Showing papers presented at "International Workshop on Antenna Technology in 2008"

A Dual Band Belt Antenna

Abstract: A novel wearable antenna for wireless communications is presented in this paper This paper has discussed the possibility of employing a belt buckle as an antenna, bringing benefits such as removability and the ability to hand portable wireless devices from the belt itself The antenna consists of a belt buckle, hinge, denim waist band and electrical connections The antenna was fed by a microstrip transmission line on the denim substrate with the antenna placed on the other side of the textile band The prototype achieves wide band, dual frequency operation and is able to cover the 245GHz and 525 GHz bands necessary for Bluetooth/WLAN and IEEE 80211 standards

A Compact MIMO DRA Antenna

Abstract: Multiple input, multiple output (MIMO) is an antenna technology for wireless communications in which multiple antennas are used at both the source (transmitter) and the destination (receiver). The antennas at each end of the communications circuit are combined to minimize the errors and to optimize the data speed. MIMO-based antennas are of interest in relation to communication such as digital TV, wireless LAN and mobile communications. MIMO arrangements are of particular interest for other communication devices. When applying a dielectric resonator antenna (DRA) type in a MIMO system and using it for the transmission of two or more signals using the same frequency, high coupling often occurs between the different antenna signals. The occurrence of the coupling may seriously degrade the performance of such an antenna. Thus, it would be beneficial to provide a DRA that can be used to simultaneously transmit and receive more than one signal at the same frequency. Also, where the incidence of coupling between these antennas, signals is reduced. DAR offers several advantages such as wide bandwidth, small size, ease of fabrication and high radiation efficiency. This paper presents characteristics of DRA antenna for 2.6 GHz (UMTS band 7).

Considerations for Reconfigurable Multi-Standard Antennas for Mobile Terminals

Abstract: Tomorrows mobile terminals shall be multi-standard platforms for various kinds of wireless applications. So far, nowadays mobiles consist of a combination of different separated modules e.g. for GSM, for Bluetooth, WLAN, etc.. Along with these different modules typically separated antennas are use, such as one for GSM/UMTS and another one for Bluetooth and yet another one for FM radio. Currently the design is heading towards multi-standard RF modules that combine several standards or operate on the principle of a software defined radio. Hence, an ubiquitous antenna module that can be attached to such a multi-standard module is required. However, different to the software algorithms and the integrated circuitries, an antenna is still bound to its physical size in terms of wavelength in order to operate efficiently. As the operating frequency of the applications under discussion range from approx. 100 MHz to 2.5 GHz standard antenna concepts for mobile terminals cannot be use because of the large bandwidth and the physical antenna size at low frequencies. The research presented in this paper intends to analyze basic requirements for such an antenna module to operate sufficiently and to propose an applicable concept under the typical constraints of consumer electronic applications and mass production issues.

Broadband Small Antenna for Portable Wireless Application

Abstract: A broadband compact antenna is implemented by modifying the full ground plane metamaterial antenna. The strip matching ground is used to enhance the impedance matching by 800% compared to the full ground plane case while maintaining its compact size as 1/10 lambda0 by 12 size of antenna ground plane. Planar inverted F antenna (PIFA) is also known for its compact size and its capability to easily operate at multiple frequencies. The simulated and measured results demonstrate that the proposed antenna should be a potential candidate to use in the modern wireless communication system.

Implanted Planar Inverted F-Antenna for Cardiac Pacemaker System

Abstract: This paper proposed a PIFA with an artificial cardiac pacemaker for use of MICS The calculation model is composed of the PIFA and the pacemaker embedded in the 2/3 muscle-equivalent phantom The distance between the surface of the phantom and the antenna is changed and the model is numerically analyzed by use of the FDTD method Numerical results show that as the distance d increases, the real part of the input impedance and the resonant frequency shift to the lower due to the high permittivity and conductivity of the human tissue However, the proposed antenna resonates well at 402-405 MHz band when the distance d is 6, 9, 12 mm According to the radiation characteristics, the maximum gain is about -28 dBi Moreover, the antenna is fabricated and the input characteristic is measured in the developed 2/3 muscle equivalent phantom The results show that the fabricated antenna works well at 400 MHz band From these results, it is expected that the proposed antenna can be used as the implanted antenna for MICS

