An antenna diversity MMIC vector modulator for HIPERLAN with lowpower consumption and calibration capability

The design and performance of a vector-modulator-based phase shifter for high-performance radio local area networks at 5.2 GHz is presented in this paper. Low power consumption is achieved using a 0.6-μm GaAs MESFET process. At a voltage supply of 1.4 V and with a current consumption between 3.5-7 mA, the gain is 0.6 dB and the 1-dB input compression point is -9 dBm. A full 360° phase control range is achieved by combining two of the three vectors, which have phase offsets of 120°, with variable amplitude. Chip size is only 1.3 mm ². The proposed vector modulator applies a new circuit configuration of variable-gain amplifiers to compensate their transmission phase errors. Within a gain control range of 20 dB, the phase error can be reduced to ±3°, which is about a factor of eight better than the results obtained by single FET amplifiers. A simple calibration procedure for the proposed vector modulators is presented to improve the manufacturing yield and to decrease the impact due to temperature changes and aging. A maximum gain error of ±0.8 dB and a maximum phase error of ±7° have been measured after applying this calibration to the designed vector modulator     

An adaptive technique for transmit antenna diversity with feedback

Transmit antenna diversity (TAD) has been employed for third-generation wireless systems. We propose an adaptive technique for TAD with feedback. It is shown that the proposed adaptive technique can efficiently increase the number of transmit antennas without significantly increasing the feedback bit rate under ideal conditions. As a result, we can increase the number of transmit antennas and expect a performance improvement. Unfortunately, the proposed adaptive technique suffers from channel variation and error propagation due to feedback error. From this, the use of the adaptive technique shall be limited: it can be effective for indoor communications and for pedestrians with a reliable feedback channel     

城区LTE 800M天线不同收发模式的应用分析

本文针对LTE 800M天线的两种主要收发模式,结合建设环境、链路预算、建设成本等因素,阐述了在城区不同场景下的选用策略,并通过实际案例进行测试和对比,论证不同模式下网络性能的差异,并对后续应用提出相关建议。     

分布式天线系统混合SC/MRC分集中断概率性能

在频率选择性复合Nakagami/lognormal衰落信道条件下,研究了层叠分布式天线系统(Cascade Distributed Antenna System--CDAS)采用混合SC/MRC分集的中断概率性能.针对中断概率性能,分析了多径密度函数(Multipath Intensity Profile MIP)衰减因子、空时分集维数、活动用户数、每比特平均接收信噪比以及衰落因子对系统性能的影响.仿真表明CDAS系统可以有效对抗衰落,提高系统容量,削弱对数正态阴影衰落影响.     

基于天线选择的自适应OFDM-STBC发射分集

基于空时分组码的正交频分复用技术(OFDM-STBC)是多天线多载波技术,将自适应功率分配技术用于OFDM-STBC,如何在载波和天线间分配能量是个关键问题.将待发射的信息分配到最有利的天线上传输接着利用载波间功率分配的算法进行载波间的功率分配,该算法的目标是使误码率最小.通过量化信道衰落简化了功率分配算法实现;通过量化功率分配因子的方式提高了无线链路的利用率.仿真结果显示:在误码率取0.1%时,对于有4个子载波的系统,较传统的算法,此算法能带来5dB的增益;随着系统载波数目的啬,性能进一步得到提高.     

Least squares frequency estimation in frequency-selective channelsand its application to transmissions with antenna diversity

A new data-aided frequency estimator for frequency-selective fading channels is introduced. The proposed estimator is developed based on a least squares (LS) error criterion and can estimate frequency offsets without the need for channel information. Statistical analysis indicates that the resulting estimate is unbiased and tends to approach the Cramer-Rao lower bound (CRLB). Simulation shows that the proposed LS method is preferable to existing techniques in mobile communications. The application of the LS estimator to systems with transmitter antenna diversity is also considered. In particular, it is demonstrated that the LS method can be successfully applied to third-generation wireless communication systems     

Characterization of a photonic active integrated antenna using a direct off-air transmission technique

This article presents a characterization study of a state-of-the-art 40 GHz mode-locked laser using a hybrid integrated microstrip patch antenna and bias-T circuit. A passive mode-locking range of 300 MHz is measured using this technique by tuning the gain and saturable absorber bias values for a maximum wireless distance of 15 cm. The passive mode-locking signal is detected by a direct off-air method from a photonic active integrated antenna. This signal can be used as a remote local oscillator to downconvert incoming signals as part of a bidirectional system for in-building/campus wide remote antenna units in next generation millimetre-wave radio-over-fibre systems.     

Design of broadband dual-polarized antenna with integrated Marchand balun

A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced(within 0.5 d B) power splitting and consistent(±5°) phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios(SWRs) of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation(> 45 d B) and cross polarization(> 30 d B) over the entire operating frequency band. Moreover, the gain(~8.6 d B) of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system(DCS), personal communications service(PCS) and 3rd generation(3G) applications.     

Successive beamforming,multiuser detection and diversity reception for multicarrier DS-CDMA system with antenna array

Code-Division Multiple-Access (CDMA) systems are interference limited,and therefore efficient interference management is necessary to enhance the performance of a CDMA system.In this paper,a successive beamforming (spatial filtering),linear decorrelating MultiUser Detection (MUD, temporal filtering) and diversity reception structure for uplink multicarrier Direct Sequence CDMA (DS-CDMA) system with antenna array are proposed.By beamforming,the antenna array suppresses interference according to the distinct array signature.Subsequently,linear decorrelating MUD is ap- plied to separate the signals of different users and eliminate Multiple Access Interference (MAI).Finally, the decorrelated signals at different subcarriers that belong to the same user are combined to achieve frequency diversity.Simulation results show that the proposed structure offers significant Bit Error Rate (BER) performance improvement by successively exploiting the space-time-frequency processing.     

