JP3989419B2 - Circularly polarized antenna - Google Patents

Description

  The present invention relates to a circularly polarized antenna, and more particularly to a circularly polarized antenna that can transmit a left-hand circularly polarized wave and a right-handed circularly polarized wave in both directions simultaneously with one planar antenna.

  Conventionally, there is a helical antenna as a three-dimensional circular polarization antenna that generates circular polarization. Further, as a circularly polarized antenna of the wire antenna, there is a turn style antenna. In this turn style antenna, two pairs of dipole antennas are arranged in a cross shape with a phase difference of 90 degrees to generate circularly polarized waves. Furthermore, there is a microstrip antenna as a circularly polarized antenna of a planar antenna.

JP 2003-051710 A

  However, the above-described helical antenna can only generate circular polarization in one direction, and at the same time cannot generate left-hand circular polarization and right-hand circular polarization in both directions, and cannot have a planar structure. There was a problem.

  Microstrip circularly polarized antennas have a planar structure, but in order to generate left-handed circularly polarized waves and right-handed circularly polarized waves simultaneously in both directions, antennas having two different turning directions are joined on the back side. In this case, the thickness of the structure of the planar antenna is increased, and an antenna having two different turning directions is formed, so that the antenna structure is complicated.

  Furthermore, turn-style antennas can generate circularly polarized waves in both directions, but when applying a phase difference, each dipole antenna cannot be integrated. There was a problem that became complicated.

  The present invention has been made in view of the above, and provides a circularly polarized antenna that can generate a left-handed circularly polarized wave and a right-handed circularly polarized wave simultaneously in both directions with a simple thin planar structure. The purpose is to do.

  In order to solve the above-described problems and achieve the object, the circularly polarized antenna according to the present invention includes a plurality of double-loop antenna elements having two loop-shaped elements in which linear or strip-shaped conductors are formed in a loop shape. The plurality of double loop antennas are arranged on the same plane at a predetermined angle with respect to a feeding central point to which the plurality of double loop antennas are connected in common, and are fed with the same amplitude and the same phase with respect to the feeding central point. A phase difference means for providing a phase difference corresponding to the predetermined angle is provided, and the polarization plane is rotated.

  In the circularly polarized antenna according to the present invention as set forth in the invention described above, the phase difference means is provided at a position opposite to a feeding point of each loop element.

  In the circularly polarized wave antenna according to the present invention as set forth in the invention described above, the phase difference means is provided between a feeding point of each loop element and the feeding center point.

  In the circularly polarized wave antenna according to the present invention, in the above invention, the plurality of dual-loop antennas are two and are arranged with an angle difference of 90 degrees from each other. It is provided between each loop element of the loop antenna element or between the feeding point of each loop element and the feeding center point, and provides a phase difference of about ¼ wavelength.

  In the circularly polarized wave antenna according to the present invention as set forth in the invention described above, the loop element is substantially rectangular.

  In the circularly polarized wave antenna according to the present invention as set forth in the invention described above, the plurality of twin-loop antenna elements are formed on a dielectric substrate.

  The circularly polarized wave antenna according to the present invention is characterized in that, in the above invention, the plus side elements and the minus side elements of the plurality of twin loop antenna elements are formed in different layers via a dielectric film. .

  The circularly polarized wave antenna according to the present invention is characterized in that, in the above invention, a protective film is formed on an upper portion of the conductor pattern on which the plurality of twin loop antenna elements are formed.

  In the circularly polarized wave antenna according to the present invention as set forth in the invention described above, the phase difference means is formed by varying the electrical length of the linear or strip conductor.

  The circularly polarized antenna according to the present invention has a plurality of dual loop antenna elements formed on the same plane, and can generate a left-hand circular polarization and a right-hand circular polarization simultaneously in both directions. Since the feeding points of the loop antenna can be connected in common, there is an effect that it is possible to easily form a circularly polarized antenna having a planar structure in which an increase in thickness is suppressed.

