Dielectric Leaky-wave Antenna Research Articles

A promising Ka band leaky-wave antenna based on a periodic structure of non-identical irregularities

This paper presents a new periodic grooved dielectric leaky-wave antenna with non-identical irregularities for an extremely high-frequency range capable of performing efficiently in the Ka band through a stable gain, a decrease in the level of the side lobes, and the achievement of a narrower main lobe beam. It consists of a dielectric waveguide antenna placed inside a channelled rectangular metallic waveguide to improve performance. A dielectric rod was used to overcome the losses related to the propagation of electromagnetic waves in metal conductors. A grooved dielectric of a 21-element linear array is used to propose a simple approach for the synthesis of such antennas based on a modified energy method and is fed by a standard waveguide. It was designed and simulated at 37.2 GHz for satellite, 5G antenna, and radar applications. The major novelty of this study is the ability to control the direction of the main lobe through non-identical irregularities in geometric parameters such as the width, height, and distance between each element. Radiation techniques have been extensively studied using simulations. A performance antenna with radiation efficiency of 99.35%, gain of 22 dBi, width of radiation pattern of 3.2 ^{circ }, and side lobe level (SLL) of {-} 18.3 dB has been achieved.

A Wide-Angle Scanning Sub-Terahertz Leaky-Wave Antenna Based on a Multilayer Dielectric Image Waveguide

This paper presents a new layered dielectric leaky-wave antenna (LWA) for the sub-terahertz (THz) frequency range capable of efficient operation at the broadside with a wide beam scanning angle and stable gain. It consists of a conductor-backed alumina dielectric image line (DIL) with two different dielectric layers mounted on top of each other for performance improvement. The upper layer is a high permittivity RO6010 substrate to enhance the directivity as a superstrate and the lower layer is a low-permittivity RT/duroid 5880 substrate stacked on the alumina DIL to prevent the probable excitation of higher-order modes in the DIL channel. A 15-element linear array of radiating overlapped discs is used to mitigate the open stop-band (OSB) problem, fed by the mentioned waveguide, was designed and simulated at frequencies around 170 GHz. The dominant mode of the layered dielectric waveguide is perturbed by the infinite space harmonics generated by two sets of overlapped discs periodically sandwiched between the layers. It exhibited a relatively wide impedance bandwidth of 28.19% (157.5–206 GHz). Its radiation mechanism has been widely studied through simulations. The results revealed that the antenna provides a wide scanning capability through the broadside from −23° to 38°, covering the frequency range between 157.5 GHz and 201.5 GHz. For an array with 15 radiating elements, the simulated peak gain in the band is 15 dBi and the broadside gain is 13.6 dBi at 172 GHz.

ANALYSIS OF A NEW LEAKY-WAVE ANTENNA FOR W-BAND APPLICATIONS

In this article, we present a dielectric leaky-wave antenna with periodic metallic patches. Its design is made using HFSS software. Analysis of the antennas radiation pattern shows that one can control the direction of the main beam and the levels of minors lobes from the diameters and numbers of the holes. This significantly reduces the weight of the antenna while improving its performance.

On the antenna efficiencies for the dielectric leaky‐wave antennas with a sinusoidal metallic diffraction grating coupled from the broad and the narrow face of the dielectric

AbstractThe antenna efficiencies of dielectric leaky‐wave antennas (DLWA) with sinusoidal metallic diffraction grating for the couplings from the narrow and the broad faces of the dielectric line are compared. It is observed that the narrow face‐coupled DLWA does not exhibit stop‐band behavior giving the opportunity of a wideband operating range while the broad face‐coupled DLWA gives much higher antenna efficiency out of the resonance region. The effects of the geometrical parameters on the antenna efficiency are also investigated. As a common property for both coupling types, choosing a larger teeth depth/amplitude or more number of periods of the sinusoidal grating provides higher antenna efficiency. On the other hand, for the broad face coupling case, the stop‐band frequency shifts significantly for the chosen different values of the grating's period. By this complementary study, an additional data is provided to the antenna designer. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26223

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.

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.

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.

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.

