便携式终端天线的分集设计

介绍了天线分集中便携式无线终端设备中天线分集系统的构成、分集天线单元的常用形式、特点、分析方法和设计以及分集信号的最终合成。     

移动台适用的平面型紧凑极化分集天线

给出一种适用于移动台的平面型紧凑极化分集天线。该天线由两个十字交叉的微带分支提供极化分集。每一分支都有单独的微带一垂直探针馈电系统，并在分支上蚀刻有一个细槽以提高两个端口的隔离度。通过电容加载大大缩短了分支长度。利用时域有限差分法，在900MHz频段对该天线进行了分析和优化。天线模型的测量结果与仿真结果基本吻合，在约5％的带宽内两个端口的隔离度大于20dB、回波损耗均低于-10dB。该天线两端口的包络相关系数远小于0．1，能够满足分集的要求。     

移动通信中的天线技术

介绍了移动通信中天线的新技术．阐述了全向高增益天线、多频段天线、极化分集天线和智能天线的实现技术以及在移动通信中的应用。     

移动台智能天线研究进展

本文介绍了适用于移动台的多端口紧凑天集天线和相应的低复杂度分集合并算法。适用于移动的台分集天线要求紧凑的天线结构，端口之间较大的隔离度以及较小的相关系数，低复杂度的算法主枯是通过离散化权值的幅度和相位来减少算法的计算量。     

无线局域网的天线分集技术

本文对分集技术做了简单综述，选择出了比较适合无线局域网的天线分集方法，并举例说明。     

MIMO的天线系统设计

系统地描述了MIMO分集性能衡量指标,并对空间分集、方向图分集、极化分集进行了概念描述。进而根据MIMO系统天线设计的要求和特点,结合新型MIMO系统天线单元和天线阵列,分析了其设计思路,同时重点设计了一种用于MIMO系统的终端阵列天线,即单层矩形切角贴片天线,并对其S 参数和方向图进行了模拟和分析。模拟结果对合理设计MIMO系统发射和接收端天线阵列具有现实意义。     

浅谈移动通信基站天线系统设计

对基站天线的基本原理、天线选型、天线参数设置、天线安装等方面进行了描述，对天线下倾角、分集距离等进行了重点讨论。     

多天线系统中的多用户分集方案的性能分析及比较

在多天线多用户无线通信系统中,可以利用用户之间彼此独立的随机衰落信道的特点,结合随机波束成型技术,或者空间分集技术,或者天线选择技术,获得多用户分集增益。然而不同多用户分集方案的系统性能不尽相同。该文分析了在多输入单输出(MISO)信道中目前几种典型的多用户分集方案的性能,给出系统吞吐率的定量表达式,并综合比较了不同用户数和不同天线数对各种多用户分集方案性能的影响,为实际多天线多用户系统设计提供了有益的参考。     

用于MIMO系统基站的寄生振子开关八木分集天线

提出了一种用于MIMO系统基站的寄生振子开关八木分集天线.采用寄生振子开关八木天线阵列组成基站分集天线系统.该天线系统充分利用基站空间,在Z向进行组阵以获取阵列增益,在水平面则利用天线方向图的可重构性来进行方向图分集.通过MIMO通信平台的外场测试,得到了多天线系统的误码率的实验数据,说明了该基站天线的确具有提高信道容量、降低误码率的作用.     

基于坐标转换法研究三振子圆极化天线

文中通过直角坐标转换的方法，分析了一种三振子天线．通过推导出的解析解，对圆极化天线进行了Matlab仿真，发现该天线在两个坐标平面上都为圆极化场，可以在这两个平面法线方向同时进行极化分集接收，改善通信质量。     

Spatial, polarization, and pattern diversity for wireless handheldterminals

This paper examines the antenna diversity configurations that improve the performance in handheld radios. Experiments using spatial, polarization, and pattern diversity were conducted for both line-of-sight (LOS) and obstructed outdoor and indoor multipath channels that experienced Ricean fading. Antenna separation, polarization, and pattern were varied independently to the extent possible. Envelope correlation, power imbalance, and diversity gain were calculated from the measurements. Diversity performance is measured by diversity gain, which is the difference in signal-to-noise ratio (SNR) between the output of a diversity combiner and the signal on a single branch, measured at a given probability level. Diversity gain increases with decreasing envelope correlation between the antenna diversity branches. However, diversity gain decreases as the power imbalance between diversity branches increases because a branch that has a weak signal has only a small contribution to the combined signal. Diversity gain values of 7-9 dB at the 99% reliability level were achieved in non-line-of-sight (NLOS) channels for all diversity configurations even with very small antenna spacings. The use of polarization diversity reduced polarization mismatches, improving SNR by up to 12 dB even in LOS channels     

Signal correlations and diversity gain of two-beam microcellantenna

The motivation of the present study is to investigate the possibility of using two independently directed antenna beams in a mobile base station to provide diversity gain and reduce fading problems in a microcellular environment. The signal correlation of the individual antenna beams is studied, and it is shown that correlation depends on beamwidth, separation angle of the antenna beams, and the location of the base-station antenna array. Signal correlations have been computed using narrow- and wide-beam antennas in two separate base-station antenna locations. Diversity gains of both antenna types have been optimized by selecting the beam orientations which minimize the signal correlation. The numerical simulations show that a considerable diversity gain can be obtained using this approach     

