The present invention generally relates to an antenna system and a method of communicating signals by the antenna system, and more particularly, to a dual circularly polarized antenna system and a method of communicating signals by the antenna system.
Wirelessly transmitted signals can be formatted in multiple ways, where the desired receiver is configured to receive the formatted signal. One example of formatting a signal is to polarize the signal, such as linear or circular polarization. Thus, the corresponding receiver typically needs an antenna that is configured to receive the signal that is polarized in a particular direction. Additionally, the antenna of the receiver can be configured to direct a beam in a particular direction in order to receive the transmitted signal.
In reference to
With regards to
According to one aspect of the present invention, an antenna system includes a substantially straight microstrip segment and a plurality of substantially straight microstrip projections. The microstrip segment has a feed point, where an electrical current is applied to the microstrip segment at the feed point. The plurality of microstrip projections extend from the microstrip segment in pairs at a predetermined angle, wherein each microstrip projection of the pair of microstrip projections extends from substantially the same location on the microstrip segment. A first microstrip projection of the plurality of microstrip projections extends from the microstrip segment on a first side of the microstrip segment and a second microstrip projection of the plurality of microstrip projections extends from the microstrip segment on a second side of the microstrip segment, such that the first and second microstrip projections at least one of emit and receive one sense of circularly polarized radiation in a first direction and another sense of circularly polarized radiation in a second direction simultaneously.
According to another aspect of the present invention, an antenna system includes a plurality of substantially straight microstrip segments, a plurality of connectors, and a plurality of substantially straight microstrip projections. The plurality of microstrip segments each have a feed point distant from the ends of the microstrip segment. At least one connector of the plurality of connectors electrically connects the plurality of microstrip segments, wherein one connector connects the microstrip segment at the feed point. The plurality of microstrip projections extend from the microstrip segment in pairs at a predetermined angle, wherein each microstrip projection of the pair of the microstrip projections extends from substantially the same location on the microstrip segment. A first microstrip projection of the plurality of microstrip projections extends from the microstrip segment on a first side of the microstrip segment and a second microstrip projection of the plurality of microstrip projections extends from the microstrip segment on a second side of the microstrip segment, such that the first and second microstrip projections at least one of emit and receive right-hand circularly polarized (RHCP) radiation in one direction and left-hand circularly polarized (LHCP) radiation in another direction simultaneously.
According to yet another aspect of the present invention, a method of communicating a signal by a dual circularly polarized antenna system includes the step of providing a plurality of substantially straight microstrip segments, wherein the microstrip segments are electrically connected subarrays. The method further includes the steps of selecting a frequency, receiving circular polarization radiation in a plurality of directions from a plurality of substantially straight microstrip projections extending from each of the microstrip segments simultaneously, scanning the subarrays for a signal at the selected frequency, rotating the plurality of microstrip segments, and receiving a signal at the selected frequency based upon scanning the subarrays and the rotational position of the plurality of microstrip segments.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
In reference to
The antenna system 30 also includes a plurality of substantially straight microstrip projections that extend from the microstrip segment in pairs at a predetermined angle θ. Each of the microstrip projections of the pair of the microstrip projections extends from substantially the same location on the microstrip segment 32. According to an alternate embodiment, the electrical current can be applied to the microstrip projections, such as, but not limited to, a midpoint of adjacent pairs of microstrip projections 36A,36B. Alternatively, the feed point 34 can be at the ends of the microstrip segment 32, according to one embodiment.