A dual spiral antenna for Ultra-wideband capsule endoscope system

Abstract: In this paper, a dual spiral antenna for ultra-wideband capsule endoscope system is proposed. Since a capsule endoscope system which transmits real-time image data in the body should have ultra-wideband characteristic, an ultra-wideband antenna is suitable for this system. When an antenna is used as capsule endoscope system, a small sized antenna is required because capsule is small enough to be swallowed. For these two conditions, the proposed antenna has dual resonance structure which is composed of two different spiral elements and single feed wire connects these two elements. The bandwidth of the proposed antenna is 411~600 MHz (189 MHz) for VSWR<2 which means the fractional bandwidth of 37.8% and it has isotropic radiation pattern. The height of the proposed antenna is 7 mm and diameter is 10 mm. Because of ultra-wideband characteristic and small size, the proposed dual spiral antenna is suitable for ultra-wideband capsule endoscope system.

Performance of a Multiband Diversity Antenna with Hand Effects

Abstract: The investigation of user interaction presented in this paper focuses on the comparison between the free space and data mode diversity performance of a tri-band "stick" phone size prototype in the uniform 3D propagation environment. A state-of-the-art phantom hand from IndexSAR is used to hold the diversity prototype in the data mode position.

Miniaturisation of Printed Disc UWB Monopoles

Abstract: In this paper, the miniaturization of a printed circular disc monopole antenna is investigated. It is shown that by halving the original antenna and adjusting the coplanar ground plane width, an even wider impedance bandwidth at the lower end can be obtained. Furthermore, a clear physical explanation is provided to illustrate the mechanism of this type of half circular disc antenna.

Rectangular Patch with Parasitic Folded Dipoles: A Reconfigurable Antenna

Abstract: In this paper, the tuning and steering of a rectangular patch antenna is controlled by switching the patch and folded dipoles configuration. This reconfigurable antenna is controlled by the changing the voltage across a number of P.I.N. diodes in the parasitic elements. This antenna with the associated RF control unit forms a reconfigurable antenna which provides one solution to a number of communications problems.

Behavior of Mobile Terminal Antennas near Human Tissue at a Wide Frequency Range

Abstract: In this paper, the behavior of the impedance bandwidth, SAR and radiation efficiency of mobile terminal antennas are studied by FDTD-based simulations at a wide frequency range, from 0.6 GHz to 6 GHz. The used models comprise a basic coupling element based antenna structure placed beside a simple dielectric block modeling the user. The results of this paper give novel information about the behavior of the bandwidth, SAR and radiation efficiency of mobile terminal antennas near the user. It is shown that even if the resonance frequency changes when dielectric material is brought close to the antenna, the frequency responses of the bandwidth or SAR do not necessarily change accordingly. It is shown also that the locations of the SAR maxima strongly depend on the permittivity of the nearby material. Close relations between the current distribution of the chassis of the antenna and the peak SAR locations are found. The results of this paper give novel information which can be utilized when designing antennas with as low interaction with the user as possible.

Body Loss Measurements of Internal Terminal Antennas in Talk Position using Real Human Operator

Abstract: Measured results of three typical internal mobile phone antennas held in talk-position by a real human operator are presented. Depending on exact placement of index finger, frequency band and type/position of radiator, total body losses ranging from 6-26 dB have been measured. In all cases, the absorption loss was much more significant than the mismatch loss. The monopole (off-ground) antenna was more affected by the head+hand than the PIFA antennas, in particular for the common placement in the bottom of the phone.

High-impedance Surface with Nonidentical Lattices

Abstract: An HIS with nonidentical lattices and its reflection properties are investigated and discussed. Using a linear reflection phase gradient from pi/2 to pi/2 with pi10 step with unit cell index across face, the surface can steer a reflected beam to 20.2deg in thetas. The pattern of the electromagnetic field reflected with the normally incident y-polarized wave is analyzed and experimented.

