太赫兹超材料相控阵天线波束宽度调控方法

太赫兹超材料相控阵由于其强大的波束操纵能力在探测与通信一体化系统中具有重要的应用价值。为了提升系统的通信和探测性能,需要太赫兹超材料相控阵能够实现宽波束和窄波束的灵活切换。提出了一种基于反相位间隔(反相)编码的太赫兹超材料相控阵天线波束宽度调控方法。通过天线3 dB波束宽度表达式和目标波束宽度逆推阵列规模,保持其相位编码不变并对该阵列规模外的其余阵元进行反相编码,旨在实现相位相反相消。仿真结果表明,所提方法可以准确地调控太赫兹超材料相控阵天线的波束宽度,实现宽波束和窄波束的灵活切换。     

Theoretical design and predictions of volute antenna performance

To provide generic design guidelines for volute antenna elements over a wide range of parameters, a theoretical formulation and algorithm for computing the antenna radiation field have been developed. The procedure relies on the vector combination of the radiation fields of the helical wires and the end connecting wires with a continuous sinusoidal current distribution along each wire of the volute. The antenna patterns of circularly polarized fields, directivity, 3-dB beamwidth, axial ratio, front-to-back power ratio, etc. can all be calculated from a given set of volute parameters. A practical design example utilizing this procedure is presented     

Design of a Compact Millimeter-Wave Microstrip Antenna with Wide Bandwidth and Broad Beamwidth

Design of a novel compact millimeter-wave microstrip antenna with wide bandwidth and broad beamwidth is presented. In the structure, multiple layers and a parasitic element as well as a coupling aperture are used to achieve wideband, while a conducting cylinder and the coupling aperture are used to obtain broad beamwidth. Finally, phased array with eight present elements has been designed as an example. Compared to traditional microstrip antennas and arrays, present antenna and array are of smaller dimension and broader beamwidth as well as wider bandwidth.     

Design of Cylindrical Conformal Millimeter-Wave Microstrip Antennas with Broad Beamwidth

This paper describes the design of a novel cylindrical millimeter-wave microstrip antenna (MA) with broad beamwidth by means of isotropic transformation (IT). A planar millimeter-wave antenna with broad beamwidth is designed first, and then IT is used to design a conformal one based on the planar structure. In addition, phased array with eight present elements has been designed as an example. Finally, numerical results are given to show that the present antenna possesses broad beamwidth and its array is of large scanning angle, which also verify the validity of the method of IT.     

Ground plane impact on quadrifilar helix antenna performance with respect to deployment heights

Quadrifilar helix antenna (QHA) has its applications in satellite communications. This paper presents the performance optimisation of input and radiation characteristics of QHA in the presence of infinite and finite metallic ground planes. For the infinite ground plane, it has been observed that input parameters such as impedance and voltage standing wave ratio (VSWR) are stable, and the antenna has broader half power beamwidth (HPBW). Smaller metallic platforms that act as finite ground planes produce better 3‐dB axial ratio beamwidth and boresight axial ratio. Deployment of QHA on smaller metallic platforms such as nanosatellites and CubeSats enhances the circularly polarised beamwidth of the antenna with improved boresight axial ratio. However, on large low earth orbit (LEO) satellites, stable input characteristics and broader HPBW have been achieved at the cost of narrow circularly polarised beamwidth and degraded boresight axial ratio.     

Low cross-polarised patch antenna with single feed

A probe-fed patch antenna that generates low cross-polarised radiated fields is presented. The probe is located in the centre of the patch conductor and a microstrip line within the patch is used to ensure that good impedance matching is achieved. Enhanced radiation performance of the printed antenna is demonstrated by theoretically and experimentally investigating a circularly polarised (CP) version of the probe-fed patch antenna and comparing the results with a conventional probe-fed CP patch. The new radiator has an axial ratio of less than 1.5 dB at broadside and a 3 dB axial ratio beamwidth of close to 200deg     

Printed figure-of-eight wire antenna for circular polarization

A new printed wire antenna with circular polarization properties is presented. The geometry of the printed wire which takes the form of a figure-of-eight has a total length of 1.3/spl lambda//sub o/ and serves as a nonresonant traveling-wave antenna. It is shown that a 3-dB axial ratio bandwidth of 15% can be achieved. The half-power and 3-dB axial ratio beamwidth is approximately /spl plusmn/45/spl deg/, while its gain is of the order of 6.5 dB.     

