Circular-waveguide-fed microstrip patch antennas

A microstrip patch antenna fed by a circular waveguide is presented. The microstrip patch built on a foam substrate is laid on the flange of the circular waveguide's open mouth. The waveguide feeds the patch by coupling energy to the patch through a narrow slot underneath the patch. Two operating frequency bands were observed and the characteristics of the antenna were measured.     

Resonant frequency of a rectangular microstrip patch on severaluniaxial substrates

A full-wave analysis for determining the resonant frequency of a rectangular microstrip patch on multiple uniaxial anisotropic layers with or without an anisotropic overlay is presented. Two independent methods are used to derive the immittance matrix for the patch, from which the resonant frequency is determined. They are the Hertz vector potentials and the modified spectral domain immittance approach. Numerical results of the resonant frequency are given for several patch configurations, including cases of a patch on a single anisotropic layer, a patch on a double layer with one layer anisotropic and one layer isotropic, a suspended patch resonator with anisotropic substrate, a patch with anisotropic overlay and a patch on two anisotropic substrates with an anisotropic overlay. Changes in the resonant frequency of up to 58% are reported as n_x/n _y is changed from 1.0 (for isotropic substrates) to 2.0     

Micromachined patch antennas

This paper presents the use of selective lateral etching based on micromachining techniques to enhance the performance of rectangular microstrip patch antennas printed on high-index wafers such as silicon, GaAs, and InP. Micromachined patch antennas on Si substrates have shown superior performance over conventional designs where the bandwidth and the efficiency have increased by as much as 64% and 28%, respectively. In this work, the silicon material is removed laterally underneath the patch antenna to produce a cavity that consists of a mixture of air and substrate with equal or unequal thicknesses. Characterization of the micromachined patch antenna is presented herein and includes a discussion on the bandwidth improvements, radiation patterns, and efficiency of the patch. In addition, antenna placement on the reduced index cavity with respect to the high-index substrate is described to achieve efficiency improvements over conventional patch antennas     

基于自适应子空间重建的杂波抑制

针对红外图像中背景杂波抑制困难的问题,提出了一种基于自适应子空间重建的杂波抑制方法.该方法首先根据稀疏编码理论,学习得到描述红外小目标的超完备字典,接着依次提取测试图像中的图像子块,并计算其在超完备字典中的表示系数,根据背景子块和红外小目标在稀疏域中表示系数的差异性,自适应地选择字典中的原子构成子空间对图像子块进行重构,从而得到原图与重构图像之间的残差图像.实验结果表明,该方法得到的残差图像,能够有效抑制杂波,提高红外图像的信噪比.     

一种新型圆极化贴片天线的研究

研究了圆极化微带贴片天线,通过在普通圆形贴片上开槽,提出了一种结构新颖的圆极化微带贴片天线.仿真以及实测结果表明,该天线具有较宽的3dB波瓣宽度(±50°)和良好的圆极化轴比性能,并且新型微带贴片天线的尺寸要远小于普通的圆形或圆环形贴片天线的尺寸.     

Accurate analysis of arbitrarily shaped patch resonators on thinsubstrates

Based on a generalized edge boundary condition (GEBC), an accurate analysis method for arbitrarily shaped microstrip patch resonators is developed. The edge of the patch and its feeding line are first discretized as a series of connected segments. Next, an equivalent voltage and an equivalent current are defined on each segment. This boundary of the patch and the feeding line can be viewed as an interface between two networks. The first takes into account the coupling under the patch. The second represents the dynamical edge effects and the coupling over the top side of the patch. This general and computer-efficient approach is then successfully applied to determine the input impedance of some commonly used probe-fed and strip-fed patch resonators     

Triple-stacked microstrip patch antenna for multiband system

A triple-stacked microstrip patch antenna is presented for a multiband system comprising cellular phone, global positioning system and personal communication services. It consists of three microstrip patches, and there is a slot on the middle patch to couple the first patch to the third patch. The measured results are in agreement with the simulated results at the frequencies of interest.     

