Tayeb A. Denidni

Novel butler matrix using CPW multilayer technology

In this paper, a novel 4 times 4 two-layer Butler matrix based on a broad-band two-layer slot-coupled directional coupler is presented and implemented at 5.8 GHz using coplanar waveguide technology. With the slot-coupled directional coupler, the proposed matrix was designed without using any crossovers as used in conventional Butler matrices, which leads to significant size reduction and loss minimization. To examine the performance of the proposed matrix, experimental prototypes of the multilayer directional coupler and the Butler matrix were fabricated and measured. Furthermore, a four-antenna array was also designed and fabricated at 5.8 GHz and then connected to the matrix to form a beamforming antenna system. As a result, four orthogonal beams at -45deg, -15deg, 15deg, and 45deg are produced. Measured results on the entire system agree well with the theoretical predictions, validating the proposed design

Ka-band analog front-end for software-defined direct conversion receiver

A six-port Ka-band front-end architecture based on direct conversion for a software-defined radio application is proposed in this paper. The direct conversion is accomplished using six-port technology. In order to demodulate various phase-shift-keying/quadrature-amplitude-modulation (PSK/QAM) modulated signals at a high bit rate, a new analog baseband circuit was specially designed according to the I/Q equations presented in the theoretical part. An experimental prototype has been fabricated and measured. Simulation and measurement results for binary PSK, quaternary PSK (QPSK), 8 PSK, 16 PSK, and 16 QAM modulated signals at a bit rate up to 40 Mb/s are presented to validate the proposed approach. A software-defined radio can be designed using the new front-end and only two analog-to-digital converters (ADCs) because the I/Q output signals are generated by analog means. Previous six-port receivers make use of four ADCs to read the six-port dc levels and require digital computations to generate the I/Q output signals. With the proposed approach, the load of the signal processor will therefore be reduced and the modulation speed can be significantly increased using the same digital signal processor.

Compact Multiband Planar Antenna for 2.4/3.5/5.2/5.8-GHz Wireless Applications

A low-profile planar monopole antenna is proposed to operate within WLAN and WiMAX frequency bands. The antenna is composed of three radiating elements together with an additional strip to control the antenna performance. An electromagnetic (EM) model of the proposed antenna is developed in CST Microwave Studio for numerical analysis and optimization. The principle of operation and parametric study on the antenna performance are provided. Two dual-band and triple-band antennas are fabricated, and experimental results are presented.

Wide band four-port butler matrix for switched multibeam antenna arrays

This paper presents the design and realization of a wide band four-port microstrip matrix to feed a switched-beam antenna array for wireless applications at 1.9 GHz. The objective of this investigation is to develop an antenna-array feeding network based on Butler with a large bandwidth in order to cover the PCS band: 1900 MHZ to 2200 MHZ. In order to meet these requirements, wide band microwave components such as hybrids and crossovers were designed and used to Butler proposed matrix. The Butler matrix is used as a beamforming network that allows to produce orthogonal beams that can be steered in different directions. To examine the performance of the proposed matrix, simulated and experimental results is presented and discussed.

Analysis and design of a cylindrical EBG-based directive antenna

In this paper, a cylindrical electromagnetic bandgap (CEBG) structure composed of infinite metallic wires is analyzed, designed and used as a model to develop a new reconfigurable directive antenna. This structure is circularly and radially periodic, and it is excited at its center using an omnidirectional source. The analysis is based on calculating the transmission and reflection coefficients of a single cylindrical frequency selective surface (FSS) and then, considering only the fundamental mode interaction, deducing the frequency response of the CEBG structure composed of multiple cylindrical FSSs. For this structure, new analytical formulas are derived, and their accuracy is assessed compared to those obtained by the finite-difference time-domain method. As in rectangularly periodic structure case, the frequency response of the CEBG structure exhibits pass-bands and bandgaps, and it is possible to obtain directive beams by introducing defects in the periodic structure. Using this concept, a new antenna was developed to obtain a controllable directive beam. An antenna prototype, without control, was designed, fabricated, and tested. An excellent agreement was obtained between theory and experiment for both return loss and radiation patterns.

Gain Enhancement of a Microstrip Patch Antenna Using a Cylindrical Electromagnetic Crystal Substrate

The performance of a circular microstrip patch antenna is improved using a new cylindrical electromagnetic bandgap (EBG) substrate. The microstrip patch antenna is fed by a coaxial probe and is integrated within a cylindrical electromagnetic bandgap substrate, based on the mushroom-like substrate, to increase the antenna gain. The cylindrical electromagnetic bandgap structure is a combination of two periodic structures with different periods. One is made of metallic rings and the other of grounding vias, which are disposed such as to form a radially and circularly periodic structure. A parametric analysis using a full-wave method was carried out in order to design the EBG structure. With the proposed concept, an antenna prototype was fabricated and tested. The radiation patterns and return loss obtained from measurements show a good impedance matching and a gain enhancement of the proposed antenna.

A Conducting Cylinder for Modeling Human Body Presence in Indoor Propagation Channel

We demonstrate that in indoor radio propagation modeling, the presence of the human body may be approximated by a conducting circular cylinder at microwave frequencies. Therefore, a perfect tool such as the uniform theory of diffraction may be used to predict the diffracted field over a smooth circular surface. To validate the model, vertically and horizontally polarized continuous wave (CW) measurements were performed at 10.5 GHz between two fixed terminals inside a room along with the presence of an obstacle (person or metallic cylinder) moving along predetermined parallel and perpendicularly crossing paths with respect to the line-of-sight direction. Results indicate that there is a strong correlation between the effects of the human body and those of a conducting circular cylinder. The simulation results successfully agree with the CW experimental measurements.

High-Gain Reconfigurable Sectoral Antenna Using an Active Cylindrical FSS Structure

A novel design of a high-gain reconfigurable sectoral antenna using an active cylindrical frequency selective surface (FSS) structure is presented. The FSS structure consists of metallic discontinuous strips with PIN diodes in their discontinuities, and it is placed cylindrically around an omnidirectional electromagnetically coupled coaxial dipole (ECCD) array. The cylindrical FSS structure is divided into two semi-cylinders. By controlling the state of diodes in each semi-cylinder, a directive radiation pattern is obtained that can be swept in the entire azimuth plane. The effect of the diode-state configuration and the radius of the cylindrical structure are carefully studied to obtain an optimum sectoral radiation pattern. In addition, a solution for increasing the matching bandwidth of the antenna is also proposed. An experimental prototype was fabricated, and the measured results show a beamwidth of 20° in elevation and 70° in the azimuth plane at 2.1 GHz with a gain of 13 dBi. With these features, the proposed antenna is suitable for base-station applications in wireless communication systems.

ULTRA WIDEBAND CPW-FED APERTURE ANTENNA WITH WLAN BAND REJECTION

In this paper, we present a new ultra wideband antenna design with band rejection for UWB applications. A CPW-fed circular patch radiates through a circular aperture, which ensures wideband impedance matching and stable omnidirectional pattern over an UWB frequency range, from 3GHz to 10.6GHz. In order to avoid interference

H-Shaped Dielectric Resonator Antenna for Wideband Applications

A novel dielectric resonator antenna design is presented for wideband applications in this letter. By using a dielectric resonator with an optimized H-shaped across section and an optimized trapezoidal patch adhered on the concave surface of the resonator as a feeding mechanism, an impedance bandwidth of about 62% (for VSWR les 2) , covering the frequency range of 3.6-6.85 GHz, is achieved. The measured results in terms of bandwidth and radiation pattern agree well with the simulated ones, confirming the theoretical design.