JP2007110183A - Circularly-polarized wave loop antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high gain circularly-polarized wave loop antenna which can receive a circularly-polarized wave incoming at a high-elevation angle. <P>SOLUTION: A first loop element 10 having perturbation conductors 12 and 13 which can receive a circularly-polarized wave, and a second loop element 20 having perturbation conductors 22 and 23 are arranged while being spaced apart vertically by a predetermined distance. A beam of the circularly-polarized wave loop antenna 1 can have a high elevation angle because a reception signal of the first loop element 10 arranged above is delayed behind a reception signal of the second loop element 20 when they are compounded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circularly polarized loop antenna capable of setting a circularly polarized beam tilt angle to an arbitrary beam tilt angle.

Currently, many communications using circular polarization are employed. For example, in the old days, it has been used for radar, and recently, it has been used for satellite broadcasting and satellite communication in mobiles. In communication using circularly polarized waves, a circularly polarized antenna is required, and conventionally, a helical antenna, a cross dipole antenna, a patch antenna, and the like are known as circularly polarized antennas. In this case, in satellite communication in a mobile body, a unidirectional characteristic type antenna such as a patch antenna has been conventionally used to receive radio waves from a satellite in the zenith direction. The antenna is attached to a place where radio waves from the satellite reach in. Alternatively, a film antenna formed on the film and capable of receiving circularly polarized waves is attached to the window glass for reception.
Japanese Patent No. 3443897 Japanese Patent Laid-Open No. 61-252701

  A patch antenna, which is a conventional circularly polarized antenna, is used as a GPS antenna mounted on a dashboard of a vehicle. However, the patch antenna has a large number of antenna components and is expensive. Further, since it is attached to a dashboard or the like, it is necessary to devise a method for attaching an antenna, and there is a problem that a space for attachment is required. Further, the helical antenna is configured by winding a conductive wire in a spiral shape, and there is a problem that a space for mounting is required in the same manner as the patch antenna. Further, in the cross dipole antenna, two equal-length dipole antennas are arranged so as to be orthogonal to each other, and power is supplied to the respective dipole antennas so that their phases are different from each other by 90 °. For this reason, the cross dipole antenna has a problem that it requires a two distributor and a 90 ° phase shifter and becomes large. By the way, when a film antenna that can receive circularly polarized waves formed on a film is attached to a window glass and received, the installation space is not necessary, but the window glass is inclined substantially vertically or at a steep angle. Therefore, the elevation angle of the beam radiated from the film loop antenna becomes low. Then, there is a problem that it becomes difficult to receive radio waves coming from the zenith direction or high elevation angle of a GPS satellite or the like. In addition, there is a problem that the gain of the film antenna that can receive circularly polarized waves is low.

  Accordingly, an object of the present invention is to provide a high-gain circularly polarized loop antenna that can receive circularly polarized waves coming from a high elevation angle.

  In order to achieve the above object, a circularly polarized loop antenna according to the present invention includes a first loop element including a loop conductor and two perturbation conductors provided in parallel to one side of the loop conductor, and a second loop element. The most important feature is that the loop elements are arranged at intervals, and the first loop element and the second loop element are fed with a phase difference.

  According to the present invention, a first loop element and a second loop element each including a loop conductor and two perturbation conductors provided in parallel to one side of the loop conductor are arranged at an interval, Since the first loop element and the second loop element are fed with a phase difference, the beam of the circularly polarized loop antenna can be tilted according to the phase difference of the feeding means. Accordingly, even when the moving body is fixed to the window glass, a beam with a high elevation angle can be formed by tilting the beam. In addition, since the signals received by the two loop conductors are combined, the gain of the circularly polarized loop antenna can be increased.