A Cavity-Backed Slot Antenna for On-Body BAN Devices

Abstract: In this paper, a cavity-backed slot antenna for on-body BAN devices has been investigated. The electric field distributions inside and around the human body are numerically analyzed by the use of the FDTD method. According to the results, in the region on and near the human body, the dominant component of electric field is vertical to the body surface, and the propagation mode is assumed to be creeping wave. On the other hand, in the region inside the human body, dominant component of electric field is horizontal to the body surface, and the propagating direction is almost vertical to the body surface. Furthermore, in order to confirm the validity of the simulated results, measurement of the electric fields around the biological-tissue equivalent phantom was performed. The results showed that the measured and simulated electric fields are agreed well, and indicated validity of the simulation. As a farther study, antenna design will be investigated in view of properties of the BAN system.

Analysis and design of a UHF RFID tag antenna with a Split Ring Resonator

Abstract: In this paper, the UHF RFID tag antenna which has a SRR as a radiating part and inductively coupled feeding method are analyzed and designed. By using a SRR, the antenna size can be reduced and using an inductively coupled feeding method, we can obtain a wide bandwidth and a simple matching technique to directly attach to a tag chip. Also equivalent circuit model of the tag antenna is presented and unknown variables are analyzed and checked. Therefore the tag antenna can be designed for various tag chips and frequency ranges.

Design of a Novel Rectangular Patch Antenna with Planar Metamaterial Patterned Substrate

Abstract: In this paper, we present a novel microstrip patch antenna specifically designed using planar metamaterial patterned substrate. It is developed based on an ordinary patch antenna, and isolated triangle gaps and crossed strip-line gaps are etched on the metal patch and ground plane respectively. This patterned substrate was demonstrated in literature to have left-handed characteristics. In this way, the wave propagating along the patch is strongly enhanced, and the working band is also significantly broadened from a few hundred MHz to a few GHz. Numerical simulation results show that this new patch antenna possesses several desirable characteristics, for instance, high efficiency, low loss and low VSWR. Also, practical experimental data show a good agreement between the simulation and measured results. It is also found that by using this antenna, most energy is radiated in the horizontal direction for specifical applications within the whole working band, while the vertical radiation being suppressed, which overthrow the characteristic of conventional patch antenna.

Ultra-Wideband Antennas with Miniaturized Size, Reduced Ground Plane Reliance, and Enhanced Diversity

Abstract: This paper reports the techniques applied in developing high performance UWB antennas with miniaturized size, reduced ground plane reliance, and enhanced diversity The fundamental idea about the design with reduced ground plane reliance is first reviewed Next, the miniaturized antenna design with less ground plane effect is introduced Last, the antenna which features the small size, less ground plane dependence, and also capable of providing enhanced diversity performance is presented

UWB Antennas and Their Applications

Abstract: The UWB antennas are proposed for applications of communication systems, various kinds of antenna test ranges, and high resolution microwave imaging. The narrower instantaneous bandwidth of UWB antennas will degrade the performance of the above applications. By using different characteristic of geometries, structures and sizes, good impedance bandwidth and instantaneous bandwidth can be achieved for these UWB antennas. In this paper, the design of various kinds of UWB antennas with wider instantaneous bandwidth will be discussed. Results of simulation and measurement of these UWB antennas will be presented. The application of these antennas is used as the feed to replace the traditional narrowband feeds for the antenna test ranges (far field range, near field range, and compact range). The test results of double ridge horn antenna measured by the antenna test ranges with either various kinds of narrowband feeds or a single UWB antenna are quite agreed.

Three Fast Ways of Measuring Receiver Sensitivity in a Reverberation Chamber

Abstract: The traditional way of evaluating receiver sensitivity is to measure the Total Isotropic Sensitivity (TIS) in an anechoic environment. Very few wireless terminals with small antennas are used in an anechoic environment. This paper will describe three alternative methods to measure the receiver sensitivity in a reverberation chamber, each of which can be done in less than 10 minutes which is much faster than measurements in anechoic chamber. The fastest method is the average fading sensitivity AFS that in contrast to TIS also be used to measure receiver sensitivity of multi antenna terminals for antenna systems with diversity and MIMO capability. The paper includes the first published TIS and AFS results for WCDMA terminals obtained in a reverberation chamber. The agreement to TIS measurements in anechoic chambers is shown to be good.

