Showing papers presented at "International Workshop on Antenna Technology in 2006"

Antenna for Handheld DVB Terminal

Abstract: For the reception of terrestrial television, traditionally Yagi or whip antennas are used. Due to their large size they cannot be used in the reception of digital television on handheld devices (DVB-H), which operate at the frequency band 470 – 702 MHz. The DVB-H system is under development and small internal antenna solutions for handheld devices are not yet available. Due to the long wavelengths, any antenna placed inside a portable terminal will be electrically small. The antenna volume is the fundamental factor determining its performance. With traditional microstrip antennas such as PIFAs the required bandwidth could not be obtained inside a pocket-size terminal. Therefore, a broadband planar antenna structure for a DVB-H receiver is presented in this paper. The antenna structure is based on the compact coupling element antenna structure [1] that was earlier applied for GSM systems [2].

Enhancing the Performance of Handset Antennas by Means of Groundplane Design

Abstract: INTRODUCTION Mobile devices are in a constant state of evolution given the increasing features and frequencies available worldwide. Today, global handset functionality is becoming an important consideration influencing customer purchasing habits. Industry dynamics have increased the drive for smaller and multi-functional wireless devices. Antenna technology has played a key role in influencing the end form factor of these mobile devices because without the antenna the device is not wireless. The present paper shows a conventional design for dual-band operation (GSM900-DCS1800) and how it can be improved for a quad-band design (GSM850-GSM900-DCS1800-DCS1900) through the FracPlane technique. This technique encapsulates both basic shaping of a groundplane to a more sophisticated space-filling and/or multilevel design for further size reduction and multi-band performance enhancement [1,4].

Non-Foster Impedance Matching for Transmit Applications

Abstract: We give experimental results showing the gain-bandwidth advantages of using non-Foster networks (i.e. containing negative inductors and capacitors) to impedance match an electrically-small antenna to a transmitter. Over a given bandwidth, non-Foster achieves up to 20 dB more transducer power gain than any passive design. The overall power efficiency advantage of non-Foster networks is limited by the required DC bias power. We demonstrate a class-B biasing strategy that, when fully developed, will make non-Foster transmit matching more efficient than any passive design. BACKGROUND

Dual Band Circularly Polarized Equilateral Triangular-Patch Array Antenna for Mobile Satellite Communications

Abstract: The Japan Aerospace Exploration Agency will launch the Engineering Test Satellite VIII (ETS-VIII) in 2006 to support the next generation of mobile satellite communications covering the area of Japan (beam coverage El=38/spl deg/ to 58/spl deg/). In this paper, a satellite-tracking left-handed circularly polarized triangular-patch array antenna is developed for ground applications. The targeted minimum gain of the antenna is set to 5 dBic at the central elevation angle (El=48/spl deg/), in the Tokyo area, for applications using data transfer of around a hundred kbps. The antenna is composed of three equilateral triangular patches for both reception and transmission units operating at 2.50 and 2.65 GHz frequency bands, respectively. The antenna was simulated by method of moments (MoM) analysis, and measurement of the fabricated antenna was performed to confirm the simulation results. The measurement results show that the frequency characteristics and the 5-dBic gain coverage in the conical-cut plane of the fabricated antenna satisfy the specifications for ETS-VIII. A prototype of the proposed antenna system is employed in outdoor experiments using a pseudosatellite and shows good performance from El=38/spl deg/ to 58/spl deg/.

Metamaterials in Antenna Applications: Classifications, Designs and Applications

Abstract: Recently the ancient Greek prefix, meta (means “beyond”), has been used to describe the composite materials with unique features that do not exist in the nature [1]. Reviewing the literature, it appears that various terminologies have been used to classify metamaterials depending on their applications. As an example, “double negative (DNG) material” refers to those materials with effective negative permittivity and permeability, which results into properties such as left-handed (LH) wave propagation and negative index of refraction (NIR). Periodic structures that prohibits the propagation of electromagnetic waves in a certain frequency band for certain arrival angles and polarization senses are classified as electromagnetic band-gap (EBG) structures. Another important category of metamaterials consist of ground planes that exhibit unique reflection characteristics other than conventional PEC, and are defined as “artificial complex ground planes”. Fig. 1 shows the three basic categories of metamaterials, with some representative applications illustrated. This invited-talk paper summarizes the results published by the author and his co-workers on this subject, with most examples addressed on the design and analysis of metamaterials for antenna applications.

