Circularly polarized aperture-coupled circular microstrip patchantennas for L-band applications

Circularly polarized aperture-coupled circular microstrip patch antennas are investigated with the goal of obtaining an 8% impedance and ellipticity bandwidth in the L-band. Three varieties-a single-feed patch with perturbation segments, a single-feed stacked patch with perturbation segments, and a dual-feed patch with a 3-dB branch line coupler as an external polarizer are considered to obtain the required performance. All the three investigated patch configurations meet the impedance bandwidth requirement, but only two varieties: the single-feed stacked patch and the dual-feed patch meet the required ellipticity bandwidth. These antennas feature more than 9-dBi gain. They use low-cost substrates and foam for bandwidth enhancement and, hence, they are attractive for applications where the production cost is of importance     

Circularly polarized single-fed wide-band microstrip patch

For more than 25 years, the circularly polarized single-fed microstrip patch was considered to be extremely narrow-band. The reported performances are almost exclusively related to single patches printed on a dielectric substrate, which partially explains the frequency characteristics. The antenna proposed is a variation of the "almost square" patch and exhibits measured axial radio of less than 2.5 dB over a 13% bandwidth. The antenna was designed for wireless applications.     

一种新型V型槽圆极化微带贴片天线

提出了一种基于非对称V型槽加载的探针馈电圆极化单层钻石形微带贴片天线。通过调节V型槽的槽宽、槽长、开槽倾角及馈电点位置可实现微带贴片天线的圆极化辐射。研究了V型槽尺寸对微带贴片天线性能的影响。结果表明:介质厚度为0.051λ_0(λ_0为中心工作波长)时,天线的阻抗带宽大于9%(VSWR≤2),圆极化带宽为3%(AR≤3),最大增益可达6.29 d Bi,最小轴比小于0.5 d B。     

Inset microstripline-fed circularly polarized microstrip antennas

Circular polarization (CP) designs of inset microstripline-fed microstrip antennas are proposed. Three designs with a single slit, two pairs of slits, and three pairs of slits are experimentally studied. Good CP performances of the proposed antennas are achieved. For the design with three pairs of slits studied here, the center CP frequency is also seen to be lowered by about 33% compared to the case without slits, which suggests that an antenna size reduction as large as 55% can be obtained if the proposed design is used in place of a conventional CP design at a fixed frequency.     

Circularly polarized microstrip antenna with a single feed

A novel circularly polarized (CP) microstrip antenna with a single coaxial feed is introduced. The antenna consists of two layers, each radiating fields which at the zenith are perpendicular to each other with 90° phase difference. The CP bandwidth is substantially higher than that of the previously reported CP microstrip antennas with two nearly degenerate modes. In principle, a perfect CP radiation is feasible without the input impedance mismatch. The CP design procedure is independent of the feed location     

Two-port higher mode circular microstrip antennas

For circular microstrip antennas, single-mode design techniques work well for the dominant mode (n=1, where n is the azimuthal dependence of the fields in the antenna), but this is not the case for zero-order (n=0) and higher order (n>1) modes, where a modal expansion is necessary. The design of higher order dominant mode circular microstrip antennas is addressed, with an example and measurements for the n=3 case. Measurements for the n =3 modes show reasonable agreement with theory in the forms of the impedance loci, but the frequency dependence is in error by the order of the bandwidth of the antenna. A design example is given for a roof-mounted circular patch for vehicular communications. The example indicates that an n=3 dominant mode patch can be used as a two-port antenna for diversity applications or with a 90° phase shifter and adder as a single-port antenna for omnidirectional coverage with (essentially) circular polarization     

Circularly polarized feed for cylindrical parabolic reflector antennas

The feed design described is a linear array of crossed dipoles above a ground plane. The radiation patterns of the longitudinal and the transverse dipoles are made equal by parallel longitudinal rods, referred to as beam forming rods or beam matching rods. When used as a circularly polarized feed for an offset parabolic cylinder antenna, aperture efficiencies (spillover included) as high as 0.89 are potentially available if the field distribution along the array is uniform. The beam patterns of the feed were computed both by the method of moments and the geometrical theory of diffraction and are compared with patterns measured on a model at 1.5 GHz. A method of matching the impedance for both linear polarizations is proposed using parallel impedance matching rods.     