基于快速傅里叶变换的局部分块视觉跟踪算法

针对视觉跟踪中目标表观变化、局部遮挡、背景干扰等问题,该文提出一种基于快速傅里叶变换的局部分块视觉跟踪算法。通过建立目标分块核岭回归模型并构建循环结构矩阵进行分块穷搜索来提高跟踪精度,利用快速傅里叶变换将时域运算变换到频域运算提高跟踪效率。首先,在包含目标的初始跟踪区域建立目标分块核岭回归模型;然后,提出通过构造循环结构矩阵进行分块穷搜索,并构建目标分块在相邻帧位置关系模型;最后,利用位置关系模型精确估计目标位置并进行分块模型更新。实验结果表明,该文算法不仅对目标表观变化、局部遮挡以及背景干扰等问题的适应能力有所增强,而且跟踪实时性较好。     

Patch antennas on externally perforated high dielectric constantsubstrates

Smaller physical size and wider bandwidth are two antenna engineering goals of great interest in the wireless world. To this end, the concept of external substrate perforation is applied to patch antennas in this paper. The goal was to overcome the undesirable features of thick and high dielectric constant substrates for patch antennas without sacrificing any of the desired features, namely, small element size and bandwidth. The idea is to use substrate perforation exterior to the patch to lower the effective dielectric constant of the substrate surrounding the patch. This change in the effective dielectric constant has been observed to help mitigate the unwanted interference pattern of edge diffraction/scattering and leaky waves. The numerical data presented in this paper were generated using the finite-difference time-domain (FDTD) technique. Using this numerical method, a patch antenna was simulated on finite-sized ground planes of two different substrate thicknesses, with and without external substrate perforation. The computations showed the directivity drop in the radiation pattern caused by substrate propagation was noticeably improved by introducing the substrate perforation external to the patch for the case of a patch antenna on a relatively thick substrate without any loss of bandwidth. Measurements of a few patch antennas fabricated on high dielectric constant substrates with and without substrate perforation are included for completeness. Good correlation between the computed results and measurements is observed     

Radial EBG cell layout for GPS patch antennas

A novel radial layout for mushroom-like electromagnetic-bandgap (EBG) cells surrounding a printed circularly-polarised patch antenna is proposed. Two radial EBG configurations surrounding a circular patch are compared to a reference patch on a conventional ground plane of the same dimension. The radial shape and displacement of the EBG cells around the patch offers improvements in terms of gain and axial-ratio compared to the reference antenna and is more suitable for circular geometries compared to conventional Cartesian layouts. In particular, the distance between the patch and the surrounding EBG cells is independent of the cell period, which can be arbitrarily chosen, and the overall layout offers footprint reduction.     

Comparative study on the mutual coupling between different sized cylindrical dielectric resonators antennas and circular microstrip patch antennas

A systematic comparative study on the mutual coupling (S/sub 21/) between dielectric resonator antennas (DRAs) and microstrip patch antennas is presented. The mutual coupling between two cylindrical probe-fed DRAs is studied for different radius to height (a/L) ratios. It is found that the mutual coupling decreases with the radius to height ratio. Comparison between mutual coupling of probe-fed cylindrical DRAs and circular microstrip patch antennas with different dielectric substrates are also studied. The mutual coupling between DRAs is 2 dB stronger than between microstrip patch antennas when the patch is etched on a dielectric substrate of a dielectric constant close to the permittivity of the DRA. The mutual coupling of the circular patch antennas reduces with the dielectric constant of the substrate.     

宽频化与小型化微带天线的研究与设计

以微带天线技术为基础,以工作于ISM频段微带贴片天线为例,采用Ansoft公司的电磁仿真软件HFSS,对不同介电常数、不同介质板厚度、矩形贴片开槽开缝、加载寄生贴片等微带贴片天线进行了仿真。通过数值分析,阐述了介电常数、基板厚度、贴片开槽、寄生贴片等因素对微带贴片天线尺寸和频带宽度的影响。仿真结果表明,设计能够实现两种性能的天线结果,天线的宽度达到36%。天线的尺寸缩小了34.2%。     

Analysis of Gunn integrated annular ring microstrip antenna

The analysis conducted on Gunn integrated annular ring microstrip antenna and evaluation of various parameters such as input impedance, voltage standing-wave radio voltage standing wave ratio (VSWR), return loss, bandwidth, radiation pattern, beamwidth, etc., as a function of bias voltage and threshold voltage reveals that the Gunn loaded patch offers wider tunability, better matching, enhanced radiated power as compared to the patch alone. Bandwidth of the Gunn loaded patch improves to 11.07% over the 7.9% bandwidth of the patch whereas the radiated power is enhanced by 3.7 dB as compared to the patch.     