自适应多天线技术

多天线技术有多种实现模式,不同的实现模式有不同的特点和应用场景。文章首先介绍了波束赋形(BF)、循环延迟分集(CDD)、空间分集(SD)、空间复用(SM)等各种多天线技术实现模式的原理。进而分析了各种多天线模式的技术特征以及他们适合的应用场景。基于这些分析,文章提出了一种多天线模式自适应切换算法,他能根据应用场景或者无线信道特征,自适应地选择最优的多天线模式来发送数据,从而进一步发挥多天线技术的优势。     

Diversity Antenna Design for Wireless Alarm Networks

Printed circuit board antennas degrade considerably when the wireless node is placed on or near metallic surfaces. One such application is wireless alarm network where nodes are placed on a metallic fence. As wireless transmission is regarded as the most expensive operation in terms of sensor node energy, it is more than a necessity to have a good antenna design. We simulate the performances of typical printed circuit board (PCB) antennas with proximity to metallic fence and simulations show that traditional antenna structures exhibit poor performance for these applications. Instead, we propose a low-cost two-antenna diversity system that utilizes two PCB antennas with different radiation pattern coverage. Antenna diversity by means of radio frequency switches was implemented for two configurations: single state antenna selection and equal-gain diversity combination. Diversity gains were calculated for free-space and over-the-fence operating conditions, and the best antenna configuration is suggested for practical applications.     

MIMO系统中的分组全分集全码率空时编码

针对未编码的多输入多输出（MIMO，Multi—Input Multi—Output）系统，提出一种复杂度适中的分组全分集全码率（GFDFR，Group—wise Full Diversity Full Rate）空时编码方案。该方案通过在发送端进行天线分组，各组独立编码，减小全分集全码率（FDFR，Full Diversity Full Rate）编码块的大小从而降低系统编解码复杂度；在频率选择性信道中，进一步对子载波分组进行独立编码，获得频率分集（或多径分集），以适中的复杂度在不降低系统分集度的情况下保证了信息的全码率传输，是一种在MIMO信道中极具实用价值的空时编码方案。     

Pattern Reconfigurable Cubic Antenna

A new single-feed reconfigurable antenna for pattern diversity is presented in this paper. The proposed structure is based on a metallic cubic cavity which radiates through rectangular slots. The pattern reconfiguration is achieved with PIN diode switches by short-circuiting slots in their center. The designed antenna can switch between three different radiation patterns which radiate in a $4pi$ steradian range and can receive any incident field polarizations. A prototype of the antenna, including PIN diodes and operating in the 5 GHz band, has been built to demonstrate the feasibility of the concept. Measurements have been conducted and three-dimensional radiation patterns are provided. Diversity performances are evaluated by calculating the envelope correlation coefficient.      

Transmit Diversity Schemes for WCDMA

Previous work on transmitter antenna diversity has shown that the use of multiple transmitter antennas at the base station results in improved performance due to increase of diversity (path diversity). This happens with no bandwidth cost, even when the signal quality along several paths is poor, but the receiver estimates the channel with accuracy. This paper evaluates the effects of channel estimation errors in the performance of the schemes designated as Space-Time Transmitter Diversity (STTD) and Selective Transmitter Diversity (STD). We consider low to medium signal to noise ratios characteristic of Wideband Code Division Multiple Access (WCDMA) networks. Different fading channel models are considered for comparison between the two schemes. The improvement due to convolutional coding associated with these techniques is also evaluated.     

System Performance of Transmit Diversity Methods and a Two Fixed-Beam System in WCDMA

Downlink transmit diversity modes for WCDMA together with a two fixed-beam antenna array system are compared relative to the single antenna sectorized system in a radio network simulator. The transmit diversity methods investigated are: space-time transmit diversity and closed-loop mode I transmit diversity. Frequency selective (COST 259) and flat fading channels are considered and their impact to speech-only and data-only services is evaluated. A third service, which highlights the system performance of the various advanced antennas, is also investigated.The results in this investigation point out that the diversity gain in flat fading channels is substantial. In frequency-selective fading, the benefits of fixed beam systems is encouraging, whereas transmit diversity methods (especially Space-Time Transmit Diversity) is unsatisfactory.     

System Performance of Transmit Diversity Methods and a Two Fixed-Beam System in WCDMA

Downlink transmit diversity modes for WCDMA together with a two fixed-beam antenna array system are compared relative to the single antenna sectorized system in a radio network simulator. The transmit diversity methods investigated are: space-time transmit diversity and closed-loop mode I transmit diversity. Frequency selective (COST 259) and flat fading channels are considered and their impact to speech-only and data-only services is evaluated. A third service, which highlights the system performance of the various advanced antennas, is also investigated.The results in this investigation point out that the diversity gain in flat fading channels is substantial. In frequency-selective fading, the benefits of fixed beam systems is encouraging, whereas transmit diversity methods (especially Space-Time Transmit Diversity) is unsatisfactory.