首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 109 毫秒
1.
Phased-array radar systems using wide-band linear-FM pulses suffer from array dispersion. This causes a loss in signal-to-noise (S/N) ratio and in radar range resolution (a broadening of the compressed-pulse width). Depending on the choice of the receiver matched filter (MF) and weighting filter (WF) one or the other of these effects may be minimized. The effects of dispersion in a square planar array with either a parallel feed or a center-fed series feed are studied. Loss in S/N ratio and in range resolution are determined for typical cases, and general curves are given for arrays with arbitrary size, scan range, and signal bandwidth. It is shown that there is an optimum or maximum-useful signal bandwidth for each array, for which the minimum S/N-loss MF-WF design is the same as the ideal-compressed-pulse-shape MF-WF design. For pulses having greater signal bandwidths, time delay steering should be used in the array.  相似文献   

2.
提出了一种工作于X波段的新型圆极化矩形介质谐振器天线。该天线是一块矩形介质谐振器嵌入到介质基板中并通过U型微带线激励。天线的接地面采用缺陷地的结构,可以通过调节该缺陷地对角的大小来产生2个正交模式实现圆极化,有效解决了一些圆极化天线馈电网络复杂的缺点。所设计天线的阻抗带宽为8.88~10.22 GHz。天线的轴比带宽为9.56~9.92 GHz,可应用于卫星广播、航空无线电导航业务和无线电定位。  相似文献   

3.
Two variations of a novel feeding technique for a wideband circularly polarized aperture-coupled microstrip antenna are described. Prototype designs for wideband linearly polarized elements are first presented, and then used for circularly polarized designs. Techniques used for design of the feed network are detailed, for both series feed and parallel feed versions. Experimental results are shown for each antenna, and results for the two designs are compared. The impedance and axial ratio bandwidths for these antennas are among the best yet achieved for microstrip antenna elements. Several design variations are also discussed  相似文献   

4.
A novel, compact, probe-fed microstrip patch antenna for operation in dual-polarization mode is proposed. The novel design is achieved by etching out a symmetric pattern of crossed slots from the surface of a square probe-fed patch. Reduction in patch size of up to 51% with respect to a traditional dual-polarized square patch operating at the same frequency is obtained. Results show linear polarizations in the +45 and -45/spl deg/ with a high isolation of 38 dB between the two ports. Moreover, the 50-/spl Omega/ feed position can be achieved by moving the feed point along the diagonal of the square patch, leading to ease in fabrication.  相似文献   

5.
提出了一种新型宽带双频圆极化射频识别(RFID)读写天线,由上层的旋转对称折合振子和缝隙加载的方形贴片以及下层的紧凑型馈电网络构成。天线具有两个外部端口,分别激励低频0.9 GHz和高频2.45 GHz双频段的圆极化辐射。借助HFSS对天线进行了建模、仿真和优化,最后采用FR4板材制作天线实物并完成了试验测试。天线的外部尺寸为0.6λ0×0.6λ0×0.1λ0(λ0为0.9 GHz频点下的自由空间波长),测试结果表明,天线在低频段和高频段的-10 dB阻抗带宽和3dB轴比带宽分别为91.1%(4.9%)和87.8%(1.3%),频段内的峰值增益为5.48 dBic(3.63 dBic),最小轴比为1.1 dB(1.2 dB),在高低频段内,天线的辐射方向图对称稳定。该天线不仅能够满足全球通用型UHF频段(0.84~0.96 GHz)和ISM频段(2.4~2.5 GHz)RFID读写应用需求,而且具有低成本、易加工等优点,在物联网领域将具有很好的应用前景。  相似文献   

6.
The analysis is presented for a microstrip feed proximity coupled monofilar Archimedean spiral four-element antenna array. Interactions between the microstrip corporate feed and the radiating elements are rigorously included. Results demonstrate that circular polarization can be achieved with proper spiral arm length. Polarization of either sense is controlled by the location of the feedline. The 3-dB axial ratio (AR) and voltage standing wave ratio (VSWR) bandwidths are 9%. The antenna is small (2R/λ0=0.33) and the interelement spacing is 0.51λ0. The microstrip feed produces a completely planar antenna system, which is compatible with microwave integrated circuits (MIC) and monolithic microwave integrated circuits (MMIC)  相似文献   

