Excitation of a Cylindrical Microstrip Antenna with Two Symmetrically Located Radiating Elements

We consider the problem of symmetric excitation of a cylindrical microstrip antenna by two plane waves. The antenna consists of two radiating elements located symmetrically with respect to the azimuth. Each element can be either a single patch or an array of patches of rectangular-cylindrical shape. The problem is reduced to solving an integral equation by the method of moments. A new representation of the Green's function is used. In this representation, the field singularity at the source and the contribution of surface waves are given in analytical form. The scattered field as a function of frequency, the resonant current distribution on the patches, and the far-field pattern are calculated. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 6, pp. 52–536, June 2005     

复合左右手技术的二元阵天线的计算及测量

为了克服微带天线的横向尺寸需要满足半个波长的限制,本文提出了一种基于复合左右手传输线技术的二元阵天线.该天线阵由结构相同的两个天线阵单元构成:天线阵单元由3个辐射片、辐射片之间的交指电容和导通辐射片和接地板的短路针组成.辐射片、短路针、天线阵的基片和接地板构成了复合左右手传输线结构.天线阵单元之间通过弓形连接线连接,通过调节弓形连接线两个端口到馈源之间的距离来调节天线阵单元之间的初始相位差.在关心频段内,数值计算得到的二元阵天线的S参数与实际测量结果符合得很好,并且零阶谐振频率与用等效电路理 关键词： 天线 异向介质 左右手传输线 增益     

Multiband rectenna for microwave applications

This paper reports a multiband rectenna (rectifier + antenna) suitable for the electromagnetic energy harvesting of the spill-over loss of microwave antennas placed on board of geostationary satellites. Such rectenna is used for powering autonomous wireless sensors for satellite health monitoring. The topology of the rectenna is presented. The experimental results demonstrate that the proposed compact rectenna can harvest efficiently the incident electromagnetic energy at three different frequencies that are close to the resonant frequencies of the cross-dipoles implemented in the antenna array.     

多频与宽频超材料吸收器

提出了多频与宽频超材料吸收器结构模型, 该吸收器是由刻蚀在介质基板两面的金属图案组成, 其正面是由不同大小的金属铜圆片和金属铜圆环结构组合而成, 反面完全覆盖金属铜. 由于不同几何大小的圆片或圆环结构的谐振频率不同, 且是相互独立的. 因此通过将两种不同几何大小的圆片与圆环结构组合, 使其在不同频率谐振, 便可得到双频吸收器; 而将三种不同几何大小的圆片和圆环结构组合便可得到三频吸收器; 同理可得到四频吸收器. 同时, 通过研究吸收器的电场分布, 验证了不同几何大小的圆片或圆环结构在不同频率谐振. 若通过优化组合圆片和圆环结构, 使其谐振频率紧密相连则可得到宽频吸收器. 关键词： 吸收器 超材料 多频 宽频     

Measurement of the resonant lengths of infrared dipole antennas

The resonant lengths of infrared dipole antennas at 10.6 and 3.39 μm are experimentally investigated. For this purpose, submicron-sized microbolometers coupled to dipole antennas with lengths between 0.7 and 20 μm were fabricated on a SiO₂-on-Si substrate. The response of the detector to 10.6 μm radiation shows a first resonance for an antenna length between 1.0 and 2.5 μm. A subsequent zero and a second attenuated resonance are observed as the antenna length increases. Similar behavior is observed for illumination at 3.39 μm, with a first resonance occurring at a length shorter than 1 μm. The results permit evaluation of an effective dielectric permittivity and shows the effect of the surface impedance of the metal on the propagation of current-wave on the antenna. The resonance behavior is further studied by changing the irradiation conditions of the detectors. Air-side and substrate-side illumination exhibit identical resonant antenna lengths, but different efficiencies of power collection. The antenna patterns as a function of incident angle have also been measured at 10.6 μm, showing a transition from a primary broadside lobe to the development of side lobes for longer antennas. Finally, an antenna response is measured at visible frequencies. Our measurements point out similarities, as well as differences, between infrared antennas and their counterparts at microwave frequencies, and provide insights useful for the design optimization of planar infrared antennas.     

