An analysis of the performance of a handset diversity antennainfluenced by head, hand, and shoulder effects at 900 MHz .II.Correlation characteristics

For pt.I see ibid., vol.50, no.3, p.830-44 (2001). In Part I of this two-part paper, we described the effective gain characteristics of the handset diversity antenna comprising a retractable whip antenna and a built-in planar inverted F antenna (PIFA). In order to achieve a high diversity effect, the correlation between the diversity branches must be small while at the same time maintaining a high effective gain, and this is contained in this paper. Further analysis includes an evaluation of the diversity gain with which the diversity effect shown by the analyses of the effective gain in Part I and the correlation in Part II is described. In addition, the mechanism for obtaining a small correlation coefficient is clarified by investigating the amplitude and phase radiation patterns when the whip length and the body inclination angle are changed. From these we obtain various numerical results that provide sufficient insight for design purposes. The validity of the analytical results is verified by an experiment in an indoor radio wave propagation environment     

A diversity antenna for very small 800-MHz band portable telephones

A diversity antenna comprising a short whip antenna top loaded with a small cylinder and a new built-in antenna has been developed for very small portable telephones in the 800-MHz band. Wire-grid analyses and whip antenna experiments yielded good radiation characteristic results when the equivalent electrical length of the whip antenna equalled a half wavelength. The built-in antenna features extreme compactness, its size being one-third that of a conventional planar inverted-F antenna. The characteristics were investigated experimentally, and an antenna of 3.5 cc volume with a gain of -1 dBd and a bandwidth of 30 MHz was designed at 879 MHz. Finally, the diversity characteristics were subjected to field measurements and a diversity correlation of 0.26 was obtained     

A novel electromagnetically coupled microstrip antenna with arotatable patch for personal handy-phone system units

In this paper, we propose a novel electromagnetically coupled microstrip antenna with a rotatable patch to overcome the problems associated with the conventional whip antenna for the personal handy-phone system (PHS). The structure of the newly developed antenna installed in actual PHS units is described. Its fundamental characteristics such as radiation pattern, bandwidth, and gain are shown. The performance of the antenna in actual propagation environments is also clarified. It is shown that this novel antenna is superior to the conventional whip antenna and achieves efficient performance in commercial PHS service     

智能天线和空间分集接收技术

智能天线和空间分集接收技术是主要的两种空间信号处理技术。本文从传播路径的无线传输特性、空时信道模型以及不同环境的多径特性出发,分析了CDMA系统存在的主要问题以及智能天线和空间分集接收技术的工作原理,着重比较了这两种技术的区别以及应用场合。     

Design and Performance Analysis of Compact Planar Inverted-L Diversity Antenna for Handheld Terminals

A compact planar inverted-L diversity antenna for handheld terminals is presented. Three diversity antennas operating at 2.15GHz are designed. The isolation is found to be higher than 13 dB and the usable bandwidth is about 13% in measurement. The measured radiation patterns of the proposed diversity antenna attain 2 dBi gain. Furthermore, the diversity performance with mean effective gain (MEG) is evaluated by taking both azimuth and elevation spectrum into account. A closed-form expression for MEG is presented. The effect of some parameters on MEG is analyzed numerically in indoor propagation environments.     

Performance Analysis of a Built-In Planar InvertedFAntenna for 800 MHz Band Portable Radio Units

The pattern averaging gain (PAG) method to estimate the average gain of mobile antennas in a multipath propagation environment is proposed. By using this method and a wire-grid model, the radiation characteristics of the planar invertedFantenna (PIFA) mounted on a portable radio case is analyzed. In particular, the variation of the antenna gain with the radio case dimensions and inclination angle of the radio case during operation is clarified. Also, the effect on antenna patterns of the operator holding the portable radio is experimentally investigated. Based on this analysis, the antenna configuration with the PIFA element mounted on the lateral side of the radio case is found to be most suitable for portable radio units. In addition, an appropriate selection of the radio case dimensions is found to result in further improvements in the antenna bandwidth.     

Radio propagation and anti-multipath techniques in the WINenvironment

The unique characteristics of wireless in-building network (WIN) systems based on microwave radio technology are addressed, focusing on the multipath propagation problem which most distinguishes radio from wired LAN media. This is followed by a discussion of the three principal techniques that have been developed within the radio communication industry to deal with this multipath problem: adaptive equalization, spread spectrum, and antenna diversity. A review of the strengths and weaknesses of each of these techniques reveals that antenna diversity is clearly the preferred choice for use in WIN systems operating in the recently allocated spectrum near 18 GHz. An example of such an antenna system is examined. It is shown how these multiple, directional antenna systems function in three types of environment     

Radio propagation characteristics for line-of-sight microcellularand personal communications