一种新型宽带圆极化介质谐振器天线设计与实现*

设计了一种宽带圆极化介质谐振器天线,为一种鼠笼形的宽带一分四90毅相移功分微带馈电网络,采用缝隙耦合对介质谐振器顺序旋转耦合馈电。天线结构紧凑、加工简单,仿真和实测结果吻合良好,其阻抗带宽和低于3dB的轴比带宽重叠部分在1.09 GHz-1.83GHz、为50.7%。增益大于3dB 及轴比小于3dB 的波束宽度均达到90°。天线工作频率覆盖四大导航系统,包括中国的北斗系统、美国的GPS 系统、欧洲的伽利略(GALTLEO)系统和俄罗斯的格洛纳斯(GLONASS )系统的频段,天线可应用于全球卫星导航定位系统和无线宽带通信系统中。     

An ultrawide-bandwidth tapered resistive TEM horn antenna

A novel stable beamwidth, ultrawide-bandwidth low-scattering antenna is presented. This antenna is a modified version of the conducting slotline bowtie hybrid (SBH) antenna with resistive sheets (Rcards) introduced into the guiding structure design. Since the resistive sheets can attenuate creeping wave fields, much smaller rolled edges are needed in the Rcard SBH antenna. Moreover, due to the Rcard's partially transparent nature with respect to electromagnetic fields, the radar cross section (RCS) associated with this new antenna is smaller than the original conducting rolled edge one. By employing an optimization process based on the concept of the genetic algorithm, one can easily design the Rcard SBH antenna to obtain a very stable antenna beamwidth and phase center in both the E- and H-planes across the entire operating frequency bandwidth. Because of its constant beamwidth, low RCS, and broad-band features, the Rcard SBH antenna is an ideal antenna for many applications such as a compact range feed. Calculated and measured results are presented to demonstrate the performance of this new antenna     

一种三馈圆极化微带天线的设计与制作

提出了一种应用于无线局域网（WLAN）通信的三馈圆极化微带天线。天线在2300～2600MHz频带内实现圆极化辐射。天线馈电网络采用三功分馈电,增加了轴比带宽;馈电网络和附加的寄生贴片展宽了阻抗带宽;延伸天线介质衬底增大了波束宽度。仿真与实测结果吻合良好。测量结果表明,天线的阻抗带宽达到46.8%（VSWR〈2）,轴比带宽达到12.2%（AR〈3dB）。     

Dual-polarized slot-coupled patch antennas on Duroid with teflonlenses for 76.5-GHz automotive radar systems

A dual-polarized 76.5-GHz microstrip patch and teflon lens antenna system was designed, constructed, and tested. A receiver (RX) array of three dual-polarized microstrip patches was coupled through a 10-cm-diameter lens to produce radiation patterns with 3° beamwidths and beam crossovers of -3 dB. The transmitter (TX) consisted of a single dual-polarized microstrip patch coupled through a 2.5-cm-diameter lens to produce a 10° beamwidth. Slot-coupled patches were used to isolate the microstrip feed circuit from the radiating elements. The antennas and feeds were fabricated on commercially available 5880 Duriod substrates. Cross-polarization levels were less than -20 dB and were typically less than -30 dB over the entire beam at the design frequency. First sidelobe levels were no greater than -15 dB and were typically closer to -20 dB. Stepped and unstepped versions of the 10-cm-diameter receive lens were designed and fabricated. Antenna system sidelobes levels were lower with the stepped lens while the cross-polarization levels were comparable     

Minimum Sidelobe Levels for Linear Arrays

A method of finding the optimum sidelobe-minimizing weights for an arbitrary linear array is derived that holds for any scan direction, beamwidth, and type of antenna element used. Optimum linear array positions are then determined via the particle swarm optimization method. Hence, the two together can give a global bound on antenna array performance with regards to sidelobe minimization. Results are presented for linear arrays of 2-6 elements for different scan angles, beamwidths and antenna elements.     

Scanning-beam microwave landing system--Multipath-errors and antenna-design philosophy

Multipath reception can cause guidance-angle errors in a microwave landing system (MLS). The antenna radiation-control problem for a scanning-beam MLS is defined and analyzed. "Centerline emphasis" is presented as a helpful design philosophy for the ground antennas. It is shown that the maximum guidance-angle error is proportional to 1) the amplitude of the indirect signal, 2) the antenna beamwidth, and 3) the time derivative of the indirect signal as the direct beam-peak scans by the receiver. This result is used in developing a rationale for the selection of the antenna beamwidth and sidelobe level (aperture size and excitation) for the azimuth and elevation guidance functions.     

