共查询到20条相似文献,搜索用时 31 毫秒
1.
Phase-only adaptive nulling with a genetic algorithm 总被引:11,自引:0,他引:11
This paper describes a new approach to adaptive phase-only nulling with phased arrays. A genetic algorithm adjusts some of the least significant bits of the beam steering phase shifters to minimize the total output power. Using small adaptive phase values results in minor deviations in the beam steering direction and small perturbations in the sidelobe level in addition to constraining the search space of the genetic algorithm. Various results are presented to show the advantages and limitations of this approach, in general, the genetic algorithm proves to be better than previous phase-only adaptive algorithms 相似文献
2.
Dau-Chyrh Chang Chang-Nan Hu Chia-I Hung Ko-Tai Ho 《Antennas and Propagation, IEEE Transactions on》1994,42(2):240-245
The performance degradation of an offset reflector antenna with off-axis scanning feed and distorted reflector surface can be improved by using a phased array feed. Generally, both analog attenuators and phase shifters are used in phased array feed. Yet, it seems to make the feed system very complicated. In this paper, a phase-only gradient search (POGS) algorithm is developed to optimize the performance of offset reflector antenna systems using phased array feed that is equipped with phase shifters only. This technique not only can greatly simplify the complexity of phased array feed, but also can provide the reflector antenna with better antenna gain and sidelobe level control capability. Simulation and experimental results are presented to illustrate the excellent performance of offset reflector, with limited beam scanning capability, can be obtained by using this less complicated phased array feed 相似文献
3.
4.
《Antennas and Propagation, IEEE Transactions on》2009,57(6):1645-1654
5.
《IEEE transactions on bio-medical engineering》1996,43(3):273-280
A computer-controlled adaptive phased array radiofrequency hyperthermia system for improved therapeutic tumor heating is experimentally investigated. Adaptive array feedback techniques are used to modify the electric-field in hyperthermia experiments with a homogeneous saline phantom target. A hyperthermia phased-array antenna system has been modified to implement adaptive nulling and adaptive focusing algorithms. The hyperthermia system is a ring phased-array antenna applicator with four independently controlled RF transmitter channels operating at a CW frequency of 100 MHz. The hyperthermia phased array is made adaptive by software modifications which invoke a gradient-search feedback algorithm that controls the amplitude and phase of each transmitter channel. The gradient-search algorithm implements the method of steepest descent for adaptive nulling (power minimization) and the method of steepest ascent for adaptive focusing (power maximization). The feedback signals are measured by electric-field short-dipole probe antennas. The measured data indicate that with an adaptive hyperthermia array it may be possible to maximize the applied electric field at a tumor position in a complex scattering target body and simultaneously minimize or reduce the electric field at target positions where undesired high-temperature regions (hot spots) occur 相似文献
6.
相控阵天线波瓣置零综合的相位加权闭环实数算法 总被引:1,自引:0,他引:1
本文提出了一种相控阵天线仅相应加权波瓣置零的新算法,此算法基于“单元零点向量法”和Gram-Schmidt正交化方法,它能有效地设置宽零点低凹口。另外,对由于 相位量化而引起的凹口电平上升也进行了分析。 相似文献
7.
Theoretical and experimental results are presented for phase-only nulling in low-sidelobe monopulse antennas. Both results are based on a gradient search algorithm that simultaneously searches for a minimum in the sum and difference channel output powers. The array's beam steering phase shifters double as the adaptive weights. Each element in the gradient is found by changing phase shifter setting by ΔΨ (the phase shifter stepsize) and measuring the change in output power. Then the phase shifter is restored to its original value, and the process repeated for all the remaining array phase shifters. The algorithm iterates as long as each new adaptive weight setting reduces the total output power. If the output does not go down, then ΔΨ is decremented by one setting and the iteration is started again. The algorithm stops when ΔΨ=0. The adaptive weights act as random perturbations to the phase taper of the array. Consequently, the sidelobe level is proportional to the size of the phase perturbations and inversely related to the number of elements. By keeping the adaptive phase shifts small, the average sidelobe level and the main beam gain do not drastically change 相似文献
8.
Visualization of radiation-pattern characteristics of phased arrays using digital phase shifters 总被引:1,自引:0,他引:1
This article presents graphical investigations of the array factor of phased arrays with digital phase shifters. A software program, based on basic antenna array theory, has been developed in MATLAB to obtain the main array characteristics (array factor and directivity). The array factors of linear arrays of different sizes with different types of phase shifters have been studied as a function of the number of bits and the frequency. Unconventional two-dimensional color graphical representations are used to identify some characteristics of the array factor of arrays with digital phase shifters that can not be so clearly and quickly visualized with conventional graphical representations. In particular, the effects of quantization on the array factor for arrays of different sizes and for phase shifters with different numbers of bits, over scanning, and frequency ranges, are shown using this representation. Numerous data are also provided. 相似文献
9.
Cown B.J. Cain F.L. Duffy E.F. 《Electromagnetic Compatibility, IEEE Transactions on》1976,(4):163-170
A statistical model was developed for predicting and describing the out-of-band pattern characteristics of phased arrays containing ferrite phase shifters. Statistical analysis techniques are necessary because experimental investigations showed that the propagation of higher-order modes at out-of-band frequencies cause phased arrays containing ferrite phase shifters not only to respond differently at out-of-band frequencies but also to exhibit random behavior. Equations were derived which relate the out-of-band pattern scanning properties, relative gain levels, median gain, and standard deviation to the in-band scan angle and the ferrite phase shifter statistics. Computer algorithms were written to both compute and graphically display the out-of-band antenna patterns. Experimentally derived phase-shift data were used as inputs to the model. The results of these investigations show that statistical analysis techniques are potentially very useful in an EMC context for characterizing out-of-band responses of phased array antennas 相似文献
10.
