Design Of Leaky-wave Antenna Research Articles

Design of continuous long slot leaky-wave antenna for millimeter wave application

A simple and efficient design scheme of the continuous long slot leaky-wave antenna is developed. The key steps involved in the scheme are summarized. First, the cut-off frequencies of slot waveguides with different slot offsets are obtained by 3D finite-difference time-domain (FDTD) method. Second, the attenuation function α ra is estimated by the aperture distribution, and the attenuation function α rs is determined by the slot radiation. Finally, the attenuation function α ra is combined with the attenuation function α rs by the coefficient K. And an example in Ka band is presented. Moreover, the return loss of the E-plane Tee-junction (ET) and the radiation pattern of leaky-wave antenna are simulated. The scheme is verified by comparing with the experimental result.

Correction of Dielectric Losses in Practical Leaky-wave Antenna Designs

In this paper, the leaky-mode theory is applied to take into account for the dielectric losses in millimetre waveband inhomogeneous leaky-wave antennas. A practical dielectric-filled cosine-tapered periodic leaky-wave antenna working in the 45 GHz band is studied, showing how the desired sidelobes level and directivity are spoilt due to the effect of the losses. An iterative procedure is used to correct the negative effects of the losses in the radiation patterns of the leaky-wave structure. It is also shown the practical limits of the proposed correction approach. The leaky-mode theory is applied for the first time to compensate the losses in a practical leaky-wave antenna in hybrid waveguide printed circuit technology. This leaky-mode theory is validated with full-wave three-dimensional finite element method simulations of the designed antenna.

Control of Leaky-Mode Propagation and Radiation Properties in Hybrid Dielectric-Waveguide Printed-Circuit Technology: Experimental Results

Experimental results are presented to show how a planar circuit, printed on a laterally shielded dielectric waveguide, can induce and control the radiation from a leaky-mode. By studying the leaky-mode complex propagation constant, a desired radiation pattern can be synthesized, controlling the main radiation characteristics (pointing direction, beamwidth, sidelobes level) for a given frequency, This technique leads to very flexible and original leaky-wave antenna designs. The experiments show to be in very good agreement with the leaky-mode theory

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.

Pattern reconfigurable leaky-wave antenna design by FDTD method and Floquet's Theorem

A pattern reconfigurable millimeter-wave coplanar waveguide leaky-wave antenna is designed by using the finite-difference time-domain (FDTD) method combined with Floquet's theorem and the simple linear interpolation technique. The concept of equivalent period is presented for mixed-periodic structures. The novel design process results in a reduction in the design time compared with that of the traditional FDTD method.

A full-wave space-domain method for the analysis of leaky-wave modes in multilayered planar open parallel-plate waveguides

This work presents a novel numerical technique for the analysis of leaky-wave modes in laterally shielded, top-open multilayered planar transmission lines. The method develops the multilayered-media boxed Green's functions for this type of electromagnetic devices, and solves the characteristic electric-field integral equation (EFIE) by using the method of moments (MoM). The analytical expressions used for the computation of the kernel of this technique are derived in this article, and results for leaky-wave modes in different practical structures are presented. The strong analytical nature of the proposed approach allows for a low-cost computational code without losing its full-wave accuracy. Comparisons with previous works are presented, showing the advantages of this new method for the analysis and design of practical millimeter-band leaky-wave antennas. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

A new two-terminal feeding active leaky-wave antenna

A new two-terminal feeding active-integrated leaky-wave antenna design is demonstrated. The X-band microstrip two-terminal feeding leaky-wave antenna is integrated with an active high-electron mobility transistor (HEMT) oscillator to produce a two-beam radiation pattern. The antenna is fed asymmetrically at both sides to excite the first higher order mode. This configuration, as compared to a single-terminal feeding leaky-wave antenna, has the advantage of the multidirection and the reduction of the reflected wave caused by the open end of the radiating element. Measured results show that the radiation directions of two beams are approximately at 34/spl deg/ and 140/spl deg/, the effectively isotropic radiated power (EIRP) is close to 17.5 dBm, and the return loss is almost less than -10 dB between 9 and 11.5 GHz.

Characteristics of guided and leaky waves on multilayer thin-film structures with planar material gratings

This paper presents the characteristics of guided (surface) waves and leaky waves on multilayer structures with planar implanted periodic dielectric blocks. A three-dimensional (3-D) integral-equation formulation in conjunction with the method of moments (MoM's) is used to find the propagation constants of the surface-wave and leaky-wave modes. The analysis deals with layered structures with irregular implants. Photonic band-gaps of both guided waves and leaky waves for rectangular air-implants are identified. Anisotropic properties of the surface waves and leaky waves are investigated. The design of leaky-wave antennas with the information of mode characteristics is discussed. The analysis is validated through the comparison with a low-frequency effective-medium approach and results for linear gratings.

