1. Field of the Invention
The subject invention relates to an antenna system. More specifically, the invention relates to a circularly polarized antenna for use with the system.
2. Description of the Related Art
Motor vehicles have traditionally been equipped to receive RF signals, particularly terrestrial broadcast signals, i.e., AM and FM radio broadcasts. Recent technological advances have created a need for reception of other RF signals, such as cellular (mobile) telephone signals, Satellite Digital Audio Radio Service (SDARS) signals, and global positioning system (GPS) signals.
To receive circularly polarized signals, such as SDARS or GPS signals, patch antennas have been used. However, these patch antennas often require that radiating elements include specialized perturbation features to generate the circular polarization with practical implications which can affect antenna performance. In order to improve reliability and performance, as well as reduce cost and create more desirable aesthetics, it is desirable to have a circularly polarized patch antenna with minimal or no perturbation features. Furthermore, prior art patch antennas often include wire feed lines which must be directly connected, i.e., soldered, to the patch antenna. Soldering a feed line to the patch antenna is impractical for certain antenna implementations as well as being a labor intensive process which often results in antenna defects. Moreover, when the antenna is implemented with a vehicle window, the vibration of the window can effect solder joints as well as having other adverse effects.
The subject invention is an antenna for receiving and/or transmitting a circularly polarized RF signal. The antenna includes a first radiating patch and a second radiating patch. The second radiating patch is disposed generally parallel to and non-planar with the first radiating patch. A feeding element is disposed between the radiating patches for feeding RF signals from and/or to the radiating patches via electromagnetic coupling. An elongated axis is defined along a longest length of each of the radiating patches. The elongated axis of the first radiating patch is disposed at about a 90 degree angle with respect to the elongated axis of the second radiating patch.
The antenna may be integrated with a window by disposing the first radiating patch on a nonconductive pane.
By utilizing patches with elongated axes disposed perpendicular to one another, the CP antenna achieves circular polarization without the need for perturbation features. This improves aesthetics of the antenna and may assist in manufacturing efforts. Furthermore, by utilizing electromagnetic coupling to feed the patches of the CP antenna, installation of the CP antenna on a nonconductive pane becomes markedly simpler and more reliable over prior art antennas where a wire feed line must be soldered to a radiating patch.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures, wherein like numerals indicate like parts throughout the several views, an antenna system 10 is shown herein. Referring to
Referring to
In the illustrated embodiment, the nonconductive pane 20 is implemented as at least one pane of glass 22. Of course, the window 16 may include more than one pane of glass 22. Those skilled in the art realize that automotive windows 12, particularly windshields, may include two panes of glass sandwiching a layer of polyvinyl butyral (PVB).
The pane of glass 22 is preferably automotive glass and more preferably soda-lime-silica glass. The pane of glass 22 defines a thickness between 1.5 and 5.0 mm, preferably 3.1 mm. The pane of glass 22 also has a relative permittivity between 5 and 9, preferably 7. Those skilled in the art, however, realize that the nonconductive pane 20 may be formed from plastic, fiberglass, or other suitable nonconductive materials.
Referring now to
The CP antenna 12 is preferably utilized to receive a CP radio frequency (RF) signal. However, those skilled in the art realize that the CP antenna 12 may also be used to transmit the CP RF signal. Specifically, the illustrated embodiment of the CP antenna 12 receives a right-hand circularly polarized (RHCP) RF signal like that produced by the GPS. However, it is to be understood that the CP antenna 12 may also receive a left-hand circularly polarized (LHCP) RF signal, such as those produced by a SDARS provider, such as Sirius XM Radio. Furthermore, the CP antenna 12 may alternatively be used to transmit and/or receive a linearly polarized RF signal.
Referring to
A second radiating patch 26 is disposed generally parallel to and non-planar with the first radiating patch 24. Said another way, the second radiating patch 26 is disposed below the first radiating patch 24. The second radiating patch 26 is formed of a conductive material. Suitable conductive materials for implementing the second radiating patch 26 include, but are not limited to, gold, silver, copper, and aluminum.
In the illustrated embodiment, as shown best in
The radiating patches 24, 26 of the CP antenna 12 in the illustrated embodiment each have an elongated shape. That is, a maximum length of each radiating patch 24, 26 is longer than a maximum width of each radiating patch. Furthermore, in the illustrated embodiment, the radiating patches 24, 26 have the same shape and dimensions as one another.
For purposes of further describing the spatial relationship between the radiating patches 24, 26, and as shown in
The first elongated axis 28 is disposed at about a 90 degree angle with respect to the second elongated axis 30. Said another way, the first elongated axis 28 is generally perpendicular to the second elongated axis 30. Said yet another way, the maximum length of the first radiating patch 24 is about 90 degrees offset from the maximum length of the second radiating patch 26. By disposing the radiating patches 24, 26 in this manner, the CP antenna 12 is able to generate circular polarization. However, the offset need not be precisely 90 degrees. An offset of +/−10 degrees from the 90 degree ideal may be suitable to generate the circular polarization.
