|Session:||Session 4A03A - Wideband and Multiband Antennas (12c)|
|Date:||Thursday, November 09, 2006|
|Time:||08:30 - 12:30|
A Slot Antenna with Beam-Changed Patterns
Wang, C.J.1; Chang, S.W.2; Lee, J.J.1
1Department of Electrical Engineering, Feng-Chia University, TAIWAN;
2Academia Sinica Institute of Astronomy & Astrophysics, TAIWAN
A coplanar waveguide (CPW)-fed wideband beam-changed slot antenna is presented in this paper. The basis for achieving such a broadband operation is to create a multi-resonator in a slot cavity. By using a modified fork-like feeding structure, several different equivalent magnetic current paths are alternatively excited when the operated frequency is changed. Due to different radiation regions, the radiation pattern, including in the end-fire or bore-sight direction, can be changed frequency-dependently. A 220% impedance bandwidth (S11 < -10 dB) is demonstrated. Simulated and measured results of the antenna are presented.
Mobile Terminal Antennas Implemented Using Direct Coupling
Holopainen, J; Villanen, J; Icheln, C; Vainikainen, P
Radio Laboratory, Helsinki University of Technology, FINLAND
The current trend in mobile terminals is that the number of systems is increasing all the time. Because of that, the volume reserved for the antennas of radio systems is decreasing. As known, at the lower RF frequencies the EMC shielding and the printed circuit board, briefly called chassis, operate as the main radiator. Normally currents to the chassis are induced with an antenna element, e.g. a PIFA or a coupling element. A further reduction in the size of a mobile terminal antenna can be achieved by replacing an antenna element by a direct feed, i.e. galvanically inducing currents on the surface of the chassis. The best way would be to cut the chassis in half and place the feed between the parts. In that case the chassis would operate as a thick dipole antenna. Because of the EMC issues, it is not always allowed to cut the chassis in parts and the chassis has to be a solid piece of metal. The feed can then be placed over an impedance discontinuity, e.g. formed by a slot, see Figure 1.
The achievable bandwidth of the antenna is very clearly affected by the resonant frequencies of the chassis. The largest bandwidth is achieved when the chassis is in resonance at the operation frequency of a system. The first order resonant frequency of a solid chassis, whose length is 130 mm, is about 900 MHz. Because a slot lengthens the current path compared to the solid case, the first order resonant frequency of the chassis decreases. This is especially important in the digital television application (DVB-H) that operates at the frequency band 470 – 702 MHz. By designing other impedance discontinuities it is possible to integrate several systems to the same antenna structure.
By using the presented idea, an antenna for DVB-H has been studied, designed and manufactured. The prototype fulfills the DVB-H system realized gain specification over the DVB-H band 470 – 702 MHz with a 4 dB margin.
A Single Matching Network Design for a Dual Band PIFA Antenna
Via Simplified Real Frequency Technique
Lindberg, P.1; Senturk, M.2; Cimen, E.3; Yarman, S.4; Rydberg, A.1; Aksen, A.3
1Uppsala University, SWEDEN;
2Kadir Has University, TURKEY;
3Isik University, TURKEY;
4Tokyo Institute of Technology, JAPAN
With the development of mobile communication systems and miniaturization of hand sets, requirements for compact antennas are rapidly growing. In this regard, Planar Inverted F Antenna (PIFA) has found internal utilization within mobile units due to its small size for both single and dual band applications [1-2]. The PIFA has many known advantages, e.g. ease of fabrication, low manufacturing cost, ground plane compatibility and conformity with complex geometries. Perhaps most importantly, it can without difficulty be matched to any impedance (by simply choosing the location of the short circuit) without matching network, and the design concept is easily extended to dual band functionality . On the other hand, it typically suffers from a narrow impedance bandwidth, which excludes the PIFA from a variety of applications. For example, modern transceiver front-ends are available with quad band support (GSM850/900/1800/1900) for global roaming. Unfortunately, this bandwidth is extremely difficult to achieve with a PIFA within the volume typically allocated for the antenna element. However, it should be kept in mind that without designing a matching network, one would never know what the real achievable bandwidth of the antenna is. Therefore, in this paper, an attempt is made to design a dual band PIFA antenna together with its matching network to asses the antenna performance. In deed, it has been experienced that careful design of the matching network results, as expected, in a substantial bandwidth improvement.
