Null steering and pattern control in linear phased arrays

Abstract EN

The principles of phased and adaptive antenna arrays have recently been applied to the design of smart antennas used in mobile and wireless communications.

The purpose is to design an antenna system capable of adjusting its array pattern according to the signal environment, in order to enhance the desired signal and suppress interference.

The goal of such antenna systems is to intelligently steer the main beam to the direction of the user, steer some array nulls towards the interfering signals and suppress the array pattern in the directions of possible grating lobes.

In this paper, we use genetic algorithms to control the array pattern in the directions other than the main beam, reduce the excessively large side lobes that appear when the inter-element spacing is comparable to the wavelength and steer array nulls towards the interfering signals.

The results indicate that nulls can be steered towards the directions of undesirable signals for conventional separation of X/2.

Also, large amplitude side lobes can be controlled and brought down to the level of the array prescribed side lobe level, when the main beam is steered away from the broadside direction or a comparable separation to the wavelength is used.

The control of the array pattern may be achieved by one of many different techniques.

Amplitude and phase (complex weights) variations, phase only, amplitude only or element position perturbations.

The element position perturbations have been used in this work to demonstrate the effectiveness of this technique.