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1.
Adaptive processing using real weights based on a direct data domain least squares approach 总被引:2,自引:0,他引:2
Choi W. Sarkar T.K. Hong Wang Mokole E.L. 《Antennas and Propagation, IEEE Transactions on》2006,54(1):182-191
In traditional, adaptive signal processing algorithms one change both the amplitude and phase of the weight vectors associated with an array at each of the antenna elements. The use of complex weights offers greater control over the array response at the expense of system complexity. However, it is easier if one requires only amplitude variation with a fixed phase for all the weight vectors associated with all the antenna elements. Because one uses only real arithmetic operations to find the amplitude of the weights connected to the antenna, the computational complexity is reduced considerably. Hence, this paper addresses the use of real weights in an adaptive system. In this paper we describe a new direct data domain least squares (D/sup 3/LS) method using real weights, which utilizes only a single snapshot of the data for adaptive processing. This technique may be useful for real time implementation of the D/sup 3/LS method on a chip. 相似文献
2.
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
3.
《Wireless Communications, IEEE Transactions on》2006,5(11):2977-2982
MIMO systems with reduced hardware complexity have attracted researchers' attention due to their high efficiency and low cost. Sub-optimum algorithms for antenna subset selection have been intensively studied in the literature. In this paper we present a new technique to maximize the capacity of multiple antenna wireless systems with reduced available RF chains. The technique is based on the adaptive formation of subarrays, i.e. the grouping of antenna elements and the application of appropriate element weights. The elements of each subarray and their weights are dynamically selected by an evolutionary optimization technique using the link capacity as a cost function 相似文献
4.
Pattern Synthesis of Conformal Array Antenna in the Presence of Platform Using Differential Evolution Algorithm 总被引:1,自引:0,他引:1
Jing-Li Guo Jian-Ying Li 《Antennas and Propagation, IEEE Transactions on》2009,57(9):2615-2621
A synthesis method based on differential evolution algorithm is proposed for conformal antenna arrays in the presence of platform. With the desired phase weights determined by the scan angle and array geometry, the amplitude weights of elements are optimized by differential evolution algorithm to drive down the side-lobes. Both the effect of platform on radiation pattern of conformal array and the mutual coupling between the elements are taken into account by calculating the antenna array and platform simultaneously using the method of moment. Application of adaptive integral method reduces the storage and computation time needed by the method of moments. 相似文献
5.
Viikari V. Kolmonen V.-M. Salo J. Raisanen A.V. 《Antennas and Propagation, IEEE Transactions on》2007,55(8):2194-2199
An antenna pattern correction technique is presented that is based on an adaptive array algorithm. In the method, the antenna pattern of the antenna under test (AUT) is measured several times at different positions in the quiet-zone. The corrected antenna pattern is obtained by taking a weighted average of the measured patterns. An array synthesis algorithm is employed for obtaining the averaging weights at each rotation angle of the AUT. The weights are adapted specifically for a given AUT. The adaptive array correction technique is demonstrated in a hologram based compact antenna test range (CATR) at 310 GHz with both a synthetic antenna and a physical test antenna. For verification, the accuracy provided by the adaptive array correction technique is compared to that provided by uniform weighting. 相似文献
6.
This paper proposes a new spatio-temporal equalization method, which simultaneously utilizes an adaptive antenna array and a decision feedback equalizer (DFE). For effective spatio-temporal equalization with less computational cost, how to split equalization functionality into spatial processing, and temporal processing is quite important. One of the answers which we have given is “incoming signals with larger time delays should be cancelled at the spatial equalization part.” The weights of both adaptive antenna array elements and taps of DFE are calculated only using the estimated channel impulse response, therefore, it requires no information on direction of arrival (DoA). We show the performance of the proposed system in multipath fading channels often encountered in indoor wireless environments and discuss the attainable bit error rate (BER), antenna patterns, and the computational complexity in comparison with other equalization methods such as spatial equalization and temporal equalization 相似文献
7.
