中等数据率无线通信的实用解决方案(下)

ＲＦ收发器设计 ＲＦ收发器的框图示于图２。系统的要求如下： １．频带９０２～９２８ＭＨｚ,低功率（＜０ｄＢｍ）传输,直接变换ＦＭ。 ２．数据率 ５７．６ｋｂｉｔｓ／Ｓ,全双工。 ３．数据译码／编码－ＡＭＩ。 ４峰值频偏－８０ｋＨｚ。 ５．ＲＦ带宽－３３０ｋＨｚ。 ６．信道数－５。 ７．信道间隔－５００ｋＨｚ。 ８．接收器第－ＩＦ频率－７３．７ＭＨｚ。 ９．接收器第二 ＩＦ频率－１０．７ＭＨｚ。 １０．基准频率一１１．２ＭＨｚ, ± １０ｐｐｍ,１００ｋＨｚ内部频率。 １１．收发信道δ－２１．９ＭＨｚ。 １２．系…     

2.30GHz—2.70GHz锁相环式频率综合技术研究

本文阐述了一个基本的Ｓ波段锁相式频率综合器，频率范围是２．３０ＧＨｚ－２．７０ＧＨｚ，频率步进为５ＭＨｚ，相位噪声指标为￡（１０ｋＨｚ）〈－９５ｄＢｃ／Ｈｚ，杂散抑制优于５０ｄ，输出功率大于１０ｄＢｍ。     

高性能PCS双工器

Ｋ&ＬＭｉｃｒｏｗａｖｅ推出了ＷＳＤ-００１３２／００１３３／００１３４型高性能ＰＣＳ双工器。这三种型号的接收频段分别为１８５０～１８７０ＭＨｚ、１８７０～１８９０ＭＨｚ和１８９０～１９１０ＭＨｚ,它们的发射频段分别为１９３０～１９５０ＭＨｚ、１９５０～１９７０ＭＨｚ和１９７０～１９９０ＭＨｚ。接收带内的插入损耗小于１．５ｄＢ,发射带内的插入损耗小于０．９ｄＢ;所有带内的回波损耗最小为１４ｄＢ,可额定发射１０ＷＣＷ和１００ＷＰＩＰ（瞬时功率）。工作温度范围为０～５０℃,大小为１０６．７ｍｍ×６３．５ｍ…     

元器件快讯

表封式压控振荡器Ｍｉｎｉ -Ｃｉｒｃｕｉｔｓ生产的ＪＴＯＳ -１５５０型宽带表封式压控振荡器的工作频率范围为１１５０～１５５０ＭＨｚ,具有２２～３２ＭＨｚ（典型）的线性调谐特性。此振荡器的典型功率输出为７ｄＢｍ,在１００ｋＨｚ的间隔下具有 -１２１ｄＢｃ／Ｈｚ的低ＳＳＢ相位噪声、 -２０ｄＢｃ的谐波压缩率和０．５～２０．０Ｖ（最小到最大）的调谐电压。这款压控振荡器尤其适用于ＧＰＳ应用系统。咨询编号 :０１１１４０更小的集成式开关国际整流器公司推出了高效、低成本强化ＩＲＩＳ集成开关 ,它将ＨＥＸＦＥＴ功率ＭＯ…     

Ka波段频率合成器

本文介绍了一种基于毫米波谐波混频、中频锁相的Ｋａ波段频率合成器的设计方案及实现结果。合成器的频率范围为２６．５￣４０ＧＨｚ,输出功率大于＋５ｄＢｍ,频率步进值为１ＭＨｚ,相噪指标为（１０ｋＨｚ）〈－６５ｄＢｃ／Ｈｚ,杂散低于－５５ｄＢｃ。     

超高频声表面波压控振荡器

本文介绍了ＵＨＦ频段声表面波压控振荡器的原理、设计与实验结果。实验制作的ＵＨＦ声表面波压控振荡器的工作频率为４１６ＭＨｚ；压控频偏＞４００ｋＨｚ；压控线性度为±３％；输出功率为７～１０ｄＢｍ。     

