AbstractâA very low-profile planar rectangular horn antenna made of a subwavelength aperture surrounded by two grooves on the conducting plate is ...
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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 4, 2005
Low-Profile Corrugated Feeder Antenna M. Beruete, I. Campillo, J. S. Dolado, J. E. Rodríguez-Seco, E. Perea, F. Falcone, Member, IEEE, and M. Sorolla, Senior Member, IEEE
Abstract—A very low-profile planar rectangular horn antenna made of a subwavelength aperture surrounded by two grooves on the conducting plate is presented. This structure exhibits good return losses and radiated beam. Its operation is based upon enhanced transmission and beaming through apertures in metallic corrugated plates. Here, the corrugated structure is designed to operate in microwaves and, moreover, a waveguide flange, which has been properly mechanized in the rear part of the structure, is employed for excitation. A new very low-profile planar feeder with reduced size is introduced that could be properly scaled for potential wireless applications. Index Terms—Corrugated plate, subwavelength aperture, very low-profile feeder, wireless local area networks (WLANs).
I. INTRODUCTION
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HE introduction of wireless local area networks (WLAN) is increasing progressively. Such systems demand lowprofile miniaturized antennas as essential elements to be integrated in laptop computers and other hardware. This has boosted a very active research looking for the development of miniaturized antennas following many different approaches [1], [2]. Recently it has been proposed the enhanced transmission phenomenon for subwavelength apertures perforated on corrugated metallic plates, which offers potential antenna applications [3]–[7]. A leaky mode theory explains this phenomenon satisfactorily [8], [9]. In this work, these concepts are employed to design a very low-profile feeder antenna that could have potential applications in WLAN if properly scaled to the corresponding frequencies. In this way, it is presented a very low-profile miniaturized planar antenna having a broad radiation beam, which is very desirable for WLAN applications, as explained in [10]. II. DESCRIPTION OF THE STRUCTURE An antenna schematic is presented in Fig. 1, [11]. The design proposed in this letter is similar to the one described in [6] and [7], but with two important differences: the proposed structure is fed using a standard waveguide and not by means of a plane wave; and the long slit is changed by a narrow slit, surrounded by one groove at each side resulting in a very efficient coupling.
Manuscript received July 12, 2005; revised August 16, 2005. This work was supported by CICYT by Project Contracts TIC2002-04528-C02-01, TIC200204528-C02-02, and E.U. FEDER. M. Beruete, F. Falcone, and M. Sorolla are with the Departamento de Ingeniería Eléctrica y Electrónica, Universidad Pública de Navarra, Campus Arrosadía, E-31006 Pamplona, Spain. I. Campillo, J. S. Dolado, J. E. Rodríguez-Seco, and E. Perea are with Labein Centro Tecnológico, Parque Tecnolögico de Bizkaia, 48160 Derio, Spain. Digital Object Identifier 10.1109/LAWP.2005.857297
Fig. 1. Schematic (not to scale) of the single slit surrounded by the corrugations. The electromagnetic wave is incident as the TE rectangular waveguide mode.
By using the commercial finite integration time domain Computer Simulation Technology (CST) microwave studio code, we have analyzed the power coupling mechanism between the rectangular waveguide and the radiated wave. It follows that the external metallic plate depth, , governs the resonant frequency of the antenna in a similar manner as mode a Fabry–Perot resonator that couples the incident power to the free space. The antenna has been designed to have a resonant frequency around 16 GHz. At this frequency, the mm) to free space wavelength ratio is slit-aperture ( around 0.1. The explanation of the improvement of the radiation pattern is based on the grooves resonance which appears when its depth . In the prototype mm which is is smaller than the approximated theoretical prediction ( mm) because an optimization process is necessary to obtain a reasonable antenna performance, see [7]. The far-field pattern simulation results of the proposed antenna are plotted in Fig. 2. In Fig. 2(a), it is shown the far-field pattern for the case of a small rectangular aperture onto a noncorrugated flat metallic plane. This results in a gain of 6 dB. In Fig. 2(b), the far-field pattern of the proposed antenna in Fig. 1 is presented. There is a clear improvement in the radiation pattern with a gain of 10.34 dB, i.e., 4.3 dB better than that of a flat plane [Fig. 2(a)]. III. EXPERIMENTAL MEASUREMENTS An antenna prototype has been fabricated by using numerical control machining [see Fig. 3(a)]. From the inspection of the
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BERUETE et al.: LOW-PROFILE CORRUGATED FEEDER ANTENNA
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Fig. 4. Reflection coefficient of the flat antenna versus frequency. Solid line: simulation result. Dashed line: measurement.
Fig. 2. 3-D far-field pattern and polar diagrams for (a) flat output plane and (b) central slit grooves antenna.
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Fig. 5. Measured gain versus frequency. Solid line: central slit antenna. Dashed line: EMCO 3115 Standard horn antenna.
Fig. 3. (a) Central slit experimental set-up.