Heng-Cheng Lin 《Antennas and Propagation, IEEE Transactions on》1982,30(2):212-223
A receiving array antenna can steer its main beam toward any direction by adjusting the complex weight in each element. However it cannot always steer one beam and one null toward two prespecified directions simultaneously with a single set of weights. The ability for an array to steer one beam and one or more nulls simultaneously is determined by five factors: 1) element positions, 2) orientations of elements, 3) antenna patterns of elements, 4) polarizations of signals, and 5) directions of the beams and/or nulls. A coefficient is defined, called spatial correlation, which includes these factors and completely characterizes array beam pointing and nulling. Its application to adaptive arrays is demonstrated. The adaptive array performance is dominated by this coefficient and can be improved by properly choosing the first three factors. Several examples on the selection of element placement in adaptive arrays are presented. 相似文献
8.
Adapting a downlink array from uplink measurements 总被引:3,自引:0,他引:3
In a frequency division duplex system, a transmitter adaptive antenna array can potentially improve the performance of a wireless downlink, but because the uplink and downlink channels have different wavelengths, and, therefore, different responses, direct downlink adaptation based on channel estimates of the uplink is generally not feasible. Instead, there has been some interest in adaptations that require only the second-order statistics of the uplink and downlink to be similar. These algorithms derive adaptive weights from the covariance of the received signal to apply to a downlink transmitter array. We make two contributions to this area. First, we introduce an array configuration employing M+1 elements with log-periodic spacing that comprises two overlapping subarrays, each with M elements, that are scaled versions of each other, with the scale factor equal to the ratio of the uplink wavelength to the downlink wavelength. This array has identical beampatterns at the two wavelengths, thus helping to fulfill the requirement that the uplink and downlink second-order statistics be the same. Second, we demonstrate that obtaining a good estimate of the uplink covariance matrix is not essential for the successful operation of the adaptive scheme. Even when the mobile is at rest and the uplink information comprises only a single snapshot from the receiver array, an adaptive scheme can improve the SNR 相似文献
9.
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
10.
Presents a case study of the design of a computationally intensive system to do adaptive nulling of interfering signals for a phased-array radar with many antenna elements. The goal of the design was to increase the computational horsepower available for this problem by about three orders of magnitude under the tight constraints of size, weight and power which are typical of an orbiting satellite. By combining the CORDIC rotation algorithm, systolic array concepts, Givens transformations, and restructurable VLSI, we built a system as small as a package of cigarettes, but capable of the equivalent of almost three billion operations per second. Our work was motivated by the severe limitations of size, weight and power which apply to computation aboard a spacecraft, although the same factors impose costs which are worth reducing in other circumstances. For an array of N antennas, the cost of the adaptive nulling computation grows as N3, so simply using more resources when N is large is not practical. The architecture developed, called MUSE (matrix update systolic experiment) determines the nulling weights for N=64 antenna elements in a sidelobe cancelling configuration. After explaining the antenna nulling system, we discuss another DSP computation that might benefit from similar architecture, technology, or algorithms: the solution of Toeplitz linear equations 相似文献
11.
计入阵元间互耦影响的阵列方向性图综合 总被引:2,自引:0,他引:2
基于自适应天线理论,在考虑了天线阵中阵元间互耦影响的情况下,对均匀和非均匀直线阵列的方向性图进行了综合,并讨论了加权值幅度和相位误差对天线阵列方向性图的影响。 相似文献
12.
Ning Xie Yuanping Zhou Li Zhang Gongbin Qian Hui Wang Xia Li 《Wireless Communications and Mobile Computing》2009,9(2):239-249
Design of a nonlinear adaptive antenna array receiver is a challenging task in wireless communications due to the limited number of antenna elements and the presence of correlated signals, which directly affect the performance of an antenna array. More importantly, a conventional nonlinear array receiver is often associated with a high computational complexity that undermines its applicability in practice. In this paper, we present a new approach to adaptive beamforming receiver that provides superior performance in antenna array overloading and in the presence of correlated signals with a low complexity. In particular, the proposed receiver requires a small data‐record size to estimate the beamformer weights, which is beneficial in applications with fast fading channels. Simulation examples illustrate the performance improvement of the proposed array receiver when it is compared to the conventional beamformers. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
13.
Voltage-controlled phase shifters are used as the adjustable elements in an adaptive phased-array antenna system for spatial filtering of narrow-band inputs. A gradient-search adaptation algorithm for adjusting phase angle is developed and applied to an adaptive antenna system which can be adapted either to enhance signals or reject interference. The transient behavior of this system during adaptation is analyzed in terms of steepest ascent/descent on a multidimensional trigonometric performance surface approximated in two regions by quadratic surfaces. 相似文献
14.