Cylindrical Transmission-Line Cloak for Microwave Frequencies

Abstract: We present design and simulations of a cylindrical electromagnetic cloak which is based on a method employing periodic meshes of transmission-line networks. The cloaked object can be a connected or non-connected mesh of inclusions composed of an arbitrary material. In the example case studied in this work, we cloak a cylindrical mesh of rods made of a perfect electric conductor. Since the period of the cloaked object's inclusions is much smaller than the wavelength of the impinging radiation, the cloaked object is effectively impenetrable to the electromagnetic fields. When placed inside the proposed cloak, the total scattering cross section of the system is shown to be highly reduced in a large bandwidth, when compared to the case without the cloak.

Removing the effect of antenna matching in isolation analyses using the concept of electromagnetic isolation

Abstract: Isolation between antennas in a multiantenna terminal plays an important role in the performance analysis of wireless systems. When comparing different methods for increasing isolation between the antennas, it is important to note that isolation depends strongly on antenna matching. The effect of matching on isolation can be removed by numerically matching two antennas simultaneously. The resulting isolation is called electromagnetic isolation and it gives the worst-case isolation between the antennas. An example of the application of this concept to the analysis of ground plane slots is presented. It is shown that the phase information in scattering and impedance matrices is essential to obtain reliable values of the electromagnetic isolation.

Design of a Novel Multiband Planar Inverted-F Antenna for Mobile Terminals

Abstract: In this paper, we propose a PIFA based multiband internal antenna that can support seven frequency bands. The antenna is designed to operate at GSM (Global System for Mobile Communications, 880-980 MHz), PCS (Personal Communication Services, 1880-1990 MHz), UMTS (Universal Mobile Telecommunications System, 1.9-2.17 GHz), WiBro (2300-2390 MHz), Bluetooth (2.4-2.48 GHz), S-DMB (Satellite-Digital Multimedia Broadcasting, 2.630 ~ 2.655 GHz) and WLAN (Wireless Local Area Network, 5.16 ~ 5.5 GHz) frequency bands. Multiple frequency bands have been realized by using slots and quarter-wave length resonating strips. A matching stub and multiple short circuiting strips are utilized for improving impedance matching across the targeted frequency bands. A prototype antenna is fabricated and characterized by measuring return loss and radiation patterns. Comparison of the measured and simulated results is given in the paper.

Multi-Ring Unit Cells for Increased Phasing Range in Single-Layer Microstrip Reflectarrays

Abstract: In this paper, we investigate planar antenna elements in the form of multi-rings of square and circular shapes, and explain the concept behind their increased phase range in a unit cell of a single layer microstrip printed reflectarray. It has been shown that the extended phase range can be obtained by utilizing similar in shape, but different in size, resonant elements. Using this principle it has been shown that two resonant elements forming a unit cell can double while three elements can almost triple the phasing range of a single resonant element unit cell, while the slope of the phase response remains almost unchanged. The issue of bandwidth improvement has not been considered. However, this can be achieved using thicker substrates similarly, as in the multi-layer approach.

A study on compact antennas and antenna miniaturization for handsets

Abstract: The compact antennas with balanced effect have been introduced with the change of their configuration. These antennas are effective to mitigate the antenna performance degradation due to the human body effect and also have flexible adjustment of antenna impedance and capacity of wideband and multi-resonance characteristics. Second, a downsizing technique of antenna for handset by utilizing a magnetic material has been investigated. Suitable configuration and arrangement of magnetic materials were found by the experiment and simulation. In a result, it was found that approximately 40% miniaturization of PIFA is possible at 900MHz and 2GHz band.

Ground Plane Effect on the Performance of a Butterfly-Shaped UWB Monopole

Abstract: The butterfly-shaped monopole antenna proposed has provided good impedance matching across the UWB band of 3.1-10.6 GHz. The antenna design consists of a novel butterfly-shaped monopole above the ground plane. The antenna has two circular or elliptical wings which are connected to the two edges of a conducting plate. The wings may form different angles with the ground plane. The radiation patterns for the proposed antenna have been studied in detail in terms of the co- and cross-polarization performance in the x-z and y-z planes. Stable radiation performance over the entire UWB frequency range has been achieved. The design has been validated by both simulations and measurements. Also, this antenna is capable of providing high gain and transmitted pulses with little distortion for UWB applications.

