Large-aperture sparse array antenna systems of moderate bandwidthfor multiple emitter location

Spatial linear prediction filter antenna systems of large aperture width (in wavelengths) are described for the superresolution estimation of multiple emitter locations over moderate bandwidths. To accomplish this task with reasonably few degrees of freedom (DOF) from the large aperture, the system uses interferometer/sparse array techniques in conjunction with a shaped reference beam which may be steered to the spatial sector of interest. Computer simulations on several multiple source examples have demonstrated that the concept is feasible, provided that true time-delay steering is used on the shaped reference beam. The optimal estimation system configuration results when time-delay steering is also applied to the interferometer elements because this focuses the sample covariance matrix and minimizes the DOF required. Transversal filters may be dispensed with under focused conditions if the bandwidth is moderate. System performance goals included high resolution with few DOF, fast response/processing time, moderate cost, and ease of frequent calibration     

星载可展构架式天线方向图快速计算

针对可展构架式天线反射面形态的具体特点,在几何光学法的基础上,采用分网积分的方法把抛物面离散,使其在口径面上成矩形网格,在网格内使积分变量分离,再利用菲涅耳积分法求解出单个网格反射后的远场场强,然后叠加所有网格产生的远场得到整个反射面的方向图.通过该算法可以直接根据电性能的要求对构架式天线进行拓扑结构设计,省略了均方根误差这个中间值,使得设计快速直观.用该算法计算一个理想抛物面天线,与Rahmat-Samii等人的结果进行比较,证明该算法精确高效.     

An implantable microwave antenna for interstitial hyperthermia

This letter presents a new microwave antenna design with greatly enhanced heating at the tip for interstitial hyperthermia. Temperature distribution patterns surrounding the new balun-fed folded dipole antenna are measured in a saline phantom under transient and steady-state conditions.     

A dipole antenna for interstitial microwave hyperthermia

An improved interstitial microwave antenna design was investigated in static phantom experiments at 915 MHz and different insertion depths. Compared with conventional interstitial antennas, the presented dipole microwave antenna shows heating patterns which are concentrated on the dipole irrespective of the insertion depth. By analogy to interstitial radiotherapy, the microwave antenna allows a high concentration of energy in the target volume with as little damage as possible to the healthy surrounding tissue. The undesired heating of healthy tissue along the feeding line observed with conventional interstitial antennas is avoided. A λ/4 sleeve on the feeding line (which does not radiate microwave energy itself to the surrounding tissue) transforms an open end, i.e. a high impedance at the generator end of the dipole antenna. The current flowing back along the outside of the outer conductor of the feeding line in the direction of the generator is zero at this point. Both dipole sections have the same terminating impedance. Since the λ/4 sleeve is mounted outside the antenna, its mechanical length is not restricted by the mechanical length of the antenna. It can be charged with dielectric materials of low dielectricity constants     

全向圆极化天线的V型振子阵设计

文中利用数值分析与计算机CAD技术，设计出由V型阵子组成的微波全向圆极化天线，并在实际应用中取得良好的效果。     

Leaky NRD guide fed microwave planar antenna

A novel and unique application of leaky waveguides as feeding systems for microwave planar antennas is presented. A new leaky nonradiative dielectric (NRD) guide based on a grating structure is proposed, and a planar array slot antenna using this leaky waveguide is constructed and measured at 23 GHz.<>     

一种大型可展开天线结构频率调整技术研究

对环形桁架可展开天线的振动问题提出了一种被动控制的方法,通过对环形桁架可展开天线施加预应力来改变环形天线第一阶固有频率,使之与激振频率错开,从而避免共振,使振幅减小,最终使振动自由衰减下来,达到抑制共振的目的。对预应力影响结构频率的原因进行了理论分析,计算了环形桁架可展开天线的带宽,对不同预应力加载方式下的环形天线的频率变化进行了仿真,最终确定了最佳的预应力加载方式。     

一种高增益微波光子天线阵列的设计

设计了一种中心频率为20 GHz的8单元微带光子天线阵列,利用微波光子技术解决了传统微波技术在高频、宽带等方面的问题。天线单元为矩形微带贴片天线,馈电网络采用具有λ/4阻抗匹配枝节设计的多级T型等分功分器。采用光子上变频技术产生20 GHz的微波信号,光载微波信号经光纤传输后由阵列天线发射。利用三维高频结构电磁场仿真对该天线阵模型的搭建和优化进行仿真,结果表明天线阵仿真阻抗带宽为1.15 GHz,在带宽内最大增益为13.6 dBi。将天线阵列应用到微波光子系统发射端,测量结果表明,最大增益可以达到6.92 dBi。该天线阵列性能良好,可广泛应用于未来移动通信网络覆盖领域。     

