Patent Grant
6911952
The present invention relates to antennas, and more particularly to crossed-slot antennas for mobile satellite and terrestrial reception.
Smaller, less visible antennas are an increasing trend in vehicle design. One approach for providing these antennas employs a crossed-slot antenna. The crossed-slot antenna can receive signals from satellite radio broadcasting systems such as satellite digital audio radio system (SDARS). Crossed-slot antennas can be as thin as a small fraction of one wavelength tall when combined with a resonant cavity. The reception characteristics and the relatively small size of crossed-slot antennas are ideal for mobile receiver applications.
Conventional fabrication techniques for crossed-slot antennas require the use of low-loss dielectric materials such as Teflon or Duroid. These materials may be prohibitively expensive for commercial applications such as high-volume automobile manufacturing. Absent these specialized low-loss materials, the internal dielectric loss of the crossed-slot antenna is unacceptably high.
Conventional fabrication methods for the crossed-slot antenna employ printed circuit boards. A circuit board is initially plated with a suitable metal, such as copper, which acts as the antenna. Typically, slots are made in the antenna using standard photolithography techniques. The printed circuit board is formed with a suitable dielectric material and acts as a cavity for the antenna.
A crossed-slot antenna according to the present invention is fabricated by forming a feed structure and a crossed-slot in a sheet of metal. Sidewalls are formed on the sheet of metal. The sidewalls are attached to a circuit board to form an air-filled cavity defined by the sheet of metal, the sidewalls, and the circuit board.
In another embodiment, a crossed-slot antenna with a solid cavity is fabricated. First and second intersecting ridges are created on one side of a sheet of plastic. A feed aperture is formed in the sheet of plastic. The sheet of plastic is plated with metal. The metal plating is removed from one side of the sheet of plastic to expose a first ridge and a second ridge. The sheet of plastic is attached to a circuit board.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements.
An exemplary crossed-slot antenna according to the present invention is shown in
The crossed-slot antenna 10 is suited for satellite radio broadcasting systems such as SDARS. Satellites in satellite radio systems broadcast information to a terrestrial repeater network, which subsequently rebroadcasts the information to a mobile receiver. Satellites typically broadcast in circular polarization, wherein the orientation of the receiver is not important. Terrestrial broadcasters, however, use vertical linear polarization. The crossed-slot antenna 10 is able to receive transmissions from both satellite and terrestrial broadcasters as will be described below.
The first slot 12 is shorter than the second slot 14. Consequently, the first slot 12 has slightly higher resonant frequency than the second slot 14. An antenna feed point 18 is positioned along a line 20 lying at a forty-five degree angle between the first slot 12 and the second slot 14. The position of the feed point 18 causes the first slot 12 and the second slot 14 to be excited equally.
The antenna 10 is designed so that the first slot 12 is out of phase with the second slot 14 by approximately ninety degrees when both slots are excited simultaneously. The antenna arrangement results in circular polarization for angles near zenith and for angles within the upper hemisphere. For angles near the horizon, the effective cross section of one of the slots approaches an infinitesimal point. The resulting radiation from the opposing slot is linearly polarized in the vertical direction.
Referring now to
Referring now to
A ground plane 40 made of a conducting material is attached to a side of the circuit board 34. The metal forming the ground plane 40 is preferably interrupted only by the feed point aperture 38. A receiver circuit 42 mounted on the circuit board 34 shares the ground plane 40 with the antenna 20a. The feed structure 30, which communicates with the circuit board 34 via the feed point aperture 38, acts as the input from the antenna 20a to the receiver circuit 42.
Using the above-described method, the circuit board 34 may be a simple, two-layer circuit board that is constructed from high loss, low cost material. The amplifiers, filters, and other circuit elements of the receiver circuit 42 are attached to the underside of the circuit board 34 using surface mount techniques. The antenna 20a is attached to the circuit board 34 by soldering the mounting tabs 28 to mounting apertures 36.
Referring now to
Referring now to
Referring now to
The antenna 20b is mounted to the circuit board 34 to form the completed alternative structure 70 as shown in FIG. 7. Because the circuit board 34 provides a single aperture 38 for attachment purposes, the alternative structure 70 is a simpler, less expensive design. The antenna 20b is aligned with the circuit board 34 using an alternative method due to the absence of mounting tabs 28 and mounting apertures 36. While this complicates the fabrication process, alternative alignment methods are well known to those skilled in the art of surface mounting techniques. The antenna 20b may be attached to the circuit board 34 using soldering paste or other attachment methods.
Referring now to
Referring now to
The plastic block 80 acts as the cavity as described in previous embodiments. The antenna 20c has a higher dielectric loss due to the plastic material filling the cavity. Additionally, antenna 20c is more expensive to produce than previous embodiments discussed herein. However, antenna 20c may be advantageous in applications wherein size is an important factor. Antenna 20c may be constructed smaller than embodiments with an air-filled cavity 52. Nonetheless, antenna 20c is less expensive to produce than conventional methods.
Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4916457 | Foy et al. | Apr 1990 | A |
| 5581266 | Peng et al. | Dec 1996 | A |
| 6593891 | Zhang | Jul 2003 | B2 |
| 6646618 | Sievenpiper | Nov 2003 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20040201533 A1 | Oct 2004 | US |