 Kathleen L. Virga and Yahya Rahmat-Samii, "Low-Profile Enhanced-Bandwidth PIFA Antennas for Wireless Communications Packaging", IEEE Transaction on Microwave Theory and Techniques, vol.45, no.10, pp.1879-1888, October 1997.
Compact Dual-Band Reduced Size PIFA Antenna for Automotive Applications
Brzeska, M.1; Chakam, G.-A.2
1Siemens VDO and University of Karlsruhe, GERMANY;
2Siemens VDO, GERMANY
Synthesis and Optimization of Pre-fractal Multiband Antennas
Azaro, R.; Zeni, E.; Massa, A.; Zambelli, M.
University of Trento, ITALY
The growing demand of electronic products employing several wireless standards for data exchange, working in different frequency bands, requires the adoption of multi-band components and devices. In this framework one of the most critical issue is the design of the radiating device since the development of a single antenna working in two or more frequency bands and belonging to a limited geometry is, in general, a hard task.
Wire antennas (basically dipoles and monopoles) can work in several frequency bands corresponding to the resonances of the structure, but multiple working frequencies are strictly linked by harmonic relationships and, in addition, their electrical performances (VSWR and gain) vary with the considered resonant frequency. Classical techniques for the development of multiband wire antennas are based on the insertion of reactive loads in the antenna structure in order to obtain and allocate multiple resonant frequencies.
In recent years the problem has been faced also exploiting the properties of fractal geometries combined with an optimization algorithm in order to optimize both antenna geometry and loads values and positions . As a matter of fact, the use of fractal geometries for antenna synthesis has been proven to be very useful in order to achieve enhanced bandwidth and miniaturization . However the insertion of additional circuital elements in the antenna structure requires longer manufacturing times and some uncertainty on antenna performances may be introduced by the tolerances of lumped components values.
In order to overcome the insertion of lumped load in the antenna geometry some degrees of freedom can be added by perturbing the characteristic fractal parameters. The synthesis of multi-band fractal antenna in the paper is faced as an optimization problem by minimizing specific cost functions written for the particular fractal structure considered. The optimization is carried out through a numerical procedure based on a Particle Swarm Optimizer (PSO)  , by optimizing only the parameters of the fractal geometry, without the insertion of any lumped load. In the paper, in order to assess the effectiveness of the synthesis procedure, numerical and experimental results obtained with some pre-fractal structures are presented and discussed.
 D. H. Werner, P. L. Werner, and K. H. Church, "Genetically engineered multiband fractal antennas," Electron. Lett., vol. 37, pp. 1150-1151, Sep. 2001.
de Castro-Galan, D.1; Gonzalez-Posadas, V.2; Martín-Pascual, C.1; Segovia-Vargas, D.1
1Universidad Carlos III de Madrid, SPAIN;
2Universidad Politécnica de Madrid, SPAIN
In this work a new integrated diplexed antenna is presented. It uses the CRLH transmission lines concept described in . These transmission lines allow controlling the phase response at two arbitrary frequencies. Using this property, a diplexer based on the rat-race hybrid can be designed . This diplexer can be integrated with a radiator to achieve a low loss, compact diplexed antenna. In this paper, a diplexed antenna operating in the UMTS bands is designed and measured.
First, the CRLH transmission lines are designed for the operating frequencies. Due to the narrow separation between both frequencies, a high number of cells are needed. This fact makes the use of lumped elements impractical. Besides, the tolerance of the components must be very tight. Because of this, the diplexer has been implemented using a dual layer printed technology.