Ultra-wideband low radar cross-section metasurface and its application on waveguide slot antenna array

A novel approach devoted to achieving ultra-wideband radar cross section reduction(RCSR) of a waveguide slot antenna array(WGSAA) while maintaining its radiation performance is proposed. Three kinds of artificial magnetic conductors(AMCs) tiles consisting of three types of basic units resonant at different frequencies are designed and arranged in a novel quadruple-triangle-type configuration to create a composite planar metasurface. The proposed metasurface is characterized by low radar feature over an ultra-wideband based on the principle of phase cancellation. Both simulated and measured results demonstrate that after the composite metasurface is used to cover part of the antenna array, an ultrawideband RCSR involving in-band and out-of-band is achieved for co-and cross-polarized incident waves based on energy cancellation, while the radiation performance is well retained. The proposed method is simple, low-cost, and easy-tofabricate, providing a new method for ultra-wideband RCSR of an antenna array. Moreover, the method proposed in this paper can easily be applied to other antenna architectures.     

基于液晶的U波段电控移相超材料

基于液晶材料(LC)的双折射特性提出了一种基于液晶材料的短十字型阵列电控超材料,超材料包括了上层石英板,金属结构阵,中间液晶介质层,金属地板以及下层石英板。相比于传统的阵列天线设计,运用了新的相位补偿方法,即通过加电改变反射阵列单元的介质基板液晶的介电常数得到的相位曲线实现0~250°的相位补偿,使得超材料实现在U波段的相位变化。仿真结果表明,通过将偏压从0增加到14 V,超材料在52 GHz时呈现250°的相移。此外,此超材料的谐振频率可从53.6 GHz连续可逆地转移到49.9 GHz。通过调节超材料液晶激励区域的介电常数即改变阵列单元的谐振特性,实现了相位补偿,为平面反射阵列天线的设计提供了一种新思路。     

基于超材料吸波体的低雷达散射截面波导缝隙阵列天线

提出利用超材料吸波体减缩波导缝隙阵列天线带内雷达散射截面的设计方法. 设计具有超薄(厚度仅为0.01λ, λ为吸波体中心频率对应波长)、无表面损耗层和高吸波率的超材料吸波体, 将其加载到波导缝隙天线E面方向辐射缝隙间的金属表面上, 并与辐射缝隙保持一定的间距. 该加载方式没有破坏天线的口径馈电振幅分布, 并利用超材料吸波体对电磁波的强吸收特性降低了天线阵的结构模式项散射. 仿真和实验结果表明, 加载超材料吸波体后天线阵的反射系数、增益、波瓣宽度保持不变, 在x极化和y极化条件下, 波导缝隙阵列天线的带内雷达散射截面减缩量均在6 dB 以上, 且在-25°-+25°范围内天线雷达散射截面均有明显的减缩, 鼻锥方向减缩超过10 dB. 该研究成果对阵列天线雷达散射截面减缩具有重要的借鉴意义和工程应用价值.     

一种新型的低散射微带天线阵设计

本文将电磁表面(electromagnetic surface, EMS)的设计思想引入到微带天线阵的设计中,在设计天线单元的同时,也将其作为EMS单元兼顾其反射特性.通过在矩形辐射贴片上开弧形缺口,得到一种新的单元结构,该单元可与原始EMS单元之间形成180°±30°有效相位差,且作为天线单元时与原始天线工作在相同谐振模式、相同频带.将两种单元以棋盘形式构成组合天线阵,在两个极化下分别基于相位对消原理和吸波原理实现了雷达散射截面(radar cross section, RCS)减缩.实测与仿真结果表明:相较于等大小的金属板,在x极化波照射下,天线阵在5.6—6.0 GHz实现了6 dB以上的RCS减缩,相对带宽为10.1%;在y极化波照射下,天线阵在5.0—7.2 GHz实现了6 dB以上的RCS减缩,相对带宽为24%.同时由于两种单元在辐射上具有较好的一致性,使得组合天线阵的辐射性能得以保持.该方法有效解决了天线阵辐射和散射难以兼顾的矛盾,为其他形式的低散射天线阵的设计提供了新的方法与思路.     

Beam reconfigurable antenna for the THz band based on a graphene high impedance surface

In this paper a reconfigurable beam antenna is proposed for THz applications, based on a switchable Graphene High Impedance Surface (G-HIS) that acts as a reflector for a primary radiator. The Graphene-HIS structure composed of two layers of graphene cells arranged in a 5×5 array, the two planes of the array are separated by a thin silicon oxide layer; patches in the same row are connected together, to be biased by a common DC voltage to the entire row; this gives the ability to control the graphene conductivity σ. The results show that the shape of the radiation pattern can be changed by changing the voltage applied to each row of G-HIS array. The antenna was fabricated and characterized using a THz-TDS laser system. Measurements are in good agreement with simulations as far as the graphene surface impedance and the resonance frequency are concerned. The scanning reflection on the antenna surface due to the change on the applied voltage is presented to show the effect of biased graphene layer on the dipole properties.     