Typically, a first microstrip projection 36A of the plurality of microstrip projections extends from a first side of the microstrip segment 32, and a second microstrip projection 36B of the plurality of microstrip projections extends from a second side of the microstrip segment 32, such that the first and second microstrip projections 36A,36B emit and/or receive circularly polarized radiation in first and second directions, as described in greater detail herein. Thus, the microstrip projections 36A,36B have an element pattern (
By way of explanation and not limitation, the pairs of microstrip projections 36A,36B can be spaced apart by approximately one wavelength of a single signal that is transmitted or received by the antenna system 30. The predetermined angle θ between the microstrip segment 32 and each of the microstrip projections 36A,36B is approximately forty-five degrees (45°), according to one embodiment. Thus, an angle φ between each of the microstrip projections 36A,36B of the pair of microstrip projections can be approximately ninety degrees (90°). When the electrical current is applied to the microstrip projections 36A,36B, the radiation emitted by the microstrip projections 36A,36B is in-phase at bore sight and out-of-phase in the upper and lower directions (i.e., north and south), since midpoints of the microstrip projections 36A,36B are not overlapping and separated by a distance (D). Further, the length of the microstrip projections 36A,36B can be approximately one-half a wavelength of a signal being transmitted or received by the antenna system 30, according to one embodiment.
With regards to both
According to an alternate embodiment shown in
According to one embodiment, an electrical current is applied to the connector 38 at a feed point 39 on the connector 38 that is distant from the midpoint of the connector 38. For purposes of explanation and not limitation, the feed point 39 can be a quarter wavelength offset from the midpoint of the connector 38, which typically results in a null of the emitted radiation pattern at bore sight, according to one embodiment. According to an alternate embodiment, the feed point 39 can be at the midpoint of the connector 38, which typically results in no nulls in the emitted radiation pattern. It should be appreciated by those skilled in the art that the feed point 39 can be located at other locations on the connector 38, resulting in nulls in the emitted radiation pattern.
The electrical current passes through the connector 38 and passes to the microstrip segments 32 of the feed points 34. Thus, first and second microstrip projections 36A,36B can be fed an electrical current in-phase, but the radiation emitted by the first and second microstrip projections 36A,36B on the first microstrip segment 32 are out-of-phase from the radiation emitted by the first and second microstrip projections 36A,36B on the second microstrip segment 32 that are connected by the connector 38 forming two radiation lobes, such as right-hand circularly polarized (RHCP) radiation in north and left-hand circularly polarization (LHCP) radiation in south. The vertically out-of-phase emitted radiation is from the electrical current being applied at feed point 39 that is offset or distant from the midpoint of the connector 38. According to one embodiment, zero radiation is emitted at bore sight when electrical current is applied to feed point 39, such that, maximum radiation is emitted off bore sight.
In reference to
According to a disclosed embodiment, each pair of microstrip segments 32 that are connected by the connector 38 forms a subarray. It should be appreciated by those skilled in the art that any number of microstrip segments 32 can be connected to form a subarray, and that any number of subarrays can be used to form an array. The subarrays can be electronically scanned, such that it can be determined if a signal is being received. When a subarray is selected, an array factor (
For purposes of explanation and not limitation, the subarrays can be scanned by applying a different electrical current to each subarray at the feed point 39, according to one embodiment. The electrical current can differ by changing the magnitude and/or phase of the electrical current, according to a disclosed embodiment.
According to one embodiment, as shown in
According to a disclosed embodiment, the rotatable surface 40, is actuated or rotated by a rotary joint 50 and motor 52. An encoder 54 can be used to determine the rotational location of the rotatable surface and the microstrip segments 32. Additionally, bearings 56 can be used for ease in rotating the rotatable surface 40.
In reference to
The signal being received by the antenna system 30 is monitored, such that, the arrays of microstrip segments 32 are electronically scanned. Thus, depending upon which signal being transmitted by the transmitter 44 and satellite 46 wants to be received, is dependent upon the array of microstrip segments 32 selected. The rotatable surface 40 can then be actuated in order to mechanically re-direct the selected array. When each array pattern (
According to a disclosed embodiment, the satellite 46 is a GEO satellite, such that if vehicle 42 is operating in North America, the antenna beam should be substantially directed towards the south in order to receive the signal re-transmitted from the satellite 46. Thus, if the signal is being transmitted as a RHCP signal, and the antenna system 30 is positioned so that the RHCP element pattern of the antenna system 30 is substantially directed towards the north, the controller actuates or rotates the rotatable surface 40 so that the RHCP element pattern of the antenna system 30 is substantially directed towards the south, such that the selected array pattern is mechanically re-directed. As the vehicle 42 is mobile and changing directions, the desired beam of the antenna system 30 can be substantially directed towards the south in order to receive the desired signal from the satellite 46, according to one embodiment. Additionally, since the plurality of microstrip projections are angled in order to steer the beam according to the predetermined angle, the antenna system 30 can be flat or embedded in the roof line of the vehicle 42 while steering the antenna beam substantially south towards the satellite 46.