To acquire a knowledge of radio propagation characteristics in the microcellular environments for personal communications services (PCS), a comprehensive measurement program was conducted by Telesis Technologies Laboratory (TTL) in the San Francisco Bay area using three base station antenna heights of 3.2 m, 8.7 m, and 13.4 m and two frequencies at 900 MHz and 1900 MHz. Five test settings were chosen in urban, suburban, and rural areas in order to study propagation in a variety of environments. This paper reports the LOS measurements in different environments, all of which show variations of signal strength with distance that have distinct near and far regions separated by a break point. It was also found that the location of the break point for different frequencies and antenna heights can be calculated based on first Fresnel zone clearance. The regression analysis reveals a slope that is less than two before the break point, while it is greater than two after the break point. This break distance can be used to define the size of microcell and to design for fast hand-off. Beyond the first Fresnel zone break distance the base station antenna height gain was observed to approximately follow the square power law of antenna height     

The elevation angle of mobile radio signal arrival

Field measurements of mobile radio signals have shown that signal arrival is concentrated in elevation angles lower than 16°. This suggests use of an omnidirectional antenna with vertical directivity, instead of the usual whip antenna, to increase average signal strength as a further improvement in the advantages of diversity reception.     

The effect of the human body on radiation properties of small-sized communication systems

The results are presented of an experimental investigation of the effect of the human body on small-sized radio communication systems equipped with whip antennas. For a frequency range of approximately 30 to 150 MHz, the qualitative relations are defined between, on the one band, the space configuration of an antenna system and the operator's body, and, on the other hand, electrical parameters such as impedance, radiation pattern, and especially gain.     

The Elevation Angle of Mobile Radio Signal Arrival

Field measurements of mobile radio signals have shown that signal arrival is concentrated in elevation angles lower than 16°. This suggests use of an omnidirectional antenna with vertical directivity, instead of the usual whip antenna, to increase average signal strength as a further improvement in the advantages of diversity reception.     

A Compact Broadband MEMS-Integrated Diversity System

A multidisciplinary-research effort encompassing compact broadband antenna design, indoor channel characterization, and an RF microelectromechanical-system (RF MEMS) technology with its application to a diversity system for indoor wireless communications is presented in this paper. We first introduce a coplanar waveguide-fed compact wideband antenna and characterize its impedance and radiation characteristics. The antenna has a 42% impedance bandwidth covering the frequency band of 4-6 GHz. Subsequently, a series of experiments are conducted to characterize the diversity performance of a system using three elements of the proposed antenna for nonline-of-sight indoor multipath environments. From these experiments, we evaluate the performance of the diversity system by calculating power correlation coefficients, power imbalance, and diversity gain. Microwave-laminate-compatible RF MEMS process technology, which has been recently developed in the author's group, is used to construct a microelectromechanically switched pattern-diversity antenna on RT/Duroid5870 microwave laminate. Radiation and impedance characteristics of this antenna are provided, and its reconfigurability capabilities for mobile environment are discussed     

Angular power distribution and mean effective gain of mobile antenna in different propagation environments

We measured the elevation angle distribution and cross-polarization power ratio of the incident power at a mobile station in different radio propagation environments at 2.15 GHz frequency. A novel measurement technique was utilized, based on a wideband channel sounder and a spherical dual-polarized antenna array at the receiver. Data were collected over 9 km of continuous measurement routes, both indoor and outdoor. Our results show that in non-line-of-sight situations, the power distribution in elevation has a shape of a double-sided exponential function, with different slopes on the negative and positive sides of the peak. The slopes and the peak elevation angle depend on the environment and base-station antenna height. The cross-polarization power ratio varied within 6.6 and 11.4 dB, being lowest for indoor and highest for urban microcell environments. We applied the experimental data for analysis of the mean effective gain (MEG) of several mobile handset antenna configurations, with and without the user's head. The obtained MEG values varied from approximately -5 dBi in free space to less than -11 dBi beside the head model. These values are considerably lower than what is typically used in system specifications. The result shows that considering only the maximum gain or total efficiency of the antenna is not enough to describe its performance in practical operating conditions. For most antennas, the environment type has little effect on the MEG, but clear differences exist between antennas. The effect of the user's head on the MEG depends on the antenna type and on which side of the head the user holds the handset.     

Identification of Radio Environments in Software Antenna for High-Speed Millimeter Wave Wireless Communication Systems

Different from smart antenna, software antenna can cope with various radio environments by selecting appropriate algorithms. In this paper, we place emphasis on the identification of radio environments in software antenna for high-speed millimeter wave wireless communication systems. According to the major impairments of radio propagation and the limitation of the adaptive algorithms, we give a criterion to categorize the environments. A spatial smoothing method to identify the environments is also proposed.     

