Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-10-31
2001-10-23
Phan, Tho G (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S790000, C343S795000, C343S830000
Reexamination Certificate
active
06307510
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of communications, and more particularly, to phased array antennas.
BACKGROUND OF THE INVENTION
Existing microwave antennas include a wide variety of configurations for various applications, such as satellite reception, remote broadcasting, or military communication. The desirable characteristics of low cost, light-weight, low profile and mass producibility are provided in general by printed circuit antennas wherein flat conductive elements are spaced from a single essentially continuous ground element by a dielectric sheet of uniform thickness. The antennas are designed in an array and may be used for communication systems such as identification of friend/foe (IFF) systems, personal communication service (PCS) systems, satellite communication systems, and aerospace systems, which require such characteristics as low cost, light weight, low profile, and a low sidelobe.
The bandwidth and directivity capabilities of such antennas, however, can be limiting for certain applications such as space applications. Furthermore, while a microstrip patch antenna is advantageous in applications requiring a conformal configuration, e.g. in aerospace systems, mounting the antenna presents challenges with respect to the manner in which it is fed such that conformality and satisfactory radiation coverage and directivity are maintained and losses to surrounding surfaces are reduced. More specifically, increasing the bandwith of a phased array antenna with a wide scan angle is conventionally achieved by dividing the frequency range into multiple bands. This approach results in a considerable increase in the size and weight of the antenna while creating a Radio Frequency (RF) interface problem. Also, gimbals have been used to mechanically obtain the required scan angle. Again, this approach increases the size and weight of the antenna, and results in a slower response time.
Thus, there is a need for a lightweight patch dipole phased array antenna with a wide frequency bandwith and a wide scan angle, and that can be conformally mountable to a surface.
SUMMARY OF THE INVENTION
In view of the foregoing background, it is therefore an object of the invention to provide a lightweight patch dipole phased array antenna with a wide frequency bandwith and a wide scan angle, and that can be conformally mountable to a surface.
This and other objects, features and advantages in accordance with the present invention are provided by a dual polarization antenna including a substrate having a ground plane and a dielectric layer adjacent thereto, and at least one antenna unit carried by the substrate. The antenna unit includes four adjacent antenna elements arranged in spaced apart relation from one another about a central feed position on the dielectric layer opposite the ground plane. Preferably, diagonal pairs of antenna elements define respective antenna dipoles thereby providing dual polarization. The antenna unit also includes an antenna feed structure comprising four coaxial feed lines, each coaxial feed line comprising an inner conductor and a tubular outer conductor in surrounding relation thereto. The outer conductors have parallel adjacent ends joined together about an axis and are connected to the ground plane. The ends of the outer conductors are tapered and arranged so that portions thereof adjacent the axis extend further beyond the ground plane in the dielectric layer and toward the antenna elements. The inner conductors preferably extend outwardly from ends of respective outer conductors, through the dielectric layer and are connected to respective antenna elements adjacent the central feed position.
Preferably, the ends of the outer conductors are symmetrically angled, and all of the antenna elements have a same shape. The ground plane may extend laterally outwardly beyond a periphery of the antenna unit, and the coaxial feed lines may diverge outwardly from contact with one another upstream from the central feed position. The antenna may also include at least one hybrid circuit carried by the substrate and connected to the antenna feed structure. Each antenna element may have a generally rectangular or a generally square shape. Furthermore, the at least one antenna unit preferably comprises a plurality of antenna units arranged in an array.
The dielectric layer preferably has a thickness in a range of about ½ an operating wavelength of the antenna, and at least one impedance matching dielectric layer may be provided on the antenna unit. This impedance matching dielectric layer may extend laterally outwardly beyond a periphery of the antenna unit. Also, the substrate is preferably flexible.
Objects, features and advantages in accordance with the present invention are also provided by a method of making an antenna including forming a substrate having a ground plane and a dielectric layer adjacent thereto, and providing at least one antenna unit on the substrate. Providing the antenna unit includes arranging four adjacent antenna elements in spaced apart relation from one another about a central feed position on the dielectric layer opposite the ground plane, and forming an antenna feed structure comprising four coaxial feed lines, each coaxial feed line comprising an inner conductor and a tubular outer conductor in surrounding relation thereto, the outer conductors having parallel adjacent ends. Forming the antenna feed structure further comprises joining together the parallel adjacent ends of the outer conductors about an axis, connecting the parallel adjacent ends of the outer conductors to the ground plane, tapering and arranging the parallel adjacent ends of the outer conductors so that portions thereof adjacent the axis extend further beyond the ground plane in the dielectric layer and toward the antenna elements, and connecting the inner conductors to respective antenna elements adjacent the central feed position, the inner conductors extending outwardly from the parallel adjacent ends of respective outer conductors.
REFERENCES:
patent: 3568204 (1971-03-01), Blaisdell
patent: 3594810 (1971-07-01), Kaloi
patent: 3995277 (1976-11-01), Olyphant, Jr.
patent: 4173019 (1979-10-01), Williams
patent: 4287603 (1981-09-01), Moser
patent: 4546358 (1985-10-01), Edlin et al.
patent: 4734660 (1988-03-01), Lofgren
patent: 5389937 (1995-02-01), Kaloi
patent: 5477233 (1995-12-01), Hemming et al.
Rawnick James J.
Taylor Robert Charles
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Phan Tho G
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