Quasi Microstrip Leaky-Wave Antenna With a Two-Dimensional Beam-Scanning Capability

A quasi microstrip leaky-wave antenna (QMLWA) with a two-dimensional (2-D) beam-scanning capability is presented in this paper. QMLWA consists of two half-width microstrip leaky-wave antennas with a phase-shifter. This new type of microstrip leaky-wave antenna has the advantages of reducing size, 2-D beam-scanning and suppressing back lobes. The main lobe scanning in H-plane ($y-z$ plane) is achieved through varying the operating frequency. When the operating frequency increases from 4.4–6 GHz, the main lobe scans from 84 $^{circ}$ to 26 $^{circ}$ in H-plane continuously. The main lobe steers in quasi-E-plane with varying the phase difference between two half-width microstrip leaky-wave antennas. The lobe scans from 78$^{circ}$ to 103$^{circ}$ in quasi-E-plane at 5.4 GHz. The experimental results show this short QMLWA (about 2 wavelengths) leaks power effectively. The back lobe in H-plane of QMLWA is suppressed 13 dB as compared with the conventional whole width MLWA at 5.4 GHz as example. The H-plane radiation characteristics of QMLWA are mainly determined by the width $s$ of half-width MLWA and the distance $D$ between two half-width MLWA together. This size-reduced QMLWA is useful in the automotive radar system and air traffic control.      

一种新型频率固定相控波束扫描的微带漏波天线

提出了一种崭新的带移相器双端口馈电微带漏波天线。通过控制微带漏波天线末端馈电端口移相器 ,其输入电流激励相位发生变化 ,成功地实现了工作频率固定下的微带漏波天线主波束扫描。当工作频率为 7GHz时 ,微带漏波天线主波束扫描范围可以达到约 2 1°。     

A Gunn-Diode Active Leaky-Wave Frequency Scanning Antenna

A frequency tunable active leaky-wave scanning antenna using Gunn-diode voltage control oscillator (VCO) as source is developed. The frequency tuning controlled by changing either the varactor diode dc bias or the Gunn diode dc bias is demonstrated. The measured scanning angle of active antenna is close to 15 degree as the Gunn VCO frequency tuned from 12.58GHz to 12.98GHz. To excite the first higher order mode of the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the middle line of the microstrip leaky wave antenna. This is a prototype of frequency scanning antenna using two terminal device, which can be easily scaled up to millimeter wave frequency region.     

Horn Image-Guide Leaky-Wave Antenna

A novel structure for a frequency-scanning millimeter-wave antenna is described. The antenna is constructed by embedding a dielectric leaky-wave antenna in a long trough with metal flares attached along both sides. The optimum flare angle for achieving maximum gain is theoretically predicted. The design of the leaky-wave antenna, which is comprised of metallic-strip perturbations on top of the dielectric guide, is also discussed.     

Active Antenna Module for Low-Cost Electronically Scanned Phased Arrays

This paper describes a low-cost compact active antenna module that includes transmit/receive/mixer electronics and a dual-polarized antenna element for half-duplex operation at 10 GHz. The system-in-package module has been fabricated in a ball-grid-array package. It is particularly suited for large low-cost low-power phased-array applications. Measurements at IF of single element gain show cross-pol reduced 18 dB. A small compact array was fabricated and measured. Simulations show that coupling between modules in a tightly packed infinite array caused a small reduction in scan range.     

基于HPSO的波束扫描反射阵天线设计

提出一种基于混合粒子群算法(HPSO)的低旁瓣波束扫描反射阵天线设计方法。在该方法中,首先利用天线实际方向图和渐变的理想方向图构建了加权的适应度函数。然后通过优化口径面相位分布搜索适应度函数的最小值,最终达到降低旁瓣的目的。同时,设计并制作了一副中心频率为12GHz 的圆极化波束扫描反射阵天线。实测结果与仿真结果较为吻合,天线在56°扫描范围内,旁瓣电平均小于-15dB,且带宽达到11. 67%。     

A Novel Reconfiguration CPW Leaky-Wave Antenna for Millimeter-Wave Application

A novel reconfigurable millimeter-wave leaky-wave antenna is proposed according to the radiation characteristics of periodically loaded coplanar waveguide and simulated by the finite-difference time-domain method. The simulated results demonstrate that the single main beam of this antenna operating at 35.0GHz can scan with small steps in the E-plane from ?90° to 90° except the angle around 0°. The main beam scanning is obtained by the antenna structure reconfiguration with nine discrete states controlled by embedded switches and two feed ports. The antenna is useful for millimeter-wave applications.     