Directive metamaterial-based subwavelength resonant cavity antennas – Applications for beam steering

This article presents the use of composite resonant metamaterials for the design of highly directive subwavelength cavity antennas. These metamaterials, composed of planar metallic patterns periodically organized on dielectric substrates, exhibit frequency dispersive phase characteristics. Different models of metamaterial-based surfaces (metasurfaces), introducing a zero degree reflection phase shift to incident waves, are firstly studied where the bandwidth and operation frequency are predicted. These surfaces are then applied in a resonant Fabry–Perot type cavity and a ray optics analysis is used to design different models of ultra-compact high-gain microstrip printed antennas. Another surface presenting a variable reflection phase by the use of a non-periodic metamaterial-based metallic strips array is designed for a passive low-profile steering beam antenna application. Finally, the incorporation of active electronic components on the metasurfaces, allowing an electronic control of the phase responses, is applied to an operation frequency reconfigurable cavity and a beam steering cavity. All these cavity antennas operate on subwavelength modes, the smallest cavity thickness being of the order of λ/60. To cite this article: A. Ourir et al., C. R. Physique 10 (2009).     

Elastic resonances of a periodic array of fluid-filled cylindrical cavities embedded in an elastic matrix

The resonant scattering by a periodic infinite array of fluid-filled cylindrical cavities in an elastic matrix is studied. The exact reflection and transmission coefficients of the array are calculated by means of a multiple scattering formalism taking into account all the interactions between the cavities. Numerical results are next given for low frequencies for which only the longitudinal and transverse zero modes propagate. A first study based on the analysis of the transmission coefficients clearly shows that the resonances of the array can be classified into two sets: those close to the resonances of a single cavity and those due to a resonant coupling between a cavity and its nearer neighbors. The resonant coupling is due to the interaction between the whispering-gallery surface waves propagating around each cavity. In the case of cavities with very close spacing, it is observed that the dispersion curves of the waves propagating along the array can also be classified into two sets: those with a positive group velocity have cut-off frequencies that correspond to the resonances of a single cavity, those with a negative group velocity have cut-off frequencies that correspond to the resonances resulting from the strong coupling. A new method for the analysis of the resonances is presented. It is based on the properties of the scattering matrix and consists in studying the resonant eigenvalues of the scattering matrix of the array once the background is removed. For the detection of very fine resonances, as well as in the separation of several resonances very close to each other, this method proves to be more efficient than one based on the analysis of the reflection and transmission coefficients.     

可调谐的低频连续引力波接收天线的研究

我们设计制造了共振频率在47.3Hz到60.5Hz之间连续可调谐的低频引力波四极天线。天线的重量为498kg,室温时在空气中加上调谐系统后Q值为4.4×10³。木文把天线的振动简化为在自由端附有—刚性质量的悬臂梁的振动。代替弹性力学的繁复计算,用材料力学的简单方法得到了可以满足要求的结果。本文对用机械方法调整频率的可能方案作了比较,并对把四极天线用于探测更低频的引力波的可能性进行了探讨。 关键词：     

Full-Wave Analyses for a Multi-Layered Microstrip Patch Antenna

This paper describes numerical modelling of a dual band multi-layered microstrip patch antenna operating at 35GHz on an in-house semi-insulating GaAs substrate. The simulated and measured resonant frequencies at both lower and upper resonant frequencies will be compared to check the accuracy of the different numerical modelling techniques.     

基于极化转换超表面的宽带低雷达散射截面缝隙天线阵

提出了一种利用极化转换超表面(PCM)来缩减雷达散射截面(RCS)并保持缝隙天线阵列辐射特性的新型天线,在不影响天线性能的情况下实现了天线的宽带RCS缩减。该PCM由45°倾斜的开槽矩形贴片周期排布构成,它被放置在缝隙阵列天线的上表面,起到RCS缩减的功能。分析了RCS缩减的特点和原理,仿真和实验结果表明,带有PCM的缝隙天线阵在x极化和y极化波冲击下,单站RCS缩减带宽为8.0～21.8 GHz。同时天线的辐射特性在阻抗带宽、增益和辐射模式等方面都能保持良好性能。     

Analysis of single band and dual band graphene based patch antenna for terahertz region

A microstrip patch antenna is designed using a very thin layer of graphene as the radiating patch, which is fed by a microstrip transmission line. The graphene based patch is designed on a silicon substrate having a dielectric constant of 11.9, to radiate at a single frequency of 2.6 THz. Further, this antenna is made to resonate at dual frequencies of 2.48 THz and 3.35 THz, by changing the substrate height, which is reported for the first time. Various antenna parameters such as return loss, VSWR, gain, efficiency and bandwidth are also determined for the single and dual band operation. For the single band operation, a bandwidth of 145.4 GHz and an efficiency of 92% was achieved. For dual band operation, a maximum bandwidth of 140.5 GHz was obtained at 3.35 THz and an efficiency of 87.3% was obtained at the first resonant frequency of 2.48 THz. The absorption cross section of the antenna is also analysed for various substrate heights and has maximum peaks at the corresponding resonating frequencies. The simulation has been carried out by using a full wave electromagnetic simulator based on FDTD method.     

