In the present paper convergence characteristics of Sample Matrix Inversion (SMI) and Least Mean Square (LMS) adaptive beam-forming algorithms (ABFA) are compared for a Smart antenna System (SAS) in a multipath environment. SAS are employed at base stations for radiating narrow beams at the desired mobile users. The ABFA are incorporated in the digital signal processors for adjusting the weights to adjust the beam on the desired user and generate null in the direction of interferer. SMI and LMS algorithms are used with SAS for improving the performance of wireless communication system by optimizing the radiation pattern according to the signal environment. This can enhance the coverage and capacity of the system in multipath environment by reducing the interference and noise. The data rate can be enhanced by mitigating fading due to cancellation of multipath components. In this paper, optimization capabilities of SMI and LMS are considered by changing the parameters. The results reveal improvement in gain, speed of convergence and reduction in side-lobe level.

In this study, a novel blind adaptive algorithm with discrete periodic variables is introduced. The proposed discrete periodic variable algorithm (DPVA) has been applied to the new designend 7-element antenna array. The DPVA is based on minimizing the output power to steer null (or nearly null) gain in the direction of interference. Discrete phase shift leads to the use of hybrid phase shifter in practice and thus reduction of implementation costs. In addition, the proposed algorithm has low computational complexity. Results show that DPVA has fast and reliable convergence. It is converged within less than 400 iterations and less than 1 millisecond time duration. The null depth created by this algorithm is 90 \(dB\) which is an indication of pure cancellation of the interference. Furthermore, the effect of a number of interference sources is investigated. It is shown that the null depth is decreased by the increase of interference sources. In the studied 7-element array, increasing the interference sources up to 6 decreases the null depth to 20 \(dB\).

In this paper a low profile, low-cost Smart antenna which has a high gain and high radiation pattern diversity is presented. This antenna is actually an advanced ESPAR antenna which is made up of a “ short monopole” and 12 “ folded monopoles” . The short monopole is in the center and is used as the driven element and the 12 folded monopoles are used as parasitic elements. The coupling between the driven element and the parasitic elements creates a capacitive load for the driven element, which causes the antenna to become low-profile. By turning on and off 12 "PIN diodes" at the bottom of the parasitic elements, the beam can be rotated. The dimensions of the proposed antenna fabricated in the S band are reduced by 30% compared to the conventional Smart antennas of this band. The antenna height is less than 24mm (0. 186λ @ 2. 4 GHz), the front to back ratio is 22. 4dB and antenna's maximum gain at 2. 4GHz is 8. 26dBi.

In this paper, the design and implementation of plasma antenna array with beam forming is discussed. The structure consists of a circular array of plasma tube enclosed in a unipolar UHF band monopole antenna. Beam forming is possible by stimulated plasma tubes. The combination of the above antenna with plasma excitation controller makes a beam forming Smart antenna. An experimental model in UHF band is fabricated that shows a good agreement between the simulated and measured results.