Improved perturbation analysis for a new omnidirectional periodic dielectric rod leaky‐wave antenna for millimeter‐wave application

AbstractThe leakage characteristics of a new millimeter wave omnidirectional periodic circular dielectric rod leaky‐wave antenna are analyzed by an improved perturbation method. The electromagnetic fields are described in terms of a radial transmission‐line network, which brings considerable physical insight into the overall behavior of the leaky‐wave antenna. The analysis yields expression for the leakage constant in a closed form so that the design procedure of the antenna becomes very convenient. It was found that the circular dielectric shell layer greatly affects the leaky characteristics of the antenna. The results obtained by the present analysis are compared with the exact solution based on the mode‐matching method. It is justified that the improved perturbation procedure yields as accurate results as the rigorous method, with extreme simplicity of the analysis and calculations. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 344–346, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10316

Radiation from Dielectric Leaky-Wave Antennas with Circular and Rectangular Apertures

ABSTRACT The dielectric leaky-wave antenna considered here consists of multiple dielectric layers above a ground plane, with a simple source such as a dipole inside the layers. The layers act as a guiding structure for the radiating leaky wave field, which propagates radially outward from the dipole source. Such an antenna may produce either a broadside beam or a scanned conical beam, depending on the chosen scan angle. For the practical case of a finite-size aperture, the radiation pattern is determined by integration of the tangential fields over the aperture. For narrow-beam structures the leaky-wave field on the aperture may extend to large distances, and hence it is important to have an efficient calculation of the radiation pattern for such cases. It is shown here how to efficiently calculate the radiation pattern for a dielectric leaky-wave antenna having a finite-size aperture that is either circular or rectangular in shape. The derived formulas apply for a dipole source inside any type of dielectric layer structure, and thus include the usual case of a microstrip antenna element on a single layer, as well as the more specific leaky-wave antenna structure considered here.

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.

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.

Radiation from one-dimensional dielectric leaky-wave antennas

Dielectric leaky-wave antennas consist of multiple dielectric layers above a ground plane, along with a simple source such as an infinite line current in the one-dimensional case. The layers act as a guiding structure for one or more leaky waves, which are responsible for producing a narrow-beam radiation pattern. Depending on the beam angle, the leaky waves may extend for a considerable distance from the source, and thus experience truncation effects due to a finite-size substrate. One of the purposes of the present investigation is to study efficient methods for calculating the patterns under such conditions. The chirp z-transform (CZT) is shown to be very efficient for this. Simple approximate formulas for calculating the radiation pattern are also investigated. In addition, a study is also made of the different contributions to the total aperture field, including the leaky-wave field, the space-wave field, and the surface-wave field. >

Radiation characteristics of uniform and nonuniform dielectric leaky-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. >

Leaky-wave antenna for square radiation pattern

A centre-fed strip loaded rectangular dielectric rod leaky-wave antenna which can produce sharp cutoff square radiation pattern with large beamwidth and low ripple amplitude is reported. It can be used as an ideal feed with low spillover for deep cylindrical paraboloids.

Improved perturbation analysis of millimeter-wave omni-directional periodic dielectric rod antenna

The characteristics of the omni-directional periodic circular dielectric rod leaky-wave antenna is analyzed by the improved perturbation method. The electromagnetic fields are described in terms of a radial transmission-line network, which brings considerable physical insight into the overall behavior of the periodic antenna. The analysis yields expression for the leakage constant in a closed form, and the design procedure of the antenna is tremendously simplified. Comparisons between the approximate and rigorous results, as well as the experiment data, are made. It is found that accuracy obtainable from the perturbation analysis is adequate for practical design purposes.

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.

New approach for computing radiation pattern of dielectric leaky-wave antenna

A novel approach based on a waveguide model is proposed for determining the complex propagation constant of a leaky wave structure by Galerkin's method. Then the far field radiation can be obtained in terms of the tangential electric fields in the Fourier transform domain. By this approach the undesirable sidelobe in the radiation pattern is shown and patterns with lower sidelobes can be obtained.

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.

Frequency scanning by leaky-wave antennas using artificial dielectrics

Frequency-scanning characteristics of an artificial dielectric leaky-wave antenna are discussed. It is experimentally observed that the beam angle changes from 10\deg to 50\deg off broadside when the frequency is changed from 8.13 to 9.05 GHz. Over this frequency range the beamwidth does not vary monotonically and changes from 7.5\deg to 6.0\deg to 7.1\deg . It is found that the artificial dielectric antenna has a better temperature stability than that for frequency scanned arrays.