We report an electronically switchable dielectric leaky wave antenna. The main beam angle can be electronically steered using p-i-n diodes. The diodes are used as switches to control the radiation from two sets of gratings with different periods, thereby switching the main beam angle. Beam steering is achieved at a single fixed frequency; no frequency sweeping is necessary. A microwave prototype demonstrates a 35/spl deg/ change in beam direction at 3.5 GHz. Measured antenna patterns agree with theoretical predictions. This approach should be scalable to millimeter-wave frequencies using diodes monolithically integrated on a semiconductor waveguide.

An electronically switchable leaky wave antenna

Propagation and radiation characteristics of 1-D dielectric-resonator-based composite right/left-handed metamaterial structures with open mesh plates are investigated as a function of configuration parameters. The complex effective permittivity and permeability are estimated from the scattering parameters of the unit-cell structure. Based on this configuration, the single-mode transmission line is designed and the backfire-to-endfire frequency-scanned leaky wave antenna is implemented. It is found from numerical simulations that the 30-cell leaky wave antenna has a gain of 10 dBi with a scanning angle of over 90deg covering backfire-to-endfire directions. The measurement results show as wide beam-steering angles as numerically predicted.

Dielectric-Resonator-Based Composite Right/Left-Handed Transmission Lines and Their Application to Leaky Wave Antenna

A compact linear array antenna fed by substrate integrated image guide (SIIG) at 94 GHz is presented. The SIIG is a low-loss dielectric waveguide which is synthesized directly on a high dielectric constant substrate or semiconductor wafer. Such a low-cost approach of integration allows for the development of directive low profile antennas for future commercial millimeter-wave products. Special attention was directed towards the radiation elements that are fabricated in printed circuit technique on top of the SIIG. Their novel design provides a wide tuning range for the radiation coefficient and excellent linear polarization purity. In addition, an optimized reflection compensation technique effectively reduces the overall return loss and permits frequency scanning through broadside direction without suffering from a stop band due to distributed Bragg reflection. Published theory concerning the scan range of this class of frequency-scannable array antennas is extended in this work. Detailed design guidelines are given along with simulation and measurement results of a prototype. The 2 cm long implementation produced a fan beam with 11 dB gain.

Substrate Integrated Image Guide Array Antenna for the Upper Millimeter-Wave Spectrum

The finite-difference time-domain (FDTD) method is used to analyze a dielectric leaky-wave antenna comprising metal strips etched on a rectangular dielectric rod The radiation patterns of the leaky-wave antenna with and without the transition are determined by using FDTD The effects of the launching discontinuity on the performance of the antenna are discussed In addition, the application of the perfectly matched layer (PML) technique to the three-dimensional (3-D) dielectric waveguide and its performance, compared to those of the Mur's (1981) first-order and super-absorbing Mur's first-order absorbing boundary conditions (ABCs) are described In addition, the effects caused by perturbation on the wave propagation characteristics of dielectric waveguide are also discussed The FDTD results are verified by a W-band experiment and found to be in good agreement

FDTD analysis of a metal-strip-loaded dielectric leaky-wave antenna

An H-polarized leaky wave antenna (LWA) employing metal strip grating (MSG) is presented. A novel feeding system based on the ridge gap waveguide (RGW) technology feeds the proposed antenna. The proposed feeding mechanism is made up of a profiled Quasi-TEM horn ridge gap waveguide, which is designed to have the same aperture width and provide uniform field excitation to the leaky wave antenna. The design is performed to provide proper matching between the launcher and the MSG to improve the antenna radiation efficiency. The proposed antenna is operating at 28.5 GHz with a scanning angle capability of -20 °
 achieving a realized gain of 24 dBi. Several numerical results using point-matching and aperture distribution method are used to analyze the proposed LWA. Moreover, measurement results are presented to illustrate the effectiveness of the novel feeding system functioning as the LWA launcher.

A Robust Horn Ridge Gap Waveguide Launcher for Metal Strip Grating Leaky Wave Antenna

An approach based on a waveguide model for analyzing the uniform and nonuniform dielectric leaky-wave structures is proposed for which the Galerkin solution method is applied. In the first part of the paper the far-field radiation of the uniform antenna is determined theoretically and experimentally in the Ku band and also the dependence of beamwidth and sidelobe level as function of strip width and frequency is demonstrated. In addition, an analysis of the antenna with a tapered-strip distribution-is presented. The second part describes a novel tapering procedure, performed by changing the width of the uniform antenna, for obtaining the radiation pattern with lower sidelobe levels. Sinusoidally and exponentially shaped dielectric leaky-wave structures are analyzed as nonuniform antennas. Finally, the radiation and scanning characteristics of these antennas are theoretically presented. >

M. Ghomi

Papers

Radiation characteristics of uniform and nonuniform dielectric leaky-wave antennas