Moctar Mouhamadou

Interference Supression of the Linear Antenna Arrays Controlled by Phase with Use of Sqp Algorithm

The performance of mobile cellular radio networks is limited by the level of cochannel interference that can be tolerated. The use of antennas arrays is very helpful in enhancing the performance and capacity of the wireless communication system. This paper presents a method for antenna pattern synthesis that suppress multiple interfering narrow or wide band signals while receiving the desired signal by controlling only the phase. Excitation phases are computed using the Sequential Quadratic Programming (SQP) technique. This method transforms the nonlinear minimization (or maximization) problem to a sequence of quadratic subproblems, based on a quadratic approximation of the Lagrangian function. 252 Mouhamadou et al.

Compact and Multiband Dielectric Resonator Antenna With Pattern Diversity for Multistandard Mobile Handheld Devices

A compact multiband antenna system using a dielectric resonator antenna (DRA) is presented in this paper. Designed to be integrated in a tablet, it is not only heavily miniaturized (λ0/15×λ0/38×λ0/94 at 800 MHz), but also able to cover three frequency bands for different wireless applications (DVB-H, WiFi and WiMAX). Since a reconfigurable radiation pattern can result in an improved quality and reliability of wireless links, two DRAs have been integrated to implement this feature on the three frequency bands. These improvements are demonstrated by the presentation of the correlation coefficient and the effective diversity gain, both measured in a reverberation chamber. The experimental measurements are in very good agreement with the simulated ones. Good overall performances are obtained, and the requirements of all three applications are perfectly met. Moreover, the antenna operative frequencies are independent of the ground plane dimensions, making this system a very good candidate for all kinds of mobile devices.

3GPP Channel Model Emulation with Analysis of MIMO-LTE Performances in Reverberation Chamber

Emulation methodology of multiple clusters channels for evaluating wireless communication devices over-the-air (OTA) performance is investigated. This methodology has been used along with the implementation of the SIMO LTE standard. It consists of evaluating effective diversity gain (EDG) level of SIMO LTE-OFDM system for different channel models according to the received power by establishing an active link between the transmitter and the receiver. The measurement process is set up in a Reverberation Chamber (RC). The obtained results are compared to the reference case of single input-single output (SISO) in order to evaluate the real improvement attained by the implemented system.

A New CLEAN Algorithm for Angle of Arrival Denoising

In a previous work, a novel technique for angle of arrival (AOA) measurement was proposed. This technique consists of sweeping the angular domain with one antenna, step by step, such that at each measurement step the received signal voltage at the rotating antenna (sensor) is measured. The signal voltage vector is the convolution between the antenna electric field pattern and the AOAs (magnitude and phase) of the incident wave. In this letter, a denoising CLEAN algorithm is modified and applied to this technique in order to eliminate spurious peaks and accurately find the AOAs of incoming waves. A set of measurements is made to evaluate the proposed algorithm. The results show the effectiveness of the denoising algorithm in reducing the noise level; a high angular precision in measured AOAs is noticed.

Triband Compact Antenna for Multistandard Terminals and User's Hand Effect

A novel compact wideband triband antenna for mobile terminals based on PIFA element is proposed. The antenna operates at the following frequency bands: Wireless-LAN 802.11 b, g, a and WiMAX 3.5 GHz. The antenna was studied by means of numerical simulations as well as the ground plane dimensions and users hand effects. The overall size of the radiating element which is 1.8×1.54×9 mm makes it suitable for use in terminals and appropriate to integrated as an internal laptop antenna. The measured bandwidths show that the proposed antenna can cover three bands (2.39–2.48 GHz), (3.36–3.76 GHz), and (4.7–6.3 GHz) and the total efficiency is better than 90%. The radiation patterns of the antenna were carried in an anechoic chamber and are given to demonstrate the antennas performance.

On the Cooperative and Non-Cooperative Relaying in WiMAX Communication Systems

This paper deals with relaying techniques in WiMAX communication system. Different cooperative and non-cooperative schemes are investigated and compared over a complete 802.16 WiMAX-OFDM chain. Realistic channel impulse responses are used. Measurement of some propagation conditions feeds the WINNER channel model in order to generate the channel coefficients belonging to different links. Besides, real characteristics of an industrial relay are taken into account. Simulation results show that the performances of the relaying techniques, at constant relay gain, depend essentially on the propagation conditions pertaining to the different links in the network. They depend also on the received powers from the direct link and the relayed link. Finally, two intuitive power allocation schemes are examined when automatic gain controller is available at the relay.

Simulation of Smart Antenna System using ADS Co-Simulate with Matlab: Direction of Arrival estimation and Interference Canceller

In this paper, we present the computer simulation for adaptive antenna system to improve the signal-to-interference ratio by steering beam pattern to track the user signal while maintaining placing the null in the direction of interference signal by updating the weight coefficients using SQP algorithm. In Advanced Design System (ADS), the signal processing co-simulates with either circuit envelope or transient simulators. Antenna and propagation models simulate the effects of radio channel, including signal fading and path loss

Performance measurements of Modified LINC transmitter for wireless applications

The LINC (Linear amplification with Nonlinear Components) transmitter efficiency is not degraded only by the power combiner, but also by the SCS (Signal Component Separator) architecture. In this article, we propose a Predistorted Modified SCS (PM-SCS) architecture and we present the measurement platform dedicated to the LINC system study. Measurement results show an efficiency improvement from 39.60% for regular LINC to 63.80% for PM-LINC.

Complex weight control of array pattern nulling: Research Articles

The new generation of System-on-Chip (SoC) incorporates digital, analogue, RF/microwave and mixed-signal components. Such circuits impose to reconsider the traditional design methods. Mixed-signal designers need novel design methodologies which will have to include accurate behavioral libraries of devices and processes into hierarchical design flows. Thus, this paper describes a behavioral modeling approach which generates neuro-fuzzy-based models for RF/microwave devices. The models, so obtained, can be easily integrated into a VHDL-AMS simulator. This modeling approach is applied to a microwave tunable phase shifter and it is illustrated by the development of a VHDL-AMS model library for RF/microwave applications.

Technique based on SQP algorithm for Antenna Array Pattern Synthesis: Beam and Null Steering

In this paper, a new technique for pattern synthesis of linear antenna arrays with prescribed nulls to the interference directions while at the same time controlling the maximum side lobe levels and null dept level by varying the amplitude-only and both the complex weights of each array element is presented. This technique is based on the sequential quadratic programming (SQP) algorithm. This method is a versatile for solving the general nonlinear constrained optimization problems. The fundamental principle of sequential approximation is to replace the given nonlinear problem by a sequence of quadratic subproblem that are easier to solve