基于双面平行带线的全空间扫描漏波天线

为了实现从后向端射到前向端射的连续波束扫描天线,该文基于双面平行带线结构提出了一种具有全空间扫描能力的漏波天线。天线单元由双面平行带线传输线和一对反向加载的开路枝节组成,两个开路枝节分别位于传输线的上导带和下导带。加载的反向开路枝节等效为一个偶极子,使得天线单元具有全向辐射性能,作为整个全空间扫描漏波天线的基础单元。为了抑制周期漏波天线中的开阻带问题,又在天线基础单元上加载了一对平衡槽以实现频率平衡条件,还加载了一对匹配槽以匹配周期结构的阻抗。最后实现了一款天线原型,经仿真与实验验证,该天线能够在7.6 GHz 到14.0 GHz的频率范围内,实现从后向端射,经侧向辐射,然后到前向端射的全空间扫描能力。     

High-Efficiency Angled-Dipole Antennas for Millimeter-Wave Phased Array Applications

A high-efficiency microstrip-fed endfire angled-dipole antenna has been developed for millimeter-wave phased array applications. The antenna is built on both sides of a Teflon substrate (epsiv_r = 2.2) and this allows a wideband feed from the single-ended microstrip line to the differential dipole. The design results in wide radiation patterns for scanning purposes with a gain of around 2.5 dB at 20-26 GHz and a cross-polarization level of < -15 dB at 24 GHz. A mutual coupling of < -23 dB is measured between adjacent elements with 6.8 mm center-to center spacing (0.50-0.54 lambda₀ at 22-24 GHz). A variant of the angled-dipole antenna with a magnetic ground plane edge was also developed, and shows a measured gain of > 6 dB at 23.2-24.6 GHz and very low mutual coupling between elements (<-23 dB for a 6.8 mm spacing). Both antennas result in a radiation efficiency of > 93% when referenced to the microstrip line feed (including mismatch loss). The usefulness of these antennas as phased array radiators is demonstrated by several eight-element linear arrays at 22-24 GHz with scan angle up to 50 degrees. The application areas are in automotive radars and high data-rate communication systems.     

Performance of a rectangular-waveguide-excited short backfire antenna employing a conical main reflector

The letter presents experimental results at X-band for a short backfire antenna employing a conical reflector, which is excited by a rectangular waveguide. It is shown that the use of a conical main reflector can lead to a compact antenna having a directive gain of 16.7?18.3 dB, sidelobe level below 13.8 dB and input VSWR better than 2.5 over a 20% bandwidth from 9?11 GHz.     

Unidirectional patterns of traveling-wave rectangular antenna

A traveling-wave rectangular antenna, for which the feeding point is placed at the center of a leg and the matching impedance is terminated at the opposite leg, is considered. This antenna has two kinds of quasi-nonsidelobe unidirectional patterns of cardioid shape; one is endfire and the other is backfire. Endfire patterns are obtained for leg lengths comparable with a wavelength, while backfire patterns are obtained when the antenna is small relative to a wavelength. In the former, the unidirectional antenna pattern for leg lengths oflambdaandlambda/4has a beamwidth of about180degand very high front-to-back ratio (FBR). When the antenna lengths change by several percent from the ideal lengths, the variation of the beamwidth is in the range of40degand the FBR is in the range of about 5 (14 dB) to infinity. In the latter, for the rectangular antenna with a leg length oflambda/10, the pattern in a plane perpendicular to the antenna has a beamwidth of160degand the pattern in a plane including the antenna has the beamwidth of124deg. When the antenna lengths vary by aboutpm30percent, the variation of the beamwidth is in the range of30degand the variation of the sidelobe level is about 4 dB. Although we used a suitable resistance instead of the matching impedance, the experimental results were almost coincidental with the theoretical patterns.     

Backfire mode zigzag antenna

A backfire mode zigzag antenna is analysed using the method of moments. The effects of the filament length of the zigzag on the -10 dB beam width is calculated. The zigzag antenna is applied to a symmetrical paraboloidal reflector antenna as a primary feed. The reflector antenna shows a relatively constant gain in the communication satellite frequency band 12.25-2.75 GHz.<>     

Ku band pattern reconfigurable substrate integrated waveguide leaky wave horn antenna

A dual band substrate integrated waveguide H plane sectoral horn antenna with reconfigurable radiation characteristics has been proposed in this paper. Designed antenna acts as a perfect broadside radiator at 16.1 GHz and perfect endfire radiator at 14.4 GHz frequency. Broadside radiation has been achieved by etching rectangular slots in the flared section of horn exhibiting a gain of 8.87 dBi. To achieve perfect endfire radiation, dielectric loading is done at the edge of horn and at this frequency antenna shows a gain of 11.3 dBi. The horn and the loaded dielectric are integrated by using the same single substrate resulting in easy fabrication and low cost. The proposed design has been fabricated and measured results are in good agreement with the simulated results.     

