Directive millimetre-wave antenna based on freeformed woodpile EBG structure

A high directivity millimetre-wave antenna based on woodpile electro-magnetic bandgap (EBG) material at W-band is presented. The woodpile EBG structure is fabricated using the ceramic extrusion freeforming technique with high purity alumina powder. The designed antenna can achieve a narrow beam without using an array. The measured half power beam widths are 14deg and 10deg for E-plane and H-plane, respectively. Measurements results are good compared with simulations     

Cylindrical EBG antenna for short range gigabit wireless communications at millimetre-wave bands

An omnidirectional millimetre-wave antenna based on a cylindrical electromagnetic bandgap (EBG) resonator is presented. The cylindrical woodpile is fabricated using the ceramic extrusion freeforming technique with high purity alumina powder. The designed antenna can achieve a narrow beam with 6.5° measured half power beam-width in the elevation plane without using an array configuration. The overall antenna gain is approximately 5 dBi at 94.2 GHz, suitable for future short range gigabit wireless communications.     

Magneto-dielectrics in electromagnetics: concept and applications

In this paper, the unique features of periodic magneto-dielectric meta-materials in electromagnetics are addressed. These materials, which are arranged in periodic configurations, are applied for the design of novel EM structures with applications in the VHF-UHF bands. The utility of these materials is demonstrated by considering two challenging problems, namely, design of miniaturized electromagnetic band-gap (EBG) structures and antennas in the VHF-UHF bands. A woodpile EBG made up of magneto-dielectric material is proposed. It is shown that the magneto-dielectric woodpile not only exhibits band-gap rejection values much higher than the ordinary dielectric woodpile, but also for the same physical dimensions it shows a rejection band at a much lower frequency. The higher rejection is a result of higher effective impedance contrasts between consecutive layers of the magneto-dielectric woodpile structure. Composite magneto-dielectrics are also shown to provide certain advantages when used as substrates for planar antennas. These substrates are used to miniaturize antennas while maintaining a relatively high bandwidth and efficiency. An artificial anisotropic meta-substrate having /spl mu//sub r/>/spl epsiv//sub r/, made up of layered magneto-dielectric and dielectric materials is designed to maximize the bandwidth of a miniaturized patch antenna. Analytical and numerical approaches, based on the anisotropic effective medium theory (AEMT) and the finite-difference time-domain (FDTD) technique, are applied to carry out the analyzes and fully characterize the performance of finite and infinite periodic magneto-dielectric meta-materials integrated into the EBG and antenna designs.     

35GHZ Patch Antenna Array Based on the Electromagnetic Band‐Gap Structure

The electromagnetic band‐gap (EBG) structure, also called photonic band‐gap structure, consisted by triangular arrays of air columns on the dielectric structure is designed and studied by using the FDTD method. According to the simulated and measured results, the EBG structure effectively suppressing surface wave for TE and TM modes is designed. The optimized EBG structure is presented.The proposed EBG structure is applied to the four‐element microstrip patch array antenna. As results of simulation and measurements, the impedance bandwidth and the gain of proposed EBG patch array antenna are improved.     

Ka 波段EBG 天线阵列的仿真与分析

电磁带隙(EBG)天线是一种可以提高天线辐射口径及增益的新型天线,本文首先以FSS 结构作为EBG 反射面,角 锥喇叭作为辐射源,设计了一种可以工作在29.7-30.2GHz,最大增益为23dB 的EBG 天线;其次,研究了7 个喇叭构成六 边形阵列时的阵列特性;最后,将EBG 天线用作单反射面多波束天线的馈源研究了波束的覆盖特性,结果表明,当波束 大小为1.12°时,多波束天线的峰值增益为44.5dB,边缘交叠电平为40.4dB,载干比大于12dB。证明了这种EBG 天线 具有良好的工作性能,为将来小型化反射面多波束天线的设计提供了一种新的思路。     

Design and implementation of electromagnetic band‐gap embedded antenna for vehicle‐to‐everything communications in vehicular systems