In reference to
At step 108, the beam is scanned. According to one embodiment, the beam is electronically scanned at elevation to determine if the signal is being received. According to a disclosed embodiment, the beam is scanned by applying different electrical currents to the subarrays. The antenna is rotated at step 110. According to a disclosed embodiment, the microstrip segments 32 are rotated by the rotatable surface 40 in order to point the beam towards the south.
At decision step 112, it is determined if the signal at the selected frequency is being received. If it is determined at decision step 112 that the signal is not being received, then the method 100 proceeds to step 114, where the antenna system 30 changes the direction of the circularly polarized radiation that is being received by pointing the beam in elevation to the side of the opposite microstrip projection 36A,36B. At step 116, the antenna is rotated. According to a disclosed embodiment, the microstrip segments 32 are rotated in order for the beam to be pointed towards the south.
However, if it is determined at decision step 112 that the signal is being received, then the method 100 proceeds to step 118, where reception of the signal is maintained. According to one embodiment, when the antenna system 30 is used with a vehicle 42, the antenna can continuously be rotated in order for the antenna to be pointing in the desired direction to continue to receive the selected frequency. The method then ends at step 120.
According to one embodiment, the antenna system 30 is a passive system, such that the antenna system 30 can both transmit and receive signals. It should be appreciated by those skilled in the art that the above description of the antenna system 30 is applicable when the antenna system 30 is configured to transmit and/or receive signals. Thus, when the electrical current is applied, the plurality of microstrip projections emit circularly polarization in a plurality of directions simultaneously, and when the antenna system 30 is receiving signals, the plurality of microstrip projections receive circularly polarized radiation in a plurality of directions simultaneously.
Advantageously, the antenna system 30 is dual circularly polarized in two different directions, which does not require any switching mechanisms, such as an RF switch, in order to alter the polarization. Instead, the antenna system 30 can change polarizations by electronically scanning the array beam in elevation to the opposite side of the antenna system 30 and rotating the microstrip segments 32. Since the antenna system 30 is a dual circularly polarized antenna, the antenna system 30 is configured to receive and/or transmit signals that typically cannot be received and/or transmitted by a single polarized antenna. Additionally, the rotatable surface 40 can position the antenna system 30 in the desired direction in order to direct the antenna beam towards the satellite 46 in order for the antenna to receive the desired signal. Further, since the plurality of microstrip projections form pairs, wherein the pair of microstrip projections 36A,36B extend from the same microstrip segment 32, the antenna system 30 is more compact and can have a single feed point for electrical current, rather then having separate paths for each set of extensions that extend in a particular direction.
The above description is considered that of preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.
Number | Name | Date | Kind |
---|---|---|---|
2081162 | Alford | May 1937 | A |
4833482 | Trinh et al. | May 1989 | A |
5712643 | Skladany | Jan 1998 | A |
6424298 | Nishikawa et al. | Jul 2002 | B1 |
7071890 | Tanaka et al. | Jul 2006 | B2 |
20040017316 | Tanaka et al. | Jan 2004 | A1 |
Number | Date | Country |
---|---|---|
1 058 339 | Dec 2000 | EP |
1 529 361 | Oct 1978 | GB |
Number | Date | Country | |
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20090058741 A1 | Mar 2009 | US |