Circularly polarized circular sector dielectric resonator antenna

A circular sector dielectric resonator antenna (DRA) with circular polarization and a single feed is investigated and demonstrated. The design utilizes the radius to height ratio and feed position of the circular sector DRA to excite two resonant modes that are spatially orthogonal in polarization and in phase quadrature. Experimental results are provided for the design and these demonstrate that the circular sector DRA produces circular polarized radiation with axial ratio less than 3 dB over a 10% bandwidth     

A mutual coupling study of linear and circular polarized microstrip antennas for diversity wireless systems

In this paper, an analysis of mutual coupling is presented to examine the benefits of orthogonal polarizations and patterns for adjacent microstrip antennas. The mutual coupling between two linear polarized antennas orientated in parallel polarizations (E and H plane) is reduced using low dielectric constant materials. The mutual coupling can be reduced an additional 20-35dB at the same inter-element spacing when adjacent elements are orientated in orthogonal polarizations, O plane. Similarly, the mutual coupling between two circular polarized antennas orientated in the parallel polarization is reduced using low dielectric constant materials. However, the reduction in mutual coupling between two circular polarized antenna elements orientated in the O plane is only an additional 1-6 dB. The mutual coupling between a linear polarized sum beam (1/2/spl lambda/) and difference beam (1/spl lambda/) antenna is reduced 20-35 dB below the case when using identical antennas only in the H- and O-planes. Compact two- and four-element multielement antennas with inter-element spacings less than 0.15/spl lambda/ are fabricated and the S parameters and radiation patterns are measured.     

Compact shorted variations of circular microstrip antennas

A circular microstrip antenna has been modified by shorting along the zero field to yield shorted semi-circular and 90° sectoral microstrip antennas. Experimental results on these antennas are presented. The shorted 90° sectoral antenna results in a size reduction of four times without any significant change in performance. The area is further reduced by partially shorting one of the edges of the 90° sectoral antenna     

Mutual coupling between circular disc microstrip antennas

The mutual coupling between microstrip antennas is studied by applying the reaction theorem and the cavity model. A semianalytic formula is derived for disc antennas which takes into account the dependence on the relative angular position of the antennas, as well as on the angular feeding point poisition. Theoretical results are in good agreement with measurements.     

Corrugated circular microstrip patch antennas for miniaturisation

New concepts for a corrugated circular microstrip patch antenna (CCMPA), which is moving in the radial direction and works at a frequency of 1.575 GHz (GPS), using linear and circular polarisation for miniaturisation are designed and fabricated. The linearly-polarised antenna has a reduction of 8.08% in patch diameter, a reduction of 21.12% in area and an increase of 1% in bandwidth compared with a circular microstrip patch antenna (CMPA). The radiation patterns of E-and H-plane for a corrugated-type antenna follow the general CMPA and the gain of the linearly-polarised antenna is 6.8 dBd. Also, the circularly-polarised antenna has a gain of 2.8 dBd and an axial ratio of 1.3 dBd at 1.575 GHz     

Space-wave efficiency of electrically thick circular microstrip antennas

A new very simple expression is presented for the space-wave efficiency of electrically thick circular microstrip antennas. It is derived from numerical results available in the literature, and is valid for the complete range of relative dielectric constants and the thicknesses of substrates which are normally used. It also provides insight into the fundamental influence of the substrate parameters on the space-wave efficiency of the circular microstrip antennas. The results obtained by using this expression are in conformity with those reported elsewhere.     