A 24-GHz Patch Array with a Power Amplifier/Low-Noise Amplifier MMIC

This paper presents an active patch array designed at 24 GHz. It can be used as a front-end component for a phased array. A series resonant array structure is chosen which is compact and easy excite. With 5 elements, the array proved a 12-dB antenna gain. A power amplifier and a low noise amplifier are designed on a single GaAs chip (PALNA). Bias switch is used in the PALNA, which greatly reduces the switch loss in a transceiver and increases the efficiency. 20-dB small signal gain is achieved in both power amplifier and low noise amplifier. The active patch array is built by the combination of the patch array and PALNA. The measured active gain of this antenna is 35-dB for the PA mode and 31-dB for the LNA mode. This active patch array can obtain an EIRP of 34 dBm with a total radiated power of 22dBm and a maximum PAE of 32%. To check the noise performance, we applied sources at both normal temperature and 77K (liquid nitrogen) and extracted the noise figure (3.5 dB) of the active antenna by the Y factor method. The results proved that the active antenna is working efficiently as both a transmitting and receiving antenna.     

Asymmetries on a three-coupled-oscillator system: Their use in a gravitational-radiation detector

Summary A system composed of three coupled oscillators having the same resonant frequency is analysed. This system, which is the representation of the real physical system composed of a resonant gravitational-wave antenna equipped with a capacitive transducer and connected to a superconducting current amplifier, presents a series of asymmetries in the normal modes. An analytical evaluation of the resonant frequencies of the three normal modes of this system is given. These three normal modes are not equivalent, and their behaviour is the object of the present paper. The quality factors of the normal modes are calculated, showing that the central-mode quality factor is very weakly affected by the lowest one of the three oscillators, namely the electricalQ. A second asymmetry is then found by calculating the spread of a pulse of energy deposited into the first oscillator: it is shown that most of this energy is detected in the central mode. These two asymmetries permit to increase the sensitivity of the system calculated for the central mode. A third asymmetry is then analysed concerning the different contribution of each oscillator to the thermal noise of each mode. Supposing, as it is in the real case, that the three oscillators are in equilibrium, but at different thermodynamic temperatures, an equivalent thermodynamic temperature is calculated for each mode. This last feature can then be used to lower the equivalent temperature of the central mode without the need of cooling all the three oscillators at the same low temperature.     

Tunable wide-angle multi-band mid-infrared linear-to-linear polarization converter based on a graphene metasurface

We present a high-efficiency tunable wide-angle multi-band reflective linear-to-linear (LTL) polarization converter, which is composed of an array of two L-shaped graphene patches with different sizes. In the mid-infrared region, the proposed converter can transform x-polarized wave into y-polarized wave at four resonant frequencies. The polarization conversion ratios of the four bands reach 94.4%, 92.7%, 99.3%, and 93.1%, respectively. By carefully choosing the geometric parameter, triple-band LTL polarization conversion can also be realized. The three polarization conversion ratios reach 91.50%, 99.20%, and 97.22%, respectively. The influence of incident angle on the performances of the LTL polarization converter is investigated, and it is found that our polarization converter shows the angle insensitivity. Also, the dynamically tunable properties of the proposed polarization converter are numerically studied by changing Fermi energy. All the simulation results are conducted by finite element method.     

一种波束扫描超材料天线的设计

设计了一种结合正方形和八边形环的波束扫描超材料平面反射阵列天线。相比于传统的阵列天线设计,运用了新的相位补偿方法,即通过组合反射阵列单元在介质基板的材料不同时得到的相位曲线实现0~360°的相位补偿,使得阵列单元的相位曲线不需要完全覆盖0~360°,并且采用埃尔米特插值的方式解决相位特性曲线线性度差的问题。该方法的优势是具有广泛适应性,降低了对阵列单元的设计要求。利用这种方法设计了几款单层平面反射阵列天线,仿真结果显示反射波束方向与预期设定值相符合,且副瓣与主瓣都相差至少15 dB。通过调节超材料固态等离子体激励区域的范围即改变阵列单元的谐振结构,实现了空间波束扫描,为平面反射阵列天线的设计提供了一种新思路。