等离子体天线技术原理分析

介绍了2类常见的等离子体天线——等离子体介质天线和等离子体反射面天线,然后分别分析了其基本工作原理,并与金属天线对比,指出了等离子体天线在雷达隐身、可重构、低互耦性方面的独特优势,最后提出了一种新型的等离子体智能天线,为等离子体天线技术的研究提供了一种新方向。     

一个宽波束天线精确定位的实验装置

本文研究了宽波束天线定向的理论,并在3厘米波段,用一个3dB带宽为60°的开口波导作为宽波束扫描接收天线,来确定辐射源的方位.运用宽波束天线走向技术可以使方位分辨力优于1°.     

机载相控阵波束指向校正

安装在机翼上的卫星通信相控阵天线,其波束指向角度信息无法由航电系统直接提供。通过三维电子罗盘测量相控阵阵面的姿态参数,结合航电系统提供的飞机姿态参数和卫星角度参数,可以完成卫星相对于阵面角度的校正。校正方法首先把机身坐标系参数转换到地球坐标系,然后再转换到阵面坐标系,从而求解指向角度。计算机仿真证明了校正方法可行,坐标变换方法正确．同时也证明姿态测量参数精度影响相控阵天线最终性能。     

等离子体通道天线的传播特性分析

文中提出了一种用于高功率微波武器系统的激光等离子体通道天线,简单阐述了该天线的具体实现方法,根据天线的工作原理,建立了等离子体通道天线的近似电磁模型.从柱坐标系下纵向分量所满足的波动方程出发,在柱坐标系中给出了纵向场与横向场的关系,利用边界条件分别导出了非磁化和磁化等离子体通道天线最严格的特征方程,并通过在极限条件下将本文结果与文献已有结果的对比,验证了文中所导结果的正确性和有效性.最后,分别数值计算了非磁化和磁化等离子体通道天线的色散曲线,为该天线的实际应用打下坚实的理论基础.     

Package-Level Integrated LTCC Antenna for RF Package Application

This paper presents a compact antenna geometry to realize an radio frequency (RF) system in package (SIP) and discusses an antenna-integrated package for an IEEE 802.11a application. The proposed compact antenna is similar to a modified U-shaped slot antenna; however, its electrical properties are quite different. A fabricated antenna demonstrates bandwidth of 180 MHz at a center frequency of 5.8 GHz, and it may be used to implement antenna-integrated packages. An antenna-integrated package is proposed consisting of the antenna placed on the top surface, internal space for integration of other IC components, a conducting layer placed between the antenna and the internal space, and finally a bottom layer. In addition, from the parametric studies it is found that the size of the package, dielectric thickness of the antenna, package height, and the number as well as the position of via holes, are critical factors of antenna characteristics     

Comprehensive Analysis and Design of Capacitive RF MEMS Switches for Reconfigurable Microstrip Patch Antenna

Wireless Personal Communications - This paper presents design of a reconfigurable micro strip patch antenna by using RF MEMS. Primarily we have analyzed the performance of different shunt...     

阵列导向矢量在智能天线自适应算法中的应用

分析了智能天线自适应算法的基本原理,针对常用算法运算量大和测向精度有限等问 题,在接收机的输出端引入阵列导向矢量信号,利用方向性因子和协方差矩阵的特殊性 质,通过多次迭代运算得出区间内的信干噪比曲线。通过对八元直线型智能天线阵列的HFSS 仿真实验表明,两组信干噪比曲线峰值均对应期望信号方向,峰值信干噪比大于30 dB ,算法抗干扰性能良好。八元阵列天线的最大增益约为18 dB,通带内驻波比小于15 , 反射系数小于-25 dB,天线系统波束搜索性能良好,而且可以实现远距离传输。     

Cassegrain Antenna With Hybrid Beam Steering Scheme for Mobile Satellite Communications

A hybrid antenna (HA) with a modified beam steering method is proposed. This antenna has a Cassegrain structure composed of two reflectors and a feeder. The parabolic-shaped main reflector is designed for high gain, while the subreflector is rotational and flat. The feeder is a phased array with arbitrary shaped aperture and 20 element antennas. The HA is capable of two-dimensional beam steering by means of two operations: rotation of the subreflector and phase control of the feed array. The subreflector is small in size and weight, so it can provide rapid beam scanning. Designed to be loaded in vehicles, the HA and can communicate with satellites on the move by tracking the beam control of the feed array. A prototype of the HA is fabricated with aluminum using a machining center operated by computerized numerical control. The prototype is operated at Ka-band for TX and K-band for RX with gains of 47 dBi and 44.4 dBi, respectively, at a steering angle of 0 $^{circ}$. The two-dimensional beam steering within $pm 2^{circ}$ with respect to 45$^{circ}$ elevation is realized by the subreflector and feed array. All radiation patterns in the beam steering zone meet ITU-R s.465-5 regulations.      

某型号雷达天线阵精度设计

精度是雷达、卫星通讯地面站和射电望远镜的一个重要性能指标。影响整个设备精度的因素很多，本文主要讨论与结构设计有关的天线阵两侧俯仰轴对天线指向精度的影响。     

Analysis of Electromagnetic Scattering from Plasma Antenna Using CG-FFT Method

A gaseous plasma column as an efficient radiator of electromagnetic waves is well known. This paper presents the scattering analysis of a plasma antenna using the conjugate gradient fast Fourier transform (CG-FFT) method. Radar cross sections (RCS) of designed plasma antenna for different plasma parameters are computed mainly. Numerical results show that the plasma antenna with appropriate parameters can offer lower RCS than the metal one. It is evident from the observed scattering characteristics that the plasma antenna can be regarded as a rod of imperfect conductor with losses.     

