Conical Horn Antenna Research Articles

Three-dimensional large-aperture lens antennas with gradient refractive index

We propose an accurate method for designing three-dimensional (3D) large-aperture metamaterial slab lens antennas with gradient refractive index (GRIN). According to the geometric optics, Fermat principle, ray-tracing technique and impedance matching, the 3D GRIN slab lenses with large apertures are accurately designed and simulated. With the aid of the effective medium theory, an X-band and a Ku-band conical horn antennas loaded with the 3D GRIN slab lenses of 250-mm diameter are experimentally realized using the drilling-hole technique on the printed circuit boards (PCBs) as the unit cells of metamaterials. Compared to the traditional dielectric lens with the same aperture, the proposed antennas have very good performance with high directivity, and the gain is increased by 2 to 5 dB. Using the same method, we design and realize a huge-aperture GRIN lens in the X band with a diameter of 1000 mm, which is composed of nearly one millions of inhomogeneous unit cells of square-ring resonators and dielectric blocks with drilling holes. Due to the huge aperture size, the electromagnetic ray paths inside and outside of the GRIN lens are verified and optimized using the ray tracing technique. Measurement results show good performance of the proposed antenna with high directivity.

Broadband Compact Horn Antennas by Using EPS-ENZ Metamaterial Lens

We present the design of a flat lens, made by a conventional material and an epsilon near-zero metamaterial, to plug up the aperture of a short horn antenna, in order to achieve radiation performances similar to the ones of the corresponding optimum horn over a broad frequency range. Lens operation is based on the phase-compensation concept: phase-fronts of the field propagating along the short flare of the horn propagate with different phase velocities in the two lens materials, resulting in an uniform phase distribution on the aperture. Starting from the theoretical study of the transmission properties of a bulk epsilon near-zero slab, we derive the analytical formulas for the design of the flat lens and validate them through full-wave numerical simulations. Then, a realistic version of the lens, realized with a wire-medium and exhibiting a near-zero real part of the effective permittivity in the frequency range of interest, is presented. Considering two examples working in the C-band, we show that the lens can be designed for both conical and pyramidal horn antennas. In both cases, the length of the horns is half the one of the corresponding optimum versions, while the obtained radiation performances are similar to those of the optimum horns over a broad frequency band. This result may open the door to several interesting applications in satellite and radar systems.

Conical horn antenna on a metal screen with a bias gyromagnetic resonator for the measurement of characteristics of an electromagnetic microwave concentrator

The paper describes an antenna based on a conical horn and magnetized gyromagnetic resonator (GR) on a metal screen which is used to measure electrical characteristics of an electromagnetic microwave concentrator. The antenna under study has improved characteristics as compared with a similar structure without a GR: significantly higher gain at low weight and overall dimensions, circular polarization field radiation with high selectivity, electrical switching of the field rotation direction and virtually inertia-free electrical tuning of radiation frequency.

Design of a Broadband Meander-Line Polarizer for 30 GHz Millimeter-Wave Satellite Communications

This paper proposes a new approach to design circularly polarized antennas for 30 GHz millimeter-wave satellite communications. Circular polarization can be obtained through the use of a meander-line polarizer (MLP) located in front of a 30 GHz linearly polarized conical horn antenna. The influences of the MLP parameters on antenna axial ratio are investigated by parametric studies. The return loss, electric field, radiation pattern, and axial ratio of the antenna are simulated and discussed. Using the proposed method, a 10.5 dBi circularly polarized antenna with an axial ratio (AR) lower than 1dB over the 28-29GHz and 30-31.5GHz frequency band can be achieved.

Pattern synthesis for multi-feed reflector antennas using invasive weed optimisation

The authors present a new optimisation method for pattern synthesis of multi-feed reflector antennas in this study. By using an invasive weed optimisation (IWO) algorithm, shaped beam antennas are designed. The results of the IWO algorithm for the synthesis of cosecant squared and contoured beam patterns are presented and compared with particle swarm optimisation algorithm results. The far-field radiation patterns of reflector antennas, fed by linear and planar array of conical horn antennas, are provided by a physical optics and the error between desired and provided radiation patterns is calculated by a root mean square method. The results show that the IWO algorithm, which provides good convergence, is stable and adaptive-to-change for different boundary conditions in pattern synthesis applications.

