UHF bent-slot antenna system for portable equipment—II: Receiving performance in urban areas

The receiving performance of UHF portable equipment with a bent-slot antenna is studied on the basis of experimental results. The received power increase in the experiment is analyzed by applying the ray and random models to urban area structures. The analysis shows that the bent-slot antenna designed with both vertical and horizontal polarization components has contributed to an increase in received power for some limited angles of wave incidence, as a result of combined reception of cross-polarized waves in an actual environment.     

UHF bent-slot antenna system for portable equipment—I

A newly developed bent-slot antenna for UHF portable communication equipment is introduced. The bent-slot antenna, modified from a half-wave slot element, is designed to have both vertical and horizontal elements and is intended to achieve the improvement of the receiving performance in the urban area. The antenna system characteristics such as current distribution, radiation pattern, gain, and input impedance are investigated both theoretically and experimentally for such parameters as the slot location, the feed point and the width and height of the equipment box. In the calculation, the equipment box is assumed as a rectangular conducting box, and the surface of the box and the slot are modeled by wire grids. The method of moments is applied to find both the electric and magnetic current distributions on wires.     

Hidden Automotive Antenna Performance and Simulation

A new printed antenna system mounted in an aperture in the roof of a car is evaluated for broadcast signal reception from 88-108 MHz. Results from simulations on the vehicle are compared with measurements. The overall performance of the antenna is also compared to common types of vehicle antennas, the roof monopole and a glass based antenna. Overall the average gain of the antennas was better than -3 dBi for vertical polarization and -10 dBi for horizontal while the input return loss was generally better than -2 dB before matching sections in the tuners and comparable with common automotive antennas. The antennas in the roof aperture offer an alternative place to mount antennas on automobiles     

矿用RFID标签天线的分析与设计

本文提出了一种用于矿井人员定位系统的结构紧凑的Hilbert分形倒F标签天线.通过HFSS软件仿真,分别给出了普通倒F天线和Hilbert分形倒F天线的回波损耗、方向图及天线增益.仿真结果表明,这2种天线性能相当,但Hilbert分形倒F天线具有更小的尺寸,更符合矿用RFID标签天线小尺寸、低功耗的要求.制作的Hilbert分形天线经测试,在2.425 GHz的中心频率下,回波损耗为-38.28 dB,带宽为190 MHz.     

利用FDTD方法比较手提电话天线的方向图,输入阻抗及人头部的比吸收率(SAR)(英文)

本文给出了利用FDTD电磁模拟方法对常用的五种个人通信手提电话的天线和人头部组织相互作用的比较研究。在研究中考虑的蜂窝通信手提电话常用的天线种类为单极子、偶极子和倒F型（IFA）天线。不均匀的实际人头模型被用于预测天线特性（包括输入阻抗，方向图和辐射效率等）和对操作作者耦合的电磁效应。天线在人头部的潜在危险影响是用1W辐射功率在人组织产生的比吸收率（SAR）来评估。     

Built-in folded monopole antenna for handsets

A built-in folded monopole antenna for handsets (BFMA) is introduced and investigated. The characteristics of the BFMA are compared with those of a planar inverted-F antenna (PIFA), which is one of the conventional handset antennas. As a result, it has been confirmed that the BFMA has smaller size and wider bandwidth compared with the PIFA.     

Realization of dual-frequency and wide-band VSWR performances usingnormal-model helical and inverted-F antennas

The effects of parasitic elements on the voltage standing wave ratios (VSWR's) of two antennas are investigated. First, a parasitic monopole is used for a normal-mode helical antenna. The VSWR investigation shows that dual-frequency operation is obtained by the parasitic element effects. The dual-frequency operation is revealed as a function of monopole position above a ground plane (monopole height). As the monopole height decreases, the separation of a higher resonance frequency f_H from a lower resonance frequency f_L increases. For a monopole length of L_MP≈0.4λ_HX , where λ_HX is the resonance wavelength of the helix, the frequency bandwidth for a VSWR=2 criterion is 12.5% in the lower frequency f_L region and 5.2% in the higher frequency f _H region, with a frequency separation ratio of f_H/f_L=2.14. Secondly, L-figured parasitic elements are used for an inverted-F antenna (IFA). The parasitic elements improve the VSWR performance. The frequency bandwidth for a VSWR=2 criterion is approximately two times as wide as that of the single IFA. It is also found that bending the horizontal sections of the IFA and parasitic elements contributes to reducing the antenna size while not significantly deteriorating the VSWR bandwidth. The radiation patterns are also presented and discussed     

