Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1996-08-08
2001-04-17
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S841000
Reexamination Certificate
active
06218989
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to miniature patch antennas, and more particularly to miniature patch antennas having polarization and space diversity, as well as to improved communications systems employing such antennas.
BACKGROUND OF THE INVENTION
A typical microstrip or miniature patch antenna has a metallic patch printed on a thin grounded dielectric substrate. In the transmitting mode, a voltage is fed to the patch that excites current on the patch and creates a vertical electric field between the patch and the ground plane. The patch resonates when its length is near &lgr;/2, leading to relatively large current and field amplitudes. Such an antenna radiates a relatively broad beam normal to the plane of the substrate. The patch antenna has a very low profile and can be fabricated using photolithographic techniques. It is easily fabricated into linear or planar arrays and readily integrated with microwave integrated circuits.
Disadvantages of early patch antenna configurations included narrow bandwidth, spurious feed radiation, poor polarization purity, limited power capacity and tolerance problems. Much of the development work relating to miniature patch antennas has been directed toward solving these problems.
For example, early miniature patch antennas used direct feeding techniques wherein the feed line runs directly into the patch. Such direct feed arrangements sacrificed bandwidth for antenna efficiency. In particular, while it was desirable to increase substrate thickness to increase bandwidth, this resulted in an increase in spurious feed radiation, increased surface wave power, and potentially increased feed inductance. More recently, noncontacting feed arrangements, such as the aperture coupled antenna have been developed. In the aperture coupled antenna, two parallel substrates are separated by a ground plane. A feed line on the bottom substrate is coupled through a small aperture in the ground plane to a patch on the top substrate. This arrangement allows a thin, high dielectric constant substrate to be used for the feed and a thick, low dielectric constant substrate to be used for the antenna element, allowing independent optimization of both the feed and the radiation functions. Further, the ground plane substantially eliminates spurious radiation from the feed from interfering with the antenna pattern or polarization purity.
Perhaps the most serious drawback of the earlier miniature patch antennas were their narrow bandwidth. Typical approaches to overcome this drawback can be characterized as either using an impedance matching network or parasitic elements.
Notwithstanding the improvements in miniature patch antennas, a need exists for a miniature patch antenna having enhanced radiation efficiency, increased antenna bandwidth and reduced electromagnetic coupling.
SUMMARY OF THE INVENTION
The aforementioned need, as well as others, are met by a miniature multi-branch patch antenna having at least two separate conducting antenna elements. The conducting antenna elements, each having a feed port, are disposed on a first surface of a planar dielectric substrate. A ground plane is disposed on a second surface of the planar dielectric substrate. Each conducting antenna element is separated from all other conducting antenna elements by a septum which is in electrical contact with a conducting ground plane.
In another embodiment, the miniature multi-branch patch antenna may further comprise a superstrate disposed on top of the conducting antenna elements and at least a portion of the substrate. In a further embodiment, the miniature multi-branch patch antenna may include the superstrate but not the septum. Both the septum and superstrate aid in suppressing undesirable coupling mechanisms.
In an additional embodiment, a communication system is formed comprising at least one miniature multi-branch patch antenna, a transmitter and a receiver.
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Chen et al., “Superstrate Loading Effects on the Circular Polarization and Crosspolarization Characteristics of a Rectangular Microstrip Patch Antenna,” IEEE Trans. Antennas and Propagation, V42(2), Feb. 1994, pp. 260-264.
Kyriacou et al., “Effects of Substrate-Superstrate Uniaxial Anisotropy on Microstrip Structures,” Elec. Letts., V30(19), Sep. 1994, pp. 1557-1558.
Pozar, D.M., “Microstrip Antennas,” Proceedings of the IEEE, vol. 80, No. 1, Jan. 1992, pp. 79-91.
Schneider Martin Victor
Tran Cuong
Breyer Wayne S.
DeMont Jason Paul
DeMont & Breyer LLC
Lucent Technologies - Inc.
Wimer Michael C.
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