Patent Grant
7436361
This invention relates generally to the transmission and reception of radio frequency signals and, more particularly to a low-profile, low-loss antenna apparatus.
In many telecommunications applications, microstrip antennas are employed. There are several types of microstrip antennas (also known as printed antennas), the most common of which is the microstrip patch antenna. A microstrip patch antenna is a narrowband, wide-beam antenna fabricated by etching an antenna element pattern in metal trace bonded to an insulating substrate. Because such antennas may be low profile, mechanically rugged and conformable, they are often employed on aircraft and spacecraft, or are incorporated into mobile radio communications devices.
Microstrip antennas are also relatively inexpensive to manufacture and design because of the simple 2-dimensional physical geometry. An advantage inherent to patch antennas is the ability to either transmit or receive (i.e. transceive) electromagnetic signals having polarization diversity. Patch antennas can easily be designed to have Vertical, Horizontal, Right Hand Circular (RHCP) or Left Hand Circular (LHCP) Polarizations with a single antenna feedpoint. This unique property allows patch antennas to be used in many types of communications links that may have varied requirements.
Another potential improvement for modern communications devices is the incorporation of waveguide architectures. Waveguides represent an effective mechanism for conveying signals with very little degradation or loss. Waveguides are commonly used in microwave communications, broadcasting, and radar installations. A waveguide consists of a rectangular or cylindrical metal tube or pipe. The electromagnetic field propagates lengthwise.
To function properly, a waveguide must have a certain minimum cross-sectional dimensions relative to the wavelength of the desired signal. If the waveguide is too narrow or the frequency is too low (i.e. the wavelength is too long), the electromagnetic fields cannot propagate. At any frequency above the cutoff (the lowest frequency at which the waveguide is large enough), the feed line will work well, although certain operating characteristics vary depending on the number of wavelengths in the cross section.
Mobility is a prime concern in the design of modern communications systems. Users are more likely than ever to require information in a variety of locales, thereby necessitating efficient mechanisms for ensuring the integrity of communicated data while minimizing the physical dimensions of individual communication system devices. Airborne TV antenna systems present a unique design challenge. Such antennas must be light weight, inexpensive, and capable of receiving dual circular-polarization (CP) radio frequency (RF) signals. Additionally, in order to be tail-mount compatible with medium size aircraft, the antennas must be able to fit in a package on the order of a 9″ swept volume.
Additionally, many current weather radars, including NEXRAD, transmit and receive radio waves with a single, horizontal polarization. However, the next generation of functionality in radar systems, such as polarimetric radar, may require a dual linear-polarization (LP) aperture.
As such it would be desirable to provide a low cost, light weight, high efficiency radiating antenna architecture capable of dual CP operation in an aircraft tail-mount compatible footprint or dual LP operation in weather radar.
Accordingly, the present invention is directed to a low-loss, dual polarized antenna. In general, the invention applies to systems where a microstrip patch antenna is combined with a waveguide for the transmission or reception of electromagnetic signals.
In an embodiment of the invention, a low-loss, dual polarized antenna is presented. The antenna may comprise: (a) a microstrip patch antenna, (b) a waveguide, and (c) a coupling interface between the antenna and waveguide. The microstrip patch antennas in the array may individually comprise: (i) a patch radiator having a defined area, and (ii) an associated microstrip. The configuration of the microstrip may dictate the polarity and phase of the signal that is either transmitted or received by the microstrip patch antenna. The polarity may be dual linearly-polarized or dual circularly polarized.
In a further embodiment of the invention, an antenna array is presented. The antenna array may comprise: (a) a plurality of microstrip antennas, and (b) a plurality of waveguides. The antenna array may further comprise: (c) a waveguide combiner.
In still a further embodiment of the invention, a method for the manufacturing of an antenna is presented. The method may comprise the step: (a) operably coupling a microstrip patch antenna to a waveguide.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention.
The numerous objects and advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which:
The following discussion is presented to enable a person skilled in the art to make and use the present teachings. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the present teachings. Thus, the present teachings are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the present teachings. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of the present teachings. Reference will now be made, in detail, to presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings.
