双极化方向回溯整流天线阵列设计与实验

提出了由双极化方向回溯Van Atta天线阵和差分整流电路组成的方向回溯整流天线阵,它能够避免接收波束未对准和收发天线极化失配而造成整流天线转换效率的急剧下降,使整流天线在宽入射角和任意极化时仍能保持稳定的直流输出.设计并测试了C波段2×2元阵列.实验结果表明,当入射波功率密度为3.43 mW/cm2时,双极化方向回溯整流天线阵列的垂直和水平极化端口归一化电压比大于0.8的入射角度范围分别为[-38°,38°]和[-31°,31°].当功率密度为4.32 mW/cm2时,两个极化端口均获得70.8%的最高整流效率.     

New 5.8-GHz circularly polarized retrodirective rectenna arrays for wireless power transmission

This paper proposes two new circularly polarized retrodirective rectenna arrays, including a 2 /spl times/ 2 array and a 4 /spl times/ 4 array. A proximity-coupled microstrip ring antenna is used as the retrodirective rectenna array element, which can automatically block harmonic signals up to the third order from reradiating by the rectifying circuit. These arrays are printed on a Rogers Duroid 5880 substrate of /spl epsiv//sub r/=2.2 with a two-layer structure, with a total thickness of 1.5748 mm (or 62 mil). The new retrodirective rectenna array can track the incoming power source signals automatically and is less sensitive to the power incident angle variations, i.e., main-beam alignment deviation. It can provide a nearly constant dc output voltage within /spl plusmn/10/spl deg/ and 90% dc output voltage within /spl plusmn/45/spl deg/. The conversion efficiencies of the two arrays are 73.3% and 55%, respectively, when the power density is 10 mW/cm/sup 2/. The retrodirective rectenna array can be used in the low-power density applications for microwave wireless power transmissions.     

Spherical retrodirective array

This paper derives the characteristics of a spherically-shaped retrodirective space array. The array can receive an incoming signal over4pisteradians, amplify, frequency translate, and modulate this signal, and then return it in the direction of the incident wave. The directivity of the array for every angle of incidence corresponds to the area illuminated by the incoming wave. In the array the retrodirective characteristic is obtained by a phase inversion technique that is realized in tunnel-diode image frequency converters. A circular cross section of the spherically-shaped retrodirective array is analyzed. The analysis is extended to the spherically-shaped array. It is shown that the effective aperture of a spherical array is smaller than the illuminated area. This reduction occurs because of a tapered amplitude distribution and a symmetrical phase error proportional to the frequency difference between incident wave and reradiated wave at the image frequency. The output spectrum of the converters in the array contains not only the image frequency signal but additional frequency components as well. Because of the phase characteristics of the spectral components, only the image frequency signal when reradiated by the array elements will add coherently in direction of the incident wave. The reradiation of the other frequency components is not collimated.     

Bow-tie surface-emitting lasers

We report a new design for surface emitting semiconductor lasers operating at 940 nm, incorporating a double-flare cavity, and distributed Bragg reflector (DBR) mirrors also providing surface emission. This design can take advantage of the modal behavior of the unstable resonator, and has shown very good mode control, with coherent emission from two facets in the same direction. We report preliminary performance results showing very promising characteristics including single-mode diffraction limited operation, and spectral behavior with 42 dB side-mode suppression. This design has exhibited promising results for increasing the current range between the lasing threshold and the filament threshold     

共面波导馈电蝶形开口振子缝隙天线

讨论了共面波导(CPW)馈电蝶形开口振子缝隙天线。在缝隙振子天线两端加入蝶形开口结构,形成振子蝶形组合结构天线。使用有限元仿真软件(Ansoft HFSS)分析了设计的天线,结果表明组合结构天线具有振子天线与蝶形天线的优点:蝶形天线的宽带特性与振子天线的高增益特性,整个天线的性能得到提高。使用了两种馈电方式:感性耦合和容性耦合,感性耦合时组合天线的带宽特性较好,从振子天线5.9%提高到10.32%;容性耦合时增益特性较好,从振子天线的3.19dB提高至6.27dB。分析了衬底厚度对天线的影响,衬底厚度的增加使谐振频率降低,但对天线带宽的影响不大。     

Dual-mode retrodirective/phased array

A method for producing a retrodirective (self-tracking) antenna, which can also be operated as a phased (selectively pointed) array through the addition of a simple switching circuit and DC bias offset adjustment, is presented. Phase adjustment to individual antenna elements is shown to be readily carried out by a simple frequency pushing technique, applied to a PLL circuit, thus replacing the requirement for additional phase shifters. Practical results when applied to a ten-element array operating at 2.4 GHz are shown for both modes of operation.     

