Analysis of the mono-groove NRD waveguide and antenna

In this paper, an improved structure of symmetric groove nonradiative dielectric (GNRD) guide, the mono groove NRD (MGNRD) guide is presented, which keeps the similar performances of the symmetric groove structure, but is more easy to fabricate in millimeter waveband. The dispersion characteristics of the MGNRD is analysed using the transverse resonance method, then a MGNRD leaky-wave antenna is constructed, calculated and tested. The theoretical and experimental data are agreement with each other, and shows a attractive prospect for application.     

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     

Multimode network analysis for dielectric leaky-wave antennas consisting of multilayer periodic structure with arbitrary dielectric distributions

The multimode network method is used to analyze the radiation characteristics of the leaky-wave antenna consisting of multilayer dielectric periodic structure with arbitrary dielectric distributions in each layer. The eigenfunction of each periodic layer is determined by Floquet theorem; and the mode matching combining with generalized transverse resonant method are used to derive the dispersion equation of the leaky-wave antenna. The complex transmission constant is calculated by Newton iterative method and the radiation characteristics of the antenna are obtained. Some antenna structures are analyzed and useful guidelines for design of the leaky-wave antennas are suggested.     

NRD leaky-wave antenna for narrow beams in 94GHz

Theoretical analyses and numerical results of NRD leaky-wave antenna are presented. The results show that the characteristics of frequency scanning and very narrow beam can be implemented by NRD leaky-wave antenna. At the freguency of 94GHz, the half-power beamwidth of 0.14° of the antenna canbe obtained when the length of the antenna is 1.5m. From 90 to 98GHz, frequency scanning is about ±7° relating to the beam angle at 94GHz. The theoretical results are compared with the experimental data.     

The Millimeter Wave Radiation of a Dielectric Leaky-Wave Antenna Coupled with a Diffraction Grating for the Broadside Radiation: Narrow-Face Interaction

A dielectric leaky-wave antenna (DLWA) coupled with a metallic diffraction grating is experimentally investigated in millimeter-waves. The interaction between dielectric line and grating is from the narrow-face of dielectric and it is contactless. Measured patterns are compared with simulated ones. The antenna parameters (HPBW, side lobe levels, etc.) are also obtained. The most significant achievement of this antenna is to obtain broadside radiation without any suppression, which occurs due to the periodicity of grating. This situation is not available for the most of the periodic leaky-wave antennas. This antenna type can be used as a broadside radiator by this property as well as a frequency scanning purposes.     

Radiation characteristics of uniform and nonuniform dielectricleaky-wave antennas

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     

Resonant type leaky-wave antenna using image NRD guide

A novel leaky-wave antenna constructed from an image non-radiating dielectric waveguide (INRDG) is presented. Unlike conventional leaky-wave antennas, the broadside radiation is realised by utilising the resonant characteristic of the leaky INRDG waveguide mode. Experimental results measured at Ku band confirm the effective performance of the antenna.     

Radiation from a dielectric-artificial dielectric slab

A leaky-wave antenna using a grounded dielectric-artificial dielectric (AD) slab is described. The propagation constant of this structure is evaluated by solving the dispersion relation. Various modes supported by this structure are discussed. This type of leaky-wave antenna is capable of producing extremely narrow beamwidths. An antenna using the dielectric-AD is compared with the AD antenna reported in [1]. It is found that for similar characteristics this modified antenna structure requires smaller thickness than the AD antenna. Theoretical and experimental results for radiation characteristics of this type of antenna are compared and found to be in good agreement.     

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

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     

Brewster angle effect on performances of omni-directional periodic rod antenna

An omni-directional periodic dielectric rod leaky-wave antenna operating in the TMoi mode is investigated. As an eigenvalue problem, the structure is analyzed theoretically with mode matching technique. The radiation characteristics of the antenna are calculated for different parameters with a particular attention directed to the Brewster angle effect on the performaces of the antenna; and some usefull guidelines for design of the antenna are thereby suggested.     

An improved calculation procedure for the radiation pattern of acylindrical leaky-wave antenna of finite size

A method is given for calculating the radiation pattern of a finite-size cylindrical leaky-wave antenna structure consisting of a single source near a planar surface that supports leaky-wave propagation. The method accounts for the finite radius of the planar surface by subtracting the radiation from that part of the leaky wave that lies beyond the physical surface, from the exact radiation pattern corresponding to an infinite planar surface. Experimental results obtained for a leaky-wave structure consisting of multiple dielectric layers above a ground plane confirm the improved accuracy of the method, particularly for the part of the radiation pattern away from the peak     

The Millimeter Wave Radiation of a Dielectric Leaky-Wave Antenna Coupled with a Diffraction Grating: Broad-Face Interaction

The millimeter wave radiation of a dielectric leaky-wave antenna (DLWA) coupled with a metallic diffraction grating with a sinusoidal height profile is experimentally investigated. The interaction between dielectric and grating is contactless and it is from the broad-face of the dielectric line. The measured field patterns are compared with the simulated HFSS patterns. Antenna parameters such as polarization, HPBW, cross-polarization and side lobe levels are measured. The effects of the geometrical parameters of the grating to the radiation are also investigated. Some results are compared with a DLWA which has another diffraction grating profile shape (rectangular). The investigated antenna can be used as a frequency scanning antenna in mm-wave radars because it has low cross and side lobe levels and narrow beam width.     