Referring to
The patch element 103 can be a relatively thin sheet of metal or other material having metallic properties capable of emitting or receiving electromagnetic signals. The patch element 103 is disposed on a first side of the first dielectric layer 105.
The first ground plane 108 is disposed on the second side of the first dielectric layer 105. The second dielectric layer 106 and third dielectric layer 107 are disposed between the first ground plane 108 and the second ground plane 109.
The stripline 104 is disposed between the second dielectric layer 106 and third dielectric layer 107. The stripline 104 may be configured so that the antenna receives or emits polarized electromagnetic signals, as will be further discussed.
The waveguide 102 is used as a low-loss conduit between the microstrip patch antenna and an external device capable of generating and/or processing electromagnetic signals (not pictured). The waveguide 102 may comprise a substantially rectangular raised ridge 110 disposed along the length of the waveguide.
Referring to
The microstrip patch antenna may also comprise a plurality of circuit board vias 211 disposed within the second dielectric layer 204 and the third dielectric layer 205 and linking the first ground plate 208 and the second ground plate 210. The board vias may comprise generally cylindrical holes through the second dielectric layer 204 and third dielectric layer 205 which are plated with a conducting material. The circuit board vias serve to extinguish “parallel plate” modes within the stripline structure. The vias tie the ground layers 207 and 208 together and so as to extinguish potential differences to exist across them. The stripline is thus permitted to act as the conductor while the top and bottom layers are at “ground” potential.
Referring to
Referring to
The waveguide 401 may also comprise a ridge 402 disposed along the center length of the individual waveguides so as to compress the lateral dimensions of a signal and ensure very low signal degradation or loss. The waveguide design dimensions are a function of the designated frequencies of operation. The significant dimension is the width of the ridge waveguide. In a particular embodiment of the invention, adjacent ridged waveguides 401 feed opposite polarizations (i.e. horizontal and vertical). As such, the effective spacing 402 for each waveguide (and thus microstrip each patch antenna sub-array) is twice the waveguide width. In order to maintain high operating performance and avoid grating lobes, the spacing must be less than a free-space wavelength. Regular non-ridged waveguides may not support array spacing this small. As such, a ridge waveguide may be used.
Each waveguide may further comprise a coupling mechanism providing a conduit for signal transfer from the waveguide 401 to a waveguide combiner (not pictured). The coupling mechanism may be may be selected from slot coupling probe coupling, proximity coupling, or edge feeding. In the presently depicted embodiment, a slot couple 403 is utilized.
The waveguide may be operably connected to the waveguide combiner via any number of methods including chemical adhesion, solder, mechanical clamps, rivets or screws. In the depicted embodiment, board-compression screw holes 404 are provided.
The waveguide may be operably connected to a microstrip patch antenna array (not pictured) via any number of methods including chemical adhesion, solder, mechanical clamps, rivets or screws. In the depicted embodiment, board-compression screw holes 405 are provided.
Referring to
In still a further embodiment, the waveguide ridge 501 may have a height 505 of from 1.75 mm to 11.9 mm and a width 506 of from 2.28 to 15.24 mm. In still a further embodiment, the waveguide ridge may have a height 505 of 7.8 mm and a width 506 of 10.0 mm.
The waveguide may be operably connected to a microstrip patch antenna array via any number of methods including chemical adhesion, solder, mechanical clamps, rivets or screws. In the depicted embodiment, board-compression screw holes 507 are provided.
Referring to
The waveguide combiner 600 may be operably connected to a plurality of waveguides (not pictured) via any number of methods including chemical adhesion, solder, mechanical clamps, rivets or screws. In the depicted embodiment, board-compression screw holes 603 are provided.
It is believed that the present invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction, and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof, it is the intention of the following claims to encompass and include such changes.
| Number | Name | Date | Kind |
|---|---|---|---|
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| 5170174 | Caer et al. | Dec 1992 | A |
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| 6864840 | Zhu et al. | Mar 2005 | B2 |
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| 6977614 | Poe et al. | Dec 2005 | B2 |
