共查询到20条相似文献,搜索用时 35 毫秒
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Mahmoud S.F. Antar Y.M.M. Hammad H.F. Freundorfer A.P. 《Antennas and Propagation, IEEE Transactions on》2004,52(8):2057-2063
The problem of optimum excitation of surface waves on a grounded dielectric slab by means of slots in the ground plane is considered. By adopting a two-dimensional (2-D) model, analysis lead to closed forms for the power launched as surface waves and power leaked as radiation. Input admittance of a single slot source and mutual admittance between two slots are derived and utilized to design a three element Yagi array of slots to achieve a prescribed ratio of forward to backward surface wave power. As a development of the 2-D model, we allow finite extent of slot excitation by assuming a Gaussian E-field distribution across the slot. The effect of the Gaussian width on the excited surface wave power is studied. The analysis is relevant to the study of surface waves on printed circuits. Specifically, it applies to the implementation of power combiners based on quasioptical slab beam that have been recently introduced in the literature for use in the millimeter wave band. 相似文献
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A TLM approach to the full-wave analysis of guided wave structures is introduced. Instead of real pulses as in the conventional TLM method, complex pulses are used. Therefore a nonreciprocal phase shift in the z -direction can be introduced and used to connect the z arms in a 3-D node directly. As a result, the 3-D array of 3-D nodes, normally required in the TLM method to calculate the propagation and attenuation constant, is reduced to only one mesh unit in the z direction (a 2-D array of 3-D nodes). The propagation constant is determined by choosing a value and then calculating the frequency at which this value is valid from the Fourier transform of the impulse response. Losses are found by computing the exponential decay of time harmonic solutions at the eigenfrequencies of the structure 相似文献
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Feng Xu Wei Hong 《Antennas and Propagation, IEEE Transactions on》2004,52(10):2612-2617
An algorithm of two-dimensional (2-D) domain decomposition finite-difference time-domain (DD-FDTD) using in sparse multicylinders scattering problem is proposed in this paper. The idea of domain decomposition is introduced to divide the sparse problem domain into several subdomains. All of subdomains are connected by means of the 2-D time domain Green's function. As a result, a great deal of meshes memory between cylinders is removed, especially when the distances between cylinders become large. Furthermore, the coupling between cylinders can be regarded as the equivalent cylindrical wave irradiations. The incident signals of the equivalent cylindrical waves are expressed as cylindrical wave input field array (CWIFA) according to Huygens principle. Then the calculation time is significantly reduced. The near-field to far-field transformation is used to obtain the equivalent cylindrical wave; as a result, the calculation time can be reduced further. The new method has been demonstrated in 2-D multicylinders scattering problem. Numerical results are in good agreement with the results obtained using classical FDTD method and moment of methods (MM). 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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Gunaratne T.K. Bruton L.T. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(3):838-850
A new discrete-domain method is proposed for the beamforming of temporally broad-band bandpass plane waves (PWs) using a real-coefficient 2-D spatio-temporal (ST) finite-impulse response (FIR) filter having a novel rectangularly symmetric double-trapezoidal-shaped passband. The arriving temporally broad-band-bandpass ST PWs are received by a 1-D uniformly distributed sensor array. The sensor signals are pre-filtered, down-shifted to the intermediate frequency (IF) band, low-pass filtered and synchronously sampled by the real IF tri-stage temporal sampler array, resulting in a real-valued 2-D sampled sequence. The beamforming operation is then carried out on this 2-D sampled sequence using the real-coefficient 2-D FIR double-trapezoidal filter. Arithmetic complexity in the hardware implementation of the 2-D FIR double-trapezoidal filter is significantly reduced by using an array of real-coefficient polyphase 1-D FIR filters. Experimental results have confirmed that this method is capable of enhancing the desired temporally broad-band-bandpass ST PWs according to their directions of arrival under severe co-channel interference. 相似文献
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An efficient technique to improve the accuracy of the finite-difference time-domain (FDTD) solutions employing incident-wave excitations is developed. In the separate-field formulation of the FDTD method, any incident wave may be efficiently introduced to the three-dimensional (3-D) computational domain by interpolating from a one-dimensional (1-D) incident-field array (IFA), which is a 1-D FDTD grid simulating the propagation of the incident wave. By considering the FDTD computational domain as a sampled system and the interpolation operation as a decimation process, signal-processing techniques are used to identify and ameliorate the errors due to aliasing. The reduction in the error is demonstrated for various cases. This technique can be used for the excitation of the FDTD grid by any incident wave. A fast technique is used to extract the amplitude and the phase of a sampled sinusoidal signal 相似文献