As presented in , the diplexer is a four port network which splits the signal from the transmitter into two equal-amplitude, 180º out-of-phase signals in one direction at one frequency, and combines two incoming signals at the other frequency into the remaining output. So, the diplexer can also be seen as a balanced-unbalanced transition (balun) at both frequencies. Therefore, a balanced radiator is needed to be integrated with the diplexer.
The second step is designing the radiator. In this case, a dual-feed printed patch antenna will be used. The radiator must be either broadband or dual band, so it can cover both frequency bands.
Finally both elements have been built and measured on its own, and then integrated. High isolation between transmitting and receiving ports and low overall losses have been achieved. The figures show the parameters for a 1900-2200 self-diplexed antenna.
Improving Radiation Pattern of Microstrip Antennas
Nikolic, M.M.; Djordjevic, A.R.
School of Electrical Engineering, University of Belgrade, SERBIA AND MONTENEGRO
Microstrip (patch) antennas usually strongly radiate in directions along the ground plane. This effect causes unwanted radiation patterns and increased coupling among antennas. In , dielectric polarization currents are identified as the physical source of this radiation.
The first aim of the present paper is to analytically evaluate the influence of the polarization currents on a simplified model of a patch antenna. Data are given to estimate the deterioration of the radiation pattern. The results are compared with numerical simulations using the program of Ref. .
The second aim is to prove that various existing techniques for improving the radiation pattern merely reduce or compensate the radiation due to the polarization currents, rather than deal with surface waves (whose effect is negligible in most practical cases). For example, micromachining the dielectric under a metallic patch  removes the polarization currents. A superstrate  introduces polarization currents that are counter-directed with respect to those in the substrate. The metallic annular ring  supports counter-directed conduction currents. The technique proposed in  also introduces counter-directed conduction currents in an array of pins that acts like a metamaterial embedded into the substrate.
The third aim of the present paper is to propose some novel technical solutions for compensating the polarization currents, like adding metallic ailerons to a patch.
All these techniques for improving the radiation pattern are compared with respect to their efficacy, bandwidth, and ease of manufacturing.
 M.M. Nikolic, A.R. Djordjevic, and A. Nehorai, "Microstrip antennas with suppressed radiation in horizontal directions and reduced coupling", IEEE Trans. on Antennas and Propagation, vol. AP-53, no. 11, November 2005, pp. 3469-3476.
 B. Kolundzija, J. Ognjanoviæ, T. Sarkar, M. Tasic, D. Olcan, B. Janic, D. Sumic, WIPL-D Pro. v5.1, WIPL-D, 2004.
 J.-G. Yook and L. Katehi, "Micromachined microstrip patch antenna with controlled mutual coupling and surface waves", IEEE Trans. Antennas Propagat., vol. 49, pp. 1282-1289, Sept. 2001.
 N.G. Alexopoulos and D.R. Jackson, "Fundamental superstrate (cover) effects on printed circuit antennas," IEEE Trans. Antennas Propagat., vol. AP-32, pp. 807-816, Aug. 1984.
 M.A. Khayat, J.T. Williams, D.R. Jackson, and S.A. Long, "Mutual coupling between reduced surface-wave microstrip antennas", IEEE Trans. Antennas Propagat., vol. 48, pp. 1581-1593, Oct. 2000.
Multi-Band Internal Monopole Antenna for Mobile Station
Kim, S.M.; Kim, Y.H.; Yang, W.G.
Department of Electronics Engineering, University of Incheon, KOREA, REPUBLIC OF
Recently, it is strongly required for the mobile station to cover multi-band with a single internal
|Abstracts assigned without a sequence or a sequence number beyond maximum presentation slots available:|
|10 - 347453 - A New Wideband Antenna: Comprising Planar-Dipole and Short-Circuited-Patch|