  Hereinafter, embodiments of a circularly polarized wave antenna according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view showing a schematic configuration of a circularly polarized antenna according to Embodiment 1 of the present invention. FIG. 2 is a plan view of the circularly polarized antenna shown in FIG. FIG. 3 is a cross-sectional view of the circularly polarized antenna shown in FIG. In FIG. 1 to FIG. 3, the circularly polarized antenna 10 includes a double-loop antenna 11 that forms loops L1 and L2 and a double-loop antenna 12 that forms loops L3 and L4. Are formed by sharing a common feeding point P on the same XY plane. This common feeding point P is formed at the center position of each of the twin loop antennas 11 and 12. The twin loop antennas 11 and 12 are orthogonally arranged with a central angle of 90 degrees.

  Each of the double loop antennas 11 and 12 has the same length from the common feeding point P to the feeding points P1 to P4 with respect to the loops L1 to L4, and is set to have the same electrical length. The dual loop antenna 11 forms loops L1 and L2 from the feed points P1 and P2 to the connecting portions P11 and P12 on the tip end side, respectively. Further, the double loop antenna 12 forms loops L3 and L4 from the feeding points P3 and P4 to the proximity portions P13 ′ and P14 ′ on the distal end side, and the proximity portions P13 ′ and P14 ′ and the connection portions P13 and P14. Are provided with phase difference portions 3 and 4 that give a phase difference of about ¼ wavelength. The phase difference portions 3 and 4 have a 180-degree bent structure having a length of about 1/8 wavelength, and can thereby give a phase advance or delay of 90 degrees.

  Here, the circularly polarized antenna 10 is formed by the band-shaped members 1 and 2 with the two dual loop antennas 11 and 12 as one antenna around the common feeding point P. The band-shaped member 1 is a conductor and is patterned on the upper surface of the dielectric substrate 6, and the band-shaped member 2 is a conductor and is patterned on the back surface of the dielectric substrate 6. The band-like members 1 and 2 are joined via through holes TH1 to TH4 provided in the dielectric substrate 6. Each of the loops L1 to L4 has a length of about one wavelength, and the through holes TH1 and TH2 are provided at positions opposed to the feeding points P1 and P2, that is, at a length of ½ wavelength from the feeding point. On the other hand, the through-holes TH3 and TH4 are provided at the front ends which are bent portions of the phase difference portions 3 and 4 extending from the positions opposed to the feeding points P3 and P4. The conductive members 1 and 2 may be linear members. Moreover, you may provide the protective films 7 and 8 formed with a dielectric material on each upper surface of the strip | belt-shaped members 1 and 2. FIG.

  The circularly polarized antenna 10 is fed to the common feed point P via the feed line 5. The feeding line 5 is fed to the common feeding point P as two balanced lines. And the linear member 1 shown with the oblique line in FIG. 1 functions as a plus side element, and the linear member 2 functions as a minus side element.

  By forming such a circularly polarized antenna 10, a right-handed circularly polarized wave is generated in the + Z direction, and a left-handed circularly polarized wave is generated in the -Z direction, both of which bound the XY plane. In the direction, circularly polarized waves having different polarization rotations can be generated simultaneously.

  Here, with reference to FIG. 4, the circularly polarized wave formation of the circularly polarized antenna 10 will be described. 4A to 4D sequentially show the electric field distribution every 90 degrees. In FIG. 4, when a maximum electric field is first generated in the loops L1 and L2, the generated electric field becomes zero because a phase delay of 90 degrees occurs in the loops L3 and L4. Here, since the loops L1 and L2 have a symmetrical structure with respect to the axis of the twin-loop antenna 12, electric fields in the same direction are generated. Therefore, the combined electric field is generated in the direction of 45 degrees on the upper right on the paper surface of FIG.

  When the phase advances 90 degrees from FIG. 4A, an electric field is generated in each of the loops L3 and L4 in the direction of 45 degrees on the upper left side of the drawing. On the other hand, in the loops L1 and L2, the electric field becomes 0 as the phase advances by 90 degrees. Therefore, the combined electric field is generated in the upper left 45 ° direction on the paper surface of FIG.

  Thereafter, when the phase advances by 180 degrees from the phase state of FIG. 4A, as shown in FIG. 4C, an electric field in the direction opposite to that of FIG. The electric field at L4 is zero. As a result, the combined electric field is generated in the direction of the lower left 45 degrees on the paper surface of FIG.

