Yann Mahe

Pattern Reconfigurable Cubic Antenna

A new single-feed reconfigurable antenna for pattern diversity is presented in this paper. The proposed structure is based on a metallic cubic cavity which radiates through rectangular slots. The pattern reconfiguration is achieved with PIN diode switches by short-circuiting slots in their center. The designed antenna can switch between three different radiation patterns which radiate in a 4pi steradian range and can receive any incident field polarizations. A prototype of the antenna, including PIN diodes and operating in the 5 GHz band, has been built to demonstrate the feasibility of the concept. Measurements have been conducted and three-dimensional radiation patterns are provided. Diversity performances are evaluated by calculating the envelope correlation coefficient.

Antenna design with control of radiation pattern and frequency bandwidth

The development of many standards in telecommunications (GSM, UMTS, Bluetooth, etc.), with different central frequencies and frequency bandwidths, increases the interest for multi frequency band or ultra wide band applications. At the same time, these applications need specific radiation patterns. So, the design of antennas for such applications constitutes an important technological problem. We aim to develop a methodology to design antennas by controlling, at the same time, their frequency bandwidth and their radiation pattern by identifying the neutral and active zones on an antenna. It has been applied to two kinds of antennas, a monopole and a patch antenna. The intention of this work is to develop a library of techniques to enlarge or reduce frequency bandwidth, or control radiation pattern.

Investigation on Cavity/Slot Antennas for Diversity and MIMO Systems: The Example of a Three-Port Antenna

The use, as diversity antennas, of electromagnetic cavities with radiated slots etched on their faces is discussed. From this kind of geometries, many antenna configurations can be designed in order to provide uncorrelated signals. As an example, a three-port antenna which combines polarization and radiation pattern diversities is presented. The structure operates in the 5 GHz band and exhibits a coupling between input ports less than -30dB in measurement. Envelope correlations between radiation patterns of each port are less than 0.035 which makes this structure well-suited for antenna diversity systems.

Collocated Microstrip Antennas for MIMO Systems With a Low Mutual Coupling Using Mode Confinement

Collocated antennas for mutiple input multiple output (MIMO) systems are presented. The structure is composed of a dual-polarized microstrip square patch combined to a dual-polarized microstrip square ring. Consequently, four different radiation patterns are available simultaneously. With a length of about one guided wavelength, the proposed structure is well suited to reduce the MIMO terminal size. The structure operates in the 5.25 GHz band and exhibits a mutual coupling between the four input ports less than -23.5 dB in simulation and -20 dB in measurement. MIMO channel capacity measurements have been performed and demonstrate that the proposed antenna system can replace a classical system based on space diversity.

A New Multimode Antenna for MIMO Systems Using a Mode Frequency Convergence Concept

A new multimode antenna is proposed in this paper. The structure is based on a mode frequency convergence concept. A microstrip square patch antenna is modified in order to force different modes to resonate at the same frequency. Then, with a common/differential excitation, these modes can be fed independently. Thus, three radiation patterns are available simultaneously, thereby producing diversity. With dimensions less than a guided wavelength (≈ 0.88λg), the proposed structure is well suited to reduce the size of multiple antennas used in diversity applications such as MIMO systems. The antenna has been designed in the 2.45 GHz band for Wi-Fi applications.

A 2.4 GHz 1-dimensional array antenna driven by vector modulators

This paper aims to develop an intelligent radio-communication prototype using multiple-antenna phased array whose bearing can be controlled electronically. Such a system has proved its efficiency in terms of gain and SNR improvement. The architecture presented in this article runs at 2.4 GHz with a bandwidth channel of 11 MHz which is well suited for WIFI 802.11b applications. This original system uses quadrature modulators as active phase-shifters, and noise sensitivity is studied and simulated to prove the interest of this architecture. A circuit is under tests and first elementary active parts RF measurements are given.

On the bandwidth enhancement of a multipolarization and reconfigurable pattern antenna for adaptive MIMO systems

A multipolarization cubic antenna concept which introduces pattern diversity for adaptive MIMO systems has been presented. The frequency bandwidth has been improved keeping radiation characteristics constant over the whole band.

Four co-located antennas for MIMO systems with a low mutual coupling using mode confinement

Multiple input multiple output (MIMO) systems can drastically improve wireless communication capacity and robustness by exploiting multipath effects. Performances of these multiple antenna systems largely depend on the correlation between received signals. To maximize the capacity, the correlation must be as low as possible. Spatial diversity is usually used to decrease this correlation. The antenna system presented in this paper is composed of four co-located antennas which are able to produce uncorrelated signals by using both magnitude and polarization diversities. Furthermore, the structure is planar and contains a ground plane which is well-suited to be integrated in a communicant terminal. The diversity potential of the structure is quantify by calculating the envelope correlation between each radiation pattern. The coupling between each access has been decreased by using vias for confinement modes.

Association of a UWB filter with a UWB antenna : Control of antenna characteristics

UWB systems become more and more attractive because they allow to use wider band and so to increase systems performances concerning data rates, in particular for short range applications. Their conception is constrained by desired characteristics and also by size and cost of devices. To reduce the whole size, a solution is to reduce the size of each device and to integrate them. In this article, we propose to connect the filter directly to the antenna. This allows to optimize the front-end characteristics and size reduction.

New Flexible Medical Compact Antenna: Design and Analysis

Some results on embedded antennas for medical wireless communication systems are presented. Medical telemetry can advantageously assist medical diagnostics. For example, you can better locate a diseased area by monitoring temperature inside the human body. In order to establish efficient wireless links in such an environment, a special attention should be paid to the antenna design. It is required to be of a low profile, very small regardless of the working frequency—434 MHz in the ISM band, safe, and cost effective. Design of the as-considered antenna is proposed based on a simple model. The approach has been demonstrated for a compact flexible antenna with a factor of 10 with respect to the half-wave antenna, rolling up inside an ingestible pill. Measured and calculated impedance behaviour and radiation characteristics of the modified patch are determined. Excellent agreement was found between experiment and theory.