Polarization diversity measurements and analysis for antenna configurations at 1800 MHz

In wireless communication systems, multipath interference has a significant impact on system design and performance. Fast fading variations are caused by the coherent summation of multiple echoes from many reflection points reaching the receive antenna. Antenna diversity is one technique that can be used to overcome multipath fading. A test system used to measure the diversity performance of an antenna pair was used to experimentally determine the complex correlation coefficient between the two antenna branches. A local mean estimation algorithm based on the channel mean square error equalization was implemented. Thus, the two parameters that determine the expected diversity gain, i.e., the complex correlation coefficient and the mean level signal difference, were estimated. The test system was used to evaluate the polarization diversity performance of different antenna pairs in Rayleigh and Rician environments, both in the absence and in the presence of a human head phantom.     

Performance of shorted microstrip patch antennas for mobilecommunications handsets at 1800 MHz

We have investigated the application of two different types of novel shorted-patch antennas for mobile communications handsets at 1800 MHz. A single shorted-patch and a stacked shorted-patch antenna offering improved bandwidth are compared with data for a λ/4 monopole. The finite-difference time-domain (FDTD) technique was used to calculate antenna characteristics such as impedance and radiation patterns for two cases: on a handset and on a handset near a (2.5-mm voxel) heterogeneous head model in an actual position of phone use. We also obtained specific absorption rate (SAR) distributions and calculated the spatial peak 1-g SAR values. In addition, the effect on SAR and antenna characteristics of including a block model of the hand was assessed. Similar performance is achieved from the single or stacked shorted-patch antenna with the latter providing greater bandwidth, 8.2% versus 9.4% with the head and hand included. Both antennas reduce the l-g spatial peak SAR value in the head by 70% relative to the monopole. The presence of the hand reduces the efficiency of all three antenna types by approximately 10%     

Experimental Evaluation of Space Diversity Schemes at a Base Station in a Microcellular Environment at 900 MHz and 1800 MHz

The aim of this paper is to evaluate experimentallythe performance of different space diversity schemesat the base station end in a semi-urban microcellularenvironment. The receiving antennas were separated inhorizontal, vertical or compound direction in order toprovide decorrelated signals. The superior receivedsignal was chosen based on the selection combiningcriterion. A measurement campaign was conducted atboth appropriate frequency bands (900 MHz and 1800 MHz) for mobiletelecommunications. Measurements wereperformed along the route containing bothline-of-sight (LOS) and non-line-of-sight (NLOS)paths. The measured data was analyzed and signalcross-correlations, signal mean levels of individualreceiving branches and diversity gains of differentreceiving antenna separations (horizontal, verticaland compound) were evaluated. According to themeasurements, low signal cross-correlations andreasonable diversity gain at the base station end canbe achieved even with 4 separation ofthe receiving antennas in any direction at both 900 MHz and 1800 MHz frequencybands. The obtained resultsalso showed that horizontal, vertical and compoundspace diversity gains are almost the same. Hence,spatially small and variable antenna configurationsfor space diversity reception can be applied at thewall installations in a microcellular environment.     

Propagation of electromagnetic waves at MHz frequencies through seawater

The nature of the ocean environment and its vast size has necessitated the development of sophisticated equipment and techniques for various underwater applications including diver-to-diver communications, ROV/AUV docking, communications and oil and gas explorations. To facilitate scientific exploration a wide variety of systems and vehicles have been developed to operate within the shallow continental shelf region or in deep oceans. For successful underwater electromagnetic (EM) wave operation, knowledge is required of the wave transmission properties of seawater over all distances both short and long. This information is required for such activities such as: sensor systems, imaging, position fixing, measurement of speed, obstacle detection and avoidance, guidance, communication of data/voice and remote control. This paper presents a new approach of EM wave propagation through seawater. The experimental results conducted in the laboratory and the real environment of seawater is presented.     

An experimental evaluation of the performance of two-branch spaceand polarization diversity schemes at 1800 MHz

