一种用于WLAN/WiMAX的小型三频带印刷单极天线

设计了一种满足WLAN和WiMAX工作所需的小型共面波导馈电的三频带印刷单极子天线单元。该单极子天线的设计采用了在倒锥形单极天线表面开缝和在底层加载枝节的结构,使其获得了小型化和三频带的性能。采用基于共面波导的馈电方式,使天线单元具备宽带匹配、结构简单、制作方便和易与其它无线通信设备集成等优点。仿真和实测结果表明,设计的天线单元在WLAN和WiAMX应用的频段上10dB阻抗带宽分别约为610MHz(2.10～2.71GHz,约25.4%),310MHz(3.48～3.79GHz,约8.9%)和360MHz(4.96～5.32GHz,约7%),增益也都在2dB以上,而且在相应工作频点上辐射方向图全向性较好。该天线能满足WLAN和WiMAX的应用所需,具有较高的工程应用价值。     

A novel low SAR water-based mobile handset antenna

The effect of mobile phones on human health is becoming a serious concern in the last decade. This paper suggests a novel water-based cellular phone antenna for reducing the electromagnetic wave radiation toward human head. Two antennas are considered: a single band PIFA operating at 1.8 GHz, and a dual band PIFA operating at 900 MHz and 1.8 GHz. The specific absorption rate (SAR) is decreased up to 0.6 W/kg by limiting the propagation of near electromagnetic fields toward the human head and therefore reducing the current density distribution. The reduction of SAR is carried out by introducing an U-edge wall made of an absorbing water material at each corner of the ground plane.     

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%     

Low-profile ultra-wideband inverted-hat monopole antenna for 50 MHz?2 GHz operation

A compact low-profile UWB monopole antenna is proposed to operate from 50 MHz up to 2 GHz. The developed double-ellipse inverted-hat antenna (IHA) is 15 inches in aperture, 6 inches tall, and achieves 215 dBi gain at 75 MHz (when it is λ/10 in aperture size) in the presence of a finite 21 inch diameter ground plane, with the corresponding frequency being 50 MHz for an infinite ground plane. Calculated and measured gain data are given with reasonable agreement. The tripleellipse IHA is investigated to resolve impedance matching issues at higher frequencies. Gain performance against antenna height and aperture are also studied. The proposed antenna is especially suited for small unmanned aerial vehicles.     

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)     

Ray-optical modeling of simulcast radio propagation channels in tunnels

Simulcast radio propagation channel characteristics inside tunnels are considered in this paper. Based on the image theory of ray optics, a simulcast radio propagation channel in a rectangular tunnel is exactly formulated. As only the field components of horizontal and vertical polarization are of interest in real implementation, the exact formulation is approximated to facilitate the numerical computation. The calculated simulcast radio propagation channels are comparable fairly to measurements at 900 MHz and 2.0 GHz. The validated ray-optical modeling approach is then applied to simulate simulcast radio propagation channel characteristics at 900 MHz and 2.0 GHz to gain deeper insight and better understanding of this type of channels in tunnels. Results show that large fluctuations occur in the capture regions of the distributed antennas for both 900 MHz and 2.0 GHz. The fluctuations in the simulcast regions are larger at 2.0 GHz than at 900 MHz. The root-mean-squared (rms) delay spread is greater in the simulcast regions than in the capture regions of the distributed antennas. This larger delay spread is mainly due to the delay introduced by the transmission medium. Large values of the rms delay spread can be avoided by a careful design of the distance between the distributed antennas.     

Design of a Compact Hexagonal Monopole Antenna for Ultra—Wideband Applications

This paper presents two design compact hexagonal monopole antennas for ultra-wideband applications. The two antennas are fed by a single microstrip line . The Zeland IE3D version 12 is employed for analysis at the frequency band of 4 to 14 GHz which has approved as a commercial UWB band. The experimental and simulation results exhibit good agreement together for antenna 1. The proposed antenna1 is able to achieve an impedance bandwidth about 111%. The proposed antenna2 is able to achieve an impedance bandwidth about (31.58%) for lower frequency and (62.54%) for upper frequency bandwidth. A simulated frequency notched band ranging from 6.05 GHz to 7.33 GHz and a measured frequency notched band ranging from 6.22 GHz to 8.99 GHz are achieved and gives one narrow band of axial ratio (1.43%). The proposed antennas can be used in wireless ultra-wideband (UWB) communications.     

