导体调制周期介质平面天线

一种新型的导体调制周期介质平面天线在毫米波段的应用业已提出,并进行了系统的研究。本文对上述天线应用二维周期导纳表面理论进行了初步的理论分析、数值计算和实验研究。所研制的8mm波段导体调制周期结构漏波天线的平面口径为9090mm2,其它各项主要性能良好。     

Antenna miniaturization and bandwidth enhancement using a reactive impedance substrate

The concept of a novel reactive impedance surface (RIS) as a substrate for planar antennas, that can miniaturize the size and significantly enhance both the bandwidth and the radiation characteristics of an antenna is introduced. Using the exact image formulation for the fields of elementary sources above impedance surfaces, it is shown that a purely reactive impedance plane with a specific surface reactance can minimize the interaction between the elementary source and its image in the RIS substrate. An RIS can be tuned anywhere between perfectly electric and magnetic conductor (PEC and PMC) surfaces offering a property to achieve the optimal bandwidth and miniaturization factor. It is demonstrated that RIS can provide performance superior to PMC when used as substrate for antennas. The RIS substrate is designed utilizing two-dimensional periodic printed metallic patches on a metal-backed high dielectric material. A simplified circuit model describing the physical phenomenon of the periodic surface is developed for simple analysis and design of the RIS substrate. Also a finite-difference time-domain (FDTD) full-wave analysis in conjunction with periodic boundary conditions and perfectly matched layer walls is applied to provide comprehensive study and analysis of complex antennas on such substrates. Examples of different planar antennas including dipole and patch antennas on RIS are considered, and their characteristics are compared with those obtained from the same antennas over PEC and PMC. The simulations compare very well with measured results obtained from a prototype /spl lambda//10 miniaturized patch antenna fabricated on an RIS substrate. This antenna shows measured relative bandwidth, gain, and radiation efficiency of BW=6.7, G=4.5 dBi, and e/sub r/=90, respectively, which constitutes the highest bandwidth, gain, and efficiency for such a small size thin planar antenna.     

The Rectangular Waveguide Board Wall Slot Array Antenna Integrated with One Dimensional Subwavelength Periodic Corrugated Grooves and Artificially Soft Surface Structure

In this letter, we propose a high gain rectangular waveguide board wall slot array antenna, which is integrated with one dimensional subwavelength periodic corrugated grooves and artificially soft surface structure. The corresponding far field radiation characteristics are investigated. The simulation results show that the gain of planar 2 × 8 slot array antenna with the introduction of corrugated grooves structure is increased to 26.1 dB, and half power beamwidth in the E plane is considerably reduced. Compared with the subwavelength periodic grooves slits array antenna proposed by Huang et al.[Appl. Phys. Lett. 91, 143512 (2007)], the side and back lobe level of this antenna are also significantly reduced by 6 dB and 10 dB, respectively. The physical mechanism for radiation-pattern improvement has been well explained by the modulation of surface wave, the reradiation of surface energy, and suppression of surplus surface wave at the grounded edge.     

A Double-Beam Radiation Leaky Wave Antenna Based on Left-Handed Material Slab with Metallic Strips Periodically Loaded

A new leaky-wave antenna structure is carefully investigated in the paper, which is based on a grounded Left-Handed material (LHM) slab periodically loaded with metal strips. A rigorous formulation similar to the spectral domain method for planar circuits is deduced to analyze the radiation characteristics of the antenna. Theoretical analysis results reveal that at specific frequency region or with proper geometrical parameters chosen, the present structure supports simultaneously two leaky modes corresponding to the forward and backward radiations. The principle of the antenna is due to the peculiar propagation properties of the unperturbed LHM grounded slab waveguide, which is totally different from the phenomenon of double or even more space harmonic mode radiations in normal periodic structures. Extensive numerical results of the leakage characteristics are given to establish useful guidelines for the design of the new type leaky wave antenna.     