Determines the mean signal level and envelope cross-correlation of 1800 MHz base station signals received in two-branch spatial and polarization diversity schemes. Measurements have been conducted with the experimental base site located in (i) two urban sites, (ii) a residential area, (iii) a rural area, and (iv) near a motorway. In each location, the effect of the random orientation of a typical mobile radio telephone handset has been studied by examining the characteristics of signals received from a mobile collinear antenna inclined at angles of 0°, 30°, 45°, 60°, and 90° to the vertical. Furthermore, the diversity gain at 90% signal reliability has been evaluated for each diversity scheme by simulating selection, equal-gain and maximal-ratio combining techniques using the recorded signals as inputs. Results have shown that 20λ separation in the horizontal plane or 15λ in the vertical plane is sufficient to obtain a cross-correlation of less than 0.7 for most of the time at 1800 MHz. Similar cross-correlation results were obtained for polarization diversity. When the antenna is inclined at 45°, a 6 dB degradation in signal level was recorded for space diversity schemes. However, the diversify gain is unaffected by tilt and remains unchanged at 5-6 dB for horizontal and 3.5-4.5 dB for vertical separation. For polarization diversity, only a little degradation is experienced because most of the energy lost on the vertical branch is recovered on the horizontal branch. The diversity gain is between 1-2 dB at 0° tilt and increases to 3-5.2 dB at 45°     

Design Template and Measurements for Antenna Planning in an Indoor Radio Environment at 1800 MHz

Recently, the demand for an accurate design on the distribution of the antennas in shopping malls is growing rapidly. To provide a guaranteed coverage inside the shopping malls, mobile operators may have installed a lot more antennas than that is really needed. This over-engineering design has increased the installation and operation cost. Therefore, the need to have a relatively more accurate indoor design is the most requesting goal in the telecommunication industry. The purpose of this paper is to derive an indoor design template, which can facilitate mobile operators to evaluate efficiently the optimized number of antennas and their locations within a premises. A tunnel propagation model is used to represent the propagation loss in an indoor environment. Measurements are also taken to derive the losses of various media. Field tests are finally performed to verify the accuracy of the distribution of RF signal strength predicted by the design template.     

Wideband characterisation of fading outdoor radio channels at 1800 MHz to support mobile radio system design

The characteristics of mobile radio channels place fundamental limits on the performance of mobile radio communication systems. Reliable information about these characteristics are obtained in this paper by analysing wideband propagation measurements, which were performed by using an high performance wideband channel sounder in mountainous areas in the German Alps and in typical urban areas in Munich. In addition to well known results obtained from propagation measurements in similar scenarios [1, 2], novel aspects of practical relevance enable for a realistic analysis of the performance of mobile radio systems in terms of the discussed channel parameters and support a compromise between system costs and the quality of signal processing with respect to the system availability and reliability.     

电力无线专网230MHz和1800MHz关键技术对比分析

电力无线专网是解决电力终端接入网的主要方案。目前有230 MHz和1800 MHz两种基于TD-LTE的技术体制,对两种技术体制从频率、覆盖能力、速率等方面进行了比较。结合电力无线专网的业务特点,分析两种技术各自的优劣势。最后,对两种技术体制从性能、产业链、业务适配性等方面进行了对比小结,给出两种技术体制各自的优劣势和适合的业务承载方式。     

浅谈GSM 900/1800MHz双频组网和优化

目前GSM移动用户数量的迅速增长．使得话务容量与有限的频率资源间的矛盾日益显现。为了进一步提高系统容量,我们采用了跳频(Hopping)、多重频率复用(MRP)、同心圆等各种小区规划的新技术,使小区间隔进一步减小、频率复用更加紧密。但即使这样,也仍然存在着一些话务热点地     

Dielectric spectroscopy of fresh fruit and vegetable tissues from 10 to 1800 MHz.

Dielectric spectroscopy data from measurements on tissue samples of nine fresh fruits and vegetables were used to study their dielectric behavior over the frequency range from 10 MHz to 1.8 GHz at 5 to 65 degrees C. Dielectric constant and loss-factor data are presented graphically for apple, avocado, banana, cantaloupe, carrot, cucumber, grape, orange, and potato, showing dielectric constants ranging from values of several hundred at 10 MHz to less than 100 at 1.8 GHz and loss factors on the order of one thousand at 10 MHz to less than 20 at 1.8 GHz. The dielectric loss factor increased consistently with increasing temperature at frequencies below 1 GHz. The dielectric constant increased with temperature at lower frequencies, but it decreased with temperature at the higher frequencies. This reversal of the sign of the temperature coefficient occurred at some point in the frequency range between 20 and 120 MHz where the temperature dependence of the dielectric constant was zero. At frequencies below this point, ionic conduction dominates the dielectric behavior, but above that point dipolar relaxation appears to control the behavior. Multiple linear regression provided equations for calculation of the loss factor in the frequency range from 10 to 300 MHz at temperatures from 5 to 65 degrees C. The data provide new information useful in understanding dielectric heating behavior and evaluating dielectric properties of such agricultural products for quality sensing applications.     