方向回溯天线发展现状

与时间反演系统的时间反转原理类似,方向回溯天线基于相位共轭原理实现系统的相位反转,从而完成系统的自动波束聚焦,是一种新型的波束自跟踪天线。本文由方向回溯天线的性能和应用两个方面出发,介绍了近十年方向回溯天线的研究现状,具体包括方向回溯天线的极化特性、频率特性、新结构等性能,以及方向回溯天线在无线功率传输、射频识别、电子对抗等领域的应用,探究了方向回溯天线的发展趋势。     

Frequency offset retrodirective antenna array

A new architecture for the Van Atta self-steering array is presented. Active antenna techniques are used to realise a compact self-steering array with enhanced retrodirective properties. The experimental performance of the array is demonstrated and a technique is described which compensates for the beam pointing error induced by antenna array element directivity     

Circularly symmetric retrodirective antenna system

A method is described by which automatically retrodirective performance may be obtained from circular arrays and circularly continuous aperture antennas. The method is also directly applicable to cylindrical antennas for two-dimensional retrodirectivity and is generalized to include a method for obtaining three-dimensional retrodirectivity. Both passive and active systems are possible, and control of the reradiated beam characteristics may be provided.     

Self-steered retrodirective arrays with amplification

Self-steered retrodirective arrays using a phase synthesizer are described. The array configuration permits combining of the signals from the individual elements at IF level. The performance of this array in noise is analyzed and compared with another type of self-steered array.     

Bow-tie slot antenna fed by CPW

A bow-tie slot antenna fed by CPW is introduced. It is designed to work in the Ku-band around 15.5 GHz. The proposed antenna is analysed both theoretically and experimentally. The presented results include the return loss and the radiation patterns. Two different geometries of the bow-tie antenna are presented and compared. The proposed antenna has several advantages such as a very large bandwidth, good control of its input impedance, and ease of fabrication. The proposed antenna has a dipole like radiation pattern which makes it suitable for mobile communication systems designed to work in the Ku-band     

A retrodirective microstrip antenna array

A Van Atta retrodirective reflector was designed and developed, using an aperture-coupled microstrip antenna array. This reflector possesses the advantage of reflecting high fields to the source point over a wide range of incidence angles and, owing to the low cost and conformability of the structure, is suitable for applications in intelligent vehicle highway systems (IVHS). An approximate theory associated with the reradiation and scattering principles of the reflector is presented for the purpose of understanding and designing the reflector. The utility of the retrodirective reflector was demonstrated by comparison with a plate reflector and a microstrip antenna array without a feed structure. Finally, a reflector with switches in the middle of the microstrip feed lines was investigated for possible applications in communications and remote identification     

Two-dimensional planar passive retrodirective array

A simple passive microstrip array design is introduced comprising four square microstrip patches interconnected with transmission lines to form a Van-Atta retrodirective array suitable as a building block in a larger two-dimensional self-tracking array. The resulting circuit measures 48/spl times/48/spl times/0.254 mm, operates at 10.24 GHz and yields 5 dB increase in return signal at bore-sight relative to a flat metal sheet having the same dimensions for incident linear polarisation. The -5 dB monostatic radar cross-section response is /spl plusmn/25/spl deg/ compared to /spl plusmn/12/spl deg/ measured for a flat metal sheet of equivalent dimensions. The reradiation characteristics of circularly polarised signals from the retrodirective structure are briefly discussed.     