94 GHz dielectric slab-line leaky-wave antenna

A leaky-wave planar antenna for millimetre-wave frequencies is described using a dielectric slab line, fed by a slotted waveguide array. The radiation of the planar antenna is induced by line discontinuities such as metallic discs on the guide surface.     

Leaky and surface waves in anisotropic printed antenna structures

The behavior of the leaky- and surface-wave modes supported by single- and double-layered grounded anisotropic dielectric structures is investigated. Simple low-frequency and high-frequency asymptotic formulas are derived for the wavenumbers. The effects of dielectric anisotropy and losses on the cutoff frequency of the TM and TE surface waves and on the H-plane radiation pattern of a leaky-wave antenna are examined     

Horn Image-Guide Leaky-Wave Antenna

A novel structure for a frequency-scanning millimeter-wave antenna is described. The antenna is constructed by embedding a dielectric leaky-wave antenna in a long trough with metal flares attached along both sides. The optimum flare angle for achieving maximum gain is theoretically predicted. The design of the leaky-wave antenna, which is comprised of metallic-strip perturbations on top of the dielectric guide, is also discussed.     

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.     

Double dielectric grating leaky-wave antenna-improved perturbation analysis

The radiation characteristics of the double dielectric grating leaky-wave antenna are analyzed by the improved perturbation method. The results indicate that under the condition of the same radiation intensity, the double dielectric grating antenna has relatively smaller dimensions than that of the single one. It is undoubtly of great importance in the case that the limitation of the weight and volume of system is strictly required. The results obtained from this paper are compared with the exact solution based on the mode matching method. It is justified that the present perturbation procedure yields as highly results as the rigorous approach with extremely simplicity of the analysis and calculations.     

Network Analysis of Millimeter-Wave Omnidirectional Periodic Dielectric Rod Antenna with Arbitrary Grating Profile

The radiation characteristics of the omnidirectional periodic circular dielectric rod leaky-wave antenna with arbitrary grating profile are investigated by the network method combining with staircase approximation. In the analysis, the arbitrary grating profiles are transformed to a multilayer rectangular periodic structure, which is represented by a radial transmission line with a series current source. As a result, the calculations are greatly simplified and the effects of grating profile on the performance of the grating antenna are systematically studied in a very efficient way. Some useftil guidelines for the design and fabrication of the omnidirectional dielectric grating antenna are thereby suggested.     

Radiation from cylindrical leaky waves

Formulas are derived for the far-infrared radiation pattern of cylindrical leaky waves propagating on a planar surface. The formulas can be used to predict the radiation pattern of a general class of leaky-wave antennas, consisting of a finite-size source which excites a radially propagating leaky wave on some planar surface. Leaky-wave antennas consisting of antenna elements embedded in dielectric layers (microstrip elements) fall into this category. Using the equivalence principle, formulas are derived for both transverse electric (TE) and transverse magnetic (TM) leaky waves with arbitrary propagation constants. The formulas allow for radiation from cylindrical apertures of arbitrary size, so that the effect of truncating the supporting planar surface with an absorbing material can be determined. Particular attention is devoted to the case of a leaky wave for which the real and imaginary parts of the complex propagation constant are equal, since this type of wave has been shown to be responsible for broadside radiation in certain leaky-wave antennas comprised of dielectric layers     

A spectral domain approach for computing the radiation characteristics of a leaky-wave antenna for millimeter waves

A new method for evaluating the complex propagation constantbetain a leaky-wave structure comprising thin metallic rectangular strips etched on a dielectric rod of rectangular cross section is described. The radiation pattern of the leaky-wave antenna can be determined oncebetais known, since Re(beta) governs the direction of the main beam and Im(beta) accounts for the beamwidth and aperture efficiency. In addition the knowledge of the dependence ofbetaon frequency allows one to design the antenna for frequency-scanning applications. The method employed in this communication is based on the spectral domain approach that formulates the eigenvalue problem in the Fourier transform domain. Computed results are shown to be in very good agreement with experimental measurements.