Sylvain Collardey

Compact Expressions for Efficiency and Bandwidth of Patch Antennas Over Lossy Magneto-Dielectric Materials

Closed-form formulas for calculating the radiation efficiency and bandwidth of patch antennas over lossy magneto-dielectric materials are proposed by using the cavity model. These expressions agree well with simulations. It is well known that the bandwidth of microstrip antennas is enhanced when the dielectric substrate is replaced by a magnetic one. Here, we confirm more generally that not only the bandwidth, but also the radiation efficiency, can be improved when the permeability (μr) is greater than the permittivity (εr).

Dual-band CPW-fed G-antenna using an EBG structure

In this paper, a configuration is proposed to improve the performance of CPW antennas placed over an EBG material for dual band on body antenna applications. The aim was to improve the performance of such type of antennas by varying the position of the EBG with respect to the antenna. Simulation results show that the gain of the antenna is improved over the required frequency bands.

Design of Small Parasitic Loaded Superdirective End-Fire Antenna Arrays

This paper presents an approach for designing parasitic loaded superdirective antenna arrays. The array current excitation coefficients calculated based on Yaghjian method are used with the array input impedance matrix to deduce the required loads for transforming the array to a parasitic one. The proposed methods practical limitations are studied via a parametric analysis on dipole-based arrays. It is also applied to design two- and three-element arrays based on an electrically small antenna (ESA). Simulation results show a very good agreement between the fully driven arrays total directivity radiation pattern and the parasitic (loaded) arrays one. Simulation results also show that the array end-fire total directivity is maximal at the design frequency. Measured results are in a very good agreement with the simulated ones.

Bandwidth Enlargement of Planar EBG Antennas

A new structure based on a combination of two PRS (partially reflective surface) is introduced and studied analytically to improve the bandwidth of the FP and EBG antennas. The original procedure developed here leads to a design method for broadening the bandwidth of planar EBG antennas.

Numerical Studies of Metallic PBG Structures

Abstract—Photonic Bandgap (PBG) materials have been investigated for their versatility in controlling the propagation of electromagnetic waves [1, 2]. In order to determine PBG structures responses, several analytical or numerical methods are used, such as: • The plane wave method applied to solve Maxwell’s equations [3]. • The transfer matrix method, based on the wire grating impedance developed by N. Marcuvitz [4]. • The Finite Element Method (FEM) exhibits, e.g., the frequency response of reflection and transmission coefficients of the PBG materials when they have infinite surfaces and are excited by plane wave. The FEM method can be also used in the case of finite structure fed by a dipole. • The Finite Difference Time Domain method (FDTD). This method solves the discretized Maxwell’s equations in the time domain and evaluates the electromagnetic field components. These EM fields are then obtained in the frequency domain thanks to a Fourier Transform.

Calculation of Small Antennas Quality Factor Using FDTD Method

The complexity in the evaluation of the radiation quality factor Q of small antenna lies in the calculation of the stored energy. Previous authors proposed several analytical expressions for simple antennas to obtain the Q, which is of practical importance because of its relationship to the antenna bandwidth. This letter presents a general numerical method to calculate the Q using finite-difference time-domain (FDTD) method giving us accurate results and can be applied to complex antennas. Examples of a linear dipole antenna, a loop antenna and an inverted L-shaped antenna along with their results are presented and compared to analytical results of the literature.

Integrating Superdirective Electrically Small Antenna Arrays in PCBs

This letter investigates integrating a two-element superdirective electrically small antenna (ESA) array in a printed circuit board (PCB). The initial array dimensions are 31 ×25 mm2, and it is integrated in a PCB of 110 ×70 mm2. Different configurations are evaluated with respect to the impedance matching, the maximum achievable directivity, and the efficiency. The obtained results show that properly integrating the array in a PCB can maintain its superdirectivity and significantly increase its radiation efficiency. Compared to the initial array, the final one achieves a gain improvement of 13.6 dB.

A design methodology for electrically small superdirective antenna arrays

This paper presents a design methodology for electrically small superdirective antenna arrays. To calculate the required current excitation coefficients the radiated electrical fields obtained from an electromagnetic simulator are integrated in Uzkov equations. The obtained parameters are, then, optimized and used for calculating the power excitation coefficients. The proposed method is deployed for designing a two-element array for an inter-element separating distance varying from 0.05λ to 0.5λ. Simulation results show that the proposed method accurately estimates the required excitation coefficients and the method is validated.

A Conical Patch Antenna Array for Agile Point-to-Point Communications in the 5.2-GHz Band

We study here a 12-element conical antenna array made of four linear subarrays angularly spaced by 90 ° and with three probe-fed radiating elements per subarray. A prototype has been designed and manufactured. The measured radiation characteristics of the elementary radiating element (active pattern) and of the subarray are found in good agreement with the simulation results. The proposed array configuration is considered as a promising solution to rotate and steer the antenna beam for ensuring point-to-point communication at 5.2 GHz.

Superdirective compact parasitic array of metamaterial-inspired electrically small antenna

A metamaterial-inspired electrically small antenna design is presented. This antenna is based on a semi-loop near field parasitic element driven by an electrically small monopole antenna. The system has a dimension of λ0/24×λ0/24 and works in the UHF band, with a simulated efficiency of 14% and an average maximum gain of -5.6dB in the matched bandwidth of 18.4MHz. This antenna is then used in a two elements compact parasitic array, in order to achieve a higher directivity. The two elements of this array are identical, but only one of them is driven, the other one is used as a parasitic element. The design of the antenna, its simulated and measured radiation performance is reported, as well as those of the parasitic array.