一种两宽带天线共口径的设计

 给出了一种两宽带天线共用一个口径的设计.天线制作在420×200mm²的PCB板上,其中一副天线由阻抗加载的矩形及倒L形金属片构成,两者之间使用了一个低通匹配网络进行连接.此天线实现30~600MHz驻波比小于3的宽带匹配,其中86~110MHz之间为陷波设计.另外一副天线采用开式套筒结构,实现了800~1200MHz驻波比小于2.2的设计.利用天线1的低通匹配网络作为天线2的开式套筒,从而实现了共口径设计.     

用于无线局域网的轴向模螺旋天线设计

根据无线局域网通信天线的要求,设计了三种工作在5GHz频段性能良好的轴向模螺旋天线,其中一种为普通螺旋天线,第二种为加绕寄生螺旋天线,第三种为锥形加绕寄生螺旋天线。通过电磁仿真软件HFSS计算及对结果分析表明,加绕寄生螺旋将改善天线的轴向辐射特性,而锥形结构将扩展天线带宽。     

Modified inverted-L monopole antenna for 2.4/5 GHz dual-band operations

A novel compact modified inverted-L monopole antenna for dual-band operation is proposed. The proposed antenna is designed to operate in 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) bands for WLAN applications in IEEE 802.11a/b and HIPERLAN/2 systems. The method to realise the desired dual-band operation is by introducing a meandered wire and a conducting triangular section to a conventional inverted-L monopole, which results in a small antenna size of 7/spl times/18 mm/sup 2/. Good impedance bandwidth performance is also observed.     

Dual-band monopole antenna with shorted parasitic element

A printed dual-band C-shaped monopole antenna with a shorted parasitic element is proposed. The proposed antenna can provide two separate impedance bandwidths of 156 MHz (about 6.4% centred at 2.45 GHz) and 2048 MHz (about 37% centred at 5.5 GHz), making it easily cover the required bandwidths for wireless local area network (WLAN) operation in the 2.4 GHz band (about 3.4% bandwidth required) and 5.2/5.8 GHz bands (about 13% bandwidth required). Furthermore, the proposed antenna shows a low-profile of 635 mm above the ground plane. Details of the proposed antenna design and experimental results are presented and discussed.     

FDTD computation of temperature rise in the human head for portabletelephones

Temperature rises in the human head for portable telephones were computed with an anatomically based head model at 900 MHz and 1.5 GHz. The specific absorption rate (SAR) in the human head was determined using the finite-difference time-domain (FDTD) method, while a bioheat equation was numerically solved also using the FDTD method. The portable telephone was modeled by a quarter-wavelength monopole antenna on a dielectric covered metal box. The source geometries considered were the telephone barely touching the ear and the telephone pressing the ear, both having a vertical alignment at the side of the head. The antenna output power was set to be consistent with the portable telephones of today: 0.6 W at 900 MHz and 0.27 W at 1.5 GHz. Computed results show that a phone time of 6-7 min yields a temperature rise of approximately 90% of the steady-state value. Application of the ANSZ/IEEE safety guidelines restricting the 1-g-averaged spatial peak SAR to 1.6 W/kg results in the maximum temperature rise in the brain of 0.06°C, and application of the ICNIRP/Japan safety guidelines restricting the 10-g-averaged spatial peak SAR to 2 W/kg results in the maximum temperature rise in the brain of 0.11°C, both at 900 MHz and 1.5 GHz     

A narrow-frame antenna for WWAN/LTE/WiMAX/WLAN mobile phones

In this paper, we present a novel narrow-frame antenna with a size of 75 × 8 × 5.8 mm³ for 5.7 in. mobile phones. The antenna mainly consists of a monopole with four branches that are coupled to a two-branch grounded strip. Our antenna is able to cover more bands than other narrow-frame antennas by excitation of several resonant modes. The improved range of the antenna covers the following eleven bands: LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, LTE2500, LTE3400 (3400–3800 MHz)/WiMAX3.5 GHz (3400–3650 MHz), WLAN5.2 GHz (5150–5350 MHz) and WLAN5.8 GHz (5725–5875 MHz). Another advantage of the proposed antenna is that it does not need any lumped element to match the antenna. The working principles of the proposed antenna are thoroughly studied. A prototype of the proposed antenna is fabricated and measured, with the results in good agreement with the simulation results.     

