A self-steered array system for microwave communications

The paper presents a self-steered algorithm that can be used to correct pointing errors in microwave communications. The algorithm is based on the fact that the output power of an optimized beamformer achieves a local maximum if the steering vector coincides with that of the desired signal, as long as the interferences are outside the mainbeam. By approximating the steering vector by its first-order Taylor series expansion in terms of the steering angles, the maximization process reduces to a two-dimensional optimization problem. Numerical results are presented to illustrate the performance achievable     

增益导引GaAlAs/GaAs锁相列阵激光器

本文报道采用氧化物掩蔽Zn扩散平面条形结构的增益导引GaAlAs/GaAs锁相列阵激光器的工艺和特性。获得了阈值电流小于200mA,输出功率大于240mW的实验结果。远场测试表明其具有良好的锁相特性。     

A carrier-phased satellite receiving array

The carrier-phased array—in which array phasing is derived from the incident modulated signal—is conceptually a very simple means of achieving automatic beam pointing in communications systems. The technique is particularly suitable for satellite reception applications, although careful consideration must be given in a practical design due to problems associated with the low signal levels derived from satellite broadcasts. In this paper, the basic principles of operation of such an array are described and the requirements of a practical system are addressed, resulting in the design and evaluation of an array system suitable for use with BPSK modulated signals from a communications satellite.     

A compact digital beamforming SMILE array for mobile communications

A compact spatial multiplexing of local elements (SMILE) scheme smart antenna array with adaptive beamforming is presented. Low-noise amplifiers are implemented as switching elements to maintain a low system noise figure and allow fast switching. The switching scheme effectively reduces N RF channels to one, reducing the amount of costly RF hardware by a factor of N. The sampling rate must be higher than the signal bandwidth based on the Nyquist criterion to ensure proper restoration of the original signal. Measured data for destination of arrival estimation, beamforming, and digital data recovery demonstrate the capability and benefits of digital beamforming with this architecture.     

Single-lobed emission from phase-locked array lasers

Phased-array lasers which emit in a single far-field lobe corresponding to the lowest-order mode are described. Single-lobed diffraction-limited operations are achieved by two simple approaches: (i) close-coupled elements and (ii) diffraction-coupled arrays.     

Robust adaptive array for wireless communications

In the application of a receiver antenna array to wireless communications, a known signal preamble is used for estimating the propagation vector at the beginning of each data frame. The estimated propagation vector is then used in linear combining of array inputs for interference suppression and demodulation of a desired user's information data stream. Since the training preamble is usually very short, conventional training methods, which estimate the propagation vector based solely on the training preamble, may incur large estimation errors. In many wireless channels, the ambient noise is known to be decidedly non-Gaussian, due to impulsive phenomena. The conventional training methods may suffer further from such impulsive noise. Moreover, performance of linear combining techniques can degrade substantially in the presence of impulsive noise. We first propose a new technique for propagation vector estimation which exploits the whole frame of the received signal. It is shown that as the length of the signal frame tends to infinity, in the absence of noise, this method can recover the propagation vector of the desired user exactly, given a small number of training symbols for that user. We then develop robust techniques for propagation vector estimation and array combining in the presence of impulsive noise. These techniques are nonlinear in nature and are based on the M-estimation method. It is seen that the proposed robust methods offer performance improvement over linear techniques in non-Gaussian noise, with little attendant increase in computational complexity. Finally, we address the extension of the proposed techniques to dispersive channels with intersymbol interference     

Phased array antennas for mobile communications

An antenna system including antenna elements and a tracking method is considered a key technology in mobile communication systems. A phased array antenna has been considered the most favorite candidate because of many attractive characteristics such as a low and compact profile, high-speed tracking and potentially low cost performance for vehicle antennas in mobile communications. On the other hand, it has several such disadvantages as beam steering error, loss in feed lines and an increase of noise level in a receiving frequency band. Some of phased array antennas have already been used in satellite communications, and some of them are under development. This paper overviewed basic performance and some examples of phased array antennas for especially satellite mobile communications.     

A two-sensor array blind beamformer for direct sequence spreadspectrum communications

We present an efficient blind beamformer dedicated to the problem of interference mitigation in direct sequence spread spectrum (DSSS) communication systems using a two-sensor array. A closed-form solution for the blind identification of the communication channel is derived by exploiting the temporal properties of the desired signal and the interference. The optimal beamformer is derived from the maximization of the signal-to-interference and noise ratio (SINR) at the output of the receiver in terms of the blindly estimated channel coefficients. Three structures of the DSSS receiver are presented. One structure consists of the blind beamformer followed by the spread spectrum demodulator. The other two structures consist of the spread spectrum demodulator followed by the blind beamformer. The performance of these structures is discussed in terms of the achieved SINR and the computational cost. Simulation results are provided to illustrate the effectiveness of the proposed blind beamformers in interference excision     

Phased array beam steering using phase-locked loops

Phase-locked loops can be used as linear voltage-controlled phase shifters for phased antenna arrays. Results are presented showing that they offer considerable flexibility, both in configuration and modes of control, in beam steering and other more complex beamforming applications.<>     

A high-brightness laser beam from a phase-locked multicore Yb-dopedfiber laser array

We observed a high-brightness laser beam emitted from a closely packed array of seven Yb-doped single-mode fiber lasers embedded in a common cladding. The measured slope efficiency, greater than 65%, was achieved by clad-pumping from one end of the fiber. A theoretical model is established to provide a physical interpretation of the measured far field radiation patterns     

An active retrodirective array for satellite communications

The concept and design of an active retrodirective array, resulting from the specialized requirements and constraints of space/earth communications, is presented. The advantages of employing active microwave gain are discussed. The attendant problem of instability is defined and several aspects of the solution, namely frequency offsetting and polarization isolation, are detailed. The latter technique makes use of orthogonally polarized "subarrays" -one for receiving and one for transmitting-intermeshed on a common aperture surface. A discussion of tolerable phase errors and the effect of element failure on the system reliability is presented. Techniques for realizing the active circuitry required for the functions of RF amplification, frequency conversion and modulation are described. An experimental model, employing strip transmission line techniques throughout, was fabricated and tested. All results, including those of array gain, retrodirectivity and simultaneous retrodirectivity from several sources at different frequencies, and effects of element removal, corresponded closely to their calculated predictions.     