Smart antennas for combined DOA and joint channel estimation intime-slotted CDMA mobile radio systems with joint detection

In cellular mobile radio systems, the directional inhomogeneity of the mobile radio channel can be exploited by smart antennas to increase the spectral efficiency. In this paper, a novel smart antenna concept applying receiver antenna diversity at the uplink receiver is investigated for a time-slotted code-division multiple-access (CDMA) mobile radio air interface termed time-division CDMA (TD-CDMA), which has been selected by the European Telecommunications Standards Institute (ETSI) in January 1998 to form part of the Universal Mobile Telecommunications System (UMTS) air interface standard. First, a combined direction-of-arrival (DOA) and joint channel estimation scheme is presented, which is based on DOA estimation using the Unitary ESPRIT algorithm and maximum likelihood estimation of the channel impulse responses associated with the estimated DOA's, which can also be used as an input for advanced mobile positioning schemes in UMTS. The performance of the combined DOA and joint channel estimation is compared with the conventional channel estimation through simulations in rural and urban propagation environments. Moreover, a novel joint data detection scheme is considered, which explicitly takes into account the signal DOA's and the associated channel impulse responses. The link level performance of a TD-CDMA mobile radio system using these novel schemes is evaluated by Monte Carlo simulations of data transmission, and average bit error rates (BER's) are determined for rural and urban propagation environments. The simulation results indicate that, depending on the propagation environment, the exploitation of the knowledge of the directional inhomogeneity of the mobile radio channel can lead to considerable system performance enhancements     

Time division adaptive retransmission for reducing signal impairments in portable radiotelephones

Multiple-antenna receiving diversity was shown previously to be effective in mitigating the effects of random angular orientation and multipath radio propagation for portable radiotelephones. It is shown that time-division adaptive retransmission used with appropriate antenna configurations can also mitigate these effects. The retransmission configurations require fewer antennas than the receiving diversity configurations for a given improvement in relative signal-to-noise ratio (S/N). Cumulative distributions of S/N were determined for adaptive retransmission and diversity using random orientation and multipath propagation models. Distributions of S/N for systems with two antennas at the portable set and two appropriately polarized antennas at the portable radiotelephone terminal (PORT) are similar to distributions for two-branch selection diversity in the fixed-orientation mobile radio environment. Systems with one portable antenna and two PORT antennas have distributions with slopes similiar to two-branch mobile radio distributions but the distributions for the portables range from 3 to 7 dB worse.     

复杂环境下电波传播损耗的测试与仿真

确定性的电波传播特性预测方法为通信装备内场仿真测试中所需的通信链路传播损耗计算提供了一条高效准确的途径。采用外场实地测试和基于射线追踪算法的确定性电波传播损耗预测软件,仿真2种手段对真实环境下某条特定通信链路的传播损耗进行了预测,给出了测试和仿真结果,分析了误差来源,表明了采用基于射线追踪算法的确定性电波传播损耗预测方法对复杂环境下通信链路传播损耗计算的可行性。     

短波地波通信链路分析与计算

短波通信在移动通信、遂行通信中多数使用鞭状天线利用地波进行通信。为评估短波地波传播特性,将短波地波传播模型与天线仿真技术相结合,采用矩量法计算陆地鞭状天线的辐射特性。计算结果表明,对应不同的通信距离,存在一个最佳频段。     

An Enhanced Approach for a Prediction Method of the Propagation Characteristics in Korean Environments at 781 MHz

In high‐speed wireless communications, an analysis of the propagation characteristics is an important process. Information on the propagation characteristics suitable for each environment significantly helps in the design of mobile communications. This paper presents the analysis results of radio propagation characteristics in outdoor environments for a new mobile wireless system at 781 MHz. To avoid the interference of Korean DTV broadcasting, we measure the channel characteristics in urban, suburban, and rural areas on Jeju Island, Republic of Korea, using a channel sounder and 4×4 antenna. The path loss (PL) measurement results differ from those of existing propagation models by more than 10 dB. To analyze the frequency characteristics for Korean propagation environments, we derive various propagation characteristic parameters: PL, delay spread, angular spread, and K‐factor. Finally, we verify the validity of the measurement results by comparing them with the actual measurement results and 3D ray‐tracing simulation results.     

Termination-dependent diversity performance of coupled antennas: network theory analysis

A new analysis of mutually coupled diversity antenna systems is presented that includes the effects of coupling on the radiation pattern and received power. This analysis, based upon the network scattering parameters, makes use of the singular value decomposition to both specify the characteristics of and analyze terminated antenna networks. The approach facilitates a simplified proof of the multiport conjugate matching condition as well as development of expressions for diversity performance as a function of various impedance terminations. Application of the analysis to coupled dipole antennas characterized using full-wave electromagnetic analysis leads to a comprehensive examination of the diversity performance obtainable for such antennas under different termination conditions. The results from this paper reveal that for closely spaced antennas, the termination can play a noticeable role in determining the diversity gain offered by coupled antennas.