24 GHz active retrodirective antenna array

A 24 GHz active Van Atta planar antenna array proposed for increasing the vehicle radar echo in a vehicle collision avoidance system is designed and demonstrated. The antenna array contains two parallel linear sub-arrays. Each sub-array is composed of four receiving microstrip antennas, four transmitting microstrip antennas and four transistor amplifiers. At the angles of -40°<&thetas;<40°, except those very close to the specular direction (&thetas;=0°), the measured backscattering field levels of the fabricated array have variations <3 dB and are at least 10 dB higher than those of a metal plate of the same size     

An active retrodirective array for satellite communications

The concept and design of an active retrodirective array, resulting from the specialized requirements and constraints of space/earth communications, is presented. The advantages of employing active microwave gain are discussed. The attendant problem of instability is defined and several aspects of the solution, namely frequency offsetting and polarization isolation, are detailed. The latter technique makes use of orthogonally polarized "subarrays" -one for receiving and one for transmitting-intermeshed on a common aperture surface. A discussion of tolerable phase errors and the effect of element failure on the system reliability is presented. Techniques for realizing the active circuitry required for the functions of RF amplification, frequency conversion and modulation are described. An experimental model, employing strip transmission line techniques throughout, was fabricated and tested. All results, including those of array gain, retrodirectivity and simultaneous retrodirectivity from several sources at different frequencies, and effects of element removal, corresponded closely to their calculated predictions.     

Large active retrodirective arrays for space applications

An active retrodirective array (ARA) electronically points a microwave beam back at the apparent source of an incident pilot signal. Retrodirectivity is the result of the phase conjugation of the pilot signal received by each element of the array. The problem of supplying the correct phase reference to the phase conjugation circuit (PCC) associated with each element of the array is solved by "central phasing." By eliminating the need for structural rigidity central phasing confers a decisive advantage on ARA's as large spaceborne antennas. A new form of central phasing suitable for very large arrays is described. ARA's may easily be modified to serve both as transmitting and receiving arrays simultaneously. ARA's are particularly suitable as solar power satellite antennas because they are inherently failsafe. Communication satellites and deep space probes are other suggested applications. A new kind of exact frequency-translating PCC is described. Such PCC's provide the ARA with input-output isolation and freedom from squint. The pointing errors caused by the radial and transverse components of the ARA's velocity, by the propagation medium, and by multipath are discussed. As part of a NASA funded program a two-element ARA breadboard has been built and tested at the Jet Propulsion Lab. Its performance is limited primarily by multipath-induced errors.     

一种基于蝴蝶结型的天线单元的设计与实现

介绍了一种基于蝴蝶结型天线形式的天线阵天线单元的设计,蝴蝶结型天线具有形式简单、频带宽、交叉极化低和增益高的优点。通过电磁仿真软件计算了天线的驻波比和方向图随频率的变化规律。分析表明,该文中的天线单元超宽带、全向,满足驻波比的要求,具有良好的应用前景。     

Phase conjugator for active retrodirective array applications

A novel phase conjugator for active retrodirective array applications is presented. The circuit provides conversion gain as well as phase conjugating operation by using active devices, and results in a simple and compact design through the use of a common port for RF and IF signals. Measurement results indicate a 3.2 dB conversion gain with an RF-IF isolation of 20 dB. This phase conjugator can be used as a component in a retrodirective array when combined with an antenna     

一种应用于2.45GHz的微带整流天线设计

为实现对低功耗负载的微波供电,设计了应用于2.45 GHz的微带整流天线。在接收天线设计中,引入了光子晶体(PBG)结构,提高了接收天线的增益和方向性;在低通滤波器部分引入了缺陷地式(DGS)结构,以相对简单的结构实现了2.8 GHz低通滤波器特性;最后通过ADS软件设计得出了用于微带传输线与整流二极管间的匹配电路。将接收天线、低通滤波器和整流电路三部分微带电路进行整合,完成整流天线的设计。通过实验测试,该整流天线的增益为4.29 dBi,最高整流效率为63%。通过引入光子晶体结构和缺陷地式结构,在保证整流天线增益和整流效率的基础上,有效地减小了天线的尺寸,简化了设计方法。     

微带整流天线的设计与试验

微带贴片整流天线质量轻,接收面积大,非常适合微波飞机、高空平台等微波输电中对天线质量要求严格的场合.提出了两种微带整流天线的设计,结合高频仿真软件ADS 2003C、IE3D V10.0对天线的设计实现方案进行了研究,给出了一整套的微带贴片整流天线的设计步骤,通过试验对各种实现方案进行了比较和对设计步骤的正确性进行了验证.