Full-wave analysis of traveling-wave electrodes with finitethickness for electro-optic modulators by the method of lines

In order to optimize broadband electrooptic modulators with traveling-wave electrodes, detailed information about the propagation constant, the field distribution, and the wave impedance of the modulating field is needed. To get accurate results for these characteristic values, the numerically efficient method of lines (MoL) is used. The MoL takes advantage of the planar structure by discretizing the wave equation in the directions parallel to the metallization plane, whereas an analytical formulation is retained for the transverse direction. Thus, not only the hybrid character of the modulating field but also the finite conductor thickness and anisotropy of the substrate are taken into account. Results for asymmetric coplanar stripline electrodes with typical dimensions on SiO₂ buffered LiNbO₃ are presented     

一种宽带分形自互补单极子天线的设计

提出一种结合分形与自互补理论的新型宽带单极子天线。辐射部分由Sierpinski分形图案的金属贴片和互补的缝隙贴片印刷在FR-4 介质板上构成,由微带线经阻抗变换后馈电。分形技术的利用使得该天线实现了20%的尺寸缩减,自互补结构则大大拓展了天线的带宽,两者的结合使得该天线在保持平面结构的同时取得优良的性能。仿真与测试得到该天线在4.98-9.93 GHz 频带内反射系数小于-10dB,具有66.4%的带宽,带内增益在1.3-3.3dBi 之间。该天线具有平面、宽带、小型化的优点,在小型化通信系统中具有良好的应用前景。     

Low-profile resonant cavity antenna with artificial magnetic conductor ground plane

A planar artificial magnetic conductor (AMC) ground plane is proposed as a means to reduce the profile of a highly directive resonant cavity antenna. The structure is formed by a printed microstrip patch antenna and a superimposed partially reflective surface. The antenna profile is reduced to approximately half by virtue of employing the AMC ground plane. A ray theory model is used to qualitatively describe the functioning of the antenna and theoretically predict the existence of quarter wavelength resonant cavities.     

A millimeter-band planar lens based on an inhomogeneous medium with forced refraction

A millimeter-band planar lens designed on the basis of an inhomogeneous medium with forced refraction, which is formed by a periodic grating of metal strips placed on the surfaces of a dielectric plate, is considered. The possibility of application of this lens as the basis for the design of a multibeam receiving antenna for a radio imaging system is analyzed. The structure of an antenna consisting of a planar lens and a multichannel feed is proposed. The results of the design of a planar lens based on an inhomogeneous medium with forced refraction are presented. A multichannel feed in the form of an array of E-plane horns is analyzed and the results of simulation of this feed with the help of an approximate technique and numerical solution of an electromagnetic problem are given. The design of the multibeam antenna and its experimental characteristics are presented. The possibility of computer correction of radiation patterns of the multibeam antenna is considered.     

LEAKY CHARACTERISTICS OF A NEW MILLIMETER WAVE ANTENNA BASED ON GROOVE GUIDE WITH AN ASYMMETRIC CONDUCTOR STRIP

A new millimeter wave leaky wave antenna is presented in this paper, which is a modification of the groove guide with an asymmetric conductor strip by introducing a dielectric slab into the conductor plane region of the groove guide antenna. The leakage property of the new antenna is carefully examined through calculations of an equivalent network, which is developed here with taking into account the coupling between different modes to guarantee the calculating accuracy. It has been found that the new leaky wave antenna is of larger leakage constant than that for the original groove guide antenna because of the introduction of the dielectric slab. Extensive numerical results of the leakage characteristics are given to establish useful guidelines for the design of the new type groove guide leaky wave antenna.     

Radiation performance improvement of wideband microstrip antenna array using wideband AMC structure

