The cylindrical antenna with nonreflecting resistive loading

The distribution of current along a center-driven cylindrical antenna is obtained when the material forming the antenna is resistive. The particular case is considered when the impedance per unit length of the antenna is a function of the distance from the end. A solution is obtained specifically when the current is represented by an outward traveling wave with no reflected wave. The admittance of the antenna and the far-field pattern is determined. Field patterns are evaluated for a wide range of lengths. These are characterized by a single major lobe with a very small minor lobe structure.     

一种新颖的宽带高增益车载全向天线

介绍了一种工作在225～800MHz的双锥柱形超宽带垂直极化全向天线结构。在两天线单元之间加同轴电缆扼流圈替代传统的0．25A0扼流杯,并在天线底部加同轴电缆扼流圈和用Г匹配方式给两天线单元馈电的方法,完成了一种具有4个倍频程的超宽带垂直极化全向天线。该天线具有良好的匹配性能和辐射特性,有效的克服了一般超宽带全向天线垂直面辐射方向图主波瓣容易偏离水平面的不足。     

一种宽频带导航天线的研究与设计

研究并设计了一款基于阿基米德螺旋天线的宽频带(覆盖GPS,BeiDou 和GLONASS 卫星导航系统的所有工作频点,即1.1 -1.7 GHz)高稳定相位中心导航天线。以带有反射腔的阿基米德螺旋天线为基础,结合三维扼流环抑制多径效应的性能,通过加载扼流环,并经有限元电磁仿真软件的参数优化设计,很大程度上改善了整个频带内天线在特定俯仰角范围内的相位稳定度。所设计的宽频带高稳定相位中心导航天线的指标达到:在GPS,BeiDou 和GLONASS 卫星导航系统的所有工作频点上,输入端口驻波比小于1.5;在俯仰角为-60°-60°的范围内,方向图轴比小于2 dB,相位稳定度在-2.7°-2.7°;同时由于扼流环的加载,天线的抗多径性能也得到了改善。研究表明,加载了三维扼流环的阿基米德螺旋天线综合性能优异,适合作为宽频带高稳定相位中心导航天线。     

Paraboloidal reflector offset fed with a corrugated conical horn

A paraboloidal reflector, offset fed with a corrugated conical horn, has been examined as a possible antenna for use in millimeter wave communications systems when minimization of interference is an important consideration. Low far-out and back-lobe radiation were primary objectives. Experimentally obtained data, representative of performance at 37 GHz, is presented. When appropriately shielded to limit spillover, levels more than 75 dB below the main beam maximum have been obtained in the far-out and back-lobe regions.     

The Millimeter Wave Radiation of a Dielectric Leaky-Wave Antenna Coupled with a Diffraction Grating: Broad-Face Interaction

The millimeter wave radiation of a dielectric leaky-wave antenna (DLWA) coupled with a metallic diffraction grating with a sinusoidal height profile is experimentally investigated. The interaction between dielectric and grating is contactless and it is from the broad-face of the dielectric line. The measured field patterns are compared with the simulated HFSS patterns. Antenna parameters such as polarization, HPBW, cross-polarization and side lobe levels are measured. The effects of the geometrical parameters of the grating to the radiation are also investigated. Some results are compared with a DLWA which has another diffraction grating profile shape (rectangular). The investigated antenna can be used as a frequency scanning antenna in mm-wave radars because it has low cross and side lobe levels and narrow beam width.     

Hemispherical coverage using a double-folded monopole

A traveling-wave current distribution can be produced on a monopole over a ground plane by inserting a resistance of suitable magnitude one-quarter wave length from its end. It has been shown that the resistor can be replaced with a modified folded dipole which has a radiation resistance approximately equal to that of the resistor. Furthermore, it was found that when the folded element was about 0.1λ above the ground plane, near hemispherical coverage was obtained in the plane of the element. In this paper, the resistor is replaced with orthogonal folded elements. The main objective is to obtain an antenna which is circularly polarized and which has near hemispherical coverage. The input impedance, current distribution, and radiation patterns of this antenna were computed using the numerical electromagnetics code (NEC); the radiation patterns and input impedance were also measured. To produce a circularly polarized wave it is necessary to tilt the folded elements. After experimenting with a number of different configurations an antenna design having directional and polarization properties approaching those that were desired was obtained. All computations and measurements were conducted near 1.6 GHz, a frequency close to that of the proposed IRIDIUM communications system and the L1 band of the Global Positioning System (GPS). The double-folded monopole may prove to be a very low cost option as a ground antenna for these systems     

