A millimeter wave dielectric waveguide antenna

This paper describes the theoretical and experimental results of a novel leaky-wave antenna incorporating a homogeneous dielectric transmission line and radiating aperture into a single structure. The primary objective of this investigation is to demonstrate the ability to control aperture radiation by simply cutting slots into a metal-free dielectric transmission line. Experimental line source antennas with identical periodic slots were designed to operate in the 35 GHz frequency region. The successful performance of these antennas resulted in the design of a dielectric line source antenna with a symmetrical amplitude taper which provided a lower sidelobe level. The design represents a significant breakthrough in achieving affordable, low-loss, lightweight antennas in the millimeter wave region. The most significant applications for this type of antenna include radar surveillance and tactical missile-seeker terminal guidance.     

Microstrip dipoles on electrically thick substrates

Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed.This research was supported by NSF Research Grant ESC 82-15408 and U.S. Army Research Grant DAAG-29-83-K-0067.     

Optimum Design of Millimeter-Wave Double-Dielectric Fresnel Zone-Plate Lens and Antenna

The microwave/millimeter-wave Fresnel-zone plate (FZP) lenses differ substantially in construction, technology and applications from their optical analogs and require specific design equations and methods of electromagnetic analysis. In this paper, optimum design equations for double-dielectric lossless FZP lens are derived. The best and worst choices of the permittivity ratio for lossless dielectrics are discussed in detail. In addition, the influence of dielectric losses on the lens thickness for given wavelength and permittivities is examined.Two versions of a 57.5-GHz double-dielectric phase-reversal zone plate are used as focusing elements of FZP lens antenna. The antenna co-polar and cross-polar radiation patterns, aperture efficiency and frequency bandwidth are analyzed numerically and contrasted with those of half-blocked FZP and horn lens antennas.     

The research of high-directive anisotropic magnetic metamaterial antenna loaded with frequency-selective surface

This paper uses a Computer Simulation Technology microwave studio to simulate the performance of a new high-directivity anisotropic magnetic metamaterial antenna loaded with a frequency-selective surface. Frequency-selective surface with cross-dipole element has a great effect on the directivity, radiation pattern, and gain of such an antenna. The experimental results show that frequency-selective surface (FSS) significantly improve the radiation performance of anisotropic magnetic metamaterial antenna. For example, as a single anisotropic magnetic metamaterial antenna, half power beam width is 4 degrees in the H planes, and the gain of this antenna is 19.5 dBi at 10 GHz, achieving a 2.1 degree increment in half power beam width, and a 7.3 dB gain increment by loading with the FSS reflector. The simulating results are consistent with our experimental results.     

圆极化高温超导微带天线阵

一个用于直接广播卫星(DBS)系统的圆极化和单一馈电网络的四单元高温超导微带天线阵,被设计和制造在一个0.5毫米厚的氧化镁衬底上,中心频率是12.2GHz。为了比较,一个天线是采用金膜制造的,另一个是采用超导薄膜钇钡铜氧(YBCO)制造的。为了提高圆极化阵的轴比特性,运用连续旋转的技术。效率、方向性、回波损耗和带宽分别在室温和液氮温度下被测试。采用超导薄膜钇钡铜氧(YBCO)制造的阵表现很好的圆极化特性,并且在温度为77K下时的增益比室温时的金膜天线阵大1.64dB。在谐振频率12.24GHz时回馈损耗为-30.6dB并且总的有效带宽大约为3.52%。这个结果显示当高温超导体用于微带天线阵时,能提高天线阵的效率。     

Curvilinear Fresnel-Zone Plate Lens Antenna: Vector Radiation Theory

A generalized vector diffraction theory of the half-open curvilinear Fresnel zone plate (FZP) tens antenna that is valid for any lens profile shape is presented. It is an extension to the vector Kirchhoff diffraction theory for the plane half-open FZP lens antenna and is based on the conical-segment lens profile approximation. An equation for the electric far-field vector is derived from which follow the expressions for the co- and cross-polarization radiation patterns and directive gain. The proposed theory is utilized for a numerical analysis and comparison of 140-GHz curvilinear half-open FZP lens antennas grouped in two distinct sets:

A twin slot antenna on a layered substrate coupled to a microstrip feed line

A method is described for calculating the input impedance as seen by the detector for a twin slot antenna structure. This technique is then used to analyze several twin slot antenna configurations, leading to improved performance.     