Spectral efficiency of distributed antenna system with random antenna layout

The downlink capacity potential of a distributed antenna system (DAS) with random antenna layout is investigated. A low complexity sub-optimal power allocation scheme among transmit antennas is proposed. Simulation results show that with the same antenna density DAS outperforms a co-located antenna system (CAS) in terms of average and outage spectral efficiency.     

Effect of channel-estimation error on QAM systems with antenna diversity

This paper studies the effect of channel estimation error and antenna diversity on multilevel quadrature amplitude modulation (M-QAM) systems over Rayleigh fading channels. Based on the characteristic function method, a general closed-form bit-error rate (BER) for M-QAM systems is presented. The effect of the inaccurate channel estimation on the performance for pilot-symbol-assisted modulation M-QAM systems with antenna diversity is investigated. Simulation results for M-QAM (M = 4, 16, 64, 256, etc.) show that the analytical method can accurately estimate the system performance. Moreover, numerical results show that with the antenna-diversity technique, the BER performance improves significantly, especially in perfect channel-estimation cases. It is also found that the channel-estimation error limits the benefit of antenna diversity. By increasing the length of the channel estimator and the amplitude of the pilot symbol, more accurate channel estimation can be achieved, so that the BER performance is improved.     

Design of an integrated UWB antenna with dual band notch characteristics

A miniaturized couple-line-fed planar ultra-wideband (UWB) antenna is proposed, which has a dual band-notched characteristic as well as two integrated monopoles. Narrowband notches are generated at frequencies of 3.5 GHz and 5.5 GHz using independently controlled bent resonators, whereas the monopoles are designed for radiation at 900 MHz and 2.4 GHz. The proposed design is simulated with full wave solvers and verified with measurements. A good agreement is observed between the simulations and measurements for the antenna's return loss, gain and radiation pattern performances.     

数字矿山矿用融合通信系统的研究与应用

通过结合我国矿山发展需求,根据国家十一五规划“把推进国民经济和社会信息化放在优先位置”、“以信息化带动工业化、以工业化促进信息化”的战略方针,通过利用现代信息技术,实现矿山矿用的数字化融合技术及可持续安全发展,是对我国矿山数字化和信息化发展建设实现资源开发与环境保护和谐统一的重要保障,对我国能源与工业信息化的发展及应用有着重要理论及实践意义.     

一种动磁场磁测系统实现方法的研究与应用

介绍了一种高频下集动磁场的产生、测量、控制于一身的动磁场综合磁测系统的实现方法,较好地解决了传统磁测方法在破坏性和非实时性等方面的缺点。该系统实现的难点及核心部分是高频交流动磁场激励源的设计制作,设计中充分利用了电力电子技术的发展成果,使用全桥逆变电路组成激励源的功率放大电路,激励源的主控部分运用单片机与FPGA配合运行的方案,具有控制合理、监督管理的实时性强等优点。结尾给出一工程实例,较好地说明了该实现思路的可行性和具体的使用效果。     

The impact of antenna diversity in packet data systems with scheduling

It has been observed through simulations of some specific scheduling algorithms that multiuser diversity gains in packet data systems with channel-aware scheduling can be reduced in the presence of any form of link diversity, such as transmit antenna diversity or wideband multipath diversity. We establish that asymptotically, in the limit of large number of transmit antennas and users, the maximum throughput achieved by any optimal scheduling algorithm in the presence of transmit diversity under signal-to-noise-ratio-only feedback can be infinitely worse than that of a system with no diversity. Our results are general and are independent of any particular scheduling algorithm.     

系统级封装的S频段射频收发模块研制

研制了一种小体积的S频段射频收发系统级封装( SIP)模块,内部集成了基于多种工艺的器件。模块接收通道一次变频,发射通道二次变频,内部集成中频和射频本振信号源。模块采用双腔结构,不同腔体之间通过绝缘子进行垂直互连,大大减小了模块体积,模块体积为40 mm×40 mm×10 mm。模块采用正向设计,其主要指标的测试结果为：接收通道动态范围-100~-40 dBm,输出信号0~2 dBm,噪声系数小于等于2.8 dB,带外抑制大于等于50 dBc;发射通道输出信号大于等于2 dBm,二次、三次谐波抑制大于等于60 dBc,杂波抑制大于等于55 dBc,相位噪声在1 kHz和10 kHz处分别小于等于-82 dBc/Hz和-91 dBc/Hz。实测结果与仿真结果基本一致。     

Analysis of sub-THz radiation detector built of planar antenna integrated with MOSFET

In this paper an approach to analysis of responsivity of MOSFET-based detectors of THz radiation has been presented. The authors have analyzed the substrate modes that affect performance of antennas that are always used as a part of detecting structures, and should be accounted for by proper choice of the substrate geometry. Then, a methodology to combine extracted properties of an arbitrary antenna with properties of the transistor channel has been described and employed to estimate responsivity of a detector built of a particular MOSFET integrated with several antenna structures. Finally, example detectors were fabricated and measured using sub-THz radiation sources operating in the combined bandwidth 220–360 GHz. Measurement results were compared with predictions which lead to conclusions on possible levels of the impedance of the transistor channel at these frequencies.