共查询到20条相似文献,搜索用时 15 毫秒
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《Electromagnetic Compatibility, IEEE Transactions on》1986,28(2):96-104
A self-steering array system is described for beam forming with nonsinusoidal waves. The array system electronically steers a main beam in the direction of the source from which the wavefront is arriving without prior knowledge of the source locatiora. The principle of monopulse tracking radar is applied to the array system so that the angular coordinate of tihe source can be determiined with respect to the array axis. If the source is in rmotion, it can be tracked on pulse-to-pulse bases. Finally, the self-steering array system is advanced further to suppress the additive thermal noise presenit with the incoming signals, and to achieve good angular resolution and accuracy. 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(7):3137-3144
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The use of the basic large-current radiator?discussed in a previous paper?and the Hertzian electric dipole as sensor is investigated. If the sensor works into a large resistive load, typically implemented by an emitter follower, its output voltage varies like the electric field strength, while a capacitive load produces an output voltage proportionate to the integral of the field strength. The maximum energy is transferred to a load impedance that is equal to the radiation resistance of the antenna. This is the same result as in the case of sinusoidal waves, but the radiation resistance for nonsinusoidal waves differs from that for sinusoidal waves. An effective aperture can be defined, which is again analogous, but not equal, to the same concept used for sinusoidal waves. 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》1986,28(4):240-248
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. 相似文献
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A two-dimensional beamforming technique is presented for two-dimensional arrays of (N × N) sensors receiving plane wavefronts with nonsinusoidal time variations in the form of a single rectangular pulse of duration T or in the form of a coded sequence of rectangular pulses with nominal time duration T. The three-dimensional energy pattern has a main beam for small angles of incidence and a number of sidelobes for large angles of incidence. For wavefronts with rectangular time variations, the maximum sidelobe has the magnitude 1/N and, for coded time variations, the maximum sidelobe exceeds 1/N. The magnitude of the sidelobes of the energy pattern can be decreased by increasing the number of sensors in the array. The resolution angle can be decreased by the ratio (N1/N2) when the number of sensors is increased from (N1 × N1) to (N2 × N2) and it can be decreased by the ratio (T1/T2) when the nominal time duration is decreased from T2 to T1. Waveform distortion results in a degradation of the resolution angle. 相似文献
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It is widely believed that a waveguide behaves like a lossless dispersive medium, which implies that only sinusoidal waves can be transmitted without distortions. This is correct for the particular solutions of Maxwell's equations that have been in use since Rayleigh's original investigation in 1897. More general solutions can be found that show that a large class of nonsinusoidal periodic waves can be transmitted distortion-free by a lossless waveguide. These solutions are readily derived for rectangular waveguides by means of the Fourier series, while a generalization of the Fourier series is required for cylindrical waveguides. 相似文献
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It has been shown that nonsinusoidal waves can propagate dispersion-free in loss-free waveguides. This situation opens the possibility of nonsinusoidal waves existing distortion-free in cavity resonators. A general solution of Maxwell's equations for nonsinusoidal waves in rectangular cavity resonators is derived. For the special case of a square wave, the electric and magnetic field strengths as functions of time and space are analyzed in detail. The implication of this analysis is that square waves or other periodic nonsinusoidal waves with various periods T can be separated by cavity resonators just as sinusoidal waves with various periods T can be separated. This paper is part of an ongoing effort to advance the technology of antennas and associated circuits for nonsinusoidal electromagnetic waves. 相似文献
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穿墙三维成像中,不同的阵列构架会直接影响阵列性能及其适用环境。利用等效阵列原理设计二维多输入多输出(MIMO)阵列,在具体分析一维STVA阵列具有最短物理尺寸的原理上,提出了利用子阵划分的方法解决等效阵列到MIMO阵列的去卷积问题。针对去卷积后得到多种MIMO阵列构型的择优问题,提出了综合尺寸的概念,利用子阵划分后的部分信息衡量去卷积后MIMO阵列的物理尺寸,最后将这种方法推广至二维MIMO阵列,设计出适用于穿墙成像的二维UWB-MIMO阵列,利用仿真实验验证了其在穿墙三维成像中的优异性能。 相似文献
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Antennas for Nonsinusoidal Waves. I. Radiators 总被引:1,自引:0,他引:1