Design Synthesis of Metasurfaces for Broadband Hybrid-Mode Horn Antennas With Enhanced Radiation Pattern and Polarization Characteristics

Metamaterial surfaces (metasurfaces) with a low effective index of refraction have been recently proposed for application in the design of hybrid-mode horn antennas, such as soft and hard horns. Here we explore designs of several metasurfaces and their use as liners for coating the interior walls of horn antennas. The design process combines the genetic algorithm optimization technique with a full-wave electromagnetic solver to create dispersion-engineered metamaterials that possess customized surface impedance properties. A metamaterial parameter extraction technique is developed and employed in the optimization process, which is based on the surface impedance expressions for a homogeneous slab backed by a perfectly conducting ground plane illuminated at near grazing incidence. The optimized metasurface is found to be equivalent to a low index metamaterial with a dispersion that can improve the performance of conventional horn antennas over the entire Ku -band while introducing negligible losses. We conclude with a numerical study of a conical horn antenna whose interior is lined with a low index metasurface. The far-field radiation patterns and aperture field distributions confirm hybrid-mode operation over a wide bandwidth, validating the proposed metasurface design methodology.

A DIRICHLET TO NEUMANN MAP BASED HYBRIDIZATION OF A MODE MATCHING AND OFFSET MOMENT METHOD FOR HORN ANTENNAS ANALYSIS

A hybrid technique for the analysis of pyramidal and conical horn antennas is presented based on an exact vector Dirichlet to Neumann (DtN) mapping mathematical formalism. The transition from the feeding waveguide to the radiating aperture is analyzed by using the mode matching technique (MMT) employing a stepped- waveguide approach. Love's field equivalence principle is employed for the definition of equivalent electric and magnetic current densities at the horn aperture. Explicitly, these currents are located at a plane parallel to the aperture but slightly shifted inwards in order to implement an offset Moment Method for their discretization, which is free of integral singularities. The unbounded area field generated by these sources is enforced to be continuous with the internal mode matching field by strictly following DtN principles. Besides that, this procedure mimics a By-moment approach ensuring the decoupling of the required number of modes from that of the sources discretization degrees of freedom. Finally, the implemented hybrid method is validated against published experimental and numerical results for a number of pyramidal and conical horn antennas including various corrugated geometries.

Analysis for Radiation Characteristics of Horn Antenna for Out of Band

The idea of this paper roots in the electromagnetic compatibility design of the whole aircraft system, in which out of band characteristics of airborne antennas are of equal importance as their characteristics in band. The definition of antenna characteristics for out of band is interpreted. Horn antennas are the main research objects in this paper. In order to make characteristic of this type antenna for out of band have a general, this paper is special to select pyramidal horn antenna and conical horn antenna. The characterization framework of horn antennas radiation characteristics for out of band is established, and the theoretical expressions of their radiation characteristics for out of band are given. In ensuring better antenna characteristics in band, four horn antennas that are different types of sizes, different frequency band width are simulated and analyzed by using electromagnetic simulation software HFSS. It is meaningful to analyze radiation characteristics and summarize different features for various performance parameters of these horn antennas for in band and out of band. Focus on characteristics of the changes for the maximum gain, 3dB beam width parameters of horn antennas within the working frequency band and out of working band. The results show that: radiation characteristics of horn antenna are the law within the working frequency band and out of working band.

The Design for WR-06 Corrugated Conical Horn Antenna and its Application in Emissivity Measurement of Microwave Radiator

This paper presents the design for a corrugated conical-horn antenna working in WR06 frequency band and its application in emissivity measurement of microwave radiator. For a calibration target of microwave radiometer, we consider design the corrugated conical-horn antenna to satisfy its measurement requirements of the emissivity of calibration target. The antenna is designed with small flare angle and low VSWR in a frequency range of 150±10GHz. The measurement results for electrical properties of antenna and emissivity of microwave radiator are presented in this paper. The results show that the performance of antenna is fit to the emissivity measurement of radiator of radiometer calibration target.

Optimization of a compact conical horn antenna system for high power microwaves in the 4 to 6 GHz range

High power microwave radiation in the 4-6 GHz range is currently being studied in compact structures. A conical horn antenna is being developed that radiates high power microwaves in the 4 to 6 GHz range into high gain and highly directive radiation patterns from the TE11 mode in the feeding circular waveguide. Utilizing finite element modeling techniques, the behavior of these high power electromagnetic waves can be accurately described inside the waveguide as well as in the near and far field regions. These techniques in turn improve the quality of high power experiments performed on the compact structure. Presented are the modeling results of high power electromagnetic parameters in the compact structure, in the near, and in the far field regions.

