Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
1999-11-29
2001-08-21
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
C343S7000MS, C343S771000
Reexamination Certificate
active
06278410
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to planar antennas, in particularly dual frequency or wide frequency band antennas, in particular slot antennas.
TECHNICAL BACKGROUND
Planar antennas are finding increasing popularity owing to their low profile, light weight, and possible conformity to supporting structures. The most serious limitation of these antennas is the narrow bandwidth of the single element. The traditional microstrip patch antenna has an impedance bandwidth of only few percent. Several methods have been used to widen the impedance bandwidth of the patch antenna. See, e.g., D. M. Pozar and D. H. Schaubert, editors, “A review of bandwidth enhancement techniques for microstrip antennas”, Microstrip Antennas, the Analysis and Design of Microstrip Antennas and Arrays, IEEE press, pp. 157-166, 1995, which is hereby incorporated by reference in its entirety. Parasitic elements can be stacked together with the driven element in a multilayer configuration. See, e.g., F. Croq and D. M. Pozar, “Millimeter wave design of wide-band slot coupled stacked microstrip antennas”, IEEE Trans. Antennas Propagation, vol. 39, pp. 1770-1776, Dec. 1991, which is hereby incorporated by reference in its entirety. The difference in size of the two resonators results in a bandwidth of 10-20%. Several log-periodically scaled microstrip patches can be series-fed to achieve an impedance bandwidth of 22%. See, e.g., H. Pues, J. Bogaers, R. Pieck and A. Van de Capelle, “Wideband quasi-log-periodic microstrip antenna”, IEE Proc. Vol. 128, Part H., pp. 159-163, June 1981, which is hereby incorporated by reference in its entirety.
SUMMARY OF THE INVENTION
The present invention may provide a planar antenna comprising: a first outer planar conductive element defining an inner hole, at least 75% of the boundary between the hole and the first outer planar conductive element being a continuously concave smooth curve; and a second planar conductive element substantially coplanar with the first outer planar conductive element, the second planar conductive element being located in the hole, at least 75% of the outer boundary of the second planar conductive element being a continuously convex smooth curve. The air or insulating space between the first and second planar conductive elements in the plane thereof forms the slot of a slot antenna. Preferably, the center of gravity of the hole of the first outer planar conductive element is offset from the center of gravity of the second planar conductive element. The smooth curve may be a circle, an ellipse, an oval, an egg-shape etc. The antenna is a slot antenna where the slot is defined by the space between the offset second and first conductive elements. The offset is preferably sufficiently great that the slot has a dimension perpendicular to the offset direction of a half the wavelength of a resonant frequency of interest. The conductive elements are preferably mounted on a substrate comprising a dielectric material. Preferably, the dielectric material is a low loss material at the resonant frequency or frequencies of the antenna. Glass or ceramic or corderite are suitable materials. The distance “h” between the inner diameter of the outer conductive element and the outer diameter of the substrate is preferably about 0.4 &lgr;
0
where &lgr;
0
is the free space wavelength at 9.66 GHz.
The antenna in accordance with the present invention may have a bandwidth of 34% without the need of stacking several layers or using parasitic elements. The antenna may be fed by a microstrip line or by a coplanar waveguide (CPW) in order to be compatible with the evolution of the microwave systems from microstrip towards coplanar technology. See for example, H-C Liu, T-S Horng and N. G. Alexopoulos, “Radiation of printed antennas with coplanar waveguide feed”, IEEE Trans. Antennas Propagat., vol. 43, pp. 1143-114 8, Oct. 1995, which is hereby incorporated by reference in its entirety. CPW lines may be preferable over microstrip lines as they may provide low radiation loss, less dispersion, less mutual coupling, and good control of their characteristic impedance.
The antenna may be built using coplanar technology. It has dual frequency operation, the first and the second resonances may be, for instance, in X-and Ku- bands respectively. The proposed antenna has wide band behavior around both resonance frequencies. It has a dipole like radiation pattern, which makes it suitable for phased array applications.
In the present invention, the word antenna is used to describe an element for radiating electromagnetic radiation in particular in short or medium wave radio frequencies as well as microwave frequencies and gigahertz and terahertz frequencies.
The dependent claims form embodiments of the present invention.
The present invention, its advantages and embodiments will now be described with reference to the following drawings.
REFERENCES:
patent: 4509209 (1985-04-01), Itoh et al.
patent: 4821040 (1989-04-01), Johnson et al.
patent: 5714961 (1998-02-01), Kot et al.
patent: 5745079 (1998-04-01), Wang et al.
Soliman et al., (1998), “Suppression of the Parasitic Modes in CPW Discontinuities Using MCM-D Technology-Application to a Novel; 3-dB Power Splitter”,IEEE Transactions on Microwave Theory and Techniques, vol. 46, No. 12, pp. 2426-2430.
Soliman et al., (1999), “CPW-FED CUSP Antenna”,Microwave and Optical Technology Letters, vol. 22, No. 4, pp. 288-290.
Beyne Eric
De Raedt Walter
Soliman Ezzeldin
Vandenbosch Guy
Interuniversitair Microelektronica Centrum
McDonnell & Boehnen Hulbert & Berghoff
Phan Tho
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