A Multi-Band Hybrid Balanced Antenna

Abstract: The design of antennas for small user equipment has for many years relied on the use of unbalanced designs – usually ingenious variants of monopoles and inverted-L antennas. As the size of the equipment is reduced, unbalanced antennas become increasingly problematical because their input impedance and radiation properties become strongly dependent on the size of the groundplane and their position on it.

Electronically Scanned Left-Handed Leaky Wave Antenna for Millimeter-Wave Automotive Applications

Abstract: In the past few years, there has been significant interest in automotive radar for pre-crash safety and adaptive cruise control systems [1], [2] using a millimeter-wave band from 76 GHz to 77 GHz. In the systems, the beam is electronically scanned in the azimuth angle to detect vehicles and obstacles. Wide beam scanning and high gain are required as the radar antenna systems. Furthermore, compact size and low cost are important for automotive applications. The left-handed leaky wave antenna (LHLWA) is able to scan the beam widely because it supports both backward and forward waves [3]. However, the conventional frequency-dependent LWLHAs are not practical for the automotive radar antenna systems. In order to overcome this drawback, much effort has been made in developing the frequency-independent LWLHAs. An electronically and continuously scanned LWLHA using the varactor diodes was presented [4], but the diodes are too lossy to use in the millimeter-wave band. Moreover, it is difficult to fabricate high gain array antennas which have hundreds of unit cells and diodes. As other problems of the conventional LHLWAs, antenna gain is not enough for radar applications because the aperture amplitude distribution of the array antennas cannot be controlled well. We have proposed a novel structure of LHLWA, which can steer the radiation angle at a fixed frequency. The antenna includes a dielectric material, which locally changes its dielectric constant in response to an external stimulus. Liquid crystal has attractive properties such as a low electric command and weak losses in the millimeter-wave band. Moreover, slots are added to the LHLWA to control the aperture amplitude distribution of the array antennas.

Antenna-in-Package Technology for Modern Radio Systems

Abstract: Antenna-in-Package (AiP) technology offers an elegant antenna solution to modern radio systems such as single-chip radios. AiP combines an antenna or antennas with a single-chip radio die into a standard surface mounted device so that the assembly cost and board area of a discrete antenna (e.g. a chip antenna) can be saved. More importantly, AiP provides a platform to codesign the antenna, package, and chip so that the single-chip radio performance can be maximized. In this paper, a mini review of AiP development is first presented. Then the design of a novel antenna in the format of a cavitydown ball grid array package in low temperature cofired ceramic (LTCC) process for 5.7-GHz single-chip radios is described. Finally, AiP designs are mentioned for modern ultrawide-band (UWB) and millimeter-wave radios.

Design of an AMC with Little Sensitivity to Angle of Incidence Using an Optimized Jerusalem Cross FSS

Abstract: In this paper, an angularly stable Artificial Magnetic Conductor (AMC) or High-Impedance Surface (HIS) is proposed The structure is made of the well know Jerusalem Cross Frequency Selective Surface (JC-FSS) placed at the interface of a metal-backed dielectric slab The paper begins by investigating the properties of a structure optimized in a prior work Innovatively, this structure is corrected and changed, and the resultant structure is optimized not completely based on time consuming optimization methods, but by utilizing the theoretical clues presented in another work for the same structure Taking these strategies, just by a simple optimization procedure and some parametric studies, such a structure is obtained that shows better angular stability compared to the initial structure, while having acceptable bandwidth and compact size Periodic method of moments (PMM) is used to analyze and study the proposed planar periodic structure Index Terms—Artificial magnetic conductor (AMC), high-impedance surface (HIS), perfect magnetic conductor (PMC), electromagnetic band gap (EBG) surface, frequency selective surface (FSS)

Improving the RF Performance of Clamshell Handsets

Abstract: The designers of handsets for mobile radio networks are subject to pressures to integrate more and more functionality into handsets whose dimensions, led by the expectations of the market, shrink with each new generation of designs. This pressure is accentuated by the demand for power created by large colour displays and cameras, while the dimensions available for batteries are stringently limited. On examining the link budget for a mobile radio system it is very obvious that the low gain of a typical handset antenna is an area capable of significant improvement. For the network operator the modest RF performance of handsets limits their coverage, while for the user it not only degrades the service they enjoy, but also significantly diminishes battery life (talk time). This article discusses the important interactions between aspects of the design of the handset and the RF performance which can be obtained from it. As will be seen, acceptable RF performance is not just a matter for the antenna designer, but depends on an understanding of the underlying issues on the part of the whole handset design team.