Design of conical DRH antennas for K and Ka frequency bands

Two conical double-ridged horn (DRH) antennas for K and Ka frequency bands are presented. Detailed simulation and experimental investigations are conducted to understand their behaviors and optimize for broadband operation. The designed antennas were fabricated with 0.01 mm accuracy and satisfactory agreement of computer simulations and experimental results was obtained. The designed conical DRH antennas have voltage standing wave ratio (VSWR) less than 2.1 and 2.2 for the frequency ranges of 18–26.5 GHz (K band) and 26.5–40 GHz (Ka band), respectively. Meanwhile, the proposed antennas exhibit low cross-polarization, low sidelobe level, and simultaneously achieve slant polarization as well as symmetrical radiation patterns in the entire operating bandwidth. An exponential impedance tapering is used at the flare section of the horns. Moreover, a new cavity back with a conical structure is used to improve the VSWR. Numerous simulations via Ansoft HFSS and CST Microwave Studio CAD tools have been made to optimize the VSWR performance of the designed antennas. Simulation results show that the VSWR of the proposed antennas is sensitive to the probe spacing from the ridge edge and the cavity back structure. The designed conical DRH antennas are most suitable as a feed for the reflectors of radar systems and satellite applications. Results for VSWR, far-field E-plane and H-plane radiation patterns, and gain of the designed antennas are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Design and experiment of a conical double-ridged horn antenna for 6-18 GHz

A broadband conical double-ridged horn (DRH) antenna with symmetrical radiation patterns, low side lobe level, and low cross polarization is presented. Experimental investigations and detailed simulations are conducted to understand its behavior and to optimize for broadband operation. Good agreement between the measurement and simulation has been achieved. The designed conical DRH antenna introduces a low voltage standing wave ratio (VSWR), which is lower than 2.3 for the frequency range of 6–18 GHz and simultaneously achieves slant polarization as well as stable far-field radiation characteristics in the entire operating bandwidth. The common impedance exponential tapering is used at the flare section of the horn. Moreover, a new cavity back with a conical structure is used to improve the VSWR. The simulated and measured results for VSWR, far field E-plane and H-plane radiation patterns, and gain of the designed antenna are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Investigation of a 1.2-GHz Magnetically Insulated Transmission Line Oscillator

A 1.2-GHz magnetically insulated transmission line oscillator (MILO) is investigated numerically and experimentally in this paper. Simulation optimization is performed with the particle-in-cell code KARAT. When the diode voltage and current are 680 kV and 53 kA, the output microwave power is 4.15 GW, the microwave frequency is 1.169 GHz, and the power efficiency is 11.5%. In order to radiate a boresight peak pattern, a TEM-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode-converting antenna is introduced into the MILO device. In the TEM-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode-converting antenna, four metal plates are inserted into the coaxial waveguide to convert the TEM into TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode, and then, the coaxial TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode is converted into circular TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> -like mode and radiated by a conical horn antenna, which generates a boresight peak pattern in a far-field region. The gain of the mode-converting antenna is 16.3 dBi, and the aperture efficiency of the conical horn antenna is 79% at 1.169 GHz. The 3-dB beamwidths are 24° in E-plane and 32° in H-plane, and the sidelobes of the radiation patterns are both less than -21 dB. In the experiments, the MILO device is driven by a 590 kV 49 kA electron beam. The measured results show that the peak microwave power is about 2.9 ± 0.3 GW, the pulse duration is above 20 ns, the microwave frequency is about 1.20 GHz, and the power conversion efficiency is about 10%. The experimental results validate the simulation prediction.

Approximate Closed-Form Expression of the Electric Field of a Conical Horn Antenna

In this paper, an approximate closed-form expression of the electric field of a conical horn with linear flare is formulated. Copolarization and cross polarization component of the electric field are calculated from the spherical field components using Ludwig's third definition of copolarization and cross polarization. The calculated field expression is found to be in close agreement with experimental results found in literature. The radiation characteristics of the conical horn are analyzed using the derived field expressions.

70% Efficient Relativistic Magnetron With Axial Extraction of Radiation Through a Horn Antenna

At the Nagaoka University of Technology (Japan), Daimon and Jiang used particle-in-cell (PIC) code simulations to demonstrate that the electronic efficiency of the A6 magnetron with axial extraction can be increased from 3% up to 37% applying different diffraction outputs, from tapered cavities in a conical horn antenna to modified expanded ones that improve magnetron matching with the antenna. This paper presents PIC code simulation results for the modified magnetron design using a transparent cathode, in contrast with Daimon and Jiang's simulations that used a solid explosive emission cathode. Furthermore, by further optimizing the magnetron parameters, we demonstrate an efficiency approaching 70% with gigawatt radiation power for an applied voltage of 400 kV. By maintaining a synchronous interaction of electrons with the operating wave, we found that the radiation power increases as the square of the diode voltage up to a diode voltage of 800 kV with short rise time that does not exceed 20 ns. In addition, we show that using a transparent cathode promotes avoiding the regime of hard excitation of magnetrons.