Radiation properties of microstrip patch antenna covered with an anisotropic dielectric layer and a plasma sheath

By using SO-FDTD method, radiation properties of microstrip patch antenna covered with an anisotropic dielectric layer and a plasma layer are investigated. Simulation results show that the resonant frequency of antenna covered with a plasma layer varies with different plasma parameters. It has been indicated that the frequency offset of antenna is as high as 120 MHz when plasma frequency changes from 1 GHz to 8 GHz. The effect on antenna covered with an anisotropic dielectric layer is analyzed, while altering the dielectric constant or thickness of dielectric layer. Finally, the peak gain of antenna in complex plasma environment is presented in detail.     

Astigmatism in tapered slot antennas

A series of scale model measurements of transverse electromagnetic mode tapered slot antennas are presented. They show that the beam launched by this type of antenna is astigmatic. It is shown how an off-axis spherical mirror can be used to correct this astigmatism to allow efficient coupling to quasi-optical systems. A millimetre wave antenna and mirror combination is described and, with the aid of solid state noise diodes, the coupling of the launched beam to a quasi-optical spectrometer is shown to be in good agreement with that predicted by the scale model measurements.     

Effects of substrate anisotropy on the dispersion of transient signals in microstrip lines

The analysis of dispersion characteristics of transient signal in microstrip lines with anisotropic substrate is developed here, with particular attention directed toward the effects of arbitrary orientations of the principal optical axis in anisotropic substrates. Numerical simulations are carried out for the propagation of transient signals, square or Guassian pulses, along microstrips with anisotropic substrates. It is shown that the dispersion characteristics is substantially affected by the change of the orientation angle of the principal optical axis in the substrate.     

Focused aperture microwave antennas operating in the near field zone

Focusing a microwave antenna is often convenient in order to produce a Fraunhofer-type pattern at short distance from the aperture. The characteristics of the radiation patterns produced by some specimens were experimentally tested and compared with theoretical predictions. Basic criteria are given to design focused antennas, once their radiation pattern characteristics are specified.     

Efficiency of quasi-optical couplers

Millimeter-wave devices are often coupled to radiation by means of a feed antenna placed at the focus of a primary lens or mirror, a technique known as quasioptical coupling. A general expression for the efficiency of such a coupler is derived.The efficiency of such a coupler depends on the relationship of the feed antenna pattern to the numerical aperture of the primary lens. An approximate general rule for coupler design is obtained. This rule is as follows. Let _o be the angle between the direction in which the feed pattern is maximum and the direction in which the pattern intensity has one-half its maximum value. Then the optimum numerical aperture of the primary lens is approximately sin (1.67 _o). The effects of focussing errors and lens aberrations can also be calculated by this technique.     

连续相位变化毫米波衍射天线

基于菲涅尔原理及卡塞格伦天线设计方法,设计了一种口面直径为200 mm的卡赛格伦菲涅耳相位修正平面天线。天线采用连续相位修正方式,由一组同心菲涅耳相位修正圆环组成,与传统卡赛格伦抛物面天线相比,该天线具有平面化结构,大大减小了天线自身重量,天线辐射性能较离散相位衍射天线有大幅度提高。在95 GHz频率下,采用物理光学法进行仿真计算,并采用近场扫描系统进行了天线性能测试,天线3 dB波束宽度分别为0.95及1.05,天线实测增益为44.1 dB,天线口面效率为65%。     

基于双天线的高精度GPS定位测向系统及其在无人水面艇上的应用

介绍了一种基于双天线的高精度GPS定位测向系统,该系统可以实现精确定位、测向。分别从硬件和软件两个方面详细介绍了双天线GPS定位测向系统,双天线GPS系统的硬件部分主要由GPS接收机、主天线和从天线组成,GPS接收机内置OEM板和底层通信板,软件部分主要解析GPS数据处理模块的软件工作流程。通过静态实验和动态实验分析系统定位、测向的精度,实验数据表明静态实验的经度的标准偏差为0.3155米,纬度的标准偏差为0.1962米,第一次静态实验的测向标准偏差为0.0981°,第二次静态实验的测向标准偏差为0.0926°。最后,将此系统应用到无人水面艇,进行直线路径跟踪水上试验。     