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prototype, it follows that relatively thin antennas are feasible. The far-field radiation pattern of prototypes has been measured in an antenna test range and an HP 8510 C Vector Network Analyzer (45 MHz–26 GHz), in the frequency range of 10–18 GHz. A calibrated standard test horn antenna was placed opposite to the antenna under test at a distance of 2 m. Both antennas were placed 1.5 m above the floor, which was properly covered with absorbing material, thus avoiding undesirable reflected radiation (anechoic conditions). The prototype under test was located on a rotary platform to measure its far-field radiation pattern [see Fig. 3(b)]. Additionally, the experimental reflection coefficient compared with the simulated one is shown in Fig. 4. A good
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agreement between the simulated coefficient and that of the fabricated one is evidenced. Approximately, the resonant fremm is 16.5 GHz. Note another quency for the value of resonance at 13 GHz that will be discussed in a future paper. By means of the gain-transfer (gain-comparison) method, the antenna gain is measured [12]. A 10 dB value at the design frequency of 16.5 GHz is obtained [see Fig. 5]. Note that the standard horn antenna has a gain of 12 dB at the same frequency. The far-field radiation patterns have been measured at the design frequency in an angular range from 0 to 180 ; see Fig. 6, where the values are normalized to the boresight gain. Reasonable good agreement with simulation can be observed in the E dB angular width is of 34 in and H planes. The measured the E plane and 60 in the H plane. IV. DISCUSSION OF THE RESULTS By inspection of Fig. 5, it can be concluded that the proposed antenna works well at the design frequency, presenting a peak of gain 2.5 dB lower than that of the standard horn antenna. This gain can be improved by using a bigger number of grooves, which would result into a more directive far-field pattern [7].
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IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 4, 2005
results are in close agreement with the simulation shown in Fig. 2(b). V. CONCLUSION A very low-profile horn antenna with reasonable gain has been designed taking advantage of a resonance for coupling the power from the waveguide to the output face. The use of grooves results in an improvement of the antenna gain and beaming. Our measurements of the gain versus frequency and of the far-field radiation pattern confirm the simulations. These results show that thin, light and flat antennas could be developed for possible applications in several wireless systems like WLAN if properly scaled to the allowed frequency bands. REFERENCES
Fig. 6. Measured far-field patterns for (a) E-cutting plane and (b) H-cutting plane. Normalized to the boresight gain.
This will be treated in detail in a subsequent paper. Nevertheless, more grooves imply a bigger structure, which can turn out to be impractical for some applications. In Fig. 6(a), E-plane beaming can be seen whereas for the H-plane [Fig. 6(b)] a less directive beam is achieved. These
[1] Y. Ge, K. P. Esselle, and T. S. Bird, “E-shaped patch antennas for highspeed wireless networks,” IEEE Trans. Antennas Propag., vol. 52, no. 12, pp. 3213–3219, Dec. 2004. [2] G. H. Huff, J. Feng, S. Zhang, G. Cung, and J. T. Bernhard, “Directional reconfigurable antennas on laptop computers: Simulation, measurement, and evaluation of candidate integration positions,” IEEE Trans. Antennas Propag., vol. 52, no. 12, pp. 3220–3227, Dec. 2004. [3] A. Hellemans, “Nanoholes permit remarkable light transmission,” IEEE Spectr., vol. 41, no. 7, pp. 13–14, Jul. 2004. [4] T. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength hole arrays,” Nature, vol. 391, pp. 667–669, Feb. 12, 1998. [5] H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martín-Moreno, F. J. García-Vidal, and T. W. Ebbesen, “Beaming of light from a subwavelength aperture,” Science, vol. 297, no. 820, 2002. [6] A. P. Hibbins, J. R. Sambles, and C. R. Lawrence, “Gratingless enhanced microwave transmission through a subwavelength aperture in a thick metal plate,” Appl. Phys. Lett., vol. 81, pp. 4461–4463, Dec. 2002. [7] M. Beruete, I. Campillo, J. S. Dolado, J. E. Rodríguez-Seco, E. Perea, and M. Sorolla, “Enhanced microwave transmission and beaming using a subwavelength slot in corrugated plane,” IEEE Antennas Wireless Propag. Lett., vol. 3, pp. 328–331, Dec. 2004. [8] A. A. Oliner and D. R. Jackson, “Leaky-wave theory for enhanced transmission through subwavelength apertures, part I: Basic features,” in Proc. IEEE Antennas and Propagation Society Symp. Radio Science Meeting, Columbus, OH, 2003, pp. 1091–1094. [9] T. Zhao, D. R. Jackson, J. T. Williams, and A. A. Oliner, “Leaky surface-plasmon theory for dramatically enhanced transmission through a subwavelength aperture, part II: Leaky-wave antenna model,” in Proc. IEEE Antennas and Propagation Society Symp. Radio Science Meeting, Columbus, OH, 2003, pp. 1095–1098. [10] H. Nakano, Y. Yamamoto, M. Seto, K. Hitosugi, and J. Yamauchi, “A half-moon antenna,” IEEE Trans. Antennas Propag., vol. 52, no. 12, pp. 3227–3244, Dec. 2004. [11] M. Beruete, M. Sorolla, I. Campillo, and J. S. Dolado, Patent submitted with Ref. Number PCT/ES2004/000 359, 2004. [12] IEEE Standard Test Procedures for Antennas, IEEE Standard 149-1979, Dec. 1979.