Backfire/endfire radiation performance of quadrifilar helical antennas

The relations between the radiation pattern and feeding method in quadrifilar helical antennas is discussed. As a result, it is found that by changing the phase of each wire the helical antenna can achieve two radiation modes; both backfire and endfire radiation. These patterns do not have a difference except in radiation direction. Antenna polarisation of quadrifilar helical antenna depends only on the helical winding direction.<>     

An improvement of parasitic dipole array using suppressor elements

A novel configuration of parasitic arrays is introduced. The characteristics of the array in both forward and backward radiation are improved by using a new element, the suppressor. The suppressor elements are aligned parallel to a radiating dipole or to a conventional endfire array such as a Yagi-Uda array. Radiation in the unwanted direction is reduced by the suppressors, and the forward gain is effectively increased. Design of the optimum antenna parameters was achieved using the moment method, and results were compared to measured values, with good agreement obtained. New arrays were compared to well-designed Yagi-Uda arrays. A new array which is aligned with two broadside suppressors and with three endfire elements had an improved forward gain of 1.5 dB and a reduced backward gain of -4 dB compared to a conventional, well designed Yagi-Uda array with five endfire elements     

Tapered slotline antennas at 802 GHz

Broken linearly tapered endfire slotline antennas (BLTSAs) were fabricated on 1.7-μm thin SiO₂-Si₃N₄ dielectric membranes. Antenna patterns in the E-, H-, and D-planes were measured at 802 GHz. The -10 dB beamwidths were found to be approximately 40° in all planes, with side lobe levels below -11 dB (-19 dB in the E-plane). The cross-polarized peaks in the D-plane were 8 dB below the copolarized peak. A theoretical model for calculating the E- and H-plane patterns of tapered slotline antenna 10 is extended to include the co- and cross-polarized D-planes. Measured and calculated patterns show good agreement     

Research on the short backfire antenna

A method of analysing the short backfire antenna is proposed. With this method, a new type backfire antenna is developed. Its gain is about 2.5dB higher than that of a normal short backfire antenna.     

短背射天线的研究

本文提出了短背射天线的一种分析方法,它较好地解释了背射天线的工作原理。按此分析方法研制的短背射天线的增益比普通短背射天线的约高2.5dB。     

一种L波段背射模螺旋馈源

螺旋天线具有较好的宽频带圆极化特性,在L或S波段体积和增益都很适中,加工制造公差要求较低,因此在该频段螺旋天线得到了广泛的应用。由背射模螺旋构成的L波段宽带馈源具有结构简单,馈电、调试方便,口面遮挡小,频带宽(大于25%),可以承受大功率等优点,可以满足L或S波段测控系统对天线的要求。用该背射模螺旋馈源研制的前馈天线的口径效率超过了53%,第一副瓣小于-20 dB,在工程中得到了很好的应用。     

5G传播损耗及链路预算

针对5G发展对室内接入天线提出的新要求,设计了一种可在N78（3.4~3.6 GHz）与N79（4.8~5.0 GHz）两个频段之间切换的频率可重构天线. 天线辐射器印制在电路板上,电路板末端带有圆形金属腔,作为八木天线与短背射天线的反射器. 对PIN二极管偏置电路进行优化,切换天线有源振子臂上一对PIN二极管开关,使天线具有两种工作模式,具备频率可重构的功能. 通过仿真软件对天线模型进行仿真分析,根据仿真结果制作了天线的实物并进行实验验证,实测表明天线具有良好的匹配与增益. 当PIN二极管导通时,天线工作在N78频段,回波损耗小于−19.58 dB,增益大于7.44 dBi;当PIN二极管断开时,天线工作在N79频段,回波损耗小于−18.58 dB,增益大于9.48 dBi.

