Antenna patterns of nonsinusoidal waves with the time variation ofa Gaussian pulse. III

For pt.II see ibid, vol.30, no.4, p.513-22 (1988). Antenna patterns such as peak-amplitude, peak-power, energy, and slope pattern are derived for a circular array receiving nonsinusoidal Gaussian pulses. The antenna amplitude and average-power patterns of sinusoidal waves are also presented for comparison to the ones for nonsinusoidal waves. Due to the large bandwidth of nonsinusoidal waves, their antenna patterns are more attractive for achieving good angular resolution than the ones for infinitely extended periodic sinusoidal waves, which lack bandwidth. The resolution angle of a circular array based on sinusoidal waves and the resolution angle based on nonsinusoidal Gaussian pulses are also derived     

Line-Array Beam-Forming And Monopulse Techniques Based on Slope Patterns of Nonsinusoidal Waveforms

Nonsinusoidal waveforms with the time variation of a rectangular pulse, received (or radiated) by a line array of sensors (or emitters), yield various antenna patterns which are very attractive for achieving good angular resolution. These antenna patterns, such as peakamplitude, peak-power, energy, and slope patterns, have been derived for various array lengths under a noiseless assumption. The slope patterns are the most attractive for angular resolution. In this paper, line-array beamforming techniques are developed to provide slope patterns for nonsinusoidal signals. The techniques employ sliding correlators (SC's) for suppressing the additive Gaussian noise present with the received signal, and pulse-shaping processors for determining the slope pattern. Computer simulation is done for deriving peak-amplitude and slope patterns for various array lengths. Also, a method for obtaining monopulse peakamplitude and slope patterns is presented.     

Three-Dimensional Antenna Patterns for Nonsinusoidal Waves

Array beam forming with nonsinusoidal waves allows a trade-off between signal power, frequency bandwidth, and array size for a small resolution angle. In addition, one can derive various antenna patterns with desiralble features for achieving good angular resolution. Such patterns are peak-amplitude, peak-power, ramp-duration, flat-duration, energy, and slope patterns that have been derived for linear arrays. In this paper, the principle of beam forming with noise-free nonsinusoidal waves received by rectangular planar arrays is discussed. Three-dimensional peak-amplitude, energy, and slope patterns are derived for planar arrays with 4 × 4, 8 × 8, 16 × 16, and 32 × 32 sensor elements.     

Antenna patterns of nonsinusoidal waves with the time variation ofa Gaussian pulse

The development of antenna theory for nonsinusoidal electromagnetic waves has been based on the idealized rectangular pulse. In practice, an antenna that is designed to operate in the mode of an electric hertzian dipole would radiate a pulse that best approximates a Gaussian one when the driving current consists of a linear transient. The principle of radiation of nonsinusoidal electromagnetic waves with the time variation of Gaussian pulses is discussed. The properties of the Gaussian pulse are presented, i.e., the autocorrelation function, energy spectral density, and spectrum. Antenna patterns, such as peak-amplitude pattern, peak-power pattern, energy pattern, and slope pattern are derived for a Gaussian pulse received (or radiated) by a linear array antenna. Computer plots of the derived antenna patterns are presented that show a considerable improvement in the angular resolution capability over that of the antenna patterns that have been derived for a rectangular pulse     

基于对数螺旋阵的波达方向估计

系统渡达方向(DOA)的估计能力受天线阵的几何结构影响很大.提出了一种新的二维天线阵列流形--对数螺旋阵,该阵列流形具有天线单元数少、天线孔径大、分辨力高的特点.通过粒子群优化方法(PSO)确定了无栅瓣的阵结构参数,计算了此阵的天线方向图并与矩形阵、圆环阵做了比较,利用MUSIC方法进行了二维空间谱估计,仿真结果表明:利用该对数螺旋多天线阵可以实现高分辨二维DOA估计.     

Array Pattern Optimization for Steerable Circular Isotropic Antenna Array Using Cat Swarm Optimization Algorithm

In this paper the steerable isotropic circular array antenna is designed for reducing the side lobe level (SLL) using evolutionary optimization technique. The optimization techniques particle swarm optimization and cat swarm optimization algorithm are used to reduce the SLL as well as to steer the main beam in specific direction. In this design of steerable circular arrays the amplitude excitations are optimized. Obtained results show that the maximum peak of SLL of the resultant patterns are as per requirement. This paper present a good performance in the array factor response and suppressed SLL for different number of array elements with different steering angle of the main beam using evolutionary optimization technique.     

