A Novel Integrated Dual-Band Antenna for all Relevant
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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/4054211 A novel integrated dual-band antenna for all relevant Wireless-LAN standards (IEEE 802.11a, b and g) Conference Paper · October 2003 DOI: 10.1109/EUMC.2003.1262887 · Source: IEEE Xplore CITATIONS 3 READS 92 5 authors, including: Some of the authors of this publication are also working on these related projects: Electromagnetic Fields in Spherical Microwave Resonators View project High-frequency oscillator View project Andreas Rennings University of Duisburg-Essen 197 PUBLICATIONS 1,484 CITATIONS SEE PROFILE Ingo Wolff IMST GMBH 567 PUBLICATIONS 6,374 CITATIONS SEE PROFILE All content following this page was uploaded by Ingo Wolff on 23 May 2014. The user has requested enhancement of the downloaded file.
Transcript of A Novel Integrated Dual-Band Antenna for all Relevant
See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/4054211
A novel integrated dual-band antenna for all relevant Wireless-LAN
standards (IEEE 802.11a, b and g)
Conference Paper · October 2003
DOI: 10.1109/EUMC.2003.1262887 · Source: IEEE Xplore
CITATIONS
3READS
92
5 authors, including:
Some of the authors of this publication are also working on these related projects:
Electromagnetic Fields in Spherical Microwave Resonators View project
High-frequency oscillator View project
Andreas Rennings
University of Duisburg-Essen
197 PUBLICATIONS 1,484 CITATIONS
SEE PROFILE
Ingo Wolff
IMST GMBH
567 PUBLICATIONS 6,374 CITATIONS
SEE PROFILE
All content following this page was uploaded by Ingo Wolff on 23 May 2014.
The user has requested enhancement of the downloaded file.
Via Via Feed
≈≈ Via
A Novel Integrated Dual-Band Antenna for all Relevant Wireless-LAN Standards (IEEE 802.11a, b and g)
A. Rennings, R. Müller, S. Otto, P. Waldow, and I. Wolff
EE Department (ATE), Duisburg-Essen University, Bismarckstr. 81, 47048 Duisburg, Germany, Tel: +49-203-379-3183, Fax: +49-203-379-3499, E-mail: [email protected]
Abstract — A novel dual-band antenna that can be used
for all relevant Wireless-LAN standards, IEEE 802.11a, b, and g, is presented. The proposed antenna is compact, cost-effectively and precisely to manufacture, with an omni-directional pattern and a sufficient bandwidth for all of the above mentioned WLAN standards. This printed antenna might be a choice for nowadays or future multi-band, multi-mode WLAN applications. The performance was simulated using commercial FDTD tools, and validated with measurements on fabricated prototypes.
I. INTRODUCTION
Wireless local area networks (WLANs) are becoming increasingly popular, since they provide high speed connectivity and easy access to networks without requiring wiring. Most of the current WLAN products being deployed are based on the IEEE 802.11b standard operating at 2.4 GHz with data delivery rates of up to 11 Mbps. The IEEE 802.11a standard is for WLAN devices in the 5 GHz band operating up to data rates of 54 Mbps. This standard provides more bandwidth and channels than the first one. Additionally, the 5 GHz spectrum has less of the interference that plagues the lower frequency band, since microwave ovens, portable phones or Bluetooth devices operate also in the 2.4 GHz ISM band. The new IEEE 802.11g standard is being developed to offer 22 Mbps up to 54 Mbps data rates at 2.4 GHz using the so-called orthogonal frequency division multiplex (OFDM) modulation. There are already multi-band, multi-mode WLAN cards available on the market, i.e., no matter where it operates, the WLAN product identifies the standard used at that location and switches to the appropriate mode, IEEE 802.11a, b or g. For the above mentioned reasons there should be a demand for multi-band antennas enabling radiation in the frequency bands of the IEEE 802.11a, b and g standards. In [1] and [2] multi-band versions of the planar inverted-F antenna (PIFA) have been published. To the best knowledge of the authors there has been no paper published on a multi-band version of the so-called integrated inverted-F antenna – a printed antenna. An antenna printed on a substrate has some advantages compared to other antennas, like the
PIFA: It is usually cheaper and more precisely to manufacture. Furthermore, the multi-band antenna presented in this paper has the advantage to have a very low profile with no additional height above the substrate.