短路针加载三角形微带贴片天线的研究

短路针加载微带贴片天线具有较低的谐振频率,特别适用于低频便携式通信设备(如手机)中.与短路针加载矩形和圆形贴片天线相比,短路针加载三角形贴片天线具有更低的谐振频率.本文基于腔模理论,利用未加载三角形贴片天线的静态模,提出了短路针加载三角形贴片天线的理论分析方法,给出了天线谐振频率、输入阻抗及反射损耗的计算公式.数值计算与实测结果相吻合,表明这种分析方法是有效的.     

Transient analysis of a space-borne microstrip patch antennailluminated by an electromagnetic pulse

The transient response of a microstrip patch antenna excited by a plane wave is studied using a finite difference algorithm applied to a total field version of Maxwell's curl equations in the time domain. A wide bandwidth study shows different behavior in the antenna, depending on the frequency and angle of incidence of the wave. At low frequencies, the voltage in a 50 Ω load is proportional to the derivative of the incident Eⁱ field. With increasing frequency, parasitic oscillations appear to be due to the short-circuited patch. In addition, at high frequencies, antenna sizes and wavelength are of the same order. The voltage contains oscillations at the frequency of the TM mode of the antenna. Two patterns of coupling appear: (1) capacitive coupling, where the current on the patch rises at the wire-metallic plane junction and spreads on the patch and on the finite ground plane; and (2) coupling due to the scattering, where the current rises at the edges of the patch and on the finite ground plane     

Center-fed microstrip patch antenna

A novel feeding scheme for microstrip patch antennas is presented, which consists of a coaxial probe and shorting pin separated by a narrow slot centrally cut at the radiating patch. The impedance and radiation characteristics of a conventional probe-fed microstrip patch antenna and the proposed microstrip patch antenna are experimentally examined and compared. The effects of the slot length on the antenna operation are also discussed.     

Design of a planar inverted-F Antenna with very wide impedance bandwidth

This letter presents a novel wideband planar inverted F-antenna, which covers GSM850/DCS1800/DCS1900/ IMT2000/WLAN/DMB services at the same time. The proposed antenna consists of a main patch with a pair of slant slits and L-shaped patch and occupies a total volume of 15/spl times/44/spl times/8mm/sup 3/. The triple frequency bands are obtained by changing the length and width of a slant slit 1 on the main patch. A very wide impedance bandwidth characteristic is achieved by optimizing not only the length and height of a L-shaped patch between the main patch and ground plane but also the length and width of a pair of slits on the main patch which is excited by the modified coplanar waveguide-feed. Good broadside radiation patterns are achieved for all six-frequency bands of interest.     

Compact active polarisation-agile antenna using square patch

A polarisation-agile active patch antenna with a compact layout has been developed. Comprising a square patch with an overlay, it has two transistors in the common base configuration, connected on adjacent sides to excite orthogonal modes of oscillation. Circular polarisation of either sense, and linear polarisation parallel to either patch side or diagonal, can be radiated     

Stacked patch antenna fed by a coplanar waveguide

A broadband patch antenna fed by a coplanar waveguide (CPW) is presented. The antenna was designed based on the stacked patch technique developed for aperture-coupled patch antennas. It is similar in configuration to a conventional stacked patch antenna, but the lower of its two patches is fed with a conductor-backed CPW Both simulation and measurement show that the antenna has bandwidth of over 10% (for |S/sub 11/| /spl les/ -10 dB) centred at 10 GHz.     

Miniaturized Dual-Mode Circular Patch Bandpass Filters With Wide Harmonic Separation

Two slots oriented orthogonal to each other are cut on a circular patch resonator. The slots bring down the fundamental resonance frequency of the patch. The second higher order mode, however, remains unaffected. This effectively miniaturizes the patch by 57.8% at the same time increases the harmonic separation by 2.51 times. By adding two more slots parallel to and on both the sides of each arm of the crossed slot, fundamental frequency can be further brought down resulting in a filter which is 87.4% smaller compared to a circular patch. The second passband appears at a frequency which is 4.66 times that of the first passband center frequency.