The configuration of a circularly polarized loop antenna according to an embodiment of the present invention is shown in FIG.
In the circularly polarized loop antenna 1 shown in FIG. 1, a first loop element 10 and a second loop element 20 are arranged with a predetermined distance apart. The first loop element 10 has a first loop conductor 11 formed in a rectangular shape, and a first perturbation conductor 12 and a second perturbation conductor 13 are arranged at equal intervals parallel to the upper side of the first loop conductor 11. It is arranged. The second loop element 20 has a second loop conductor 21 formed in a rectangular shape, and the first perturbation conductor 22 and the second perturbation conductor 23 are arranged at equal intervals parallel to the upper side of the second loop conductor 21. Are arranged. The first loop element 10 can transmit and receive circularly polarized waves by the action of the two first perturbation conductors 12 and the second perturbation conductors 13 arranged close to the upper side of the first loop conductor 11. The same applies to the second loop element 20, and the circularly polarized wave can be transmitted and received by the action of the two first perturbation conductors 22 and the second perturbation conductors 23 arranged close to the upper side of the second loop conductor 21. ing. The first loop element 10 and the second loop element 20 can easily adjust the circular polarization characteristic and the axial ratio characteristic by adjusting the distance between the two perturbation conductors. become.

  The first loop conductor 11 and the second loop conductor 21 have a length of about 1λ when the wavelength of the operating center frequency of the circularly polarized loop antenna 1 is λ, and the height H and width W are circularly polarized. The resonance characteristics of the wave loop antenna 1 are affected and each has a length of about λ / 4. Further, the distance D1 between the upper side of the first loop conductor 11 and the first perturbation conductor 12 in the first loop element 10 and the distance D2 between the first perturbation conductor 12 and the second perturbation conductor 13 are the circularly polarized loop antenna 1. The circularly polarized wave characteristic and the axial ratio characteristic are affected, and the interval is set to about 0.025λ to 0.03λ. This distance is the same as the distance between the upper side of the second loop conductor 21 and the first perturbation conductor 22 in the second loop element 20 and the distance between the first perturbation conductor 22 and the second perturbation conductor 23. The interval is about 0.025λ to 0.03λ.

  A feeding point 14 is provided below the first loop element 10, and power is fed from the feeding point 14 to the first loop element 10. Further, a feeding point 24 is provided below the second loop element 20, and power is fed from the feeding point 24 to the second loop element 20. A feeding line 15 is connected to the feeding point 14, and the feeding line 15 is connected to a feeding line 25 led out from the second loop element 20 and is connected to the feeding unit 30. The second loop element 20 is connected to the power feeding unit 30 via the power feeding line 25. Then, the reception signal of the first loop element 10 and the reception signal of the second loop element 20 are combined and output from the power feeding unit 30. When the circularly polarized loop antenna 1 is a GPS antenna, a cable derived from a GPS receiver is connected to the power supply unit 30. Here, when viewed from the feeding unit 30, the length from the feeding unit 30 to the feeding point 24 is longer than the feeding point 14 by the length L <b> 1 of the feeding line 15. For this reason, the received signal at the feeding point 14 reaches the feeding unit 30 with a phase delayed by a time corresponding to the length L1, and is combined with the received signal at the feeding point 24. That is, the beam formed by the first loop element 10 and the second loop element 20 tilts in the zenith direction. This beam tilt angle is an angle corresponding to the length L 1 of the feeder line 15.

The distance D3 between the power supply lines 15 affects the impedance characteristics of the power supply lines, and is about 0.003λ. Further, the interval between the feeder lines 25 is the same as the interval between the feeder lines 15. Further, the distance L2 between the first loop conductor 10 and the second loop element 20 affects the isolation characteristics between the first loop conductor 10 and the second loop element 20, and a distance of about 0.15λ. It is said that. Further, the length D4 is set so as to straddle one of the power supply lines 25 so as not to contact one of the power supply lines 15, and is made as short as possible.
The circularly polarized loop antenna 1 according to the present invention includes a film antenna formed by forming a first loop element 10 and a second loop element 20 and feed lines 15 and 25 by applying a conductive paint on a film, or by vapor deposition or sticking. It can be. Moreover, it can also be set as the printed antenna which printed the 1st loop element 10, the 2nd loop element 20, and the feeder lines 15 and 25 on the printed circuit board instead of the film.