7.
A circularly polarized feed array for a spacecraft reflector antenna is described that was constructed by using linearly polarized microstrip elements. The array has seven subarrays which form a single cluster as part of a large overlapping cluster reflector feed array. Each of the seven subarrays consists of four linearly polarized microstrip elements. The array achieved a better than 0.8-dB axial ratio at the array pattern peak and better then 3 dB antenna gain to 20° from the peak, across a 7.5% frequency bandwidth. A teardrop-shaped feed probe was used to achieve wideband input impedance matching for the relatively thick microstrip substrate. The low impedance and axial ratio bandwidths were achieved using a relatively thick honeycomb substrate with the impedance-matching feed probes  相似文献   

8.
高隔离度双极化微带天线直线阵的设计   总被引:4,自引:0,他引:4       下载免费PDF全文
梁仙灵  钟顺时  汪伟 《电子学报》2005,33(3):553-555
本文介绍一种新型的1×16双极化微带天线直线阵的设计.该天线采用双极化角馈方形贴片单元,阵列的垂直极化端口采用共面馈电,水平极化端口采用口径耦合,并在馈电网络中应用反相馈电技术.实验结果表明,天线二端口驻波比小于1.5的相对带宽分别达到15%和13.5%,两端口之间的隔离度在频带内高于33dB,最大达到43dB.本直线阵可用作星载综合口径雷达系统的天线子阵,便于与有源收发器件结合.  相似文献   

9.
A novel circularly polarised (CP), single-fed microstrip antenna is presented. The antenna consists of a stacked structure of almost square patches. The proposed design has a reduced antenna size compared to the conventional CP microstrip antenna at a given operating frequency. The impedance and axial ratio bandwidths are large and CP radiation quality is excellent over the entire upper hemisphere. The proposed antenna is suitable for global positioning system (GPS) applications.  相似文献   

10.
A compact circularly polarised printed antenna is presented. The antenna consists of a synchronous subarray of shorted patches with the required feed network etched on a high dielectric constant substrate located below the ground-plane of the antenna. The 10 dB return loss and the 3dB axial ratio bandwidths are 8.5 and 11.3%, respectively. The overall size of the proposed antenna is 0.195 λ0×0.195 λ0×0.0523λ0  相似文献   

11.
A design for dual-frequency microstrip antennas with conical radiation patterns is studied. The dual-frequency operation is achieved by exciting two different resonant modes of the square microstrip patch antenna with four symmetrical shorting walls. Then, a method to enhance the impedance bandwidths of the dual-frequency antenna is proposed, and the experimental results show bandwidths are increased by 19 and 31% at the lower and higher operating frequencies, respectively. Simulation analyses are also performed to support the measured results.  相似文献   

12.
Harris角点在金属材料硬度检测中的应用   总被引:1,自引:1,他引:0  
为了检测金属材料硬度,采用规定形状的压头在抛光材料表面挤压一个不规则方形,测量方形对角线的长度可得出所测材料硬度指标。提出一种利用图像处理技术实现方形对角线长度的精确测量实现材料硬度检测的新方法。应用Harris算子求取方形边缘的角点,再将图像分为四部分后,对每个半边缘进行最小二乘法直线拟合,求得方形的顶角便可得出方形对角线的像素距离。通过对游标卡尺图片进行映射处理求得计算基准,最终得出方形对角线实际长度。实验表明该算法实现了无需人工参与的全自动对角线检测算法精度和速度直接影响了整个检测过程的精度和速度。长度精度达到微米级别,求解材料硬度达到了2%的误差要求。该方法具有很快的计算速度,可用于实时的材料硬度全自动检测工程中。  相似文献   

13.
We investigate possible configurations for dual-band waveguide diplexing assemblies appropriate for use as feed systems for dual-reflector antennas. Specific applications are where the bands are well separated and, individually, have relatively wide bandwidths. Two crucial problems are addressed: the demanding bandwidth requirements of the feed horn and the subsequent means of diplexing the signals. We present results arising from the analysis of candidate systems and discuss a preferred option in detail.  相似文献   