声表面波VCO的研制

介绍了１５５．５２ＭＨｚ、６２２．０８ＭＨｚ声表面波（ＳＡＷ）、１２４４．１６ＭＨｚ浅体波（ＳＴＷ）压控振荡器（ＶＣＯ）的原理、设计和性能。采用低插损、高Ｑ值的ＳＡＷ延迟线和ＳＴＷ谐振器，高性能微波放大器，变容二极管电移相器，使振荡器具有非常低的相位噪声（＜－１４０ｄＢｃ／Ｈｚａｔ１００ｋＨｚ）、高输出功率（＞９ｄＢｍ）、低温度－频率漂移（＜±３５ｐｐｍ，温度范围：－５～６０℃）、大频率调谐范围（＞４００ｐｐｍ）。     

低插损极窄带声表面波滤波器设计

利用集总参数等效电路模型计算了声表面波双模耦合谐振滤波器的频响．通过改变谐振器各个参量使滤波器指标满足要求．在ＳＴ石英基片上成功研制出中心频率２２８ＭＨｚ，△ｆ－３ｄＢ＝１５０ｋＨｚ，插损为３ｄＢ，阻带抑制小于－５０ｄＢ的铁路专用寻呼机用滤波器。理论计算与实验结果一致。     

声表面波波导耦合双模谐振窄带滤波器

本文利用集总参数等效电路模型计算了声表面波波导耦合双模谐振窄带滤波器的频率响应。讨论了谐振器各设计参量对滤波器性能的影响。在Ｘ－１１２°ＹＬｉＴａＯ＿３基片上实验制作了中心频率１１４ＭＨｚ左右，Δｆ＿（－３ｄＢ）分别为７０ｋＨｚ和４０ｋＨｚ的二极和四极窄带滤波器。对二极滤波器，阻带抑制小于一３０ｄＢ；对四极滤波器，阻带抑制小于一５０ｄＢ；匹配后插损３ｄＢ。理论计算与实验结果一致。     

宽频偏声表面波压控振荡器研究

介绍宽频偏声表面波压控振荡器的实验研究。这种声表面波压控振荡器的工作频率为１８．３～１９．２ＭＨｚ，分四个频段进行数字信号控制，每一频段的压控频偏均大于３００ｋＨｚ，单边带相位噪声优于－１００ｄＢｃ／Ｈｚ／１ｋＨｚ，平均压控灵敏度大于５０ｋＨｚ／Ｖ。     

UHF频段陆地卫星移动通信业务多径效应测量

UHF测段陆地卫星移动业务多径实验于1999年6月至8月间利用日本GMS140E气象卫星为信标,分别在河南郑州至开封高速公路、林州至上党方向公路以及石家庄至阳泉高速公路段进行。地面接收系统和数据处理设备安置于汽车上。此项实验的目的是为地面卫星移动通信系统的设计提供重要的信道参数。本文给出了不同环境下多径效应的累计分布特性以及相应的预测模型。     

The attenuation of UHF radio signals by houses

The results of a measurement program that was conducted to determine the attenuation of UHF radio signals penetrating to the inside of a typical house is presented. This program is part of a study to determine the feasibility of using direct satellite communication to disseminate disaster warning messages. The measurements were made in a manner to determine the building attenuation as a function of frequency, construction type, climate, and the elevation angle to the signal source. Attenuation measurements were made in five cities: Boulder, CO, Duluth, MN, Kansas City, MO Little Rock, AR, and Houston, TX. The measurements were made at three frequencies, 860 MHz, 1550 MHz, and 2569 MHz, using the ATS-6 geosynchronous satellite as a signal source. Most measurements were made on two principal house types; wood frame with a wood outside surface, and wood-frame with a brick-veneer outside surface. The average measured building attenuation for all houses and all frequencies was 6.3 dB.     

Vesicoureteral reflux in children: a phantom study of microwave heating and radiometric thermometry of pediatric bladder

We have investigated the use of microwave heating and radiometry to safely heat urine inside a pediatric bladder. The medical application for this research is to create a safe and reliable method to detect vesicoureteral reflux, a pediatric disorder, where urine flow is reversed and flows from the bladder back up into the kidney. Using fat and muscle tissue models, we have performed both experimental and numerical simulations of a pediatric bladder model using planar dual concentric conductor microstrip antennas at 915 MHz for microwave heating. A planar elliptical antenna connected to a 500 MHz bandwidth microwave radiometer centered at 3.5 GHz was used for noninvasive temperature measurement inside tissue. Temperatures were measured in the phantom models at points during the experiment with implanted fiberoptic sensors, and 2-D distributions in cut planes at depth in the phantom with an infrared camera at the end of the experiment. Cycling between 20 s with 20 Watts power for heating, and 10?s without power to allow for undisturbed microwave radiometry measurements, the experimental results show that the target tissue temperature inside the phantom increases fast and that the radiometer provides useful measurements of spatially averaged temperature of the illuminated volume. The presented numerical and experimental results show excellent concordance, which confirms that the proposed system for microwave heating and radiometry is applicable for safe and reliable heating of pediatric bladder.     