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A modified path-following algorithm using a known algebraic path 总被引:9,自引:0,他引:9
Jong-Hwan Lee Chul-Mok Lee Kyun-Kyung Lee 《Signal Processing, IEEE Transactions on》1999,47(5):1407-1409
A new computationally efficient path-following algorithm is presented for source localization that uses a uniform linear sensor array. An algebraic relation is demonstrated between the bearing of a source under a plane wave assumption and the actual source bearing and range. This relation can be used as a path to follow to the peak of the 2-D MUSIC spectrum. As a result, in the case of an array that has m sensors with n sources, this new algorithm can reduce the number of searches to n independent 1-D searches following the known algebraic path 相似文献
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该文提出一种通过预测到达任务区域路径信噪比,自适应地为天波超视距雷达选择工作频点的方法。利用2维阵列的俯仰维分辨能力,克服了传统方法无法从返回散射电离图中分离多模/多径信号的缺陷。雷达通过电离层探测设备和2维接收阵列,获取返回散射数据、环境干扰数据和电离层状态数据。然后利用电离层模型和状态数据,推算各频点对任务区域的照射路径。运用2维自适应波束形成抑制环境干扰噪声,并处理返回散射数据以预测各路径回波强度。最后计算各频点路径在脉冲压缩后的信噪比,选择信噪比最大值的频率为最优工作频点。 相似文献
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A method of ultrasonic three-dimensional (3-D) vector velocimetry, which is derived by extending the previously proposed two-dimensional (2-D) vector velocimetry, is presented. In the proposed method, the three vector components of velocity to be measured are defined as the velocity in the beam axial direction, and angle velocities in two transverse directions. To derive the three components of velocity, signals detected by a 2-D array transducer are first 2-D Fourier transformed in the spatial domain parallel to the 2-D array transducer and then are one-dimensional (1-D) Fourier transformed in the time domain. The advantage of the proposed method is that it uses a linear signal processing, so it can simultaneously measure individual velocities of multiple scatterers. Computer simulations clearly demonstrate the effectiveness of the proposed method 相似文献
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对比传统的基于球面波分解的近程目标太赫兹全息成像算法,以驻定相位法为理论基础对成像算法进行推导,得到了相同的成像补偿公式。采取图像熵的判决准则分析阵元误差对成像结果的影响,为成像系统阵元位置精确度的设计提供理论依据。针对三维目标距离过近出现非补偿距离平面成像结果散焦的现象,对传统成像算法的缺陷进行分析,提出了基于循环补偿与投影合成相结合的近程目标太赫兹三维全息成像方法。220 GHz条件下的Matlab仿真结果验证了所提方法的有效性,实现了三维目标的聚焦成像。 相似文献
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波达方向估计是智能天线的重要功能之一,对于相干信号角度模糊问题通常严重影响了方向判断的精准度.文中根据一维空间平滑基本理论和算法,对二维六边形阵列相干信号MUSIC算法波达方向估计问题进行了理论分析和仿真实验,提出了平面六边形阵列到十字形阵列的变换方法,成功地把一维平滑技术应用到平面六边形阵列,仿真表明,这种变换可以有效地消除相干信号的角度模糊问题. 相似文献
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A patented technique for suppressing the sidelobes of an array antenna is considered. This technique involves the addition of two elements, one at each end of the array, which together produce an interferometer pattern used for the cancellation of sidelobes. It is shown here that the technique is most effective for uniform illumination and that there then exists an optimum fixed position for the added elements. The amplitude of the excitation of the auxiliary elements determines the angular location of the region of sidelobe reduction while the phase of the excitation tracks the beamsteering phase of the array. Thus, this technique is seen to be easily implemented in an array controlled by coupled oscillators. The technique generalizes in a straightforward manner to two-dimensional (2-D) arrays in which case a set of auxiliary elements on the perimeter of the array is required. A 2-D oscillator controlled array of this type is described here with which one can produce a main beam and a sidelobe suppression region that can be independently positioned anywhere in a hemisphere provided they do not coincide 相似文献
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Hsi-Tseng Chou Hsien-Kwei Ho 《Antennas and Propagation, IEEE Transactions on》2004,52(2):388-396
Forward-backward method (FBM) was successfully developed for the analysis of electromagnetic radiation/scattering from one-dimensional (1-D) phased array in an efficiency appealing fashion. The FBM applications to treat 2-D array problems are developed in this paper. Acceleration algorithm, performing better than the novel spectrum acceleration algorithm used for 1-D FBM computation, is also developed for this 2-D FBM so the unique advantages of high efficiency and O(N/sub tot/) computational complexity as in the 1-D problems can be retained where N/sub tot/ is the total number of array element. Numerical examples are presented to demonstrate its validity. 相似文献
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An L-shaped array for estimating 2-D directions of wave arrival 总被引:15,自引:0,他引:15
A simple structured 2-D array, the L-shaped array, is presented. The L-shaped array consists of two uniform linear arrays (ULA) connected orthogonally at one end of each ULA. It is shown that the Cramer-Rao bounds (CRB) of the estimated wave directions based on the L-shaped array are about 37% smaller than those for the cross array. The CRB indicates the accuracy potential because it is the (reachable) lower bound on the variance of any unbiased estimate. An efficient maximum likelihood algorithm is developed utilizing the ULA structure inherent in the L-shaped array 相似文献