RF Photonic Techniques for Same Frequency Simultaneous Duplex Antenna Operation

Same frequency, broadband, simultaneous transmit/ receive on the same antenna is facilitated by employing a balanced architecture to cancel that part of the transmit signal that leaks into the receive path. The concurrent detection of the receive signal and the cancellation of the transmitter leakage into the receive path are accomplished in the optical domain with a dual-port optical modulator and a differential photodetector pair.     

A Compact Direction-Finding Antenna for HF Remote Sensing

A compact four-element antenna, along with a numerical direction-finding algorithm, is analyzed using computer simulations that model sea-echo data obtained with an HF pulsed Doppler radar. The algorithm consists of closed-form expressions and is capable of deriving the angles-of-arrival for one or two signals impinging upon the antenna. Errors associated with the calculated angles are presented as a function of signal-to-noise ratio. In addition, it is demonstrated that preaveraging antenna voltages over independent data samples can decrease the angle errors and extend the range of the radar.     

RF Front-End Passive Circuit Implementation Including Antenna for ZigBee Applications

This paper presents a front-end passive circuit module for ZigBee applications using low-temperature co-fired ceramic technology. The front-end part consists of an antenna, a bandpass filter, a switch, and two baluns. In antenna design, the solenoid shape is employed for reducing the size of the antenna, resulting in an overall size of 9times16.4times1.82 mm³ and a gain of -1.4 dBi. As for the filter, two types of filters are suggested. First, the lumped-type filter employing a high-Q spiral inductor has more than 20-dB attenuation at both stopbands, very near to the passband. Secondly, the semilumped-type filter adopting an edge coupled line and a loading capacitor provides a group delay of below 5 ns and is adequate for the full module structure due to the structure flexibility. A balun is evaluated using lumped components instead of a transmission line and, thus, it provides an insertion loss of only 0.3 dB and a phase difference of 180deg between balanced signals. Based on these components, an RF front-end module including attaching pads for an RF integrated circuit (IC) and baseband IC is implemented. In case of using the lumped-type filter, the insertion loss of the front-end module is 6.5 dB, and the group delay is below 7 ns. In case of adopting the semilumped-type filter, the insertion loss is 6.2 dB, and the group delay is below 4 ns. The overall size of the former and latter is 25.14times28.5times0.68 mm³ and 25.66times25.58times1.17 mm³, respectively     

Optical Fiber Technique for Remote Stabilization of RF Phase

We demonstrate an optical-fiber-based technique to deliver a radio-frequency reference phase to a remote location. Using a reflected portion of the RF amplitude-modulated optical signal from the remote location in a feedback loop, we show that the remote phase can be kept within ± 0.3° of the desired value, independent of temperature variations along a fiber length of 2 km or more. The instrument is designed to operate at 416 MHz, and works satisfactorily over a ± 10% RF bandwidth. In addition, an automatic phase ranging circuit allows the device to maintain phase stabilization over an infinite number of phase cycles. The system is presently being installed at the Molonglo Observatory Synthesis Telescope near Canberra, Australia.     

大口径反射面天线射频性能的近场聚焦测量

简要介绍了反射面天线近场聚焦测量方法,推导出了有限测试距离时用副反射面纵向偏焦补偿近场相差的计算公式,分析了近场聚焦测量与远场测量的数据结果,并给出了仿真和试验实例,仿真与试验结果吻合较好,近场聚焦法是一种可用于大口径天线性能测量的有效方法。     

Performance Analysis of the ITER Plasma Position Reflectometry (PPR) Ex-vessel Transmission Lines

As the design of the ITER Plasma Position Reflectometry (PPR) diagnostic progresses, some segments of the transmission line have become fully specified and estimations of their performance can already be obtained. This work presents the calculations carried out for the longest section of the PPR, which is in final state of design and will be the main contributor to the total system performance. Considering the 88.9 mm circular corrugated waveguide (CCWG) that was previously chosen, signal degradation calculations have been performed. Different degradation sources have been studied: ohmic attenuation losses for CCWG; mode conversion losses for gaps, mitre bends, waveguide sag and different types of misalignments; reflection and absorption losses due to microwave windows and coupling losses to free space Gaussian beam. Contributions from all these sources have been integrated to give a global estimation of performance in the transmission lines segments under study.     

自补偿型射频等离子体探针

自补偿型郎缪尔探针是克服射频场对等离子体诊断产生干扰的有效工具。本文对这种探针的特性进行了分析。     

Analysis of Single‐RF MIMO Receiver with Beam‐Switching Antenna

This paper proposes a single‐RF MIMO receiver that adopts a beam‐switching antenna (BSA) instead of a conventional array antenna. The beauty of the proposed single‐RF MIMO receiver with BSA is that it can be deployed in a very small physical space while achieving a full spatial multiplexing gain. Our analysis has revealed that the use of a BSA inevitably results in the spectrum spreading effect at the RF output, which in turn causes an SNR decrease and adjacent channel interference (ACI). Two novel receiver techniques are proposed to mitigate the issues of redundant sub‐band suppression and ACI avoidance. Numerical analysis results verify the performance improvement from the proposed receiver techniques.