Time-resolved imaging of millimeter waves using visible continuum from the positive column of a Cs–Xe dc discharge

We present a high-sensitivity technique for time-resolved imaging of millimeter waves (MMWs) using the visible continuum (VC) from the positive column (PC) of a medium-pressure Cs–Xe dc discharge. For the MMW imaging application, a uniform plasma slab of the PC of a Cs–Xe discharge with 10×8 cm2 aperture and 2 cm in thickness was generated for 45 Torr xenon. The imaging technique is based on the fact that the intensity of the e-Xe bremsstrahlung continuum from the PC increases in the visible region when the electrons in the plasma are heated by MMWs. It is shown that in the MMW intensity range from zero to the threshold of the microwave-induced plasma breakdown, the intensity of the VC from the PC of a Cs–Xe discharge increases approximately as a second-order polynomial function of the MMW intensity. The obtained experimental data agree well with our calculations of the dependence of the VC intensity on electron temperature. The Ka-band MMW field patterns at the output of conical horn antennas and in the quasioptical beam were imaged using the discharge technique. It is shown that the technique can be used for time-resolved measurement of the profiles of watt- and subwatt-level MMWs. An energy flux sensitivity of the technique of about 10 μJ/cm2 in the Ka-band was demonstrated. The temporal resolution of the technique is about 0.8 μs. Our modeling of the transient behavior of the electron temperature in the PC shows that the time history of the electron temperature variation coincides well with the measured time history of the VC intensity variation.

Pattern squint elimination for quad-ridged conical and pyramidal horn antennas using bended probes

This article describes a new technique for pattern squint elimination of quad-ridged conical and pyramidal horn antennas by introducing bended coaxial probes. Because of the phase difference and mutual coupling between vertical and horizontal polarizations, the radiation patterns of the conventional quad-ridged conical and pyramidal horn antennas squint over a wide bandwidth. The proposed technique substantially reduces the phase difference and coupling between the two probes, so a significant improvement in the radiation patterns over the frequency band of 8–18 GHz can be achieved. The designed modified horn antennas are most suitable as a feed element in reflectors of radar systems and EMC applications. The proposed modified antennas have a voltage standing wave ratio (VSWR) less than 2.2 for the frequency range of 8–18 GHz. Moreover, the proposed antennas exhibit high gain, dual-polarization performance, good isolation, low SLL, low back lobe, low cross polarization, and satisfactory far-field radiation characteristics for the entire frequency band. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.

Quad-ridged conical horn antenna for wideband applications

This article presents a quad-ridged conical horn antenna with high gain and low side lobe level for broadband applications. To the best of authors' knowledge, the proposed structure presented in this article is completely new. The designed antenna introduces a low VSWR, which is lower than 2.2 for the frequency range of 8–18 GHz, and simultaneously achieves high gain as well as dual-polarizations with high isolation between the corresponding excitations. The common impedance exponential tapering is used at the flare section of the horn, and a coax to waveguide transition, namely quadruple-ridged circular waveguide, with a conical cavity is used to improve the VSWR. The proposed antenna structure is designed and simulated by two well established packages, namely the CST microwave studio and the Ansoft HFSS, showing there is a close agreement between the results obtained by the aforementioned softwares. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.

Conical Horn Antennas Employing an Offset Moment Method and Mode Matching Technique

A Hybrid technique for the analysis of conical horn antennas is presented based on a rigorous description of the horn aperture-free space discontinuity. The transition from the feeding waveguide to the radiating aperture is analyzed by using the mode matching technique (MMT) employing a stepped-waveguide approach. The discontinuity between the horn aperture and free space is modeled by combining an offset Moment Method with the MMT for the last waveguide section. Results for the input standing wave ratio are given and compared with commercial software results which demonstrate the very good performance of the method.

Double-ridged conical horn antenna for wideband applications

In this article, the design and analysis of a double-ridged conical horn antenna with high gain and low cross polarization for wideband applications is presented. Double-ridged pyramidal horn antennas have been investigated in many references. There are no papers in the literature which are devoted to design and analysis of double-ridged conical horn antenna. The designed antenna has a voltage standing wave ratio (VSWR) less than 2.1 for the frequency range of 8–18 GHz. Moreover, the proposed antenna exhibits extremely low cross polarization, low side lobe level, high gain, and stable far-field radiation characteristics in the entire operating bandwidth. A new technique for synthesizing of the horn flare section is introduced. A coaxial line to circular double-ridged waveguide transition is introduced for coaxial feeding of the designed antenna. The proposed antenna is simulated with commercially available packages such as CST microwave studio and Ansoft HFSS in the operating frequency range. Simulation results for the VSWR, radiation patterns, and gain of the designed antenna over the frequency band 8–18 GHz are presented and discussed. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.