基于SIW的多波束CTS阵列天线设计

文中设计了一款基于基片集成波导(SIW)的毫米波高增益多波束连续横向枝节(CTS)阵列天线,它通过切换馈电端口实现多波束功能。该天线整体结构简单,采用印刷电路板工艺实现。天线主要包含馈电喇叭、平面波转换结构以及辐射结构三个部分,由三层基板构成。馈源为基于SIW的馈电喇叭,并在口径处添加匹配结构以提高其辐射性能;平面波转换结构由SIW抛物面和渐变耦合槽组成,可将馈电喇叭辐射出的柱面波转换为幅度服从泰勒分布的平面波进而为CTS阵列馈电,因此天线具有低副瓣的特性;辐射结构为1×8的CTS阵列,通过优化缝隙宽度以保证每个单元辐射出相等的能量。天线工作在30 GHz,通过切换馈电端口可在±20°范围内实现波束切换,天线测试结果与仿真结果吻合,验证了设计的合理性。     

内嵌结构光子晶体在F 型微带天线中的应用

对常用的正方晶格光子晶体结构进行改进优化,设计出一种新型内嵌结构式二维光子晶体,即在普 通正方晶格光子晶体内部嵌入同类晶格的光子晶体。将该结构光子晶体应用到F 型微带天线中,采用平面波展开 法,进行大量仿真计算。结果表明:与传统的微带天线相比,加入该结构光子晶体后的微带天线回波损耗由 -18. 2465dB 降低到-41. 0624dB。天线具有更好的阻抗特性和辐射效率,方向图有所改善,背瓣辐射最大处减少约 5dB。这种新型的光子晶体微带天线达到了提高天线性能的目的。     

Band-notched inverted-cone monopole antenna for compact UWB systems

A microstrip-fed planar ultra-wideband monopole antenna with bandnotch characteristics is proposed. The antenna size is compact (18 x 30 mm) and operates over an extremely wide band of 3-16 GHz. The proposed design consists of an inverted cone as the radiating patch and a tapered ground plane. Wideband matching is obtained by properly shaping the ground. A pair of symmetrically placed quarter wave slot resonators is embedded in the ground plane for rejecting the 5-6 GHz WLAN band. Results indicate a stable and omnidirectional radiation pattern with an average gain of 3 dBi and a sharp reduction in gain at notched frequencies. Moreover, measured group delay and transmission characteristics show excellent transient response.     

Development of a compact transverse slot array antenna using corrugation in groove gap waveguide technology

We present the proof of concept of a compact slot array antenna with proper side lobe level in groove gap waveguide (GGW) technology. Four transverse slots are etched at the GGW broad wall along with the nulls of standing TE₁₀ wave existing inside the shorted GGW. To decrease the sidelobes and antenna size, corrugations are applied through the wave path inside the GGW. Proper use of corrugations can reduce the wavelength inside the GGW leading to reduction of the distance between adjacent transverse slots, which can help to suppress the grating lobe problem and consequently enhance the radiation efficiency, which is a challenge in transvers slot array antennas. The designed antenna is optimized to achieve maximum gain, lowest grating lobe level, and return loss at 15 GHz using HFSS simulator. The achieved gain is about 13 dBi, and the SLL is better than 15 dB. To confirm the simulation results, the designed antenna was fabricated and tested. Both simulation and measurement results confirm that the grating lobes are well suppressed at the antenna operating frequency.     

Broadband quasi-microstrip antenna

A new printed microwave antenna is presented. The antenna is a hybrid between a wire antenna array and a microstrip patch antenna. Although the size, cost, and efficiency are comparable to the microstrip patch, the voltage standing wave ratio 2:1 bandwidth of the antenna presented here is above 20%. The radiation pattern of the antenna does not change appreciably within the bandwidth, and the theoretical efficiency for optimal antennas remains above approximately 80% within the bandwidth. Measurements on several antennas around 2 and 4 GHz are presented, as well as theoretical results obtained using a full-wave analysis     

利用太阳辐射测量阵地上的雷达天线

太阳辐射出大量噪声电磁波,人们可以利用太阳辐射的噪声电磁波测量阵地上雷达的天线波瓣和增益。VHF雷达的波瓣受到地面反射的强烈影响,这些影响也可通过本文提出的方法测出。     

一种紧凑型双圆极化有源接收天线设计

设计了一种S波段紧凑型双圆极化有源接收天线,该有源接收天线将微带贴片天线与90°混合电桥、低噪声放大器集成设计,既实现了有源天线的整体小型化又提高了各器件间的连接效率;并通过背馈玻璃绝缘子和一种半差分的方式馈电,在改善微带贴片天线方向图对称性的同时,简化了传统差分式馈电的复杂结构.仿真和实测结果表明,该有源接收天线在2.2~2.3 GHz内端口驻波比小于1.47,噪声系数小于0.73 dB,主瓣内轴比小于2.4 dB,G/T值大于-13.9 dB/K,与已有公开文献的有源接收单元天线相比,在保持结构紧凑的同时,其G/T值有较大幅度提升.     