Specific Features of Multibeam Directional Patterns in Analog-Digitial Active Phased Antenna Arrays

Journal of Communications Technology and Electronics - Formation of multibeam directional patterns in active phased antenna arrays (APAAs) with the known analog-digital signal control at the...     

Airborne Conical Antenna Arrays

Journal of Communications Technology and Electronics - The study presents an algorithm and the results of analysis of the sum-and-difference directional characteristics of an airborne conical...     

Leaky-Wave Slot Array Antenna Fed by a Dual Reflector System

A leaky-wave slot array antenna fed by a dual offset Gregorian reflector system is realized by pins in a parallel plate waveguide. The radiating part of the antenna is composed by parallel slots etched on one side of the same parallel plate waveguide. The dual offset Gregorian reflector system is fed by an arrangement constituted by two vias and a grid, also constituted by pins. Also this feed arrangement realizes a leaky type of radiation, this time inside the parallel plate waveguide. A prototype of the antenna has been designed, manufactured and successfully tested. The low profile, low cost and high efficiency of the antenna render it suited for a variety of radar or telecom applications.     

宽带低交叉极化超材料漏波天线的设计

基于基片集成波导结构提出了一种新型双层电磁超材料单元，并验证了其左手特性。将超材料单元应用于漏波天线的设计，所设计的天线由15个双层电磁超材料单元组成。将设计好的天线进行加工测试，测试与仿真结果吻合较好，表明漏波天线的工作频带为7.20~12.70GHz，在工作频带内可实现从后向-78°到前向+80°的连续主波束扫描，天线在工作频带内的测试增益均大于10dBi，峰值增益为15.2dBi，3dB增益带宽达到50.2%。此外，该漏波天线具有很低的交叉极化电平，交叉极化始终比主极化低至少30dB。相比于新近文献报道的同类型超材料漏波天线，所设计的天线具有更加优越的电气性能。     

A CPS Leaky-Wave Antenna With Reduced Beam Squinting Using NRI-TL Metamaterials

A reduced beam-squinting printed leaky-wave antenna (LWA) is proposed, comprising cascaded negative-refractive-index transmission-line (NRI-TL) metamaterial unit cells. Each NRI-TL unit cell is implemented in co-planar strip (CPS) technology and consists of a host TL loaded with series interdigitated capacitors and shunt meandered inductors. Periodic analysis is applied to the NRI-TL unit cell in order to extract the dispersion and Bloch impedance characteristics. Subsequently, the angular variation of the main radiated beam with frequency or ldquobeam squintingrdquo is derived, based on the expression for the Bloch propagation constant of the NRI-TL line. It is shown that by operating the LWA in the upper right-handed band where the phase and group velocities are closest to the speed of light, the beam squinting that the antenna experiences can be minimized. The theoretical performance of the LWA is verified through full-wave simulations and measurements of a fabricated prototype designed to produce a radiated beam at an angle of at GHz. This 20-element NRI-TL LWA exhibits a measured return-loss bandwidth below dB of 0.91 GHz (18.2%), and an average beam squint of 0.031/MHz. The proposed NRI-TL LWA is uniplanar, differential and broadband, and therefore suitable for integration with other microwave components and devices.     

Time-Reversal Detection Using Antenna Arrays

The paper studies detection of a target buried in a rich scattering medium by time reversal. We use a multi-static configuration with receive and transmit arrays of antennas. In time reversal, the backscattered field is recorded, time reversed, and retransmitted (mathematically or physically) into the same scattering medium. We derive two array detectors: the time-reversal channel matched filter when the target channel response is known; and the time-reversal generalized-likelihood ratio test (TR-GLRT) when the target channel response is unknown. The noise added in the initial probing step to the time-reversal signal makes the analysis of the TR-GLRT detector non trivial. The paper derives closed form expressions for the signal-to-noise ratio gain provided by this detector over the corresponding conventional clutter subtraction energy detector in the two extreme conditions of weak and strong (electronic additive) noise and shows that time reversal provides, under weak noise, the optimal waveform shape to probe the environment. We analyze the impact of the array configuration on the detection performance. Finally, experiments with electromagnetic data collected in a multipath scattering laboratory environment confirm our analytical results. Under the realistic conditions tested, time reversal provides detection gains over conventional detection that range from 2 to 4.7 dB.      