15.
For pt. I see IEEE Trans. Veh. Technol. A smart antenna, i.e., a blind adaptive antenna array, has attracted much attention to improve the capacity of a future code-division multiple-access wireless communications system. It has been demonstrated that there is significant improvement in data demodulation through lab simulations and field experiments by employing a smart antenna of multiple elements. However, only one element is used for the pseudonoise (PN) code acquisition process, which is a coarse PN code synchronization prior to data demodulation. This paper proposes a simple and practical PN code acquisition scheme, which employs all elements in the smart antenna. Also, this paper uses an adaptive threshold for the PN code acquisition. Simulation results demonstrate that the proposed scheme can significantly improve the PN code acquisition performance, e.g., the PN code acquisition time will be half as long by employing five elements rather than the single element at a given bit-energy-to-interference power spectral density ratio. 相似文献
16.
A method for designing near optimal, tapered subarrays for adaptive interference cancellation is proposed. The design method simultaneously produces a complete ordered set of fixed beam definitions, or nonadaptive weight vectors. The designer may choose to implement the first K of these if he or she wishes to have exactly K adaptive weights. In other words, the digital-adaptive processing is done in beam space, such that the beams are designed using the proposed method. To facilitate an RF implementation of the nonadaptive beamformer, each auxiliary beam uses only a designer-specified number of the elements in the aperture, thereby reducing the number of waveguide connections required. This design approach is fundamentally different from conventional subarray design approaches in that the new designs utilize cost functions related to interference cancellation. 相似文献
17.
Generating a plane wave with a linear array of line sources 总被引:1,自引:0,他引:1
Creating a plane wave across an antenna under test is important for accurate antenna measurements. This paper optimizes the location and weightings of an array of line sources in order to approximate a plane wave at a given location in space. The amplitude and phase ripples across a desired test aperture are optimized to be much less than that of a uniform array with the same number of elements. Results are presented for a nine-element array with optimized amplitude and phase weights, with optimized weights and spacing in the x-direction, and with optimized weights and spacing in the x and z directions. The optimized approximate plane wave is a significant improvement over a uniform array or a single line source. 相似文献
18.
Airborne or spaceborne radar systems often require tests before deployment to verify how well the system detects targets and suppresses clutter and jammer signals. The radar antenna diameter can be large and thus the conventional far-field test distance is impractical to implement. The theory and simulations of phase-focused near-field testing for adaptive phased array antennas is discussed. With near-field source deployment, standard phased-array near-field phase focusing provides far-field adaptive nulling equivalent performance at a range distance of one aperture diameter from the adaptive antenna under test. Both main beam clutter sources and sidelobe jammer sources are addressed. The phased array antenna elements analyzed are one-half wavelength dipoles over the ground plane. Bandwidth, polarization, array mutual coupling, and finite array edge effects are taken into account. Numerical simulations of an adaptive antenna that has multiple displaced phase centers indicate that near-field and far-field testing can be equivalent 相似文献
19.
该文设计了一款工作在2.45GHz并可实现60°扫描范围的方向图可控天线阵列。该天线阵列引入介电常数可控的铁电材料作为基板,通过外加直流偏置改变铁电材料的介电常数,从而实现单元馈电相位的连续变化。该天线阵列由馈电结构、隔直结构、移相器及天线阵元4部分组成,各部分分别集成在地板两侧的2个金属层上。不同于其他设计,该天线仅通过控制外加直流偏置电压的大小实现天线最大波束-30°~30°范围内的变化;此外,天线设计了一种新颖的直流偏置电路,减小了天线的设计复杂度,使设计的天线具有更高的实用价值。 相似文献
20.
阵列部分单元相位加权波瓣综合 总被引:9,自引:4,他引:5
从自适应信号处理的角度出发,描述了阵列天线部分单元仅相位加权波瓣综合方法,并通过计算实例验证了该方法的正确性。该方法可用在天线波瓣图中设置宽凹口以对付宽带宽角干扰,亦可用于机载雷达天线不对称波瓣赋形以抑制地海杂波等。部分单元相位加权波瓣综合方法比满阵单元相位加权波瓣综合方法更具有实现性和灵活性。 相似文献