We proposed a novel electromagnetic band‐gap (EBG) cell‐embedded antenna structure for reducing the interference that radiates at the antenna edge in wireless access in vehicular environment (WAVE) communication systems for vehicle‐to‐everything communications. To suppress the radiation of surface waves from the ground plane and vehicle, EBG cells were inserted between micropatch arrays. A simulation was also performed to determine the optimum EBG cell structure located above the ground plane in a conformal linear microstrip patch array antenna. The characteristics such as return loss, peak gain, and radiation patterns obtained using the fabricated EBG cell‐embedded antenna were superior to those obtained without the EBG cells. A return loss of 35.14 dB, peak gain of 10.15 dBi at 80°, and improvement of 2.037 dB max at the field of view in the radiation beam patterns were obtained using the proposed WAVE antenna.     

An External Calibration Scheme for DBF Antenna Arrays

A novel calibration scheme is presented that is especially suited for complex digital beamforming (DBF) antenna arrays at millimeter-wave frequencies. Calibration data is extracted by sampling the field of each radiator at certain locations near the array by fixed probe antennas. A scalable calibration model for evaluation of the measured data is described. First tests are performed on a small passive array representing a unit cell of larger arrays. The calibration scheme is subsequently applied to and tested on a 64 element DBF transmit antenna array.      

一体化侦测阵列天线技术研究

本文在一种宽带偶极子单元天线的基础上,对由单元天线组成的常规侦测阵列进行改进设计,通过组阵方式实现了一种新颖的一体化侦测阵列天线。文章运用HFSS 电磁仿真软件结合干涉仪测向原理分别对两种侦测阵列进行性能比较。结果表明,新颖的一体化阵列实现了既包括常规侦测阵列的功能,又利用其组阵后的波束形成及其控制灵活等特 点,较单元天线实现更高的天线增益,这对提高系统的灵敏度和多功能性有很大帮助,比较适合应用于宽带一体化侦测系统。     

Performance enhancement of a compact wideband patch antenna array using EBG structures

In this paper, a compact wideband linear microstrip phased array antenna (MPAA) is proposed. To reduce the size of MPAA, a compact wideband aperture coupled microstrip patch antenna (MPA) is utilized as array element. Size reduction of the array element is performed through incorporating an interdigital capacitor (IDC) in the patch and a metamaterial (MTM) unit cell close to slot in the ground plane of the antenna. By cutting two vertical slits from the slot, further compacting of the slot in the ground plane of array element is obtained. By this technique dimensions of the patch and slot are reduced by 12.9% and 12.2%, respectively. Furthermore, dimensions of the MPAA are reduced through decreasing the spacing between array elements causing the antenna performance degradation. To overcome this shortage and improve the radiation characteristics of the proposed MPAA, an electromagnetic bandgap structure (EBG) is utilized. The effect of implementing EBG cells on the reflection coefficient of the elements in the MPAA during beam scanning is studied in details. The maximum measured gain, bandwidth and cross-polarization level of the fabricated MPAA are 13.3 dBi, 24.4% and −40 dB, respectively making it a good candidate for monopulse tracking radar applications. The measurement results confirm the simulation results.     

Integrated horn antennas for millimeter-wave applications

This paper reviews the development of integrated horn antennas since their introduction in 1987. The integrated horn is fabricated by suspending a dipole antenna on a thin dielectric membrane in a pyramidal cavity etched in silicon. Recent progress resulted in optimized low and high-gain designs with single and double-polarizations for remote-sensing and communication applications. A fullwave analysis technique have resulted in an integrated antenna with performance comparable to that of waveguide-fed corrugated horn antennas. The integrated horn design can be easily extended to large arrays for imaging and phased array applications while still leaving plenty of room for the rf and w processing circuitry. Theoretical and experimental results at microwave frequencies and at 90, 240 and 802 GHz will be presented.     