新型强耦合宽带双圆极化阵列天线

空间飞行器由于受到动力和负载的限制, 需要尽可能使搭载的天线轻质小型化.文中提出了一种新型强耦合双圆极化轻质天线.天线单元采用H型缝隙耦合和增加寄生贴片方法, 提高了天线带宽.同时, 通过在辐射贴片、寄生贴片上开圆形槽, 以及金属反射板栅格化的处理, 明显地减轻了天线的质量.采用这种新型天线单元, 设计了8单元的宽带双圆极化阵列天线.仿真结果表明:该阵列天线的中心频率为433 MHz, 左旋和右旋圆极化的相对轴比(Axial Ratio, AR)带宽(AR < 3 dB)分别达到了24.4%和23.2%, 有效实现了小型轻质化宽频带双圆极化阵列天线.     

Experimental study of large rectenna array for microwave energytransmission

For a field experiment on microwave power transmission (MPT) which was jointly conducted by the Radio Atmospheric Science Center of Kyoto University, Robe University, and Kansai Electric Power Company from 1994 to 1995, we had developed and tested a new type of rectenna (rectifying antenna) based on a circular microstrip antenna (CMA). A square shape of array with an area of 3.2 m×3.6 m was then constructed using the developed rectennas for experiment. The whole rectenna array is composed of 256 sub-arrays, each with nine rectenna elements. We place the rectenna sub-array with better RF-DC conversion efficiency in the central area of the whole rectenna array. Such spatial optimization is needed because the power density of the microwave beam used in the experiment has a spatial gradient with a peak at the center of the beam. We then examined dependence of the rectenna array characteristics on the electrical connection of the sub-arrays. The difference of the output DC power of the whole array for five different electrical connections is within 5%. The load characteristics, therefore, suffers little change even if the electrical connection of the rectenna sub-array is changed     

一种可用于相控阵的双点馈多层圆极化微带天线

设计出了一种双背馈空气夹层微带圆极化天线单元,该天线单元具有13％的阻抗带宽,最大辐射方向上轴比2．5dB。用该天线单元以顺序旋转的方式组成四元阵,再用八个该天线单元和两组一分八功分器组成八单元阵列,研究了该阵列天线圆极化波束分别指向天线阵法向和偏转30°时的辐射特性和极化特性。该天线单元组阵圆极化轴比特性好,易于实现波束扫描,适合用于有源相控阵系统。     

对一种圆形阵列天线的研究

主要分析了一种带有反射面圆形阵列天线。首先根据方向性增强原理，对一般性的不带反射面的圆形阵列天线进行了理论上的分析，计算得到了阵列天线各个阵元的配相，然后根据镜像原理，得到了在中心带有反射面时圆形阵列天线的辐射方向图、增益等天线的技术指标。最后对实际制作的天线进行测量，得到的结果与理论分析的结果相对比，天线在辐射方向上的吻合非常好，达到了设计的要求。     

SAR distributions in interstitial microwave antenna arrays with asingle dipole displacement

The use of interstitial microwave antenna array hyperthermia (IMAAH) as a treatment for cancer, in conjunction with radiation therapy and chemotherapy, has been investigated widely. The heating pattern produced by a coherently phased 915 MHz asymmetric antenna array displays the maximum power deposition in the array center. The authors report on the effect of variable insertion depth between antennas of an array on the heating patterns produced. The study of this heating behavior demonstrates a similar effect to that of the variably phased arrays, showing a shift of the heating peak towards the periphery of the tumor, offering a more simple method for the clinical treatment of such tumors     

A multielement high power monopulse feed with low sidelobe and high aperture efficiency

A multielement high power monopulse feed was investigated for excitation of a phased array. This feed has the advantages of high antenna efficiency, effective independent sidelobe control for the sum and difference patterns, and high power handling capability. A 32-element device has been designed which yields theoretical sidelobe levels less than -31 dB for both the sum and difference patterns over the 2800 to 3200 MHz frequency band. The aperture efficiency is 69.5 percent which includes 0.1 dB spillover loss and 1.40 dB tapering loss. The difference slope efficiency defined as the actual slope gain over the maximum possible value is 50 percent at midband. An experimental feed was constructed to verify the predicted performance characteristics. Measured data on both the radiation patterns and the antenna gain agreed very Well with the analytical results. The measured sidelobe level is below -30 dB for all sum and difference beams over the 2800 to 3200 MHz. In addition, this feed can be designed for low power intensity at the feed aperture so that very high power operation can be attained.     