An efficient moderate-size vertical-incidence ionosonde antenna for 2-20-MHz polarization studies

A wide cone-angle conical spiral antenna which has been developed for use as a circularly polarized vertical-incidence ionosonde antenna is described. It exhibits an 80-degree beamwidth, 5-dB gain, axial ratio of 1.2:1 and SWR less than 2:1 typically over the band 2-20 MHz. The entire structure is only 38 meters high and 52 meters in diameter. Extensive measurements on models and the full-size antenna are presented which show that the polarization and radiation patterns are quite uniform over the entire operating band. In particular, the radiation pattern shows no evidence of sidelobes at low elevation angles which could cause unwanted oblique returns. The discovery of a beam-reversing phenomenon in spiral antennas is described along with its elimination by geometry control. An example of ionosphere mode selection by means of polarization control with the full-size antenna is presented.     

Gain and G/T of multielement receive antennas with activebeamforming networks

A basic system-level model for the gain and G/T of active multielement receive antennas is presented that covers arbitrary beamforming networks and direct radiating arrays, as well as array-fed systems with one or more focusing elements (reflectors or lenses). Since the model is based on measurable parameters and uses definitions, which are consistent with conventional communication system analysis terms, it can be applied directly to the analysis and design of systems using such antennas and can be used to support the specification, design, and test of such antennas as well, measurement possibilities for the basic parameters are discussed and the characteristic parameters of generic active beamforming networks are derived and compared. Finally, the impact of the different parameters on the overall antenna gain and G/T is illustrated by one application example that covers a reconfigurable multifeed reflector antenna with selectable beamwidth. The presented theory has been verified successfully in the frame of a classified EHF antenna development whose details cannot be reported here     

Circularly polarized twisted loop antenna

A novel wire-loop antenna is introduced for circular polarization. By introducing a small gap at the middle of two nonradiating sides of a one-wavelength square wire loop, a 90/spl deg/ time-phase difference between the currents on the other two radiating sides can be achieved. Then by twisting the square loop to make the radiating sides orthogonal the necessary conditions are satisfied for circularly polarized radiation. The antenna yields nearly ideally circular polarization at broadside as well as excellent input impedance properties near the design frequency. The radiation pattern has a broad beamwidth and good rotational symmetry about the axis. For a demonstrator operating at 1 GHz, a 3-dB axial ratio was maintained over /spl plusmn/30/spl deg/. The mechanism of circular polarization is analyzed based on numerical simulation. Experimental results are presented to verify the theoretical predictions made.     

基于孔径长度域重采样的快速恒定束宽波束形成

为解决宽带阵列天线波束宽度抖动的问题,在分析阵元权系数和阵列方向图傅里叶变换关系的基础上,提出了一种基于孔径长度域重采样的快速恒定束宽宽带波束形成方法。该方法通过期望方向图的傅里叶反变换获取孔径长度域上的权系数曲线,然后用不同的采样间隔对该权系数曲线进行重采样得到不同频率下的阵元权系数。由于仅需进行一次积分运算,该方法具有运算量小、速度快的特点。为使阵列方向图在恒定束宽的基础上具有更好的方向性,通过对孔径长度域拟合度的分析给出了期望方向图的设计方法。仿真结果表明所提方法可以快速形成方向性较好的宽带阵列恒定束宽方向图。     

Wide-scan spherical-lens antennas for automotive radars

A new approach to wide scan-angle antennas at millimeter-wave frequencies is introduced with special focus on ease of manufacturing and reliability. The system is composed of planar feed antennas (tapered-slot antennas), which are positioned around a homogeneous spherical Teflon lens. Beam scanning can be achieved by switching between the antenna elements. The spherical-lens system is analyzed through a combined ray-optics/diffraction method. It is found that a maximum efficiency of 50%-55% can be achieved using Teflon, Rexolite, or quartz lenses. The efficiency includes taper, spillover, and reflection loss. Calculations also indicate that the maximum lens diameter is 30-40 λ₀, which results in a maximum directivity of 39.5-42 dB. Measurements done on a single-element feed and a 5-cm Teflon lens agree very well with theory and result in a 3-dB beamwidth of 5.5° and better than -20-dB sidelobe levels at 77 GHz. Absolute gain measurements show a system efficiency of 46%-48% (including dielectric loss). A 23- and 33-element antenna array with a scan angle of ±90° and a -3.5- and -6-dB crossover, respectively, in the far-field patterns was also demonstrated. The 23-element array resulted in virtually no gain loss over the entire 90° scan angle. This represents, to our knowledge, the first wide scan-angle antenna at millimeter-wave frequencies     

圆极化微带阵列天线的设计

研究了圆极化微带阵列天线的设计方法。重点讨论了用双馈电正方形单元天线实现圆极化、高增益阵列天线的实现方法,并利用Ansoft HFSS 软件进行仿真分析,仿真结果显示,在工作频带内天线增益>13 dB,驻波<1.3,方向图E面波瓣宽度>33°,H面波瓣宽度>33°。