14.
A circularly polarized cross-dipole fed square horn feed for C-band antenna system is designed to have a minimum axial ratio when radiating into free space. This type of feed can be used for dual band antennas in space. An analysis of multipactor break-down in the feed is also given.  相似文献   

15.
We normally feed a rectangular patch along the centerline of the H-plane (the non-resonant width). This is done to eliminate excitation of the patch in a mode along the other axis. The second mode radiates cross polarization. This article provides the tolerance requirements, given the cross polarization. The rectangular microstrip patch radiates its peak cross polarization in the diagonal planes, even when the antenna is fed perfectly. This cross polarization is low. When we locate the feed along the centerline of the H-plane of the patch, the impedance match to the TM01 mode is poor, and the antenna does not radiate significant power at boresight to the patch. Often we design a square patch, so that we can radiate orthogonal-linear polarizations (or dual-circular polarizations) by using two feeds. If we fail to place the feed probe, aperture, or microstrip line along the H-plane axis, the cross-polarization level rises  相似文献   

16.
A circularly polarized stacked patch microstrip antenna and a 2?×?2 subarray for circular polarization are proposed in this paper. The proposed design has the input impedance bandwidth and axial ratio bandwidth of about 10% and 4.7% respectively. Circular polarization is obtained with the help of slits cut in the patch. A size reduction of around 37% is also achieved with the help of the slits. A subarray based on sequentially rotated feeding technique for circular polarization is also presented in this paper. Array element was deigned using a high dielectric constant laminate for feed network. In addition to low boresight axial-ratio, the subarray has impedance and 3-dB axial-ratio bandwidths of 12% and 8% respectively.  相似文献   

17.
潘宗达  高原 《现代雷达》1999,21(2):87-90
根据微扰理论和保角变换理论,探讨了方波导对角微扰以及对角插入介质片后的相移特性,并研制了几种新型的波导圆极化器,理论与实测数据吻合较好。  相似文献   

18.
An analysis is presented for a microstrip-feed proximity-coupled ring antenna and a four-element array. Interactions between the embedded microstrip feed and the radiating element(s) are rigorously included. Results demonstrate that circular polarization of both senses can be achieved with a ring antenna with proper design of two inner stubs located at angles of ±45° with respect to the feedline. Theory and experiment demonstrate an axial ratio 3-dB bandwidth of 1% and the voltage standing wave ratio (VSWR) <2 bandwidth of 6.1%. The axial ratio bandwidth is typical for a microstrip antenna with perturbations, while the VSWR bandwidth is larger than for the circular or rectangular patch with perturbations. A mutual coupling study between two elements shows that the axial ratio is less than 2 dB for interelement spacing greater than 0.55λeff, while the VSWR <2 for all spacings considered. A comparison between theory and experiment is provided for a 2×2 element array. The benefits of sequentially rotating the antenna elements in an array environment are presented. The axial ratio and VSWR bandwidths are both increased to 6.1% and 18% for a four-element array. A single-element antenna with two orthogonal feeds to provide both senses of polarization is demonstrated. The ring antenna is small (D/λ0=0.325), the substrate thickness is thin (H/λ0~0.035), and the microstrip feed produces a completely planar antenna system, which is compatible with microwave and millimeter integrated circuits (MICs), and monolithic microwave integrated circuits (MMICs)  相似文献   

19.
20.
基于四阶累积量对角切片的短波自适应通信信号检测   总被引:3,自引:0,他引:3  
短波自适应通信信号的检测是现代电子战信号处理的一个重要研究课题,本文提出了基于四阶累积量对角切片的短波自适应通信信号检测方法.文章推导了有限长度信号四阶累积量对角切片的分段估计方法,分析了其渐进性能,分析表明该估计方法降低了估计方差;论文介绍了信号检测原理,借助于计算机仿真研究了高斯白噪声和色噪声及不同信噪比下不同检测方法的性能.仿真对比结果验证了该方法的有效性.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号