NOVEL TERAHERTZ PHOTOCONDUCTIVE ANTENNAS

The photoconductive (PC) antenna is a key device for the recent terahertz (THz) photonics based on laser-pumped generation and detection of THz radiation. In this paper we report on two new types of PC antennas: the Schottky PC antenna and the multi-contacts PC antenna. The former one is able to detect THz radiation intensity without the time-delay scan and useful for applications where spectroscopic information is not important, such as the THz intensity imaging. The latter one is useful for the polarization sensitive THz spectroscopy, such as the THz ellipsometry. The characteristic features of these new types of PC antennas are studied by using a THz time-domain spectroscopy system.     

Study of a microstrip antenna on anisotropic metamaterials

The annular ring microstrip antennas on metamaterial substrates are modeled and analyzed using full-wave analysis in conjunction with Ansoft HFSS^TM. The influence of the permeability tensor of the split ring resonator medium on the resonant characteristics of the antenna is considered. Numerical results for typical resonant frequency behavior and return loss are presented as function of the metamaterial properties and antenna structural parameters.     

Design of 45-degree Linearly Polarized Substrate Integrated Waveguide-fed Slot Array Antennas

This paper presents a method of designing substrate integrated waveguide-fed (SIW-fed) slot array antennas. The design theory is based on the circuit model of slot and via as well as the reflection canceling. To prove the feasibility of this method, a 10-element K-band SIW-fed 45-degree linearly polarized slot array antenna with uniform power distribution is designed. By full-wave simulation, the antenna has a good impedance bandwidth of 7.5% and uniform power distribution. Besides, a maximum gain of 15.3dBi is obtained in the broadside and the cross polarization is suppressed below -23.5dB in the boresight. This type of SIW-fed slot array antennas can be a good candidate for microwave and millimeter-wave applications, especially for auto-motive collision-avoidance radar systems.     

Toward the theory of a loop antenna in an anisotropic plasma

We consider the problem of determining the current distribution along a loop antenna consisting of an infinitely thin perfectly conducting strip coiled into a ring. The antenna is immersed in an anisotropic plasma medium perpendicular to the external magnetic field and is excited by a given EMF. Primary attention is focused on the frequency band in which the excitation of electrostatic waves is possible. The problem is reduced to solving a system of integral equations with logarithmic and singular kernels. Using the solution of these equations, we found expressions for the antenna current distribution and input impedance. The analysis of these expressions is presented. Radiophysical Research Institute, Lobachevsky State University, Nizhny Novgorod, Russia. Translated from izvestiya Vysshikh Uchbnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 358–373, March, 1998.     

Scattering Parameters of FSS on Anisotropic Layers at Millimeter Wave Frequencies

The analysis of periodic structures on anisotropic substrates is presented for incident millimeter waves. Frequency selective surface structures composed by a periodic array of conducting crossed dipoles on anisotropic layers are analyzed. A full-wave analysis for the problem of scattering is performed. The formulation uses the moment method in combination with the immitance approach, in the Fourier domain, to determine the scattering parameters of the considered structures. A set of entire-domain type basis functions is used in the expansion for the unknown induced current. This analysis is computationally efficient, and its accuracy is verified by the agreement between results obtained in this work and those available in the literature, for particular cases.     

Effective medium theory applied to frequency selective surfaces on periodic substrates

We apply the effective medium theory combined with the conventional periodic method of moments （MoM） to analyze frequency selective surfaces （FSSs） on periodic and anisotropic substrates. Based on the effective medium theory, even periodic and anisotropic substrates can be considered homogeneous; thus, the Green’s function can be obtained. The resulting integral equation can then be solved by the MoM using rooftop basis functions and Galerkin testing functions. We analyze an example using this technique, and the numerical results agree with Fallahi’s full-vector semi-analytical method, showing an increasing difference between the results as the frequencies increase. These results show that the proposed method is effective for analyzing FSSs on periodic and anisotropic substrates.