Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1998-10-28
2001-02-27
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S754000, C343S853000
Reexamination Certificate
active
06195047
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention is related in general to the field of antennas. More particularly, the invention is related to an integrated microelectromechanical phase shifting reflect array antenna.
BACKGROUND OF THE INVENTION
Many radar, electronic warfare and communication systems require a circularly polarized antenna with high gain and low axial ratio. Conventional mechanically scanned reflector antennas can meet these specifications. However, they are bulky, difficult to install, and subject to performance degradation in winds. Planar phased arrays may also be employed in these applications. However, these antennas are costly because of the large number of expensive GaAs Monolithic microwave integrated circuit components, including an amplifier and phase shifter at each array element as well as a feed manifold and complex packaging. Furthermore, attempts to feed each microstrip element from a common input/output port becomes impractical due to the high losses incurred in the long microstrip transmission lines, especially in large arrays.
Conventional microstrip reflect array antennas use an array of microstrip antennas as collecting and radiating elements. Conventional reflect array antennas use either delay lines of fixed lengths connected to each microstrip radiator to produced a fixed beam or use an electronic phase shifter connected to each microstrip radiator to produce an electronically scanning beam. These conventional reflect array antennas are not desirable because the fixed beam reflect arrays suffer from gain ripple over the reflect array operating bandwidth, and the electronically scanned reflect array suffer from high cost and high loss phase shifters.
It is also known that any desired phase variation across a circularly polarized array can be achieved by mechanically rotating the individual circularly polarized array elements. Miniature mechanical motors or rotators have been used to rotate each array element to the appropriate angular orientation. However, the use of such mechanical rotation devices and the controllers introduce mechanical reliability problems. Further, the manufacturing process of such antennas are labor intensive and costly.
In U.S. Pat. No. 4,053,895 entitled “Electronically Scanned Microstrip Antenna Array” issued to Malagisi on Oct. 11, 1977, antennas having at least two pairs of diametrically opposed short circuit shunt switches placed at different angles around the periphery of a microstrip disk is described. The shunt switches connect the periphery of the microstrip disk to a ground reference plane. Phase shifting of the circularly polarized reflect array elements is achieved by varying the angular position of the short-circuit plane created by diametrically opposed pairs of diode shunt switches. This antenna is of limited utility because of the complicated labor intensive manufacturing process required to connect the shunt switches and their bias network between the microstrip disk and ground, as well as the cost of the circuitry required to control the diodes.
SUMMARY OF THE INVENTION
Accordingly, there is a need for a low loss and cost effective phase shifting array antenna. In accordance with the present invention, an array element and a phase shifting array antenna are provided which eliminate or substantially reduce the disadvantages associated with prior antennas.
In one aspect of the invention, a phase shifting array antenna includes antenna elements that have a non-electrically conductive substrate having first and second sides, an electrically conductive patch formed on the first side of the substrate, and a ground plane formed on the second side of the non-electrically conductive substrate. At least two pairs of integrated microelectromechanical switches are arranged diametrically opposed across the patch on the first side of the substrate, each microelectromechanical switch having a first electrode electrically coupled to the patch and a second electrode electrically coupled to the ground plane, the first and second electrodes being operable to be capacitively coupled, thereby creating a short circuit plane across the patch. A sealing structure hermetically packages the microelectromechanical switches.
In another aspect of the invention, an antenna element includes a first portion and a second portion. The first portion includes a non-electrically conductive substrate having first and second sides, an electrically conductive patch formed on the first side of the substrate, a ground plane formed on the second side of the non-electrically conductive substrate, and lower electrodes of at least two pairs of microelectromechanical switches arranged diametrically opposed across the patch and electrically coupled to the patch. The second portion includes a controller integrated circuit, upper electrodes of the at least two pairs of microelectromechanical switches electrically coupled to the controller integrated circuit, the first and second electrodes being operable to be capacitively coupled, thereby creating a short circuit plane across the patch. The array element further includes a sealing structure disposed between the first and second portions and bonding the first and second portions together and hermetically packaging the at least two pairs of microelectromechanical switches.
In yet another aspect of the invention, an integrated phase shifting array antenna includes a non-electrically conductive substrate having first and second sides, a plurality of array elements arranged in a predetermined pattern on the first side of the substrate, and a ground plane formed on the second side of the non-electrically conductive substrate. Each array element includes an electrically conductive patch formed on the first side of the substrate, and a plurality of pairs of integrated microelectromechanical switches arranged diametrically opposed across the patch on the first side of the substrate, each microelectromechanical switch having a first electrode electrically coupled to the patch and a second electrode electrically coupled to the ground plane, the first and second electrodes being operable to be capacitively coupled, thereby creating a short circuit plane across the patch. A sealing structure is disposed about the integrated microelectromechanical switches for hermetically packaging and sealing the microelectromechanical switches.
In yet another aspect of the invention, a method of fabricating a phase shifting array antenna includes the steps of forming a plurality of electrically conductive patches arranged in a predetermined pattern on a first surface of a non-electrically conductive substrate, forming lower electrodes of at least two pairs of microelectromechanical switches disposed diametrically across each patch, forming a ground plane on a second surface of the substrate, and forming an electrical connection between each lower electrode to the ground plane. Further, the method includes the steps of forming upper electrodes of the at least two pairs of microelectromechanical switches for each patch, forming sealing structures disposed about the upper and lower electrodes of the at least two pairs of microelectromechanical switches, and bonding the sealing structures together thereby hermetically sealing and packaging the microelectromechanical switches.
REFERENCES:
patent: 4053895 (1977-10-01), Malagisi
patent: 4684952 (1987-08-01), Munson et al.
patent: 4777490 (1988-10-01), Sharma et al.
Colin, Jean-Marie, “Phased Array Radars in France: Present & Future”, IEEE, pp. 458-462, Jun. 1996.
Huang, John, “Bandwidth Study of Microstrip Reflectarray and a Novel Phased Refletcarray Concept”, IEEE, pp. 582-585, May 1995.
Huang, John and Ronald J. Pogorzelski, “A Ka-Band Microstrip Reflectarray with Elements Having Variable Rotation Angles”, IEEE, vol. 46, No. 5, pp. 650-656, May 1998.
Oberhard, M.L. and Y. T. Lo, “Simple Method of Experimentally Investigating Scanning Microstrip Antenna Array without Phase-Shifting Devies”, Electronic Letters, vol. 25. No. 16, pp. 1042-1043, Aug. 3, 1989.
Swenson, G.W. Jr and
Baker & Botts L.L.P.
Raytheon Company
Wimer Michael C.
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