This paper presents a dual-band planar antenna array for ISM band applications (2.4 GHz and 2.45 GHz). This antenna is proposed for indoor applications and enables adaptive beamforming and angle of arrival (AOA) estimation. An adaptive beamforming algorithm is applied for a planar antenna array, which is able to steer its main beam and nulls in azimuth and elevation planes over a wide frequency band. Planar antenna array operates as a spatial filter in 3D space, processing the received signals with weighting schemes. A planar antenna array is designed for AOA estimation in azimuth and elevation planes by using MUltiple SIgnal Classification (MUSIC) based on subspace algorithm. The Base Station (BS) equipped with this planar antenna is preferred to be at the center position on the room ceiling to cover all sectors of the room. It is designed to use four directional triangular elements arranged to form a square planar antenna array. Planar antenna with four elliptical slotted triangular elements (PAFESTE) is used to obtain optimal directivity in four directions in azimuth plane with specific orientation of 30? in elevation plane. It is characterized by half power beamwidth in elevation plane of about 60? and half power beamwidth in azimuth plane of about 90?.
Smart antenna (SA) is beam-steering antenna which represents an emerging technology to improve the performance of wireless networks [
Adaptive antenna array is composed of several antenna elements; each element is weighted by pre-defined algorithm. Adaptive antenna array optimizes this algorithm according to user’s requirement, so that the output matches with signals of interest in forming the best antenna pattern. This antenna system is able to detect the existence of the signal source automatically, forms the main beam in the direction of signals of interest, and produces notches in the direction of signals of interference [
This paper presents analysis of 4-antenna elements arranged in a 2 × 2 rectangular planar antenna array. It also studies the impact of the different array elements on the interference signals. Dual-band planar antenna array, namely planar antenna with four elliptical slotted triangular elements (PAFESTE) is proposed to cover the room with frequency and radiation pattern diversity. This prototype is designed to address the challenges of indoor applications. The antenna is intended to augment a wireless devices operating as coordinator or base station (BS). The proposed design is optimized to be installed on the ceiling of any large indoor space. The antenna is implemented by combining four patches pointing to different directions. The radiation pattern direction of PAFESTE is designed to be in direction of 30˚ in elevation plane with a half power beamwidth (HPBW) of 60˚ in elevation plane and HPBW of 90˚ in azimuth plane. Four beams would cover the four sectors of the room. The system can allocate a target by estimating both the azimuth
A planar antenna array with four elliptical slotted triangular elements (PAFESTE) is proposed as a simple configuration with a minimum number of elements to cover all sectors inside a room. The proposed square planar antenna array consists of identical isosceles four triangular elements of identical characteristics. These elements are printed on the top of a square grounded dielectric slab. The HFSS model of PAFESTE with inner and outer dimensions is shown in
Each isosceles triangular patch antenna exhibits a radiation pattern with a peak at 30˚ in elevation plane and a maximum gain of 0.2166 dBi at 2.4 GHz. The peak of the radiation pattern is at 10˚ in elevation plane and the maximum gain is −0.0613 dBi at 2.45 GHz as shown in
At 2.4 GHz the proposed antenna is characterized by half power beamwidth in elevation plane of about 60˚ and half power beamwidth in azimuth plane of about 90˚ as shown in
Linear arrays lack the ability to scan in 3-D space. However it is necessary for portable devices to scan the main beam in any direction of
signal processing. This structure can perform beamforming in azimuth and elevation angles in 3-D space.
The planar array PAFESTE is considered as a rectangular planar antenna array in the x-y plane. It can be viewed as M linear arrays of N elements or as N linear arrays of M elements creating
where
The analysis in [
where
A complex quantity
where W is the weight vector, T denotes transpose matrix operation and
In an adaptive array, the weights are adapted by minimizing certain criterion to maximize the signal-to-interfe- rence plus noise ratio (SINR) at the array output [
The analysis of adaptive beamforming in [
For adaptive beamforming, each element output of the
and due to the ith interfering signal
where
The total array output is given by:
There are eight unknowns to be determined, the four real parts and the four imaginary parts of the four complex weights such that the
For convenience, we define the
where both
Furthermore, the four matrices
From Equation (11), solution to Equation (9) is given by
The
where both
The proposed antenna array has a half power beamwidth
The gain of each element is modeled using the following parametric function [
where
T the incoming signal of interest arrives is assumed to be at angle
If the
The AOA estimation algorithms are directly associated with the received signals. Data from an array of sensors are collected, and the objective is to locate point sources assumed to be radiating energy that is detectable by the sensors. Mathematically, such problems are modelled using MUSIC (MUltiple SIgnal Classification), which is a high resolution direction finding (DF) algorithm [
An antenna array is composed of identical elements with directional radiation pattern; each element receives a time-delayed version of the same plane wave with wavelength
For the case where V uncorrelated sources transmit signals to
where
The array response matrix
For a set of data observations L:
where X and
The incident signals are assumed to be sinusoidal baseband frequency modulated signals of uncorrelated sources with different phase shift impinge on the proposed
where H denotes Hermitian (or complex-conjugate transpose) matrix operation. The signal subspace and the noise subspace are gotten by eigendecomposition of the autocovariance matrix of the received data. The MUSIC spatial spectrum equation in [
A new smart antenna “PAFESTE” is introduced to be used in wireless applications in the frequency range from 2.4 GHz to 2.45 GHz bands. The PAFESTE is a planar antenna array, which is designed to be applicable for indoor applications. The proposed antenna is simulated by using HFSS. An adaptive beamforming algorithm is applied for the proposed planar antenna array, which is able to steer its main beam and nulls in azimuth and elevation planes. The subspace based technique, MUSIC algorithm is used to estimate the direction of arrival of the signal that impinges on the PAFESTE. The adaptive beamforming algorithm exhibits a good accuracy and precision results in azimuth and elevation planes, where the shift between the peak of the desired signal and the interferers is about 15 dB for the HPBW of 90˚ and 10 dB for the HPBW of 60˚, so there are no dead points and the planar antenna array operates as a spatial filter in 3D space.
R. Elsamnty,A. M. Attiya,E. A. F. Abdallah,A. H. Ammar, (2016) Beamforming and Angle-of-Arrival Estimation of Square Planar Antenna Array. Open Journal of Antennas and Propagation,04,13-23. doi: 10.4236/ojapr.2016.42002