Reconfigurable Single-Armed Square Spiral Microstrip Antenna Design

Abstract: In the past decade, wireless technologies have advanced dramatically [1-2]. Software Defined Radio (SDR) and Multiple-Input and Multiple-Output (MIMO) are two emerging technologies to deliver the desired functionality over a wide range of frequencies and provide dramatic increases in throughput. To support and enable the cutting edge wireless technologies, antenna designs need to meet the dynamic requirements for different frequency operating bands, radiation patterns and polarizations. Reconfigurable antennas are good candidates to meet those requirements. Several researchers have developed multiple reconfigurable antenna designs in various structures to deliver antenna frequency tunability, pattern reformability, and polarization selection with PIN diodes, MESFETs and RF MEMs [3-8]. In this paper, a frequency and pattern reconfigurable single-armed square spiral microstrip antenna is presented. Simulations indicate an average 3-7dBi gain can be achieved with this small single-armed square spiral antenna.

Compact Triple-Arm Multi-Band Monopole Antenna

Abstract: This paper presents a multi-band, compact, lightweight and low-cost monopole antenna suitable for applications in the wireless local area network (WLAN) and DCS1800/PCS1900 bands. The antenna has a thin substrate, small area and is fed by a microstrip line, which can be directly connected with the associated microwave circuits. The computed and measured results for 1.8, 2.4, 4.9, 5.2 and 5.8 GHz band cases are presented.

Dual Band Button Antennas for Wearable Applications

Abstract: A novel structure for wearable WLAN applications is presented. This antenna is a top loaded monopole and is shaped as a button. The antenna is easily disguised and is less sensitive to the clothing fabric than printed patches. The antenna is dual band at 2400MHz and 5200MHz with the omni-directional radiation patterns required for transmission with other wearable devices located both on and off a user’s body.

A Discussion on Small Antennas Operating with Small Finite Ground Planes

Abstract: In the design of small device integrated antennas, there are a number of physical properties that together establish the antenna’s electrical performance characteristics. With small wire antennas, these physical properties include overall wire length, wire diameter, geometry and perhaps most important, the antenna’s overall height and occupied volume. Many times, the performance properties of the small antenna are determined through simulation or measurement, where the small antenna is located on an infinite or large conducting ground plane. With small device integrated antennas, the ground plane dimensions may be less than the operating wavelength and may closely approach the size of the antenna. These factors can substantially affect the performance characteristics of the small antenna. In fact, the ground plane itself becomes an integral component of the radiating structure and must be included in determining the antenna’s effective electrical size. Here, we examine the performance properties of several small antenna configurations located on a device sized ground plane. We consider the relative effects of the ground plane size and the antenna’s location on the ground plane, in terms of how these factors establish the antenna’s performance characteristics.

Low Profile and Wide bandwidth Characteristics of Top Loaded Monopole Antenna with Shorting Post

Abstract: Demands on electrically small antennas are increasing in the field of mobile communications systems, such as satellite navigation systems, cellular systems and wireless LANs. In these communications systems, the antenna radiation pattern is required to be uniform radiation pattern in horizontal plane. A monopole antenna is most popular antenna for such applications because of its simple structure. Currently, in these applications, antennas with low profiles and wide frequency band characteristics are strongly desired.

Fundamental Bandwidth Limitation for Small Antennas on a Platform

Abstract: Classical theory on fundamental gain bandwidth limitation for antennas constrained by their electrical size has been extensively examined, and is collectively referred to here as the Chu theory [1]. However, there are major shortcomings and ambiguities in the Chu theory when applied to real world problems, as pointed out recently by this author [2]. One problem is the case of an antenna on a platform, as depicted in Fig. 1, where the antenna is generally inseparable from the transceiver/platform. In fact, in some designs the main radiator is the platform or transceiver, not the antenna per se. Thus, the extent and size of the antenna become ambiguous. Also, the Chu theory is valid only for high Q (Quality factor). With the platform becoming part of it, the antenna’s effective size is increased and its Q can be lowered beyond the realm of the Chu theory.