Out-of-Band Response of Antenna Arrays

The response of antenna arrays to out-of-band frequencies has been analyzed using the effective-aperture approach. An average value of effective aperture can be obtained by averaging the incidence angle and the polarization of the incidence field. Far-field patterns have also been calculated by treating the array element excitations as random variables. The randomness in the element excitations causes a decrease in directivity and an increase in sidelobe level. Out-of-band measurements on a slotted-waveguide array confirm these trends.     

相位共轭天线阵研究

基于广义相位共轭条件,研究了相位共轭天线阵实现方向回溯功能的原理,详细分析了射频混频和中频混频两种实现方式的工作方式并讨论了各自的优缺点。理论推导了相位共轭天线阵的远场表达式,提出了射频泄漏系数的概念,仿真研究了射频泄漏系数对方向回溯场的影响,为方向回溯天线阵的进一步研究奠定了基础。     

基于漏泄矩形波导的低副瓣漏波天线

设计了一种基于长直缝隙漏泄矩形波导的低副瓣漏波天线.基于有效辐射段理论将漏波天线等效成线源模型,分析线源模型的有效辐射段结构,然后针对天线某一副瓣对应的有效辐射段,缩小该处的缝隙宽度直接抑制该副瓣水平,同时通过增大天线主瓣对应的有效辐射段缝隙宽度间接抑制副瓣水平.两种方法都能不同程度实现天线的低副瓣特性,利用仿真软件验...     

Periodic Leaky-Wave Antenna for Millimeter Wave Applications Based on Substrate Integrated Waveguide

Substrate integrated waveguides (SIW) are built up of periodically arranged metallic via-holes or via-slots. The leakage loss of SIW structures increases with the distance between the via-holes or via-slots. An open periodic waveguide with a large via distance supports the propagation of leaky-wave modes and can thus be used for the design of a leaky-wave antenna. In this paper, this leakage loss is studied in detail and used to design a periodic leaky-wave antenna. The proposed concept represents an excellent choice for applications in the millimeter-wave band. Due to its versatility, the finite difference frequency domain method for periodic guided-wave or leaky-wave structures is used to analyze the characteristics of the proposed periodic leaky-wave antenna. Two modes (${rm TE}_{10}$ and ${rm TE}_{20}$) are investigated and their different leaky-wave properties are analyzed. Based on the proposed leaky-mode analysis method, a novel periodic leaky-wave antenna at 28–34 GHz is designed and fabricated.      

Maximal-Ratio Eigen-Combining for Smarter Antenna Arrays

In typical mobile wireless scenarios, signals are received with power azimuth angle spectrum (p.a.s.) of variable azimuth angle spread (AS). Therefore, conventional maximum average signal-to-noise ratio beamforming (BF) or maximal-ratio combining (MRC) may not necessarily be effective in terms of performance or signal processing complexity. A newer, more flexible, approach, called maximal-ratio eigen-combining (MREC) is analyzed and found to generalize BF and MRC. For imperfectly-known channels we study both suboptimal and optimal eigen-/combining. MREC-based analysis is shown to simplify MRC performance investigations for correlated channel gains. For MPSK signals, we present average error probability (AEP) expressions for MREC, BF, and MRC, that are new or generalizations of our previous work. Furthermore, we propose a performance-complexity tradeoff criterion (PCTC) for MREC-receiver adaptation to changing AS. Numerical evaluations for typical urban scenarios with realistic Laplacian p.a.s. of random AS demonstrate that PCTC-based MREC is an interesting alternative to BF and MRC, for smart antenna arrays     

Scattering Characteristics of Ultra-Wideband Antenna Arrays

Journal of Communications Technology and Electronics - This paper presents a study of the monostatic and bistatic radar cross-section (RCS) of three planar two-dimensionally periodic antenna arrays...     

基于复合左右手材料的圆柱共形漏波天线设计

提出了一种基于复合左右手材料的平衡式圆柱共形漏波天线。天线单元由圆柱共形介质波导构成,通过在波导上表面蚀刻矩形缝隙槽结构,在引入串联电容的同时实现电磁波能量的连续泄漏,从而得到所需要的辐射特性。同时在波导结构中采用金属化通孔,引入并联电感, 实现了电磁波的左手传输特性。所设计的天线在平衡频点 15.6 GHz 处具有良好的边射特性。所提出的复合左右手漏波天线的阻抗带宽为 4.3 GHz(13.5~17.8 GHz),在天线阻抗带宽范围内天线主波束可以从-57°连续扫描到+30°。