Accurate DOA estimation using array antenna with arbitrary geometry

The so called universal steering vector (USV) whose locus is equivalent to the array element pattern is applied to the direction of arrival (DOA) estimation by multiple signal classification (MUSIC) algorithm. It is shown that if the USV which includes the effect of the mutual coupling between the array elements is used, the compensation for the received voltage to remove the effect of the mutual coupling is not required any more. The USV for array antennas with arbitrary geometry is derived and evaluated efficiently by using the method of moments (MoM) so that the DOA estimation can be performed accurately by using the array antenna with arbitrary geometry. Numerical examples of the DOA estimation by a dipole array antenna, and an antenna array composed of a monopole antenna and a planar inverted-F antenna (PIFA) mounted on a mobile handset are presented to demonstrate the effectiveness of the proposed method.     

Three-dimensional performance of an LMS adaptive array withinverted-F elements

The performance of an adaptive array with two inverted-F elements is analyzed by using the method of moments. A random signal model for mobile communication in a typical urban area is used. Three-dimensional analysis is applied to give a clear expression of the array output signal-to-interference plus noise ratio (SINR) performance. Also, a factor called SINR pattern angle ratio (PAR) is introduced with which a quantitative evaluation of the SINR patterns becomes possible. By using the PAR, the array performance for different array parameters such as inverted-F antenna (IFA) element orientations, interelement spacings and incident signal directions are computed. As a result, the IFA element is found preferable to a quarterwave monopole array in the assumed signal environment     

Hidden antennas for vehicles

The introduction of new telematics and broadcast systems into vehicles has led to a requirement for multiple antennas that can be hidden from view. This paper commences by presenting the results of simulations to identify the components of a car's structure that influence the radiation pattern of a printed VHF antenna on the rear windscreen. Two dual-band antenna designs are then presented for operation in the 900 and 1800 MHz telephone bands. The first is a planar inverted-F antenna that can be concealed in the bumpers, the second a hybrid structure based on the top-loaded monopole principle and mounted beneath the vehicle's roof.     

A New Class of Miniature Embedded Inverted-F Antennas (IFAs) for 2.4 GHz WLAN Application

A new class of miniature printed embedded inverted-F antennas are proposed for operation in the 2.4–2.485 GHz wireless local-area network band. One of the proposed antennas on FR4 substrate (dielectric constant = 4.4) measures 9.2 mm by 4.1 mm and has a bandwidth of 3.5%. The peak gain of this antenna is 1.4 dBi. An overall size reduction of 70% is achieved compared to a conventional inverted-F antenna. Effects of dielectric loss tangent and material conductivity on the bandwidth and efficiency of these antennas are also investigated. Finally, two embedded antenna elements are analyzed to demonstrate the feasibility for a decoupled antenna pair consisting of switched and combining diversity schemes.     

A planar diversity antenna for handheld PCS devices

A polarization diversity antenna (PDA) is described, and its performance is compared to that of a monopole antenna at frequencies near 900 MHz. Numerical modeling of each antenna, using the finite-difference time-domain (FDTD) technique, incorporates a cellular telephone handset in the vertical orientation, the user's head and hand, and the mobile communications environment. Results indicate that the two modes of the PDA are sufficiently uncorrelated for diversity operation and that, overall, the values of the mean effective gain (MEG), efficiency, and averaged specific absorption rate (SAR) in the head are better for the PDA than for the monopole antenna. However, in terms of the MEG, the PDA is more sensitive than the monopole antenna to the presence of the user's body. For the PDA, most of the power absorbed in the user's body is deposited in the hand, whereas for the monopole antenna, most of the absorbed power is deposited in the head. For both antennas, the MEG depends on the environment (urban or suburban)     

Application of the finite-difference time-domain method to theanalysis of mobile antennas

A review of the finite-difference time-domain (FDTD) method is presented and then employed to model and predict the radiation patterns of three basic configurations of mobile antennas. The directive gain and the input impedance are also calculated. The antennas' configurations considered are a quarter-wavelength monopole mounted on a conducting box, a bent-slot half-wavelength dipole flush mounted on a conducting box, and a quarter-wavelength monopole mounted on the top of an automobile. Three-feed models are discussed and the contour integral is used to model the wire antenna. Transformation of the near field data, resulting from the FDTD, to obtain the radiation patterns is discussed based on the equivalence principle. The radiation patterns obtained using the FDTD compare well with published results     

Pattern diversity for single RF user terminals in multiuser environments

Although the utilization of multiple antennas enhances significantly the performance of multiuser systems, it is prohibitive for mobile devices due to size and power restrictions. In order to alleviate this problem we propose an alternative mobile architecture, built on compact antenna structures with fast beamforming capabilities. It is shown that the proposed architecture combined with a simple training procedure, enhances the average throughput of a multiuser system. The performance is compared with that of user devices with one or three antenna elements employing maximal ratio combining.     