Small UHF RFID Label Antenna Design and Limitations

Abstract: Radio Frequency Identification (RFID) is emerging as an unrivalled contender for automatic object identification technology, its adoption being driven primarily by the potential cost savings in the application of the technology to supply chain management [1]. In general RFID system components include RFID labels, Interrogators (transceivers) and backend control and data collection systems [2]. The mass utilization of RFID technology is hindered by the cost of RFID labels. The cost of producing a label can be separated into IC design, IC manufacture, antenna manufacture, antenna and IC assembly, and packaging. Significant barriers to reducing the cost are the lack of a streamlined process for attaching a RFID label antennas to RFID ICs (about 0.25 mm in size) and the cost of manufacturing antennas, which currently cost around 3 4 US cents per label. Hence this paper focuses on low cost passive RFID labels with the aim of reducing passive labels costs.

A Miniature Broadband Dielectric Resonator Antenna (DRA) Operating at 2.4GHz

Abstract: This paper presents a study on a broadband DRA using a new feed technique developed at Antenova Ltd, UK. The DRA is designed to operate at 2.4GHz for IEEE802.11b/g applications and has a length of only 0.12λ. Characteristics of the prototype DRA are assessed using both a Finite Integration Technique simulation and experimental measurements.

A Left-Handed Dipole Concept

Abstract: Left-handed materials, which exhibit simultaneously negative permittivity and permeability, were first investigated theoretically by Veselago in 1968 [1]. Since they were successfully implemented with split ring resonators and wire strips [2], left-handed materials have been applied for microwave applications, transmission lines [3], couplers [4], resonators [5], phase shifters [6] and the like. With regard to antennas, backfire-to-endfire leaky wave antennas [7][8] were developed. An infinitesimal dipole immersed in left-handed material has been studied theoretically, [9], and beyond this there have been no other publications on use of left handed materials for small antennas to the best of the authors knowledge. We propose a new concept involving the use of left-handed material in a small dipole antenna. The concept and simulated radiation properties are presented.

Degenerate Band Edge Crystals and Periodic Assemblies for Antenna Applications

Abstract: Artificially manufactured materials such as periodic band gap structures are of growing interest because of their extraordinary characteristics. Regular band gap (RBG) photonic crystals have already been considered for RF applications, such as filters, waveguides, etc. [1]. One of the fundamental properties of photonic crystals is the vanishing group velocity, ω ∂ / 0 = ∂k of the supported propagating mode at the band edge (Fig. 1a). Such wave slow down results in the accumulation of electromagnetic energy leading to field amplitude growths. However, the transmittance of the ordinary band gap crystals vanishes at the band edge. Therefore, ordinary photonic crystals are not suited for operation close to the band edge for radiating structures.

Composite Right/Left-Handed Metamaterial Antennas

Abstract: The transmission line (TL) approach to composite right/left-handed (CRLH) metamaterials has led to various novel microwave devices [1]. In particular, the extraordinary properties of the CRLH metamaterial have been used to realize antennas not possible with conventional materials alone. The purpose of this paper is to review the CRLH metamaterial’s unique features which have been used to realize novel leaky-wave antennas, compact planar antennas, and infinite wavelength resonant antennas at the authors’ research laboratory.

A Compact Wide-Band Shorted Folded Antenna

Abstract: Planar monopole antennas are easy to construct from a single metal plate and able to offer attractive performance in terms of impedance bandwidth and radiation properties [1]. However, the necessity of compactness has induced the research community to investigate folded radiation elements [2 and 3]. But, at the same time, by reducing the overall dimensions of planar monopole antennas distortions in the radiation pattern and drawbacks in the impedance bandwidth can be introduced. Special feeding techniques and particular grounding systems have to be designed in order to obtain an acceptable compromise between compact dimensions and interesting performance [4, 5 and 6]. The novel and compact wide-band shorted folded antenna presented in this paper offers a working bandwidth of 4.6GHz between 1.6GHz and 7.2GHz (IBR=4.5;1). Good radiation properties and acceptable omni-directionality are obtained throughout the operating bandwidth. The use of a vertical ground plane and a microstrip feeding system permit a dramatic reduction of dimensions when compared to a planar monopole antenna with same characteristics. In this paper, we present another promising bandwidth-enhancement technique, which consists of grounding the radiating element with the vertical ground plane. This solution is shown to only moderately disturb the radiation properties of the antenna. As a consequence of performance and reduced dimensions, this antenna represents a significant candidate for in-door, mobile and vehicular applications where the coverage of different communication protocols is required. Numerical simulation have been obtained by CST Microwave Studio and compared to experimental results of the constructed prototype. A good agreement is achieved.