During the last years numerous applications of nonsinusoidal electromagnetic waves have been discussed in this TRANSACTIONS. The next step is the implementation of these applications. It is generally accepted that the antennas pose the greatest diMculty. In a series of papers on radiators, sensors, and arrays, we will investigate antennas, both theoretically and experimentally. Sufficient information is provided to permit anybody who is equiped for work with pulses of about I-ns duration to build simple radiators and sensors. 相似文献
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The calculation of the electric and magnetic field strength produced by a radiator is usually done only for distances large compared with the geometric dimensions of the radiator. This approach makes it Impossible to obtain exact relations between the power fed to the radiator by the driver, the voltage between the radiator terminals, the power radiated to or received from the near zone, and the power radiated to the far zone. This paper develops a solution for the large-current radiator that can be evaluated numerically by computer for any distance, and thus permits the calculation of the power flowing at any time through the surface of the radiator. The knowledge of this power is the basis for the design of efficient radiators. 相似文献
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S. E. Bankov 《Journal of Communications Technology and Electronics》2018,63(9):968-979
A 2D frequency-scanned array focused in the near-field zone is analyzed. A method for the synthesis of this array ensuring perfect field focusing in two points at two frequencies is proposed. Array scanning in two planes (longitudinal and transverse) is analyzed with the use of an approximate model. The motion trajectory of the focal spot (scanning arc) and optical aberrations associated with scanning are studied. Different variants of determination of the scanning arc, using the criterion of the maximum field intensity and the criterion of the maximum aperture efficiency of the array, are considered. It is shown that application of bifocal arrays can improve main quality indices as compared to those of single-focus arrays. 相似文献
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本文阐述大型两维发光二极管(LED)阵列的设计、制造及其在虚拟显示象源中的应用.利用双台面蚀刻工艺,由铟镓铝磷(InGaAlP)系材料制成LED象素.边长为10μm的正方形LED在峰值发射波长约650nm时,外量子效率为0.5%,亮度达10fL,而阵列功耗仅为2.9mW.LED阵列由240行×144列(~VGA/8)个象素组成,象素节距为20μm,显示速度每秒60帧,按行主导矩阵寻址方式来驱动.象素在恒定电流下以脉宽调制来驱动,灰度达16级.本文对阵列亮度的均匀性作了分析.取样图象、图形及灰度图象皆证明,LED阵列可用作虚拟显示的单色象源. 相似文献
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在非均匀杂波和密集目标环境下,由于没有足够的独立同分布(IID)训练样本,传统空时自适应处理(STAP)方法的杂波抑制性能严重下降。针对以上问题,该文提出一种对阵元误差稳健的机载面阵雷达非均匀杂波抑制方法。该方法首先根据雷达系统参数先验知识构造杂波表示基矩阵。然后在考虑阵元误差的情况下,基于最小二乘准则迭代地估计杂波表示系数和阵元误差,最后利用估计得到的最优杂波表示系数和阵元误差直接在阵元脉冲域进行杂波对消。该方法无须估计待检测单元统计特性;没有孔径损失;不需要训练样本;即使在距离模糊情况下也能有效地抑制密集目标环境下机载面阵雷达回波数据中的非均匀杂波。仿真结果验证了该文方法的有效性。
相似文献18.
This paper proposes a novel incoherent optical code-division multiple-access (OCDMA) transceiver design, as a promising network access employing a newly introduced prime code family named as double-padded modified prime code as spreading sequences, based on the 2-D optical modulation scheme deploying frequency and polarization shift keying. Hereafter, it is referred to as F-PolSK. The novel F-PolSK-OCDMA system has been accurately analyzed taking into account the presence of 1) optical amplified spontaneous emission noise; 2) electronic receiver noise; 3) photo-diode shot-noise; and 4) multiple-access interference (MAI). The application of the optical tapped-delay lines at the receiver as a CDMA-decoder has also been investigated. The evaluation of 2-D array modulation in conjunction with OCDMA indicates that the binary combination of this hybrid scheme enhances the overall system performance. The results reveal that the proposed architecture can easily accommodate greater number of users and consume less power as compared with previous schemes. On the other hand, in polarization modulation since the optical beam power is constant, the system has immunity against the self- and cross-phase modulations. Besides, the system security is much enhanced due to 2-D advanced modulation in optical domain. 相似文献
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针对现有MIMO雷达发射方向图设计方法无法直接推广到平面阵MIMO雷达的问题,在平面阵方向图可以由水平和垂直方向的线阵方向图合成的思想基础上,该文提出一种应用基波束和概率选择方法设计平面阵MIMO雷达发射方向图的方法。该方法首先将期望方向图沿方位角累加,形成1维俯仰角方向图,建立垂直方向线阵的俯仰角基波束集合和该集合元素的概率选择优化模型;其次针对每个俯仰角对应的1维方位角期望方向图,建立水平方向线阵的方位角基波束集合和该集合元素的概率选择优化模型;最后合成2维基波束集合和集合中元素的选择概率,并求得平面阵MIMO雷达的发射方向图和发射信号。该方法中的优化问题都是凸问题,可以求得全局最优解。 相似文献
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该文设计了一种平面印刷偶极子波束扫描寄生阵列天线,可用于移动终端设备以提高通信质量和系统容量。通过改变加载在寄生单元中的电抗值可以控制天线的最大辐射方向。天线基本结构用电磁场全波软件设计,所需加载的电抗值通过差分进化算法(DE)优化得出。实测的天线主波束方向在xoy平面内-34~38之间扫描;在各方向上,中心工作频率上的增益在3.6~4.9 dBi之间变化,反射系数小于-10 dB的频带在5.63~5.96 GHz之间,带宽为330 MHz。实测结果表明,天线具有良好的波束扫描性能,采用的设计和优化方法准确高效。 相似文献