Broadband high-gain planar leaky-wave antennas

High-gain, low-cost, planar antennas have attracted a lot of interest in recent years, with regard to applications as fixed wireless access, satellite reception and various point-to-point radio links. Microstrip patch arrays have primarily been good candidates, but the complex feeding mechanisms degrade the antenna performance. A method of producing a high gain planar antenna with a simple feed has been proposed in an earlier study. This technique utilises a partially reflective surface (PRS) to introduce a leaky wave and beamforming effect when placed in front of a waveguide aperture in a ground plane. The partial reflection can be obtained from periodic arrays, also referred to as Frequency Selective Surfaces (FSSs) when used for their filtering properties. The research effort in this thesis focuses on the theory underpinning the beamforming effect of single and double-layer PRSs in a leaky-wave antenna configuration and subsequently on novel leaky-wave antenna designs. [Continues.

Cylindrical electromagnetic bandgap structures for directive base station antennas

This work presents a new method to realize directive base station antennas by incorporating cylindrical electromagnetic bandgap (EBG) structures. The EBG structure behaves as a partially reflecting surface (PRS) and significantly enhances the E-plane directivity of a simple radiating dipole positioned in front of a metallic cylinder. A novel cylindrical antenna that operates at 2.4 GHz is simulated and presented

Dual subwavelength fabry-perot cavities for broadband highly directive antennas

A new concept for designing broadband and subwavelength profile Fabry-Perot-type antennas is introduced. A novel multilayer periodic array design is proposed, yielding two subwavelength-profile Fabry-Perot cavities that significantly enhance the bandwidth performance of the resulting highly directive antenna. The design is based on two optimized double-layer periodic arrays of dissimilar dimensions, each double-layer array consisting of a capacitive artificial magnetic conductor (AMC) layer and an inductive partially reflective surface (PRS) layer printed on either side of a dielectric substrate. They are placed at about a quarter-wavelength distance from a ground plane and from each other. Thus, two air cavities are created with a total profile of less than \lambda/2. The proposed antenna has been simulated in CST Microwave Studio, achieving 18.3 dBi directivity with 8% bandwidth.</p

Closely coupled metallodielectric electromagnetic band-gap structures formed by double-layer dipole and tripole arrays

The concept of closely coupled metallodielectric electromagnetic band-gap (CCMEBG) structures is introduced and investigated using two-dimensional (2-D) double-layer dipole and tripole arrays. An efficient numerical method based on a set of coupled integral equations is used to simulate the double-layer array response. The arrays are placed in close proximity to each other and shifted appropriately in order to produce maximum element coupling. Measurements are presented for oblique plane wave and surface wave incidences. A substantial decrease of the stopband center frequency is observed with the CCMEBG design for both element geometries. Furthermore, wider bandwidth and improved angular stability as compared to single-layer MEBG is obtained. The tripole arrays arranged on a hexagonal lattice exhibit common stopband for any polarization of the incident field due to the symmetry of the element in conjunction with the lattice. The lowering of the resonance for up to 4 to 1 in simulation results emerges as the layers are separated by less than λ/1200 (0.1 mm at 2.5 GHz)