Influence of Angular Stability of EBG Structures on Low Profile Dipole Antenna Performance

Abstract: In this paper the broadband diamond dipole antenna performance above an Electromagnetic Bandgap (EBG) structure composed of an array of square metallic patches and Jerusalem crosses without any vias over a PEC backed dielectric substrate is investigated and compared to each other. The result shows that angular stability of the EBG structures does not significantly affect on the performance of the antenna. INTRODUCTION EBG structures are used to mimic magnetic conductors over a limited frequency range for use as a ground plane in low-profile antenna configurations in addition other microwave applications. Previous research shows that EBG surfaces can act as AMC ground planes by utilizing a periodic patch with or without vias [1,2]. Both methods are capable of creating the AMC condition indicative of a reflection coefficient with magnitude of 1 (in the ideal lossless case) and phase of 0°. But it has been demonstrated that for the EBG structure (with or without vias) with square patches, the surface impedance strongly depends on the incidence angle and polarization type (TM or TE). As a consequence, these artificial surfaces tend to represent a magnetic wall only for a relatively small part of the angular spectrum of the antenna radiation [3,4]. So it is of interest to investigate the influence of the angular stability of the EBG structure on low profile antenna performance. In this paper, a wideband dipole antenna has been placed on top of the two different EBG structures without any vias. One of the shapes is square, which has poor angular stability and another one is based on Jerusalem cross which has been reported as more stable [4]. Characteristics of the wide band dipole antenna such as S11, radiation pattern and gain are investigated in details on the mentioned EBG structures. ANTENNA DESIGN A dipole antenna was used as a broadband linearly polarized antenna element. Fig. 1 shows the geometry of the dipole antenna made on 0.5 mm thick FR4 substrate ( 4 . 4 = r ε ), 2 mm above the EBG structures which consist of the element array on top of a 3 mm PEC backed substrate with dielectric constant of 2.2. Thus, the overall height of the dipole antenna from the bottom ground plane of the EBG structure is 5.5 mm. (0.09 GHz 5 λ ). Each side of the square forming the dipole is 17 mm. The balun, which is used to connect the coax to the dipole, is a wideband microstrip tapered balun . To achieve the same resonance frequency for the square and Jerusalem cross, the thickness and permittivity of the substrate has been assumed to be the same. But due to the effect of element shape on the resonance frequency, their cell sizes are slightly different. In Fig. 2 the unit cell of the square EBG and Jerusalem cross EBG with dimensions and the related reflection phases, which have been obtained by HFSS simulations, are shown. 253 0-7803-9444-5/06/$20.00 © 2006 IEEE.

Development and Investigation of the Transmission Mechanism of the Wearable Devices Using the Human Body as a Transmission Channel

Abstract: INTRODUCTION As cellular phones, personal digital assistants (PDAs), pocket video games, and other information and communication devices become smaller and more widespread, we have begun to adorn our bodies with these appliances and the opportunities to use these small computers have been increased in our everyday lives. We can say with fair certainty that miniaturization of these devices will evolve, and we will meet the ubiquitous computing society [1]. However, currently there is no method for these personal devices to exchange data directly. If these devices are wire-connected, it is clearly impractical because they easily become tangled, so some sort of short-range wireless technology is required. The concept for networking these personal devices has been proposed as Personal Area Networks (PANs) which use the human body as a transmission channel [2]. Although many studies have been made on the development of wearable devices using the human body as a transmission channel, little is known about the transmission mechanism of such devices in the physical layer [2]-[8]. Figs. 1 3 show a few examples of communication systems of the PANs [5]. When a user wearing the transmitter touches the electrode of the receiver, a transmission channel is formed using the human body. In this case, the receiver recognizes the user's ID and it can be personalized. The merit of this system is that the data is exchanged through daily natural actions, such as simply touching the receiver. This communication system uses the near field region of the electromagnetic wave generated by the device which is eventually coupled to the human body by electrodes. Hence, the structure of electrodes is one of the key issues for the transmission using human body. The difference of the transmission power caused by the electrode structure needs to be considered in detail.