A Double-sided Printed Dipole Array with an Electromagnetic Band-Gap Reflector

Electromagnetic band-gap (EBG) structures have unique properties in controlling the propagation of electromagnetic wave and have been applied to a wide range of electromagnetic devices design. In this paper, a double-sided printed dipole (DSPD) array backed by an EBG reflector is proposed for achieving a low-profile design as well as gain enhancement. Simulation results show that a reduction of more than 55% in antenna height can be obtained by placing the DSPD array over an EBG reflector rather than a perfect electric conductor (PEC) reflector. And the obtained gain of the antenna with an EBG reflector is about 1.9 dB higher than that with a PEC reflector at the operating frequency 2.77 GHz. The EBG reflector can be utilized to reduce a cavity-backed antenna height and enhance the antenna radiation efficiency. The design has a good potential application to antenna arrays with more elements in wireless communication.     

Arrays and New Antenna Topologies for Increasing THz Power Generation Using Photomixers

Power limitations in CW THz generation imposed by conventional photomixers (“antenna emitters”, AEs) are the major drawbacks on THz generation. From the antenna point of view, two different strategies are proposed to increase the generated power: optimized arrays and lenses arrangements and the use of new dielectric horn antennas. Then, using multiple small lenses, one per each single element, instead of a large one, bigger than the array, makes the generated power much higher. In addition, horn antennas etched in the substrate are considered in order to reduce the energy distribution scattering. Finally, some manufacturing issues are discussed.     

Feed network for dual beam reflector antennas

A primary feed network for doubly curved shaped-beam reflector antennas is described which allows simultaneous signal reception on two distinct elevation plane patterns such that the underside falloff separation between a fixed lower beam and a higher beam can be substantially varied in a lossless manner. A three-element feed array is employed wherein two elements of the array are interconnected by means of a sum-difference hybrid. The sum port generates the fixed low beam while the difference port generates an orthogonal beam pattern suitable for RF combining with an independent high beam generated by the third array element. Adjustment of the combining amplitude and phase relationships permits the variation of the underside falloff separation. The fixed low beam is, of course, also used for transmission at high power. Design parameters for a typical surveillance radar application axe discussed for a linearly polarized case. Calculated antenna patterns and free-space coverage diagrams are presented. The complexities of extending the feed network concept to handle switchable linear/circular polarization cases and an integral directional beacon pattern for L band systems are indicated.     

Investigation of the characteristics of low-cost and lightweight horn array antennas with novel monolithic waveguide feeding networks

3D printed X-Ku band single horn antenna and 2 × 1 and 2 × 2 pyramidal horn array antennas with novel lightweight and monolithic waveguide feeding networks (WFNs) are proposed at 10–15 GHz for satellite communications and radar systems to increase the gain. Proposed novel fabrication method consists of two main steps that are to make the skeleton of horn array antenna from acrylonitrile butadiene styrene (ABS) thermoplastic via 3D printer and to perform copper plating over all surface of antenna by using the electroless plating and electroplating processes. The WFN structures with 3λ element spacing designed and realized by using WR75 waveguide T-junction, E-type bend, and UDR 120 flange. Qualitative agreement between measurement and simulation via CST Microwave Studio is obtained with max 1 dB due to high precision and surface roughness. The gains of array antennas are increased by about 1.5 dB and 3 dB, respectively compared to the single antenna. VSWRs of array antennas are 0.3 dB and 0.6 dB, respectively higher than the single one. In the study, proposed 3D printed components not only with 90% lighter weight than, but also with 80% cheaper than commercial products, and horn arrays with -40 dB cross-polarization values.     

