed, and results are compared with those obtained via standard schemes.
"Evaluation of a Neural-Network-Based Adaptive Beamforming Scheme with Magnitude-Only Constraints," Progress In Electromagnetics Research B,
Vol. 11, 1-14, 2009. doi:10.2528/PIERB08092303
2. Bach-Andersen, J., H. Boche, A. Bourdoux, J. Fonollosa, T. Kaiser, and W. Utschick (eds.), Smart Antennas: State of Art, Hindawi, New York, NY, 2004.
3. Rabideau, D. J., "Clutter and jammer multipath cancellation in airborne adaptive radar," IEEE Trans. Aerospace Electron. Syst., Vol. 36, 565-583, 2000. doi:10.1109/7.845243
4. Ray, J. K., M. E. Cannon, and P. Fenton, "Adaptive GPS code and carrier multipath mitigation using a multiantenna system," IEEE Trans. Aerospace Electron. Syst., Vol. 37, 183-195, 2001. doi:10.1109/7.913677
5. Mouhamadou, M., P. Vaudon, and M. Rammal, "Smart antenna array patterns synthesis: Null steering and multi-user beamforming by phase control," Progress In Electromagnetics Research, Vol. 60, 95-106, 2006. doi:10.2528/PIER05112801
6. Fakoukakis, F. E., S. G. Diamantis, A. P. Orfanides, and G. A. Kyriacou, "Development of an adaptive and a switched beam smart antenna system for wireless communications," Journal of Electromagnetic Waves and Applications, Vol. 20, 399-408, 2006. doi:10.1163/156939306775701722
7. Mukhopadhyay, M., B. K. Sarkar, and A. Chakraborty, "Augmentation of anti-jam GPS system using smart antenna with a simple DOA estimation algorithm," Progress In Electromagnetics Research, Vol. 67, 231-249, 2007. doi:10.2528/PIER06090504
8. Mahmoud, K. R., M. El-Adawy, S. M. M. Ibrahem, R. Bansal, and S. H. Zainud-Deen, "A comparison between circular and hexagonal array geometries for smart antenna systems using particle swarm optimization algorithm," Progress In Electromagnetics Research, Vol. 72, 75-90, 2007. doi:10.2528/PIER07030904
9. Bresler, Y., V. U. Reddy, and T. Kailath, "Optimum beamforming for coherent signal and interferences," IEEE Trans. Acoust. Speech Signal Process., Vol. 36, 833-843, 1988. doi:10.1109/29.1594
10. Schmidt, R. O., "Multiple emitter location and signal parameter estimation," IEEE Trans. Antennas Propagat., Vol. 34, 276-280, 1986. doi:10.1109/TAP.1986.1143830
11. Roy, R. and T. Kailath, "ESPRIT — Estimation of signal parameters via rotational invariance techniques," IEEE Trans. Acoust. Speech Signal Process., Vol. 37, 984-995, 1989. doi:10.1109/29.32276
12. Haykin, S., Neural Networks, Mac-Millan, New York, NY, 1994.
13. Rayas-Sanchez, J. E., "EM-based optimization of microwave circuits using artificial neural networks: The state-of-the-art," IEEE Trans. Microwave Theory Tech., Vol. 52, 420-435, 2004. doi:10.1109/TMTT.2003.820897
14. Ayestaran, R. G., F. Las-Heras, and J. A. Martinez, "Non uniform-antenna array synthesis using neural networks," Journal of Electromagnetic Waves and Applications, Vol. 21, 1001-1011, 2007.
15. Mohamed, M. D. A., E. A. Soliman, and M. A. El-Gamal, "Optimization and characterization of electromagnetically coupled patch antennas using RBF neural networks," Journal of Electromagnetic Waves and Applications, Vol. 20, 1101-1114, 2006. doi:10.1163/156939306776930240
16. El Zooghby, A. H., C. G. Christodoulou, and M. Georgiopoulos, "Neural network-based adaptive beamforming for one-and two-dimensional antenna arrays," IEEE Trans. Antennas Propagat., Vol. 46, 1891-1893, 1998. doi:10.1109/8.743843
18. Fletcher, R., Practical Methods of Optimization, Wiley, New York, NY, 1990.
19. Haupt, R. L. and D. H. Werner, Genetic Algorithms in Electromagnetics, Wiley-IEEE Press, Hoboke, NJ, 2007.
20. Park, J. and I. W. Sandberg, "Universal approximation using radial basis function networks," Neural Comput, Vol. 3, 246-257, 1991. doi:10.1162/neco.19126.96.36.199
21. Chen, S., C. F. N. Cowan, and P. M. Grant, "Orthogonal least squares learning algorithm for radial basis function networks," IEEE Trans. Neural Networks, Vol. 2, 302-309, 1991. doi:10.1109/72.80341
22. Higham, D. J. and N. J. Higham, MATLAB Guide, SIAM, Philadelphia, PA, 2005.
23. Zhang, M., S. Xu, and J. Fulcher, "Neuron-adaptive higher order neural-network models for automated financial data modeling," IEEE Trans. Neural Networks, Vol. 13, 188-204, 2002. doi:10.1109/72.977302
24. Rastko, R. and F. L. Lewis, "Neural-network approximation of piecewise continuous functions: Application to friction compensation," IEEE Trans. Neural Networks, Vol. 13, 745-751, 2002. doi:10.1109/TNN.2002.1000141