In this paper, the radiation performance of an antenna array is improved by designing a new wideband artificial magnetic conductor (AMC). The proposed AMC surface operates at the frequency of 3 GHz with ±90^° reflection phase bandwidth of 22%. In order to identify the key design parameters of the AMC structure, a parametric study is performed. To improve the radiation performance of the antenna array, an AMC reflector is developed through utilizing an array of 2 × 8 periodic patches of AMC unit cells. By this technique, the front to back ratio of the designed antenna array is enhanced about 16.27 dB. It is concluded that tuning of the AMC dimensions for controlling the reflection coefficient at each port of antenna array during beam steering is necessary. Because of the using of the AMC surfaces as a reflector instead of conventional PEC surfaces, size reduction of the antenna array in the order of 20% is achieved. In this study, a circuit model for single element of the antenna array with considering AMC loading effect is introduced, which predicts the bandwidth behaviour of the proposed antenna. The final designed antenna array exhibits low level of cross polarization making it well‐suited for tracking radars and electronic warfare applications. The proposed antenna with the AMC reflector is fabricated and measured. The measured ?10 dB impedance bandwidth and peak gain of the proposed antenna is 20% (2.7‐3.25 GHz) and 13.4 dBi, respectively, which are compatible with the simulation results.     

Theory of aperture-coupled hemispherical dielectric resonator antennas with radiating elements

A new approach based on hybrid volume-surface integral equation (VSIE) formulation in combination with spherical dyadic Green's function (DGF) is presented in this paper to analyze aperture-coupled multilayer hemispherical dielectric resonator antennas (DRA) with conformal conducting patches. Hybrid VSIE is used for the planar part of the structure and is solved with the aid of spatial-domain method of moments (MoM) in order to compute magnetic surface current in a slot cut in a finite planar perfect electric conductor (PEC) sheet. Multilayer spherical electromagnetic DGFs are used to compute loading effects of hemispherical dielectric resonators and conformal patches on antenna characteristics. The effects of variation in some parameters of the structure on the return loss of the antenna are studied. Accuracy of the presented method is validated by comparing the results obtained from the proposed method with those of CAD simulations.     

MM-Wave integrated phased arrays with ferrite control

A new class of electrically scanned antenna arrays for the millimeter wave range is described. The antenna is based on a planar integrated ferrite travelling wave structure and is controlled by the magnetization of ferrite elements. Experimental antennas operating in the 8-mm wave range have the following electrical parameters: beamwidth 2 to 4°, two dimensional scanning ±20°, loss about 3 to 4 dB     

Analysis for a dielectrically filled parallel-plate waveguide withfinite number of periodic slots in its upper wall as a leaky-waveantenna

A dielectrically filled parallel-plate waveguide (PPW) with finite number of periodic slots in its upper plate is analyzed as a leaky-wave antenna structure for E-polarization case. The characteristics of the finite periodic structure such as input impedance matching, antenna efficiency, gain, and radiation pattern are investigated. In particular, phenomena such as total reflection and transmission occurring in the practical finite periodic structure, associated with the coupling point and the real solution (propagation constant), respectively, in the fast wave region observed for the infinite open periodic structure case, are described in detail     

基于宽带吸波体的低雷达散射截面平面印刷磁电偶极子天线设计

该文设计了一种工作于X波段的平面印刷磁电偶极子天线,并设计了一种加载集总电阻的宽入射角、极化不敏感、宽频带吸波体(WBMA)。当平面波垂直入射时,吸波体在7.2~12.6 GHz范围内的吸波率大于90%,入射角增加至45时仍能在X波段保持90％以上的吸波率。通过将WBMA加载在天线四周,实现了天线雷达散射截面(RCS)的大幅缩减。实测和仿真结果表明:不同极化波垂直入射时,天线单站RCS减缩3 dB带宽为6.6~14.4 GHz,最大减缩量达23.8 dB。中心频点10 GHz处,TE极化波照射时,双站RCS能实现90角域内的减缩,TM极化波照射时,在35角域内实现了减缩,同时天线辐射性能几乎保持不变。     

一种基于电磁超材料的抗干扰天线

设计了一种基于电磁超材料的抗干扰天线.该抗干扰天线由矩形波导腔体,铺设于波导腔体底部宽边的电磁超材料以及位于波导腔体上部宽边的辐射缝隙构成.当电磁超材料表现为完美电导体时,该抗干扰天线同传统波导缝隙天线类似,可高效辐射电磁波.当电磁超材料表现为完美磁导体时,该抗干扰天线的性能与带阻滤波器相似,可抑制特定频段的干扰电磁波.该抗干扰天线实现了天线与滤波器的高度集成,结构紧凑.仿真与测试结果显示该抗干扰天线在工作频段具有良好的辐射特性,同时对干扰频段电磁波的抑制可达40 dB.     