Design Of A Wide-Band Printed Antenna Using A Genetic Algorithm On An Array Of Overlapping Sub-Patches

Abstract: Printed planar rectangular monopoles have shown to be useful wideband antennas for communication systems [1]. These antennas can be easily integrated due to fabrication on printed circuit boards. Attempts to enhance bandwidth with shorting posts or bevels have been successfully made [2]. Optimization by Genetic Algorithms yield great potential in finding non-conventional solutions and has been successfully applied to patch antennas [3, 4]. The printed monopole antenna described in this paper was designed and optimized using a genetic algorithm. In previous use of sub-patches in GA implementations, problems on lattice points were reported [5]. Such problems are overcome by letting the sub-patches overlap to ensure electrical connection on the corners of these patches.

UWB Antennas in Body Area Networks

Abstract: The behavior of different UWB antennas in an on-body scenario is analyzed. Different orientations of directional antennas and different spacings between planar antennas and the body are investigated. Time domain channel parameters, e.g. mean delay and delay spread, are extracted from measurement data. The distribution of the channel parameters allows classification of the different antennas with respect to each parameter.

Low SAR Ferrite Handset Antenna Design

Abstract: The benefits resulting from the inclusion of ferrite in material loaded antennas are investigated, initially through the use of a spherical analytic model and then through a TLM simulation tool applied to a rectangular slab geometry. It is observed that a material with equality of relative permittivity and permeability in combination with specific positioning of the antenna in relation to the head, can result in the definitive smallsize, high efficiency and bandwidth, low Specific Absorption Rate (SAR) antenna. The accuracy of the simulations is validated both through efficiency and SAR measurements of three material coated monopole samples. Further research into optimizing the above attributes and translating them into a handset antenna leads to a multi-band antenna design covering the GSM 1800, 1900, UMTS and Bluetooth bands, with a SAR value reduced by 88% compared to conventional phones and an efficiency of 38% at 1.8GHz. A tri-band antenna design is also presented, utilizing currently available lossy ferrite material and it is considered as the first step towards the feasibility of the ultimate low SAR multi-band ferrite handset antenna, until further material development specifically for antenna applications takes place.

A Miniature Packaged Rectenna for Wireless Power Transmission and Data Telemetry

Abstract: Embedded wireless sensors are becoming crucial for many safety critical applications. Sensor batteries must be charged as needed to support high data rate communications. A miniature packaged circularly polarized rectenna is proposed. With the help of an integrated band-reject filter the proposed rectenna achieves a conversion efficiency of 74% and suppresses the second harmonic emission at 11 GHz by more than 50 dB.

A Study on High Gain Circular Waveguide Array Antenna Using Metamaterial Structure

Abstract: A new method of improving the gain of circular waveguide array antenna using metamaterial structure is presented in this paper. The electromagnetic characteristics of metamaterial and high-gain circular waveguide antenna with the metamaterial structure are studied by using the numerical simulation method, which were also compared with those of the conventional circular waveguide antenna. The simulation results show that this method is effective and the metamaterial structure can realize congregating the radiation energy, so the gain of the antenna is increased and the side lobe level is decreased. Keywords-Metamaterial structure; Circular waveguide antenna arrays; High-gain In this paper, we present a new high gain circular waveguide array antenna design using metamaterials structure. The properties of metamaterial structure and the radiation characteristics of the array antennas are investigated by numerical method. Our studies demonstrate that the metamaterial structure can realize an effective refraction index which can be close to zero and congregate the radiation energy, and the array antenna with metamaterial structure can obtain a great improvement of the antenna gain, in comparison with the conventional array antenna. II. PRINCIPAL CHARACTERISTICS OF METAMATERIAL STRUCTURE The metamaterial,which is studied in this paper, is composed of copper grids with a square lattice and whose period is equal to a mm (in the x-axis and y-axis directions). The grids' spacing in the z-axis direction is H mm, and the edge of the square holes of the copper grids is (a-r)mm. the structure of the metamaterial is shown in figure 1.