概述了国内外射频MEMS移相器的研究情况,分析了射频MEMS技术给相控阵系统设计带来的优
势如:降低系统功耗,实现宽带阵列、自适应阵列与低成本相控阵等,介绍了国外MEMS相控
阵天线实例与毫米波MEMS相控阵系统方案。 相似文献
11.
A theory for analyzing the behavior of adaptive phased array antennas illuminated by a near-field interference test source is presented. Conventional phased array near-field focusing is used to produce an equivalent far-field antenna pattern at a range distance of one to two aperture diameters from the adaptive antenna under test. The antenna is assumed to be a linear array of isotropic receive elements. The interferer is assumed to be a bandlimited noise source radiating from an isotropic antenna. The theory is developed for both partially and fully adaptive arrays. Results are presented for the fully adaptive array case with single and multiple interferers. The results indicate that near-field and far-field adaptive nulling can be equivalent. The adaptive nulling characteristics studied in detail are the array radiation patterns, adaptive cancellation, covariance matrix eigenvalues, and adaptive array weights 相似文献
12.
Most adaptive array research has not directly addressed the problem of nulling in a monopulse antenna. Placing a null in the sum does not automatically place a null in the difference pattern and vice versa. Nulls may be placed in the two patterns with the use of separate adaptive weights and controls for the sum and difference channels. However, this requires two sets of adaptive hardware for one antenna. A technique for simultaneous hulling in the sum and difference channels of a monopulse phased array using one set of adaptive weights shared by both channels is described. First, the technique is described for amplitude and phase nulling, then for phase only hulling. In each case, the ability to simultaneously null in both channels with one set of variable weights is theoretically demonstrated. 相似文献
13.
Optical phased array technology is introduced and the steering performances of liquid crystal phased array are discussed, several factors affecting the beam steering performances are analyzed completely, also simple models for some typical factors are developed. Then, a new method based on iterating and modifying the output phase pattern of liquid crystal phase shifters is proposed. Using this method, the modified voltages applied on electrodes of liquid crystal phase shifters can be obtained, after applying the voltages, the influence of factors can be compensated to some extent; the steering angle accuracy and efficiency with liquid crystal phased array can be improved. Through the simulation for the angle range from 0° to -1 °, the error of steering angle can be reduced three orders of magnitude, and the efficiency can be increased almost 30% after several iterations. 相似文献
14.
Diode Phase Shifters for Array Antennas 总被引:1,自引:0,他引:1
《Microwave Theory and Techniques》1974,22(6):658-674
This paper contains considerations for diode phase shifters used for phased array antenna control. The categories are: 1) areas in which ferrite and diode phase shifters differ, 2) diode phase-shifter circuits, 3) the nature and typical performance of p-i-n diodes, 4) the requirements of a driver and a typical circuit, and 5) measured performance of phase shifters in L, S, C, and X bands. 相似文献
15.
16.
基于DDS的有源相控阵天线 总被引:7,自引:0,他引:7
有源相控阵天线不仅能提高通信系统的性能,而且还能扩充其功能,所以在通信领域的应用越来越广泛.本文介绍一种没有高频移相器的8单元有源相控阵天线系统,它由平面天线阵、数字T/R组件、接收DBF和系统控制分析软件等组成.其基本原理是在发射模式下,利用直接数字合成(DDS)代替传统的高频移相器和衰减器.由于DDS的工作频率比较低,需要通过上变频到系统所需要的工作频率(2.0GHz).在发射模式下,通过控制DDS完成发射波束形成所必需的幅度、相位加权和上变频所必需的本振信号;在接收模式下,则利用DDS技术产生接收信号下变频所必需的本振信号,然后采用DBF技术形成接收波束.文中详细介绍了基于DDS的有源相控阵天线的实现方法和实验结果.通过8单元基于DDS的有源相控阵天线系统的研究,证实了DDS技术在相控阵天线中应用的显著优点和相控阵天线在通信领域具有潜在应用市场. 相似文献
17.
在相控阵雷达中,为了降低雷达信号被敌方侦收设备截获的概率,需要在阵列发射方向图某一角度形成零点。对此,提出一种快速相位加权方向图置零方法。该方法依据零点位置设置虚拟干扰,并构建干扰协方差矩阵;根据最小输出功率准则,建立零点生成数学模型;最后通过单坐标迭代算法求解相位权值。计算机仿真结果验证了该方法的正确性和有效性。 相似文献
18.
Reddy C.A. Janardhanan K.V. Mukundan K.K. Shenoy K.S.V. 《Antennas and Propagation, IEEE Transactions on》1990,38(4):573-575
A novel concept is described for feeding and phasing a large linear array of N antenna elements using only three or five feed points and phase shifters and still achieving beam switching. The idea consists of drastically reducing the number of input points by interlacing a small numer of serially fed subarrays which are suitably phased. This so-called interlaced phased array (IPA) concept was tested using an array of 15 four-element Yagi antennas with a spacing equal to 0.8 wavelengths and found feasible. Some of the distinct advantages of the IPA in comparison with a conventional system of beam switching are reduced power loss, reduced phasing errors, reduced cost, increased reliability resulting from greatly reduced number of phase shifters, and better symmetry of off-zenith beams 相似文献
19.
20.
对K波段相控阵单元进行了详细论述,给出了介质加载的圆形波导辐射器的仿真方向图,辐射单元方向图在自由空间的波束宽度达92°.由于阵列当中互耦的影响,阵列当中单元天线波束宽度变宽,波束宽度可达98°,能够满足阵列扫描的要求.在每个单元后接一个铁氧体移相器,再由单T形组合网络合成为1个馈电端口,制造出了K波段1×8单元相控阵天线,并给出了不同扫描角的测试结果. 相似文献