Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Reexamination Certificate
2000-10-31
2003-01-28
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
C343S797000
Reexamination Certificate
active
06512487
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. The simplest forms of printed circuit antennas are microstrip antennas wherein flat conductive elements are spaced from a single essentially continuous ground element by a dielectric sheet of uniform thickness. An example of a microstrip antenna is disclosed in U.S. Pat. No. 3,995,277 to Olyphant.
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, lightweight, low profile, and a low sidelobe.
The bandwidth and directivity capabilities of such antennas, however, can be limiting for certain applications. While the use of electromagnetically coupled microstrip patch pairs can increase bandwidth, obtaining this benefit presents significant design challenges, particularly where maintenance of a low profile and broad beamwidth is desirable. Also, the use of an array of microstrip patches can improve directivity by providing a predetermined scan angle. However, utilizing an array of microstrip patches presents a dilemma. The scan angle can be increased if the array elements are spaced closer together, but closer spacing can increase undesirable coupling between antenna elements thereby degrading performance.
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 phased array antenna with a wide frequency bandwidth and a wide scan angle, and that is 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 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 wideband phased array antenna including an array of dipole antenna elements on a flexible substrate. Each dipole antenna element comprises a medial feed portion and a pair of legs extending outwardly therefrom, and adjacent legs of adjacent dipole antenna elements have respective spaced apart end portions to provide increased capacitive coupling between the adjacent dipole antenna elements. The spaced apart end portions have a predetermined shape and are relatively positioned to provide increased capacitive coupling between the adjacent dipole antenna elements. Preferably, the spaced apart end portions in adjacent legs comprise interdigitated portions, and each leg comprises an elongated body portion, an enlarged width end portion connected to an end of the elongated body portion, and a plurality of fingers, e.g. four, extending outwardly from said enlarged width end portion.
The wideband phased array antenna has a desired frequency range and the spacing between the end portions of adjacent legs is less than about one-half a wavelength of a highest desired frequency. Also, the array of dipole antenna elements may include first and second sets of orthogonal dipole antenna elements to provide dual polarization. A ground plane is preferably provided adjacent the array of dipole antenna elements and is spaced from the array of dipole antenna elements less than about one-half a wavelength of a highest desired frequency.
Preferably, each dipole antenna element comprises a printed conductive layer, and the array of dipole antenna elements are arranged at a density in a range of about 100 to 900 per square foot. The array of dipole antenna elements are sized and relatively positioned so that the wideband phased array antenna is operable over a frequency range of about 2 to 30 Ghz, and at a scan angle of about ±60 degrees. There may be at least one dielectric layer on the array of dipole antenna elements, and the flexible substrate may be supported on a rigid mounting member having a non-planar three-dimensional shape.
Features and advantages in accordance with the present invention are also provided by a method of making a wideband phased array antenna including forming an array of dipole antenna elements on a flexible substrate, where each dipole antenna element comprises a medial feed portion and a pair of legs extending outwardly therefrom. Forming the array of dipole antenna elements includes shaping and positioning respective spaced apart end portions of adjacent legs of adjacent dipole antenna elements to provide increased capacitive coupling between the adjacent dipole antenna elements. Shaping and positioning the respective spaced apart end portions preferably comprises forming interdigitated portions.
REFERENCES:
patent: 3016536 (1962-01-01), Fubini
patent: 3747114 (1973-07-01), Shyhalla
patent: 3995277 (1976-11-01), Olyphant, Jr.
patent: 4131896 (1978-12-01), Miller
patent: 4173019 (1979-10-01), Williams
patent: 4514734 (1985-04-01), Cermignani et al.
patent: 5485167 (1996-01-01), Wong et al.
Durham Timothy Earl
Munk Benedikt A.
Taylor Robert Charles
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Harris Corporation
Wimer Michael C.
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