In the illustrated embodiment, as shown in
In the illustrated embodiment, the CP antenna 12 also includes a ground plane 32 disposed between the radiating patches 24, 26. The ground plane 32 is generally parallel to, and non-planar with, each of the radiating patches 24, 26. The ground plane 32 is formed of a conductive material. Suitable conductive materials for implementing the ground plane 32 include, but are not limited to, gold, silver, copper, and aluminum.
Referring to
In the illustrated embodiment, the legs 38, 40 are disposed at about a 45 degree angle with respect to each of the elongated axes 28, 30 of the radiating patches 24, 26. This angle of the legs 38, 40 with respect to the elongated axes 28, 30 assists in generation of the circular polarization of the CP antenna 12. However, the offset need not be precisely 45 degrees. An offset of +/−10 degrees from the 45 degree ideal may be suitable to assist in generation of the circular polarization.
A transmission line 44 is attachable to the coplanar waveguide 34 for transmitting RF signals to/from the CP antenna 12. In the illustrated embodiment, the transmission line 44 is unbalanced having a center conductor 46 surrounded by a shield 48 connectable to the coplanar waveguide 34 as shown in
The coplanar waveguide 34 also preferably includes an impedance matching portion 50. Specifically, in the illustrated embodiment, the dimensions of the legs 38, 40 of the slot 36 are varied to implement the impedance matching portion 50. More specifically, a width of the impedance matching portion 50 is wider than a width of the feeding portion 42. By varying the width and/or a length of the impedance matching portion 50, the impedance of the coplanar waveguide 34 may be matched to an impedance of the transmission line 44. Importantly, by varying the slot 36 dimensions, the CP antenna 12 may be impedance matched with the transmission line 44 without using additional electric elements, such as resistors, capacitors, or inductors.
The CP antenna 12 of the illustrated embodiment also includes a first dielectric layer 52 and a second dielectric layer 54. The first dielectric layer 52 is disposed between the first radiating patch 24 and the ground plane 32 and the second dielectric layer 54 is disposed between the ground plane 32 and the second radiating patch 26.
The CP antenna 12 may also include a reflector 56 for reflecting RF signals towards at least one of the radiating patches 24, 26. In the illustrated embodiment, the reflector 56 is disposed generally parallel to, and non-planar with, the ground plane 32 and the radiating patches 24, 26. Specifically, one of the radiating patches 24, 26 is sandwiched between the reflector 56 and the ground plane 32. More specifically, as can be seen in
Referring now to
The radiating patches 60, 62 of the illustrated embodiment each have a generally square shape with each radiating patch 60, 62 having the same dimensions as the other. However, those skilled in the art realize other suitable shapes may be implemented. Also in the illustrated embodiment, the LP antenna 14 also includes a ground plane 64 disposed between the radiating patches 60, 62. The ground plane 64 is generally parallel to, and non-planar with, each of the radiating patches 60, 62. The ground plane 64 is formed of a conductive material. Suitable conductive materials for implementing the ground plane 64 include, but are not limited to, gold, silver, copper, and aluminum.
Referring to
A transmission line 76 is attachable to the coplanar waveguide 66 for transmitting RF signals to/from the LP antenna 14. In the illustrated embodiment, the transmission line 76 is unbalanced having a center conductor 78 surrounded by a shield 80 connectable to the coplanar waveguide 66 as shown in
The coplanar waveguide 66 also preferably includes an impedance matching portion 82. Specifically, in the illustrated embodiment, the dimensions of the legs 70, 72 of the slot 68 are varied to implement the impedance matching portion 82. More specifically, a width of the impedance matching portion 82 is wider than a width of the feeding portion 74. By varying the width and/or a length of the impedance matching portion 82, the impedance of the coplanar waveguide 66 may be matched to an impedance of the transmission line 76.
Referring again to
The LP antenna 14 may also include a reflector 88 for reflecting RF signals towards at least one of the radiating patches 60, 62. In the illustrated embodiment, the reflector 88 is disposed generally parallel to, and non-planar with, the ground plane 64 and the radiating patches 60, 62. Specifically, one of the radiating patches 60, 62 is sandwiched between the reflector 88 and the ground plane 64. More specifically, as can be seen in
Referring to
To maintain suitable performance, a distance di between each antenna 12, 14 is preferably at least half the wavelength λ of the minimum operating frequency that is desired. That is, di≧λmax/2. However, smaller distances di may be achieved by properly considering coupling effects between the antennas 12, 14, as may be realized by those skilled in the art.
The illustrated embodiments of the system 10, as shown in
The antennas 12, 14 are in communication with at least one receiver 92, 93, 94, 95. Specifically, in the illustrated embodiments, the antennas 12, 14 are in communication with a first receiver 92, a second receiver 93, a third receiver 94, and a fourth receiver 95. Of course, those skilled in the art realize that the number of receivers may be modified based on various factors without departing from the scope of the invention.
In a first embodiment, as shown in
In a second embodiment, as shown in
The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.
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Number | Date | Country | |
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20110221652 A1 | Sep 2011 | US |