Optimum coupling of a Gaussian beam to a corner reflector with a four-wavelength antenna

The coupling of a Gaussian radiation beam to a corner reflector with a four-wavelength long wire antenna was studied theoretically and experimentally. The antenna configuration in conjunction with a Schottky barrier diode is recently used widely as a fast submillimeter wave detector. The optimum angle focusing the radiation to the antenna has been obtained and is 11° (half-width at the 8.7dB points).     

一种新型VHF/UHF双频宽带车载全向天线

提出了一种工作在VHF/UHF频段的双频段宽带垂直极化车载鞭状天线。天线在VHF中馈车载鞭状天线的下辐射体顶端加一个UHF频段8λ40 MHz/4同轴扼流套,将上辐射体分为三段并在段间串接两个λ840 MHz/2倒相线圈,在天线底部加同轴扼流圈,完成了一种VHF中馈鞭状天线与一副UHF三元串联馈电直线阵天线复合的新型VHF/UHF双频段超宽频带垂直极化车载全向天线。该天线在VHF频段(30 MHz~225 MHz),UHF频段(800 MHz~880 MHz)内均具有良好的辐射特性。增益在VHF频段为1.5~4.5 dB i,在UHF频段大于6 dB i。     

A monopole antenna loaded with a modified folded dipole

A traveling-wave distribution of current can be produced on a linear antenna by inserting a resistance of suitable magnitude one-quarter wavelength from its end. In this study the resistor is replaced with a modified folded dipole which has a radiation resistance approximately equal to that of the matching resistor. Thus the input section has a traveling wave distribution up to the inserted antenna, as before, but now the power that was previously dissipated in the resistor is also radiated. Input impedance, current distribution, and radiation patterns of this antenna are computed, and input impedance and radiation patterns are also measured. Horizontally polarized patterns are similar to those of a horizontal dipole over a ground plane, and vertically polarized patterns in a plane orthogonal to the folded element are similar to those of a monopole over a ground plane. Coverage is also obtained in the zenith direction in the plane of the folded element, as long as it is not an integral number of half wavelengths above the ground plane. The peaks and nulls can be controlled by adjusting the monopole height accordingly and it is possible to achieve near hemispherical coverage     

阵列天线的切比雪夫方向图综合

阵列天线是指由多个离散的辐射元,按一定规律排列组成的天线系统.其具有高增益,强方向性,主瓣可控等特性.文中研究了利用切比雪夫法对阵列天线输入不同参数:馈源单元数N,馈源间距d,副瓣电平SLL,得出参数改变对阵列天线方向图的综合影响,通过工程示例论证出切比雪夫法用于方向图综合的优缺点.为切比雪夫法用于天线方向图综合比较提供了一种有效的参考方法.     

Electromagnetic radiation from a prolate spheroidal antenna enclosed in a confocal spheroidal radome

The solution of electromagnetic radiation from a prolate spheroidal antenna, excited by a delta voltage across an infinitesimally narrow gap and enclosed in a confocal radome, is obtained. The method used is that of separating the scalar wave equation in prolate spheroidal coordinates and representing the solution in terms of prolate spheroidal wave functions. A simplified solution of the electric and magnetic fields, taking into account the symmetry of the antenna in the /spl phi/ direction, is obtained. Boundary conditions are then applied on the tangential fields to obtain a linear system of equations. The system of equations is cast into matrix form and solved using an iterative technique for the unknown expansion coefficients of the fields. Radiation patterns of the antenna are obtained and presented here for the first time.     

Circular polarization microstrip antenna on a conical surface

A theoretical model to analyze the performance of a circular polarization microstrip antenna printed on a conical surface is presented. The radiation pattern of the antenna is simulated by the radiation from its four radiating edges (two axial and two circumferential). The electromagnetic field is expanded in terms of spherical wave modes and it is shown that the circular polarization is obtained by exciting in the antenna two spherical TE_r orthogonal modes with 90° phase difference. The impedance analysis is based on the cavity model. Experimental data fits well the theoretical predictions of the model     

A Miniaturized Ground Edge Current Choke—Design, Measurement, and Applications

We propose a miniaturized microwave current choke for blocking the current flowing along the edge of a substrate's ground plane. The proposed current choke is composed of a printed inductor and a printed capacitor, which possesses a size much smaller than a conventional quarter-wavelength current choke. By introducing the choke at one side of the ground plane, an effective electrical open circuit is performed for reflecting the ground edge current. The size of the proposed ground edge current choke (GECC) is as small as around 0.06 wavelength in free space. Two applications of the GECC are presented in this paper. The first is the radiation pattern regulation of a printed monopole antenna with long ground plane. The GECC in this application reflects the induced traveling-wave current along the ground plane edge and changes it to a standing-wave one, thus regulating the tilted radiation pattern due to the traveling-wave current to a broadside pattern. The other application is the decoupling of two nearby monopole antennas. By placing the proposed compact GECC in between the antennas, it is found that the isolation between the antenna ports can be enhanced from 8 dB to 32 dB. The experimental results agree well with the simulation, which demonstrate the feasibility of the proposed GECC.