Application of the high-gain substrate-superstrate configuration to dielectric leaky-wave antennas

The high-gain substrate-superstrate configuration, which was proposed to increase the gain in printed circuit antennas, is applied to dielectric leaky-wave antennas (LWAs) to improve its frequency response. Analysis of a slitted suspended dielectric rectangular waveguide is carried out using a full-wave method. It is proved that the minimum values of the leakage constant of the leaky-wave mode for the suspended configuration are related to the high-gain resonance conditions. Moreover, it is found that the suspended LWA exhibits very small beamwidth variations in a large frequency bandwidth. It is well-known that inhomogeneous filled LWAs suffer from variation of beamwidth as the angle of maximum radiation is scanned with frequency. The proposed topology can be adjusted so that a flat response of the beamwidth can be obtained in a large frequency band, while maintaining the frequency-scanning behavior of the LWA.     

Novel Microwave Network for the Leaky-Wave Analysis of Evanescent Fields in Stub-Loaded Structures

In this paper, a new transverse equivalent network for the modal analysis of stub-loaded leaky-wave antennas is developed. The derived network is useful for the study of the radiation of evanescent fields that occurs when they reach the top aperture of the parallel-plate stub. This transverse network is based, for the first time, on a nonhybrid formulation of the constituent parallel-plates modes of order 1 (TE₁ ^Z and TE₁ ^Z ). The obtained network is an alternative to the one based on hybrid TE₁ ^Vand TE₁ ^V modes, and leads to a simpler transverse resonance equation. The new equivalent network is validated by obtaining leaky-mode dispersion curves for a previously studied leaky-wave antenna in non- radiative dielectric guide technology.     

Microstrip Leaky-Wave Antenna With Control of Leakage Rate and Only One Main Beam in the Azimuthal Plane

An original leaky-wave antenna (LWA), conceived from a microstrip line which is laterally shielded by parallel plates, is presented in this paper. This structure shows, for the first time, that the leakage rate of a microstrip leaky-mode can be easily controlled while negligibly affecting the pointing direction. The antenna is based on the radiation from the second higher order mode of the microstrip line, which is perturbed by the addition of the two conductor walls to control the level of the leakage rate. The parallel-plates also serve as a mechanism to obtain a single main beam in the azimuthal plane, therefore improving the radiation pattern compared to common dual-beam second-higher order mode microstrip LWAs. The proposed antenna is analyzed by obtaining the corresponding leaky-mode complex propagation constant, which is calculated by a specific method of moments approach. The modal results obtained from the leaky-mode dispersion curves are validated with analysis performed on a three-dimensional structure using commercial finite element method solver. Also, a prototype is fabricated to experimentally confirm the advantages of this novel leaky-wave line source.     

W-Band Planar Wide-Angle Scanning Antenna Architecture

This paper proposes a hybrid scanning antenna architecture for applications in mm-wave intelligent mobile sensing and communications. We experimentally demonstrate suitable W-band leaky-wave antenna prototypes in substrate integrated waveguide (SIW) technology. Three SIW antennas have been designed that within a 6.5 % fractional bandwidth provide beam scanning over three adjacent angular sectors. Prototypes have been fabricated and their performance has been experimentally evaluated. The measured radiation patterns have shown three frequency scanning beams covering angles from 11 to 56 degrees with beamwidth of 10?±?3 degrees within the 88-94 GHz frequency range.     

Analysis and design of periodic leaky-wave antennas for the millimeter waveband in hybrid waveguide-planar technology

This work presents a full-wave integral equation approach specifically conceived for the analysis and design of laterally-shielded rectangular dielectric waveguides, periodically loaded with planar perturbations of rectangular shape. This type of open periodic waveguide supports the propagation of leaky-wave modes, which can be used to build leaky-wave antennas which exhibit many desirable features for millimeter waveband applications. The particularities of the leaky-mode analysis theory are described in this paper, and comparisons with other methods are presented for validation purposes. Using this leaky-mode analysis method, a novel periodic leaky-wave antenna is presented and designed. This novel antenna shows some important improvements with respect to the features of previously proposed antennas. The results of the designed radiation patterns are validated with three-dimensional electromagnetic analysis using commercial software.     

Printed-circuit leaky-wave antenna with pointing and illumination flexibility

A novel leaky-wave antenna, based on a periodic set of slots printed on a rectangular dielectric waveguide is conceived in this work. The antenna presents the ability to independently control the aperture illumination and the pointing direction, by only modifying the photoetched printed-circuit layout. The working mechanism is described using a leaky-mode dispersion analysis, and cosine-tapered designs are performed at 50 GHz. The radiation patterns are obtained using HFSS analysis to check the reduction of sidelobes levels, and the capacity to tune the pointing direction over a wide range of elevation angles.     

Simple control of the polarisation in uniform hybrid waveguide-planar leaky-wave antennas

A simple and original mechanism to control the polarisation of uniform hybrid waveguide-planar leaky-wave antennas is proposed. The operation is based on introducing simple modifications of the planar dimensions of the structure cross-section, which is shown to control the horizontal and vertical components of the radiated fields. The proposed antenna dispenses with the need for periodic elements, commonly used in flexible polarised leaky-wave antennas, and therefore significantly reduces the design complexity. Parametric curves have been obtained to assist in the simple and efficient design of the proposed antenna. The novel mechanism is illustrated by means of several antenna prototypes operating at 5.7 GHz, producing linear, elliptical and circular polarisations. Commercial three-dimensional finite element method has been used for the simulations, and the results are validated with experimental testing.