Tailoring the AMC and EBG characteristics of periodic metallic arrays printed on grounded dielectric substrate

The artificial magnetic conductor (AMC) and electromagnetic band gap (EBG) characteristics of planar periodic metallic arrays printed on grounded dielectric substrate are investigated. The currents induced on the arrays are presented for the first time and their study reveals two distinct resonance phenomena associated with these surfaces. A new technique is presented to tailor the spectral position of the AMC operation and the EBG. Square patch arrays with fixed element size and variable periodicities are employed as working examples to demonstrate the dependence of the spectral AMC and EBG characteristics on array parameters. It is revealed that as the array periodicity is increased, the AMC frequency is increased, while the EBG frequency is reduced. This is shown to occur due to the different nature of the resonance phenomena and the associated underlying physical mechanisms that produce the two effects. The effect of substrate thickness is also investigated. Full wave method of moments (MoM) has been employed for the derivation of the reflection characteristics, the currents and the dispersion relations. A uniplanar array with simultaneous AMC and EBG operation is demonstrated theoretically and experimentally.     

Further discrete optimizations for continuous aperture illuminations

Two applications of an iterative procedure to establish a means of optimizing theoretical low sidelobe antenna patterns are discussed. Examples described consider discrete element linear array antennas where the parameters involved in the optimization process are coefficients ordinarily associated with continuous aperture illuminations. One application uses the iterative procedure to control far-out sidelobe levels of the far-field pattern to establish array element excitations appropriate for low sidelobe behavior throughout the entire visible region of space. The other application uses the procedure to establish beam port amplitude weightings at a minimum number of beam ports in a multibeam feed network also suitable for low sidelobe antenna pattern behavior.     

EBG Superstrate Array Configuration for the WAAS Space Segment

Two different electromagnetic bandgap (EBG) superstrate array antenna configurations, intended for the Wide Area Augmentation Service space segment, are presented in this paper. The described antenna configurations take advantage of the directivity enhancement produced by a semireflective sheet placed parallel to a metallic ground plane. The first design presented is realized using a 2$,times,$ 2 circularly polarized (CP) patch array illuminating an EBG superstrate composed of a square pattern of circular holes etched in a thin metallic sheet. The second design consists of a 2$,times,$ 2 CP helix array feeding a hexagonal pattern of holes etched into a metallic EBG superstrate. Both configurations have been designed, breadboarded, and measured, and excellent agreement between simulations and measurements has been recorded. The accurate control of the antenna pattern phase center variation with both the frequency and the antenna field of view, necessary for the intended navigation antenna application, has been the principal challenge of this work. The EBG technology designs presented here are simpler than conventional navigation antennas and can lead to cost reduction, beamforming network simplification, and height reduction while offering similar radio-frequency performances to equivalent products realized in conventional technology.      

EBG结构在35GHz微带阵列天线中应用

分别采用理论计算和实验测试法分析介质基片上钻孔型电磁带隙(EBG)结构的阻带特性,得出了一致结论.依据仿真与测试结果,设计了一种同时抑制TE和TM模的EBG结构,并应用于4单元35GHz微带型阵列天线.测试结果表明:该EBG结构微带阵列天线带宽增加约1倍,增益提高了1.3dBi.     

EBG 结构改善天线辐射特性初步研究

本文研究了高阻表面型EBG,其蘑菇形二维周期结构具有紧致特性,周期和单元尺寸远小于工作波长,非常适 合于阵列天线设计,它的表面波抑制特性有助于改善天线性能。采用Mushroom-like EBG 结构形式,针对12GHz 频率完成 初始结构参数选取,利用同轴探针模型给予验证。随后加载于波导缝隙阵列,采用HFSS 模拟软件,通过优化设计,降 低了方向图副瓣及后瓣,其中对第二副瓣和后瓣的抑制优于2dB,前向辐射也有所增加,达到了改善天线辐射特性的目的。     

Experimental woodpile EBG waveguides, bends and power dividers at microwave frequencies

Experimental waveguides, bends and power dividers in the woodpile electromagnetic bandgap (EBG) material at Ku-band are demonstrated. Prototypes are fabricated from alumina, and use an efficient waveguide transition to enable high quality measurements. Low-loss transmission is demonstrated for a waveguide and a 90/spl deg/ bend, and near equal power division shown for a woodpile EBG waveguide power divider. The components have the potential to be scaled for applications at millimetre-wave and terahertz frequencies