  As described above, the beam tilt angle can be set by adjusting the phase according to the length L1 of the feed line 15. FIG. 2 shows a correspondence table between the feed line length L1 and the beam tilt angle. Referring to FIG. 2, when it is desired to obtain 20 degrees as the beam tilt angle, the feed line length L1 may be set to about 0.15λ, and when it is desired to obtain 45 degrees as the beam tilt angle, the feed line length L1 is set to about 0.1 mm. It can be determined that 32λ is used, and when it is desired to obtain a beam tilt angle of 70 degrees, the feed line length L1 may be set to about 0.45λ. Thus, the beam tilt angle can be set to an arbitrary angle. For this reason, even if the circularly polarized loop antenna 1 as a film antenna is attached to a window glass of a moving body, the elevation angle of the beam formed by the circularly polarized loop antenna 1 can be tilted in the zenith direction, The beam can be directed to communication satellites such as GPS satellites. Further, the beam of the circularly polarized loop antenna 1 can be directed not only to the communication satellite but also to the elevation angle direction of a desired communication station.

In the circularly polarized loop antenna 1, the feed line length L1 is set to about 0.35λ, and the radiation characteristic of the circularly polarized loop antenna 1 in the XZ plane when the dimensions are set as described above is shown in FIG. In FIG. 3, the Z direction is the zenith direction, and the XY plane is a horizontal plane parallel to the ground plane. Referring to FIG. 3, an elevation angle of about 50 degrees is obtained. Further, since the circularly polarized loop antenna 1 synthesizes and outputs the signals respectively received by the first loop element 10 and the second loop element 20, it seems to exhibit higher gain characteristics than a single loop antenna. become.
Further, FIG. 4 shows the radiation characteristics of the circularly polarized loop antenna 1 in the XY plane when the feed line length L1 is set to about 0.35λ in the circularly polarized loop antenna 1 and the dimensions are set as described above. In FIG. 4, the XY plane is a horizontal plane parallel to the ground plane, and the direction (Z direction) perpendicular to the paper surface is the zenith direction. Referring to FIG. 4, it can be seen that a favorable axial ratio characteristic is obtained with almost non-directional characteristics. 3 and 4 has a frequency of 1.57542 GHz, which is a frequency used in GPS. Note that the frequency occupation bandwidth in GPS is 2.046 MHz.

  Next, the frequency characteristic of the voltage standing wave ratio (VSWR) of the circularly polarized loop antenna 1 when the feed line length L1 is set to about 0.35λ in the circularly polarized loop antenna 1 and the dimensions described above are shown. FIG. 6 shows a Smith chart showing the frequency characteristics of the impedance shown in FIG. Referring to FIG. 5 and FIG. 6, it can be seen that the normalized impedance at a frequency of about 1530 MHz to 1700 MHz is a value near 1 and a favorable VSWR value of VSWR 2.0 or less is obtained. Note that the frequency 1.57542 GHz of the marker 1 in FIGS. 5 and 6 is a frequency used in GPS, and a good VSWR value of 1.49 is obtained at the frequency indicated by the marker 1. The frequency 1.5893 GHz of the marker 2 is a frequency at which the best VSWR is obtained, and the best value of VSWR 1.477 is obtained at the frequency indicated by the marker 2.

  As described above, the circularly polarized loop antenna 1 of the present invention includes the first loop element 10 and the second loop element 20 that are spaced apart from each other when attached to a substantially vertical surface such as a window glass. And the signals received by the first loop element 10 and the second loop element 20 are combined and output. At this time, since the received signal of the first loop element 10 disposed above is delayed and synthesized by the length L1 of the feeder line 15, the circularly polarized loop antenna 1 attached to a substantially vertical surface is synthesized. Can be tilted toward the zenith. That is, when the circularly polarized loop antenna 1 is attached to the rear window glass of the vehicle 40 as shown in FIG. 7, a beam 41 having a high elevation angle as shown in the figure can be formed. The beam tilt angle of the beam 41 can be adjusted by changing the length L1 of the feeder line 15.