The bent backfire zigzag--A vertically- polarized frequency-independent antenna

A new type of vertically-polarized, unidirectional frequency-independent antenna over ground is described. The antenna was first derived from the log-periodic (LP) zigzag by making a right-angle bend along the axis of the planar device. The result is a simple structure which has a maximum height slightly greater than one-quarter wavelength at the lowest frequency of operation. The simple, but useful analysis employed rests upon the assumption that the principles of operation of an LP antenna structure are related to those of a uniformly periodic antenna structure of the same type. This analysis is applicable to other types of frequency-independent antennas also. Experimental data are presented for a wide range of the parameters of the Bent LP Zigzag, and a design procedure is outlined.     

A new wideband planar antenna with band-notch functionality at GPS,Bluetooth and WiFi bands for integration in portable wireless systems

Empirical results are presented for a novel miniature planar antenna that operates over a wide bandwidth (500 MHz to 3.05G Hz). The antenna consists of dual-square radiating patches separated by two narrow vertical stubs to reject interferences from GPS, Bluetooth and WiFi bands. Radiating patches and stubs are surrounded by a ground-plane conductor, and the antenna is fed through a common coplanar waveguide transmission line (CPW-TL). The two vertical stubs generate pass-band resonances enabling wideband operation across the following communications standards: cellular, APMS, JCDMA, GSM, DCS, PCS, KPCS, IMT-2000, WCDMA, UMTS and WiMAX. Embedded in the ground-plane conductor is an H-shaped dielectric slit, which has been rotated by 90°, whose function is to reject interferences from GPS, Bluetooth and WiFi bands. Measurements results confirm the antenna exhibits notched characteristics at frequency bands of GPS (1574.4–1576.4 MHz), Bluetooth (2402–2480 MHz) and WiFi (2412–2483.5 MHz). The impedance bandwidth of the antenna is 2.55G Hz for VSWR < 2, which corresponds to a fractional bandwidth of 143.66%. Measured results also confirm that the antenna radiates omnidirectionally in the E-plane with appreciable gain performance over its operating frequency range. The antenna has dimensions of 15 × 15 × 0.8 mm³.     

新型舰载超短波宽带平面天线

设计出一种新型舰载超短波宽带天线,该天线采用平面非对称偶极子形式,上辐射面为椭圆拟合结构,下辐射面为指数渐变梯形结构。采用时域有限差分法(FDTD)计算了天线的输入阻抗和辐射方向图。在13.3∶1的频带内,天线的电压驻波比小于2.9,水平面方向图失真度小于3.8 dB,而天线高度仅为0.326λmax.理论值与实验结果进行了比较,两者吻合较好     

Characteristics of a small planar loop antenna

Small planar-type loop antennas used in pagers have fixed directivity patterns. As a result, the received signal strength depends on the orientation of the antenna. A new type of small planar loop antenna (PLA) is, therefore, proposed. The position of the conductor posts can be changed and MOSFETs are adopted for switching the conductor posts. If the positions of the posts can be switched at will, then the dependence of the received signal on the orientation of the antenna can be minimized. Fundamental experiments were performed in order to investigate the characteristics of polarization switching. Polarization directivity was measured while switching each conductor alternately. The receiving characteristics are affected by a cable connected to the receiver. Therefore, the transmission characteristics are measured by using an internal oscillator. As a result, meaningful results were obtained and the possibility of polarization diversity was shown     

漏波天线中阻带的应用及抑制

周期性结构会引入阻带.有些阻带对有些漏波天线有用,如可用于抑制某些不需要的传播模.但阻带对大部分周期性漏波天线是不利的,如边射阻带使得主波束在边射方向不能连续扫描.文中讨论了周期性结构阻带在漏波天线中的应用及抑制.给出了一个阻带应用实例:微带漏波天线一般工作于EH1模,在激励其EH1模时往往会激发不希望的EH0模,在微...