基于量子微粒群的综合孔径圆环阵排列方法

稀疏天线阵列设计是综合孔径微波辐射计的一个重要研究内容。圆环阵因其可实现(u,v)平面基线零冗余、结构简单以及共形、波束旋转对称等特点而备受关注。针对均匀圆环阵UV覆盖不均匀的问题,提出基于量子微粒群优化(QPSO)的综合孔径圆环阵排列方法,以改善圆环阵的UV覆盖。该方法引入量子行为的搜索机制,并设计一种新的圆环阵优化目标函数;与现有方法相比,该方法在提高全局搜索效率的同时,大大降低计算复杂度,且能更好地度量圆环阵UV覆盖的均匀程度。数值仿真结果验证了本文方法的有效性。     

Ka频段卫通相控阵封装天线设计与实现

针对卫星通信对终端天线低剖面、低功耗、极化可变及发射控制等需求,采用平板相控阵架构、极化可变阵列、稀疏布阵等技术,研制了一台基于单板集成封装技术的Ka频段卫星通信相控阵天线。该天线满足高轨同步卫星宽带应用需求和适航符合性验证试验DO-160G要求,经长时间跑车和飞行试验,其性能优良,可靠性高。     

5.835 GHz微带阵列天线的设计

为了降低目前电子不停车收费(electronic toll collection, ETC)系统中存在的邻道干扰、跟车干扰等问题,设计了一种5.835 GHz的微带阵列天线.首先使用对方形贴片切角的方式实现了天线的圆极化,然后通过对4个天线单元运用旋转与相位补偿的方式进行了轴比(axial ratio, AR)带宽的提升,并最终以改进后的4单元作为微带阵列天线的辐射单元.在低旁瓣和高定向方面,本文基于道尔夫-切比雪夫幅度分布的方法进行了不等幅馈电的馈电网络设计.通过大量的电磁仿真,最终确定了天线的最优结构,并进行了实物加工和测量.实测结果表明,阻抗带宽为5.67～5.88 GHz,在5.7～5.9 GHz频段内,增益大于15 dB,AR小于3 dB,E面半功率波瓣宽度小于12°,实测结果与仿真结果具有较好的一致性.该天线具有低旁瓣、圆极化、高定向的特点,为ETC系统路侧单元阵列天线提供了一种新颖的天线结构.     

ETC用5.835GHz微带阵列天线的设计

设计了一种ETC用低旁瓣圆极化微带阵列天线,应用于电子收费(ETC)的路测单元(RSU)。为实现低旁瓣、圆极化的效果,对2个微带天线单元运用旋转与相位补偿的方法进行轴比改进,并以改进后的2单元作为辐射单元制作了一款基于道尔夫-切比雪夫幅度分布的微带天线阵列。经过仿真与实际测量,该天线具有很好的低旁瓣、圆极化的效果。该天线对于ETC系统以及其他类似的天线系统具有很好的理论与实际意义。     

Aperture-Sparsity Analysis of Ultrawideband Two-Dimensional Focused Array

We investigate the effects of aperture sparsity on the focusing performance and the angular-resolution capability of a two-dimensional focused array antenna excited by ultrawideband (UWB) impulse waveforms. The UWB-focusing array is characterized by a planar square aperture and a design parameter referred to as array spatial bandwidth. Spatial bandwidth is a function of the number of array elements, inter-element spacing, and frequency bandwidth. Performance analysis is carried out by generating computer plots of three-dimensional and two-dimensional antenna patterns for different values of array spatial bandwidth that hold for large aperture sparsity and large aperture density. The antenna patterns are peak-amplitude pattern, peak-power pattern, and energy pattern, whose narrow beamwidth and low sidelobe level are robust against aperture sparsity that may be caused by removed or failed elements. The half-power beamwidth (HPBW) of the antenna patterns, the focal distance, and the far-field distance of the UWB-focused array are expressed in terms of array spatial bandwidth. Computer simulation results show that UWB-focused-array beamforming based on impulse waveforms achieves efficient focusing of the radiation energy in the radiation-near-field region and beyond, and yields improvement in focusing performance and angular resolution for increased values of array spatial bandwidth. Such practical advantages are achieved without encountering grating lobes, large sidelobe level, or distortion of the radiation beam pattern that often limit the performance of the conventional narrowband phased array antennas.      

Ka波段圆极化平板阵列天线设计

本文设计了一种规模为 8×8 的 Ka 波段圆极化平板阵列天线。2×2 子阵为一个圆极化基本单元,子阵馈电方波导腔体中插入极化膜片形成圆极化特性,使用全并馈 E 面波导功分网络对 16 个子阵实现等幅同相馈电。设计的阵列天线实现了良好的圆极化特性与高增益特性。     

K波段圆极化相控阵天线的研究

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.     

Improved resolution capability via virtual expansion of array

A new method for improving the resolution capability of a sensor array is presented. The basic idea of the proposed approach is to increase the effective aperture size by virtually expanding the sensor spacing of the original antenna array and then to construct the steering matrix of the virtual array using the proper transformation matrix. Superior resolution capabilities achieved with this method in comparison with the standard MUSIC algorithm are shown by simulation results for narrowband incoherent signals incident on a uniform circular array