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.

In this paper, the performance of a cylindrical dielectric resonator antenna (DRA) is improved using a new cylindrical electromagnetic bandgap substrate. The DRA is fed by a coaxial probe and integrated within a cylindrical electromagnetic bandgap (EBG) substrate to increase the antenna gain. The cylindrical electromagnetic bandgap structure is composed of two distinctive periodic structures. The first structure is made of metallic rings, while the second is formed of grounding vias, which are placed radially and circularly. To describe and optimize this EBG stucture, a parametric study using a finite integration method was carried out. Furthermore, an antenna prototype was fabricated and measured to validate the proposed concept. The radiation patterns and return loss obtained from measurements demonstrate a good performance in terms of impedance matching and gain enhancement.

A new microstrip fed low profile broadband dielectric resonator antenna is proposed. The antenna is composed of a dielectric resonator, a microstrip fed stepped patch and an intermediate substrate. The stepped patch and the intermediate substrate allow to widen the matching bandwidth. Using a finite integration method (CST Microwave), a parametric investigation was performed for the optimization. To validate the proposed design, a prototype of the optimized antenna was fabricated and measured. The predicted results are compared with the measured data, and a good agreement is achieved. The proposed antenna offers a fractional bandwidth of 50% around the center frequency 10.16 GHz, and relatively stable radiation patterns in the matching band.

In this paper, we propose a new method for designing dual polarized beam switching antennas by using reconfigurable radial waveguides excited by central probes and feeding multiple radiating elements. The power distribution of the radiating elements is controlled by Cylindrical Electromagnetic Band Gap (CEBG) structures made of metallic wires loaded with PIN diodes. The proposed technique allows azimuth beam switching and multiple-beams, with arbitrary and well controlled polarizations, using low dc voltage. First, a new rectangular periodic structure is used as a model for analyzing the transmission and reflection coefficients for different diode states. Then, numerical and experimental results are presented for a reconfigurable radial waveguide power divider and for the radiating elements. Finally, numerical and experimental results are presented and discussed for a complete dual polarized antenna operating at WIFI 5GHz band (5.18-5.825GHz).

A deterministic analysis of spatial diversity is presented in connection with radar systems. A numerical technique based on physical optics is used for our analysis. Contrary to statistical models, the proposed technique takes into account accurate near-field radar cross section of the target, and radiation characteristics of transmitting and receiving antennas. The power scattered by the target and received by multiple antennas as a function of the target aspect angle and distance is analyzed. Two combining methods of received powers are tested and statistical analysis is performed showing that, using spatial diversity, the angular range can be increased significantly and the standard deviation of the target response can be reduced. In order to validate our analysis and proposed scheme, experimental measurements were carried out using a metallic plate and a car as targets. This work has potential applications in automotive collision warning/avoidance radar systems.