Dual-frequency planar inverted-F antenna

Cellular telephone handsets are now being designed to have dual-mode capabilities. In particular, there is a requirement for internal antennas for GSM and DCS1800 systems. This paper describes a novel planar dual-band inverted-F antenna for cellular handsets, which operates at the 0.9-GHz and 1.8-GHz bands. The dual-band antenna has almost the same size as a conventional inverted-F antenna operating at 0.9 GHz and has an isolation between bands of better than 17 dB. The bandwidths of the antenna are close to those required for the above systems. Good dual-band action is also obtained for other frequency ratios in the range of 1.3-2.4. Studies also show that the dual-band antenna can operate with one or two feeds. A finite-difference time-domain analysis has been shown to give calculated results close to those measured     

Small-sized low-profile antenna to replace monopole antennas

The authors compare the operating characteristics of a compact flat plate antenna with those of a classical quarter-wavelength monopole for portable telephone applications. Similar performances are obtained for both antennas, proving that the low-profile antenna offers an attractive alternative to other monopolar antenna structures for small-sized transceiver units     

宽带平面直角双频单极天线

对于超宽带系统,需要具备可工作频率为3.1~10.6GHz的宽带天线。本文介绍了四种宽带平面单极天线,分别为圆形平面单极天线、平面直角单极天线、平面双频单极天线和平面直角双频单极天线。其中平面直角单极天线兼具宽频和全向特性,平面双频单极天线和平面直角双频单极天线在两个谐振点都具有宽带特性,平面直角双频单极天线在整个频带内水平面的辐射方向图几乎都可以达到全向。     

Phased array antennas for mobile communications

An antenna system including antenna elements and a tracking method is considered a key technology in mobile communication systems. A phased array antenna has been considered the most favorite candidate because of many attractive characteristics such as a low and compact profile, high-speed tracking and potentially low cost performance for vehicle antennas in mobile communications. On the other hand, it has several such disadvantages as beam steering error, loss in feed lines and an increase of noise level in a receiving frequency band. Some of phased array antennas have already been used in satellite communications, and some of them are under development. This paper overviewed basic performance and some examples of phased array antennas for especially satellite mobile communications.     

A radio access system with distributed antennas

This paper analyzes a radio access system that has multiple antennas spatially distributed throughout each cell, instead of a single antenna at each cell. The same signal is simulcast by each antenna in the cell. The signals at a given cell could be multiplexed and modulated for radio transmission at a single node, then transmitted on a coaxial cable distribution system to and from the distributed antennas in a cell. Frequency translation and radio frequency (RF) amplification may need to be performed at each antenna, except for indoor applications with short coaxial cables. This paper presents calculations of signal-to-interference ratios (SIR) and handoff performance for cells with distributed antennas. It is shown that the use of distributed antennas can substantially increase the SIR above a system with a single antenna per cell, and this increase is quantified. It is also shown that increasing the number of antennas results in better overall handoff performance, with a lower number of handoffs and higher received signal power. Minimizing the number of handoffs will reduce the impact of wireless services on network elements     

A Frequency Tuning Method for a Planar Inverted-F Antenna

A novel method is presented for electrically tuning the frequency of a planar inverted-F antenna (PIFA). A tuning circuit, comprising an RF switch and discrete passive components, has been completely integrated into the antenna element, which is thus free of dc wires. The proposed tuning method has been demonstrated with a dual-band PIFA capable of operating in four frequency bands. The antenna covers the GSM850, GSM900, GSM1800, PCS1900 and UMTS frequency ranges with over 40% total efficiency. The impact of the tuning circuit on the antenna's efficiency and radiation pattern have been experimentally studied through comparison with the performance of a reference antenna not incorporating the tuning circuit. The proposed frequency tuning concept can be extended to more complex PIFA structures as well as other types of antennas to give enhanced electrical performance.