Antenna height dependence of 800 MHz attenuation measured in houses

Signal levels around and within four suburban houses were measured at 800 MHz. The measurements were made from an instrumentation van having erectable 27-ft and 12.5-ft-high antennas. The dependence of attenuation on the height of antennas is needed in designing portable radio communication systems that can accommodate low-power radio communication sets. The height dependence of the trends in the data are consistent with the simple model of reflection from the ground.     

光纤分布系统中G/L1800 MHz合路干扰研究

介绍了光纤分布系统中DCS和LTE信号合路的2种典型设计,研究合路情况下两系统间的干扰问题,对2种合路方案的特点进行分析。最后,根据试验结论提出相应的对策和室分部署建议。     

Modeling of the internal fields distribution in human inner hearing system exposed to 900 and 1800 MHz

This paper investigates the internal electric and magnetic field distribution and the specific absorption rate (SAR) values in a magnetic resonance imaging-based model of the inner hearing system exposed to 900 and 1800 MHz. The internal fields distributions were calculated using the Finite Integration Technique. The estimation of the field values was evaluated along lines passing through that target organ, specifically from the vestibular to the cochlear region and from the apex to the base of the cochlea. The specific findings are: 1) higher internal fields strength and SAR value in the vestibular region rather than in the auditory region, especially for the inner ear closer to the external source; 2) higher internal fields strength in the basal and apical region of the cochlea than in the middle one; 3) local differences in the internal fields distribution and SAR value, comparing the head models including or not the inner auditory system model; 4) results' variability evaluated by changing the head-source mutual position and the dielectric properties of the inner hearing system.     

Temperature dependence of the IR water-vapor absorption

The temperature dependence of both line and continuum absorption of water vapor has been measured in the 9 to 11 μm wavelength range between room temperature and 345 K. The measurements have been performed with the aid of CO₂-laser photoacoustic spectroscopy. The results are discussed and compared with existing theoretical calculations. The temperature dependence of the continuum absorption is in reasonable agreement with predictions from the dimer model.     

无限大导体表面孔缝耦合电磁能量分析

为有效设计电子设备，有必要了解它的最坏电磁工作环境，知道有多少电磁场通过耦合进入系统。采用矩量法分析了任意平面波通过无限大平板上小孔耦合的电磁能量，计算了电磁波通过了小孔耦合能量传输系数。     

微波传能发射系统电磁辐射安全性研究

无线传能系统工作时在周围空间会激发高频电磁场,因此对无线传能系统有较高的电磁兼容性指标要求.文中通过对无线微波传能系统发射天线周围环境的电磁辐射进行建模和分析,以及微波传能基站对周围环境的电磁影响,研究了无线微波传能发射端周围空间电磁辐射的安全性.发射功率为500 W时,通过计算人体头部的比吸收率值,根据国际射频暴露的安全导则,基于理论分析和仿真实验界定了人体电磁暴露的安全区域,划定基站天线主波束、旁瓣、后瓣的安全距离分别为25 m、3 m、2 m,并给出了无线微波传能基站部署的参考方案,对于无线微波传能的实际应用具有重要的参考意义.     

Antenna-gain measurement of handheld terminals at 900 MHz

This paper presents antenna-gain measurements of handheld terminals by the random-field measurement (RFM) method. We have measured the relative antenna gain for different-sized terminal boxes in indoor and outdoor environments to show a gain decrease caused by the box size. The measured results are explained by calculating the average gain of the horizontal radiation pattern. To find the effect by a different human carrier, we also measured the antenna gain for several parameters, such as weight, height, head parameters, and the antenna protruding length from the head. We present a correlation factor of the antenna-gain deviation due to different human carriers     

Field-Strength Measurements of Microwave-Oven Leakage at 915 MHz

Measurements of electric field strength of microwave emissions from microwave ovens in the 915-MHz industrial-scientificmedical (ISM) band are reported. Field strengths were determined at 10 and 1000 ft under laboratory conditions and in the vicinity of two large condominium buildings, containing 385 ovens, in Ft. Lauderdale, Florida. Monitoring equipment consisted of dipole and log-periodic antennas feeding the input of a spectrum analyzer which was interfaced to a minicomputer system for automatic data acquisition and analysis. Under controlled conditions, the tested oven produced maximum field strengths of 123.5 dBuV/m and 81.0 dB,uV/m at distances of 10 and 1000 ft, respectively. Fields as high as 79.0 dBuVm were observed at the Florida location, approximately 500 ft from the buildings. Additional measurements were made of band occupancy and the effects of load placement in the oven, orientation of the oven, and polarization of the emerging fields.