Capacitively-Loaded Loop Antenna for Multi-Band Mobile Handsets

Abstract: Due to the low profile and the simple structure, the planar monopole antennas and the planar inverted-F antennas (PIFA) have been very attractive in the mobile handset applications. Although the planar loop antennas possess similar features, they have not been discussed extensively. Moreover, the urging requirement for multi-band operations makes the handset antenna design more and more challenging. In this paper, we present a capacitively-loaded loop antenna with a low profile, simple structure, and multi-band capabilities. The operation principles are discussed. A prototype antenna is designed, fabricated, and tested. The impedance and radiation performances are shown to be satisfactory throughout the designed operating bands.

Miniaturization of UWB Antennas and its Influence on Antenna-Transceiver Performance

Abstract: A modified small-size tapered monopole antenna is optimized for ultra wideband applications in co-design with the transceiver. Our optimization procedure aims at finding an antenna not only with low VSWR, but also miniaturizing the antenna at the same time. Our proposed optimization algorithm, real-coded compact genetic algorithm, RCCGA, has lowered the antenna area more than 48% compared to previous work for 3.1 to 11.7 GHz bandwidth operation. Design with the need for co-design and co-integration of the whole system the optimized antenna area is even more miniaturized and this paper explains in detail the trade off between antenna size, antenna performance and transceiver performance.

Diversity in On-Body Communications Channels

Abstract: On-body communication channels are used in an increasing number of applications, including headsets and wristwatch controllers for mobile phones, and systems for emergency personnel and for personal medical support. In channels for such systems the movement of the body causes significant fading, in addition to that caused by scattering from the local environment. This can be mitigated using diversity methods. Measurement results of space, and pattern diversity at 2.45 GHz, using two antenna types is presented and results indicate that useful diversity gain can be obtained, which is dependent on the specific channel and antenna type. A switched beam antenna is also used to estimate ray angle of arrival statistics and results are given. Simulation of channel and antenna performance whilst the body is moving is also an important challenge and progress is also described. The work has been performed at the Universities of Birmingham, Pisa and Bari.

Systematic Uncertainty of Radiation Efficiency Based on Some Formulas for Wheeler Method

Abstract: In evaluating the performance of the small antenna, one of the most important parameters is the radiation efficiency as well as the radiation power. If the input power of the antenna is measured, the radiation power can be determined by multiplying the radiation efficiency by the input power. One of the techniques for measuring the radiation efficiency is the pattern integral method which needs a long measurement time for raising its precision. On the other hand, the Wheeler method is a technique which needs a short measurement time because of requiring reflection coefficients of the antenna under test in free space and shielding which can suppress the radiation from the antenna. However, the Wheeler method faces the problem of having some dips in the efficiency We have studied some solutions of avoiding the dips. However, the uncertainty of the Wheeler method has been hardly reported, as far as the authors know. In this paper, we tried to assess systematic uncertainty of some formulas for evaluating the radiation efficiency of the small antenna using the Wheeler method. As the evaluation formulas are analytically described, the systematic uncertainty for the formulas can be analytically evaluated, too. In this paper, we showed the expressions for the systematic uncertainty. Then, the systematic uncertainty was assessed by using the measured reflection coefficients in free space and the shielding. We discussed the relationship between the measured efficiency and uncertainty.

Development of a Handset Adaptive Antenna Using Phased-Array of Switched-Beam Elements

Abstract: This paper presents the development of a handset adaptive antenna using a constant modulus algorithm (CMA). The antenna is a switched-beam phased array antenna which can assist initialization of CMA. The method to improve convergence property of CMA exploits a beam with maximum received power from several switched-beams of the antenna as an initial beam. A square patch of one wavelength width provides a bidirectional pattern that beam switching can be accomplished by switching a feeding probe position. A single stub is designed to match the input impedance. The signal processing unit is implemented on Field Programmable Gate Array (FPGA). Simulation results in term of signal-to-interference plus noise ratio (SINR) are shown to validate that the proposed antenna has a good performance and is suitable for installation on a handset.

UWB Switched-Beam Array Antenna Employing UWB Butler Matrix

Abstract: In this paper, we show that the design of a UWB Butler matrix can be accomplished using couplers and phase shifters in microstrip/slot technology. As a result of the proposed approach, we present the design of a 4-element switched-beam array antenna operating between 3.1 and 10.6 GHz. An UWB switched-beam array antenna formed by four tapered slot antennas and a 4x4 Butler matrix has been presented.