一种应用于5G毫米波通信的双极化有源相控阵模组

针对5G毫米波通信,研制了一种双极化有源相控阵天线模组。厚度为2 mm的多层PCB正面印制阵列天线,在其背面集成多通道波束成形芯片,通过中间层实现天线与芯片的互连以及供电、控制等。测试结果表明,研制的板状4×4双极化相控阵模组在E面和H面均实现了不小于±40度的波束扫描范围（不大于3 dB的电平下降）和低于-18 dB的归一化交叉极化电平,在24～27.5 GHz的频率范围内实现了V极化和H极化分别为42.6～45.7 dBm和43.5～46.1 dBm的等效全向辐射功率（EIRP）。     

Downlink adaptive array algorithms for cellular mobile communications

The capacity of wireless downlink communication to mobile receivers in a dense urban environment is limited primarily by co-channel interference. Downlink adaptive arrays can be used to mitigate this limitation by maximizing the power transmitted to desired in-cell mobiles in the reference cell while minimizing power to co-channel mobiles in neighboring cells. This is accomplished by using uplink measurements to estimate downlink covariance matrices and then solving a generalized eigenvalue problem. Several algorithms are proposed to adaptively estimate the optimal solution and are evaluated using a simplified signal model that allows efficient deterministic performance calculations.     

A frame synchronization method for adaptive array antennas in digital mobile communications

This paper proposes a frame synchronization method for an adaptive array antenna (AAA) used in digital mobile communications. The proposed scheme, which is based on the maximum likelihood estimation (MLE), calculates error signals by subtracting a training sequence convolved with an estimated channel impulse response from the AAA outputs and searches for the timing that minimizes the mean squared errors. Because the proposed scheme can effectively exploit delayed paths of the desired signal, it can improve the synchronization performance on frequency-selective fading channels. Computer simulations show that the proposed scheme can operate properly even in interference-rich fading environments and that it can significantly improve the synchronization performance.     

Phase modulation of a loop phase-locked grid oscillator array

In this letter, we describe a method for phase modulation of a loop phase-locked grid oscillator array and report results obtained in a test bed implementation of the method. The key to the scheme lies in introducing the phase-locked loop (PLL) in such a way that the modulating data stream is introduced in parallel with the loop rather than through it, thereby circumventing the bandwidth limitation of the PLL. The experiment was performed at 4.7 GHz with a phase-locked grid oscillator array. The grid oscillator was successfully modulated by a 1 MHz signal, which is ten times higher than the bandwidth of the phase-locked loop     

窄波束全向接收的自适应天线阵研究

为了实现对短波频段全空域低信噪比信号的良好接收，本文提出了一种窄波束全向接收的知适应天线阵。文中首先简要回顾了自适应天线阵的基本理论，并针地短波波段频程较宽的特点，提出了一种接收信号频率决定阵元间距的阵元间距动态可变组阵方案，文末通过计算机仿真比较了该方案实现的窄波束全向接收自适应天线阵和常规短波天线阵的性能。     

Fault-tolerant communications for wafer-scale integration of a processor array

This paper describes schemes for introducing fault-tolerance into a two-dimensional orthogonal array of cells with nearest neighbour communication paths. The schemes are designed to tolerate a large number of faults and are therefore applicable to the yield-enhancement of large-area VLSI circuits. Simulation results are presented which show the superiority of the schemes over previous proposals and indicate that the nearest neighbour interconnections need not be a barrier to the desirable goal of integrating an array computer onto a whole-wafer circuit.     

频率方向图复合可重构寄生单极子天线阵列

提出了一种能应用于无线通讯系统的新型介质支撑开关寄生阵列天线。基于八木天线原理,天线可以实现频率及方向图的复合可重构。所引入的开关用来切换不同状态的工作频率并实现方向图的扫描。地支结构用来改善天线的阻抗匹配并展宽频带。测量结果表明：天线阵列可以在保证回波损耗小于-10 dB的情况下完全覆盖1710~1880 MHz、1850~1990 MHz及2400~2480 MHz三个移动通信频段,并可以方便地实现频率切换及方向图扫描。     

CW operation of a cleaved-coupled-cavity array of phase-locked GaAlAs lasers

Tunable single-longitudinal-mode operation has been obtained at power levels up to 50 mW from a continuously operating cleaved-coupled-cavity array of phase-locked diode lasers. In addition, conversion of a multilobed to a single-lobed radiation pattern was observed as a function of current supplied to the control segment of the coupled cavity.     

Dual-band six-element switched parasitic array for smart antennacellular communications systems

Simulation results for a dual-band switched parasitic smart antenna array designed for cellular communications systems are presented. The array consists of six loaded monopole elements on an infinite ground plane and offers five switched directions equally spaced through 360°. At 900 and 1900 MHz, the 10 dB bandwidths are 15 and 13%, respectively. The antenna covers the azimuth plane with a maximum gain of 4 dBi and a minimum gain of 2 dBi. The front-to-back ratios of the radiation patterns are better than -15 dB. The design is robust in terms of manufacturing and environmental tolerances