一种宽带宽波束移动终端卫星通信天线

提出一种实用型宽带宽波束移动终端卫星通信天线。该天线采用双臂渐变螺旋以及锥形反射板的结构提高了常规双臂螺旋天线的性能。结合HFSS 软件与理论分析进行了天线结构参数设计,并进行了仿真和实验。仿真结果与测试结果吻合良好。该天线采用左旋圆极化方式,中心工作频率为1. 6GHz,工作频带150MHz,波束宽度大于110毅,且天线结构简单、牢固、易于加工,适合于各类小型移动卫星通信终端,以及高纬度地区的卫星通信。     

Mobile satellite system fade statistics for shadowing and multipathfrom roadside trees at UHF and L-band

Field tests related to planned mobile satellite systems (MSS) were performed, and results that add to the existing database of propagation measurements at L-band (1.5 GHz) are described. They are considered particularly useful in that propagation effects were studied systematically with repeated and controlled runs pertaining to different path elevation angles, road types, and path geometries defining shadowing and line-of-sight modes. In addition, simultaneous L-band and UHF measurements were performed for the purpose of establishing scaling factors applicable to previous UHF (870 MHz) results. The control of the experimental parameters was made possible by using a helicopter as the source platform and a mobile van which housed the receiver     

High-stability L-band radiometer measurements of saltwater

L-band radiometer brightness temperature measurements of a saltwater pond were made as a function of salinity and temperature. A precision L-band radiometer with stability better than 0.1 K per day was used for these measurements. The L-band measurements are in good agreement with three dielectric constant models over a temperature range from 8/spl deg/C to 32/spl deg/C and a salinity range from 25-40 psu. Based on this experiment, these dielectric models will provide an excellent basis for the algorithm development and design of the future National Aeronautics and Space Administration Aquarius satellite mission.     

Fade measurements at L-band and UHF in mountainous terrainfor land mobile satellite systems

Fading results related to land mobile satellite communications at L-band (1502 MHz) and UHF (870 MHz) are described. These results were derived from an experiment performed in a series of canyon passes in the Boulder, Colorado region of the USA. The experimental configuration involved a helicopter as the source platform, which maintained a relatively fixed geometry with a mobile van containing the receiver and data-acquisition system. An unobstructed line of sight between the radiating sources and the receiving van was, for the most part, also maintained. In this configuration, the dominant mechanism causing signal fading (or enhancement) is a result of multipath. The resulting fade distributions demonstrated that at the 1% and 5% levels, 5.5 and 2.6 dB fades were on the average exceeded at L-band and 4.8 and 2.4 dB at UHF, respectively, for a path elevation angle of 45°. The canyon results as compared with previous roadside-tree-shadowing results demonstrate that the deciding factor dictating fade margin for future land mobile satellite systems is tree shadowing rather than fades caused by multipath     

光学遥感基础实验过程

敦煌辐射校正场,是我国为实现对地观测卫星传感器的辐射校正于１９９６年确定的陆地校正场．校正场实验的目的是准确把握场地的遥感光学特性,用于校正模式模型的建立以及实施卫星传感器的校正的同步观测．校正场实验是光学遥感基础实验过程较为系统和完整的范例之一．     

QoS provisioning by power control for video communication via satellite links

Video transmissions over satellite links are sensitive to signal fades because of rain, especially in the tropics. We performed a video‐streaming experiment over a satellite link for 24 days distributed over 1 year to investigate the effects of rain fade. Based on the measurements, models for the relationships between rainfall rate, power level, packet loss, and video quality are proposed. Furthermore, for both uplink and downlink channel, an adaptive closed loop power control algorithm, with a Proportional–Integral–Derivative controller is designed. This is used for the mitigation of the rain‐induced attenuation in order to guarantee a certain level of Quality of Service and Quality of Experience. Simulation results show the effectiveness of the proposed power control solution and its ability to sustain video quality levels in spite of rain fades. Copyright © 2014 John Wiley & Sons, Ltd.