II. BASIC DESIGN CONSIDERATIONS FOR THE NOVEL DUAL-BAND ANTENNA
In this section the development of the multi-band antenna is outlined. Starting point was an ordinary integrated inverted-F antenna (I-IFA) as presented in [3]. Our new antenna concept is based on a modified I-IFA that is even more compact than the ordinary one. Because of its shape, depicted in Fig. 1, this antenna is named integrated folded-h antenna (I-FhA). Two of these folded-h antennas have been connected as depicted in Fig. 2 to form a multi-resonant structure.
Ground Plane Fig. 1: Top view of the integrated folded-h antenna (I-FhA)
Fig. 2: Fusion of two folded h-antennas for multi-band operation
III. FDTD-SIMULATIONS AND MEASUREMENTS OF PROTOTYPES PRINTED ON A PCMCIA CARD
With the basic considerations of section II as a first design the 3D FDTD field simulator EMPIRE™ [4] and CST MICROWAVE STUDIO™ [5] have been used to simulate and optimize the proposed antenna. During that optimization it turned out that the antenna structure
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depicted in Fig. 3 (dimensions in mm) fulfills the dual-band requirements the best. The L-shaped connector to the ground plane on the left hand side was sufficient for the design, therefore the other one on the right hand side (see Fig. 2) has been removed. Since a possible application of the proposed antenna is the integration into a multi-band, multi-mode WLAN PCMCIA card, such a PCMCIA board is used as carrier for the antenna. Its dimensions are approx. 50 mm x 100 mm. The substrate parameters were RT/duroid 5870 with an εr of 2.33 and a thickness of 508 µm (20 mil).
Fig. 3: Top view of the antenna with dimensions in mm The SMA connector was modeled by using a short
coaxial line within the EMPIRE simulation. For the six boundaries PMLs have been used to emulate the free space condition. The simulated and measured return loss in dB of the proposed antenna is shown in Fig. 4. The difference between the EMPIRE result and the measurement in the frequency range from 5 to 6 GHz might be caused by an non-accurate modeling of the SMA-to-microstrip line transition. The S11-measurement has been carried out with the HP NWA 8722C.
Fig. 4: Simulated and measured return loss of dual-band antenna
For the 2.4 GHz ISM band (2.4 to 2.4835 GHz) the antenna has a sufficient bandwidth of approx. 100 MHz at 10dB. The IEEE 802.11a standard is using three subbands within the 5 GHz ISM band. The first subband is from 5.15 to 5.25 GHz and it allows up to 16 dBm transmitting RF power. The second one is from 5.25 to 5.35 GHz with 23 dBm maximum power, and the third one, mainly intended for outdoor applications, is from 5.725 to 5.825 GHz with 29 dBm max. power. In these subbands the antenna has an excellent return loss below 15dB. Because of the additional notch between 5.5 and 6.0 GHz, one might call it a triple-band antenna. Altogether it has a bandwidth of 1.3 GHz (from 4.8 to 6.1 GHz) or 23% at 10dB. Some prototypes of the antenna have been fabricated to validate the simulations with measured data. In Fig. 5/6 one of the prototypes printed on RT/duroid 5870, representing the PCMCIA card, is shown.
Fig. 5: Photo of one of the fabricated prototypes
Fig. 6: Top view of the fabricated antenna printed on RT/duroid A possible application as an antenna for a dual-standard Wireless-LAN PCMCIA card “inside” a laptop computer is shown in Fig. 7.
Fig. 7: One possible application for the proposed antenna
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In Fig. 8 to 10 the magnitude of the current density on the antenna is depicted at 2.45, 5.3 and 5.8 GHz. The field plots give a very good inside which part of the antenna is resonant at a certain frequency.