Simple design of dual-beam leaky-wave antennas in microstrips

The paper describes the design of microstrip leaky-wave antennas for single and dual-beam applications. Dispersion curves for the first higher order mode are given by analytical expressions with the help of a simple cavity model. From knowledge of the propagation characteristics, the radiation patterns of the leaky-wave antennas are easily computed. The antennas are excited by open-ended CPW lines which both present a good coupling efficiency and high potentiality for the insertion of active circuits. Several C-band applications on various substrates are presented, showing the usefulness and the easy design of microstrip leaky-wave antennas for the realisation of steerable dual-beam patterns.

Leakage characteristics of groove guide having a conductor strip

A full-wave characterization of the groove guide having a conductor strip is made based on the mode-matching procedure. All of the constituents of the structure, including a coupling strip, grooves and a radiating open end, are treated in a concise and rigorous way by using the generalized scattering matrix technique. Numerical results show that a set of channel guide leaky modes is also present in this structure in addition to the groove guide leaky mode. The complex propagation behaviors of both the groove guide leaky mode and the channel guide leaky mode are illustrated for various waveguide geometric parameters, and some conclusions regarding the design of leaky wave antennas using this structure are drawn. >

Study of a new leaky-wave antenna for millimeter waves based on the V-groove guide

In this paper a new type of leaky-wave antenna for millimeter waves using an asymmetric strip in the V-groove guide is presented. The longitudinally continuous asymmetric metal strip provides the mechanism that transforms the initially bound mode into a leaky mode. A complete transverse equivalent network is presented for analysis and design of this new leaky-wave antenna. Numerical results for the antenna's performance characteristics are given.

Surface wave diffraction by a finite metal grating and numerical model for design of leaky-wave antennas

The electrodynamic problem of surface wave diffraction by a finite grating made of thin metal rods and placed on the dielectric plate is studied. Green's function of a dielectric slab situated on a metal substrate is used for mathematics. The system of algebraic linear equations, in unknown complex amplitudes of currents in the rods is obtained in a particular case of normal incidence of the traveling wave on the grating. The effective algorithm for numerical investigation of all diffraction characteristics of the structure is also elaborated. An example of the diffraction model application for design of a leaky-wave antenna in the millimeter waveband is presented. >

A leaky-wave antenna in nonradiative dielectric waveguide

A leaky-wave mechanism in a nonradiative dielectric (NRD) waveguide is described. The antenna used in the analysis consists of a long slot in one ground plane of the NRD guide; the currents present in the side walls cause the slot to radiate as a traveling-wave antenna. The antenna was designed to operate at 9.5 GHz to reduce the costs involved in working at high frequencies. The analysis of the slot follows the procedure outlined by L.O. Goldstone and A.A. Oliner (1959). A simple expression for the amount of coupling from the guide is derived under certain assumption made because information on the reactances necessary to model the slot is not as yet available. The theoretical coupling values verified by measurement and the design, construction, and performance of both leaky-wave antennas are described. >

A new leaky wave antenna for millimeter waves using an asymmetric strip in groove guide, Part II: Design considerations

part I of this pair of companion papers describes a new type of leaky wave antenna for millimeter wavelengths and presents derivations of the parameters of the transverse equivalent network that accurately characterizes its leaky wave behavior. From a resonance of this transverse equivalent network, one obtains a dispersion relation in closed form from which numerical values of the leaky wave behavior have been obtained. Part II begins with this dispersion relation and a brief discussion of the numerical procedure employed. The relations between these leaky wave properties and the design of leaky wave antennas form the main concern of Part II. In this context, design aspects are discussed, including optimization considerations and the fact that they are frequency independent, and then a variety of numerical results are presented, together with their relevance to leaky wave antenna performance. It is seen that this antenna is capable of systematic design and is versatile with respect to the scan angle and beamwidth of the radiation.

Leaky-wave antennas using artificial dielectrics at millimeter wave frequencies

A novel approach for the design of leaky-wave antennas using artificial dielectrics at millimeter wave frequencies is discussed. The general radiation characteristics of leaky-wave structures of finite length are presented. The feasibility of frequency scanning and dielectric scanning (changing the direction of the beam by varying the relative permittivity of the electrically controlled liquid artificial dielectric medium) of a leaky-wave antenna using rodded artificial dielectric is investigated theoretically. Calculations shown that the beam angle changes from 20° to 50° off broadside when the frequency is changed from 31.1 to 35.4 GHz or the permittivity of the embedding medium of the artificial dielectric is changed from 1.6 to 2.04. Over a scan range of about 40° the beamwidth is almost constant. For large scan range, the beamwidth of a dielectric-scanned antenna (DSA) is about 15 percent less than the frequency-scanned antenna (FSA). The gain of a DSA is greater than the FSA and also has less variation over the scan range. The power efficiency is approximately the same for both the antenna types with worst case efficiency being about 85 percent.