The cap-choke catheter antenna for microwave ablation treatment

A matched-dipole type catheter antenna is described for intracavitary and/or transluminal microwave treatment of diseases that may be responsive to thermal ablation therapy. This cap-choke antenna consists of an annular cap and coaxial choke design that can yield specific absorption rate (SAR) distributions in, and can produce heating of, tissue surrounding the distal end of the catheter antenna. The cap-choke antenna is simple in construction, provides the desired SAR distribution, and is efficient, i.e., the measured power reflection coefficient is 2% in tissue equivalent phantom modeling materials     

Optical feed for a phased array microwave antenna

Microwave signals for all array elements in a phared array microwave antenna are simultaneously generated by spatial sampling of a moving sinusoidal interference pattern formed between two frequency-offset injection-locked laser diodes. The offset and radar frequency of 3.2 GHz were generated by a Bragg cell. A nearly distortionless antenna beam pattern and 180° steering are demonstrated in a linear seven-element array.     

Effects of measurement errors on microwave antenna holography

The effects of measurement errors appearing during the implementation of the microwave holographic technique are investigated in detail, and many representative results are presented based on computer simulations. The numerical results are tailored for cases applicable to the utilization of the holographic technique for the NASA's Deep Space Network antennas, although the methodology of analysis is applicable to any antenna. Many system measurement topics are presented and summarized     

新型高功率微波模式转换天线研究

给出了一种新型高功率微波模式转换天线,该天线将同轴插板式模式转换器和一种新型喇叭有机结合,可直接辐射高功率微波源输出的同轴TEM模或TM01模,具有结构尺寸小、口径效率高、轴向辐射、容易实现等优点.优化设计了一个中心频率为3.8GHz的天线,长度约300mm、口径为280mm,在中心频率上增益为19dBi、反射损耗为-20dB,在3.7～ 4.1GHz的频率范围内增益大于18.7dBi、反射损耗小于-15dB.     

An omnidirectional microwave antenna for use on spacecraft

The qualitative theory, design, and development of a parallel-plate waveguide-fed antenna, suitable for flush-mounted broad-band spacecraft applications, are presented. The antenna makes use of wedge-like metal posts placed uniformly about the periphery of the feed plates to provide both structural strength and practical interconnection routes for cables without disrupting the antenna impedance and patterns. Measurements taken on the antenna, which is mounted on spheroids up to 50 wavelengths in circumference, are presented; equatorial patterns are omnidirectional withinpm 0.25dB, and polar patterns have beam widths similar to a half-wave dipole.     

一种六边形缝隙宽带微波天线设计

提出了一种适用于工业、科学、医学(ISM)频段的六边形缝隙天线的设计方法,采用基于全波分析矩量法的电磁场仿真软件进行分析,结果表明,与传统的正方形缝隙天线相比,天线的阻抗带宽由30%增加到了48.5%(|S11|<-10 dB)。进行了天线S参数测量,对天线通带起始频率5.24 GHz、谐振频率5.8 GHz和截止频率8.59 GHz三处频点的方向图进行了测量,测量结果和仿真结果一致,为拓展微带贴片天线带宽提供了一种新颖的方法。     

Imaging of scatterers on microwave antenna test ranges

A circular synthetic aperture imaging technique for evaluating the performance of antenna far-field test ranges is presented. Using multifrequency data, the fields incident on the region occupied by the scanning antenna are used to produce microwave images showing the distribution and level of scattering artifacts on the test site. Results are presented for S- and X-band ranges on a large outdoor antenna measurement facility. Various primary scatterers are identified, together with a source of secondary illumination of scattering objects     

Periodically modulated dielectrically filled waveguide as a microwave antenna

Complex solutions to a determinantal equation have been found numerically and employed to predict the properties of a frequency-scanning forward-radiating antenna obtained through a superposition of two waves propagating in oblique angles on an infinite periodic structure. The range of parameters of a usable antenna has been examined.     

PBG结构在微带有源天线中的应用

微带有源天线的应用具有降低通信系统的复杂度、减小系统尺寸的优点,但由于天线与有源器件集成在一起,有源器件产生的谐波可以引起天线的伪辐射。该文研究了PBG(Photonic Band-Gap)结构在有源天线中的应用。计算和实验结果都表明PBG结构的应用可以大大降低谐波引起的辐射,从而改善了系统的性能。     

微波通信天线选择与优化方法研究

简述微波天线在通信中应用的广泛性和重要性,在时第一菲涅尔区、衰落因子和相对余隙等重要因素详细分析的基础上,提出选择微波天线时应注意的问题,并提出采用分集接收、自适应均衡、阻抗匹配和避雷保护等技术改善微波天线的性能.进而提出微波天线选择的优化方案.     

Direct fibre-optic transmission of entire microwave satellite antenna signals

The entire 500 MHz bandwidth multicarrier C-band microwave signal spectrum from a satellite antenna is transmitted over low-loss optical fibre. The optical system introduces 1dB or less of degradation for both low-spectral-density QPSK signals and high-spectral-density FM video signals present in typical satellite transmission systems. For the video signals, the signal/noise ratio after AM conversion was reduced from 56 dB to 55dB.