Circularly polarized rectangularly bent slot antennas backed by arectangular cavity

Rectangularly bent slot antennas backed by a rectangular cavity for circular polarization are proposed. Characteristics of three types of cavity-backed rectangularly bent slot antennas for circular polarization-the single square loop slot, the two-element square loop slot, and the two-arm square spiral slot antenna-are analyzed numerically. The generalized network formulation based on the equivalence principle is given in terms of the method of moments. The magnetic currents on the thin rectangularly bent slots in the presence of the backing cavity are obtained and used to calculate the input impedance, radiation pattern, and axial ratio. Experimental results on the input impedance, radiation pattern, and axial ratio are in good agreement with calculated data     

Green's function calculations on circular microstrip patch antennas

Green's function calculations have been applied to solve the radiation problem of circular microstrip patch antennas. The patch is fed by either a microstrip line or a coax line to be approximated as delta-function-like sources. The resultant Galerkin elements involve only one-fold Sommerfeld-type integrals. The resonant frequency, impedance, and far-field pattern have thus been calculated, which compared nicely with measurements     

宽带高增益圆极化微带天线与阵列

设计了一副宽带高增益圆极化微带天线,并进行组阵分析。天线中心频率2.6 GHz,通过增加寄生贴片和空气层来提高天线单元的增益和带宽。上下两层介质板上边长不同的切角方形贴片分别激励一个低频与高频的圆极化模,有效地拓宽了轴比带宽。仿真结果表明,反射系数|S11|<-10 dB带宽21.8%,3 dB轴比带宽12.0%,中心频率点增益9.0 dBi。对天线单元进行加工测试,与仿真结果较为吻合。设计了2×4元阵列,并进行了仿真,增益提升至17.5 dBi,3 dB轴比带宽10.4%。     

宽带宽角圆极化微带贴片天线设计

提出一种新的宽带宽角圆极化微带天线设计方法 ,在利用 L探针进行近耦合馈电的基础上 ,通过薄介质基片加载 ,使贴片天线的阻抗带宽 ( VSWR≤ 2 )和宽角轴比带宽 ( 4 5°圆锥空域内 AR≤ 3d B)达到 2 0 %以上 ,同时保持了微带天线的固有优点 :剖面低 (厚度小于 0 .1中心频率波长 )。利用该方法设计的试验天线的带宽达到2 1 % ,从而证实了该方法的正确性和实用性     

用于高功率微波测量的圆极化微带阵列天线

在进行高功率微波(HPM)辐射场测量时,测量天线的极化匹配对测量精度影响较大。为提高测量精度,介绍一种微带圆极化阵列天线,采用功分器作为馈电网络,获得了小于1 d B的轴比,与非阵列圆极化微带天线相比,使轴比降低约1 d B。因此,当采用该圆极化阵列天线测量线极化微波的远场辐射时,使极化失配对测量结果的影响由±13%降至±3.6%左右。     

Analysis of circularly polarized square ring and crossed-strip microstrip antennas

Segmentation technique coupled with cavity model have been used to analyze square ring and crossed-strip microstrip patch antennas for circular polarization. This technique is found to predict the characteristics of antennas correctly, as is evident from the close agreement between the calculated and measured results for resonant frequency, input impedance, radiation patterns, and bandwidth. Square ring antenna has been found to have larger impedance bandwidth and axial ratio bandwidth because of lowerQ. Crossed-strip antenna has larger size and thus fabrication tolerances can be relaxed.     

Design of aperture-coupled annular-ring microstrip antennas for circular polarization

The design of an aperture-coupled annular-ring microstrip antenna for circular polarization (CP) is presented. The CP radiation of the annular-ring microstrip antenna is achieved by a series microstrip-line-feed configuration through the coupling of a ring slot in the ground plane. The key parameters of the proposed design are investigated using a commercial simulation software based on the Method of Moments to show how to obtain the 50 /spl Omega/ input impedance and optimum axial ratio. The proposed design can be applied to the annular-ring microstrip antennas with different inner radii and substrate thickness, and several antenna prototypes are constructed and measured. Details of the experimental results of the CP performance are presented and discussed.