Also, as shown in FIG. 8, when the circularly polarized loop antenna 1 is attached to the window glass on both sides of the vehicle 50, high elevation beams 51a and 51b as shown in the figure can be formed on both sides. . The beam tilt angles of the beams 51a and 51b can be adjusted by changing the length L1 of the feeder line 15, respectively.
The circularly polarized loop antenna 1 of the present invention may be attached to a substantially horizontal surface. In this case, the first loop element 10 and the second loop element 20 are arranged apart from each other in the horizontal direction. For this reason, the beam of the circularly polarized loop antenna 1 attached to a substantially horizontal surface can be tilted from the zenith direction. In addition, it goes without saying that the circularly polarized loop antenna 1 of the present invention may be attached to the inclined surface.

  Although the circular polarization loop antenna applied to the film antenna that can be attached to the window glass of the moving body has been described above, the present invention is not limited to this, and the circular polarization loop antenna of the film antenna used for other than the moving body is described. Can be applied. Moreover, you may make it comprise the circularly polarized loop antenna 1 of the shape shown in FIG. 1 by bending a conductive wire or a conductive pipe. The circularly polarized loop antenna of the present invention can be used for communication using various circularly polarized waves as well as GPS.

It is a figure which shows the structure of the circular polarization loop antenna of the Example of this invention. It is a graph which shows the corresponding table | surface of the feed line length and beam tilt angle in the circularly polarized loop antenna of the Example of this invention. It is a figure which shows the radiation characteristic of the XZ plane of the circularly polarized loop antenna of the Example of this invention. It is a figure which shows the radiation characteristic of the XY plane of the circularly polarized loop antenna of the Example of this invention. It is a figure which shows the frequency characteristic of VSWR of the circularly polarized loop antenna of the Example of this invention. It is a Smith chart which shows the frequency characteristic of the impedance of the circularly polarized loop antenna of the Example of this invention. It is a figure which shows an example of the beam formed when the circularly polarized loop antenna of this invention is attached to the window glass of the rear part of a vehicle. It is a figure which shows an example of the beam formed when the circularly polarized loop antenna of this invention is attached to the window glass of the both sides of a vehicle.

Explanation of symbols

1 circularly polarized loop antenna, 10 loop conductor, 10 loop element, 11 loop conductor, 12 perturbation conductor, 13 perturbation conductor, 14 feed point, 15 feed line, 20 loop element, 21 loop conductor, 22 perturbation conductor, 23 perturbation conductor , 24 feeding point, 25 feeding, 25 feeding line, 30 feeding part, 40 vehicle, 41 beam, 50 vehicle, 51a beam, 51b beam

Claims (4)

A first loop element having a first loop conductor and two perturbation conductors provided at predetermined intervals substantially parallel to one side of the first loop conductor;
A second loop conductor, and two perturbation conductors provided at predetermined intervals substantially parallel to one side of the second loop conductor, and disposed at a distance from the first loop element. A second loop element,
Power supply means for supplying power by giving a phase difference to the first loop element and the second loop element;
A circularly polarized loop antenna comprising:   The first loop element and the second loop element are spaced apart from each other in the vertical direction, and the length of a feeder line that feeds power to the first loop element and the second loop element The circularly polarized loop antenna according to claim 1, wherein a phase difference is given.   The first loop element and the second loop element are formed on an insulating film, and the power supply line for supplying power to the first loop element and the second loop element is also on the insulating film. The circularly polarized loop antenna according to claim 1, wherein the circularly polarized loop antenna is formed as a film antenna. The circularly polarized loop antenna according to claim 3, wherein the film antenna is a film antenna that can be attached to a window glass of a moving body.

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