     

A Study of Ultrawideband Antennas for Near-Field Imaging

A compact ultrawideband (UWB) antenna has been designed for UWB cancer detection systems. The numerical analysis and experimental characterization of a printed monopole antenna fed by a 50-Omega coplanar waveguide (CPW) and operating in a lossy coupling medium is presented. A detailed 3D model of the antenna and the biological environment has been constructed and simulated in XFDTD and HFSS. The near-field pattern of the antenna in the proximity of a multilayer human body model and the effect of the human body on the input matching of the antenna are studied. Experimental results show that the return loss is below -9.6 dB from 3.4 GHz to 9.9 GHz     

Radiation characteristics of a waveguide-excited short backfire-fedparabolic reflector operating in Q-band

Presents measured results at 31-38 GHz of the radiation characteristics of a 0.252 m diameter parabolic dish fed at the prime focus by a short backfire antenna. The feed consists of an experimentally optimised design of a short backfire antenna, having a conical main reflector of 15° slant angle. The measured radiation patterns of the reflector system generally agree quite well with the prediction based on aperture field integration     

A 24-GHz high-gain Yagi-Uda antenna array

A compact 24-GHz Yagi-Uda antenna has been developed using standard design tables and simple scaling to take into account the added capacitance due to the supporting dielectric substrate. The antenna results in a directivity of 9.3 dB, a front-to-back ratio of 11 dB, and a bandwidth of 2.5-3%. The Yagi-Uda antenna has been implemented in an 11-beam system using a planar array and a 2-inch Teflon spherical lens. The measured patterns show a 22 dB gain beam, a cross-polarization level of -24 dB, and a crossover level of -6 dB. The design method presented in this paper is quite straightforward, and can be used to develop low-, medium-, and even high-gain endfire Yagi-Uda antennas.     

Design of Dual‐Band MIMO Antenna with High Isolation for WLAN Mobile Terminal

In this paper, we propose a dual‐band multiple‐input multiple‐output (MIMO) antenna with high isolation for WLAN applications (2.45 GHz and 5.2 GHz). The proposed antenna is composed of a mobile communication terminal board, eight radiators, a coaxial feed line, and slots for isolation. The measured ?10 dB impedance bandwidths are 10.1% (2.35 GHz to 2.6 GHz) and 3.85% (5.1 GHz to 5.3 GHz) at each frequency band. The proposed four‐element MIMO antenna has an isolation of better than 35 dB at 2.45 GHz and 45 dB at 5.2 GHz between each element. The antenna gain is 3.2 dBi at 2.45 GHz and 4.2 dBi at 5.2 GHz.     

基于二元偶极子阵的边射端射可重构RFID阅读器天线设计

基于射频识别应用场景中存在的一些T型结构，如楼内、地下矿井等存在的一些T型通道，为做好这些场景中的信号覆盖，本文提出了一种新颖的边射端射可重构的RFID阅读器天线。天线由可重构的馈电网络和两个相距半波长的偶极子组成，天线边射和双向端射的可重构特性通过控制馈电网络中的开关状态实现。为了验证天线性能，对其进行了加工测试。测试结果表明，天线在边射和端射状态下的阻抗带宽和增益分别为2.7%(900～925 MHz),4.15 dBi和1.9%(905～923 MHz),2.10 dBi,与仿真结果基本一致。该天线具有结构简单、小型化、低剖面等优势，在射频识别系统中有一定的应用价值。     

一种新型布局的圆极化微带天线阵优化设计

提出了一款高增益低副瓣新型圆极化微带天线阵。单元天线采用叠层切角圆极化微带结构,通过八边形边界布局和顺序旋转交叠组阵技术,实现了天线阵方向性图的对称性和圆极化辐射性能的最优化;馈电网络采用威尔金森功分器和最大平坦式阻抗变换器实现不等功分宽带阻抗匹配,通过改进馈电方向寻求对称结构,简化了馈电网络的设计。制作了天线阵实物并进行了测量。测试结果表明:天线在3.2~4.6 GHz频段内S₁₁<-10 dB,阻抗相对带宽36%;在3.8~4.5 GHz频段内顶点轴比小于3 dB,圆极化相对带宽17%;在4~4.4 GHz频段内天线增益均在15 dB以上,最高增益达17 dB。     

Active feedback microstrip leaky wave antenna-synthesiser designwith suppressed back lobe radiation

The design of an active leaky-wave antenna which integrates the antenna with a feedback synthesizer is introduced. The measurement result shows that the antenna has very low back lobe radiation compared with that of traditional single-terminal feeding leaky-wave antennas. Single frequency measurement shows that the radiated power difference between the main beam and back lobe is >15 dB at 8.2 GHz. For the designed feedback synthesizer antenna, the measured radiated power difference between the main beam and back lobe is >15 dB at 9.25 GHz, and the scanning angle is ~5° as the synthesizer frequency sweeps from 9.25 to 9.37 GHz