Fig. 8: Simulated current density |J(x,y,h)| @ 2.45 GHz
Fig. 9: Simulated current density |J(x,y,h)| @ 5.3 GHz
Fig. 10: Simulated current density |J(x,y,h)| @ 5.8 GHz
Another important issue is the radiation pattern. Fig. 9 to 11 illustrate the with EMPIRE simulated directivity pattern of the dual-band antenna at 2.45 GHz - the center frequency in the lower ISM band - and at 5.5 GHz in the middle of the three subbands of the 802.11a standard. In the xy-cut the radiation pattern is nearly omni-directional for both frequencies – except in the direction of the ground plane at ϕ = 270°. There is a notch, since the ground plane acts as reflector. A user in the vicinity of the
antenna should operate in that direction to minimize radiation into the human body.
Fig. 11: Directivity pattern of |Eϕ| and |Eθ| in dBi @ 2.45 and 5.5 GHz, (xy-cut, θ = 90°)
Fig. 12: Directivity pattern of |Eϕ|and |Eθ| in dBi @ 2.45 and 5.5 GHz, (yz-cut, ϕ = 0°)
To give the reader a three-dimensional impression of the quasi omni-directional pattern, the simulated 3D directivity pattern (total polarization) is depicted for two different frequencies at 2.45 and 5.5 GHz in Fig. 14/15. It has been simulated with the CST tool. The notch in the direction of the ground plane is located at the bottom side of the pattern and can therefore not be seen.
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Fig. 13: Directivity pattern of |Eϕ|and |Eθ| in dBi @ 2.45 and 5.5 GHz, (yz-cut, ϕ = 90°)
Fig. 14: 3D directivity pattern in dBi @ 2.45 GHz
Fig. 15: 3D directivity pattern in dBi @ 5.5 GHz
Another important issue - especially for the 802.11b networks, since it uses direct sequence spread spectrum (DSSS) modulation with a relatively wide channel, nearly 30 MHz - is the multi-path propagation. This bandwidth leaves enough room for lower frequency elements of the DSSS signal to reflect off obstacles much different than the higher frequency elements of the signal. To overcome problems caused by multi-path propagation one can use two antennas with a different orientation for each radio in order to increase the odds of receiving a better signal on either of the antennas. Future research will focus on that topic. The standards 802.11a and 802.11g use the OFDM modulation, where the information is transmitted on many narrow sub-channels. Therefore the impact of multi-path propagation is reduced.
IV. CONCLUSION
In this paper, an integrated antenna with multi-band properties, printed on a PCMCIA card, was presented. This design is compact, cost-effectively and precisely to manufacture, and has an omni-directional pattern with sufficient bandwidth for all relevant WLAN standards, IEEE 802.11a, b, g. The presented antenna might be a candidate for nowadays or future multi-band, multi-mode WLAN applications.
REFERENCES
[1] Z. D. Liu, P. S. Hall, and D. Wake, "Dual-frequency planar inverted-F antenna," IEEE Trans. Antennas and Propagation, vol. 45, no. 10, pp. 1451-1458, 1997.
[2] M.-S. Tong, M. Yang, Y. Cheng, and R. Mittra, "Finite-difference time-domain analysis of a stacked dual-frequency microstrip planar inverted-F antenna for mobile telephone handsets," IEEE Trans. Antennas and Propagation, vol. 49, no. 3, pp. 367-376, 2001.
[3] M. Ali and G. Hayes, "Analysis of integrated inverted-F antennas for Bluetooth applications," 2000 IEEE AP-S Conference on Antennas and Propagation for Wireless Communication, Massachusetts, pp. 21-24, Nov. 2000.
[4] IMST GmbH, “User manual for the 3D EM time domain simulator Empire”, www.empire.de/empire.pdf, June 2002.
[5] CST GmbH, “User manual for CST MICROWAVE STUDIO”.
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