一种适用于GSM DCS和ISM频段的PIFA天线

移动通信业务的多样化要求多种业务共用一副天线,以节省终端内的有限空间。在平面倒F天线(PIFA)的基础上加载一种新型的缝隙结构,得到一种适用于GSM900、DCS1800和ISMWLAN2.4GHz三个频段的小型宽带移动终端天线。仿真结果表明,该天线在三个频段上的相对阻抗带宽分别达到6.5%、7.5%和3.4%,尤其是在GSM900MHz频段的阻抗带宽比其他同类型天线展宽1倍。该天线具有较好的频率特性和辐射特性,完全适合多频移动通信终端应用。     

Study of the coupling between human head and cellular phone helical antennas

The interaction between normal-mode helical antennas and human head models is analyzed, using both a novel accurate semi-analytical method and finite-difference time-domain (FDTD) simulations. The semi-analytical method is based on the combination of Green's functions theory with the method of moments (Green/MoM) and is able to model arbitrarily shaped wire antennas radiating in the close proximity of layered lossy dielectric spheres representing simplified models of the human head. The purpose of the development of the Green/MoM technique is to provide a reliable tool for preliminary (worst case) estimation of human head exposure to the field generated by different antenna configurations with emphasis on the helical antenna, representing the most diffused antenna type used in modern cellular handsets. Furthermore, the accurate semi-analytical character of the Green/MoM technique permits the accuracy assessment of purely numerical techniques, such as the FDTD, which is currently the most widely used computational method in mobile communication dosimetric problems, since it allows modeling of anatomically based head models. After appropriate benchmarking, FDTD simulations are used to study the interaction between a heterogeneous anatomically correct model of the human head exposed to a normal-mode helix monopole operating at 1710 MHz mounted on the top of a metal box representing a realistic mobile communication terminal. The study of both canonical and realistic exposure problems includes computations of specific absorption rates (SARs) inside the human head, total power absorbed by the head and assessment of antenna performance. Emphasis is placed on the comparative dosimetric assessment between adults and children head models.     

Extremely compact dual-band PIFAs for MIMO application

A MIMO structure consisting of two extremely compact planar inverted-F antennas (PIFAs) (λ/60 x (λ/20 x (λ/60) is proposed for GSM 900 MHz and 2.4 GHz wireless local area network applications. The miniaturisation of each antenna is achieved through a spiral-shaped PIFA and a capacitive load, forming a LC resonator. Both antennas have a good impedance bandwidth of 0.88?0.945 and 2.39? 2.48 GHz for 0.9 and 2.4 GHz band, respectively. The two PIFA antennas are polarised orthogonally to each other, and isolation better than 228 dB is achieved in both bands without any structure etched on the ground. The predicted results are compared with the measured data and good agreement is found.     

Triple-frequency planar monopole antenna for side-feed communication device on GSM/DCS/PCS operation

A novel side-feed planar monopole antenna capable of triple-frequency operation at about 900, 1800 and 1900 MHz is presented. The planar monopole antenna occupies a small area of 6/spl times/31 mm, and is easily made using thin copper. The planar monopole antenna can be side-fed and mounted perpendicularly to the main circuit board of a communication device so that it offers a novel design with a free degree of feed point so as to save device space, resulting in a low profile to the system ground plane. In addition, the obtained impedance bandwidths of the proposed antenna at about 900, 1800 and 1900 MHz can cover the GSM (890-960 MHz), DCS (1710-1880 MHz) and PCS (1850-1990 MHz) bands.     

Miniaturized integrated antennas for far-field wireless powering

This paper describes a series of high-efficiency miniaturized antennas of different sizes that can be integrated with the same wireless-powered RFID chip. Since this RFID chip has power scavenging capability in different ISM bands, several integrated on-chip and off-chip antennas in the three ISM bands of 900 MHz, 2.4 GHz and 5.8 GHz are designed, including one antenna integrated on chip. All proposed antennas are derived from a new planar antenna structure which can be designed toward arbitrary input impedance within a given area constraint. The measurement results for the presented antennas show a different read range. The resulting read range versus antenna size diagram specifies the best operating frequency band for a given read range and occupied area. Though this diagram depends on the chip's specifications like the power-on sensitivity and input impedance, it can be generated for any chip. In addition, the measurement results concerning read range and radiation patterns for the proposed antennas are presented and compared with simulation results, showing very good agreement.     

Signal correlation between two normal-mode helical antennas for diversity reception in a multipath environment

The spatial correlation coefficient of signals received by two normal-mode helical antennas in a multipath environment characterized by Clarke's model is rigorously obtained. A new formula relating the signal correlation coefficient to the mutual impedance is derived. The mutual impedance is defined and calculated in a new manner. Our findings show that: 1) the envelope correlation coefficient of two helical antennas is greater than that of two monopole antennas; 2) the envelope correlation coefficient is dependent on the antenna terminal load and the mutual impedance and an optimal antenna load can be determined to produce the smallest correlation coefficient; and 3) the frequency response of the envelope correlation coefficient resembles that of the voltage standing-wave ratio.