  Further, when the phase advances 270 degrees from the phase state of FIG. 4A, as shown in FIG. 4D, an electric field in the direction opposite to that in FIG. 4B is generated in the loops L3 and L4, and the loop L1 , L2 is zero. As a result, the combined electric field is generated in the direction of 45 degrees at the lower right on the paper surface of FIG.

  When the phase further advances by 90 degrees from the phase state of FIG. 4D, the electric field distribution shown in FIG. 4A is generated, and the combined electric field is generated in the upper right 45 direction. By repeating this process, the resultant electric field causes counterclockwise polarization rotation in the plane of FIG. 4, that is, the XY plane, and right-handed right-handed circular polarization occurs in the + Z direction. , A left-handed circularly polarized wave is generated in the −Z direction. Note that by reversing the vertical positions of the band-like members 1 and 2, a left-handed circularly polarized wave is generated in the + Z direction and a right-handed circularly polarized wave is generated in the −Z direction. By turning the entire wave antenna 10 upside down, a left-handed circularly polarized wave can be generated in the + Z direction and a right-handed circularly polarized wave can be generated in the −Z direction.

  Similarly, turn-style antennas can simultaneously generate circularly polarized waves with different polarization rotations from both sides, but due to the characteristics of dipole antennas, each orthogonal antenna operates as one antenna, so the center of each antenna It is difficult to provide a phase difference by supplying power from a position.

  Therefore, when the present invention is applied to a dipole antenna, a dipole antenna is formed at each of the loops L1 to L4, and each dipole antenna is fed via a central feed point. It may be formed so as to give a phase difference of 90 degrees.

  Here, FIG. 5 is a diagram showing the YZ plane directivity of left-handed circularly polarized radiation radiated in the −Z direction. FIG. 6 is a diagram showing the YZ plane directivity of right-handed circularly polarized radiation radiated in the + Z direction. 5 and 6, the directivity having the maximum gain in the Z-axis direction can be obtained for both the left-handed circularly polarized wave and the right-handed circularly polarized wave that are simultaneously radiated, and the directivity almost omnidirectional with respect to each hemisphere. Can be obtained.

  FIG. 7 shows the ratio band characteristic of the axial ratio of the circularly polarized antenna 10 shown in FIG. As shown in FIG. 7, with this circularly polarized wave antenna 10, it was possible to obtain a good antenna characteristic within an axial ratio of 5 dB with a relative bandwidth of 7%.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the above-described first embodiment, the phase difference portions 3 and 4 are provided on the loops L3 and L4 so as to provide a phase difference of 90 degrees with respect to the loops L1 and L2. The phase difference portions 3 and 4 are not provided, and instead of the phase difference portions 3 and 4, phase difference portions 23 and 24 are provided between the common feeding point P and the feeding points P3 and P4 (see FIG. 8). Other configurations are the same as those of the first embodiment.

  Also in this second embodiment, since the phase difference portions 23 and 24 perform the same operation as the phase difference portions 3 and 4, the electromagnetic field generates a right-handed circularly polarized wave in the + Z direction and in the −Z direction. Generates left-handed circular polarization. As a result, it is possible to simultaneously generate circularly polarized waves having different polarization rotations in both directions on the Z axis with respect to the XY plane.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In each of the first and second embodiments described above, the loops L1 to L4 have a substantially rectangular shape to facilitate pattern formation. However, in this third embodiment, a circularly polarized antenna having a loop as an original circle is used. Realized.

  FIG. 9 is a plan view showing a configuration of a circularly polarized antenna according to Embodiment 3 of the present invention. In FIG. 9, the circularly polarized antenna 30 is obtained by changing the shape of each of the loops L1 to L4 shown in the first embodiment to circular loops L31 to L34. In this case, the loop length is about one wavelength. Other configurations are the same as those of the first embodiment.

  Even in the circular loop shape shown in the third embodiment, similarly to the first embodiment, it is possible to simultaneously generate circularly polarized waves having different polarization rotations in both directions. As in the second embodiment, a phase difference portion may be provided between the common feeding point P and the feeding points P3 and P4.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In Embodiments 1 to 3 described above, two twin-loop antennas are arranged orthogonally around a common feeding point. However, in this embodiment, four twin-loop antennas are connected to a common feeding point. It is arranged every 45 degrees around the point.

  10 is a plan view showing a configuration of a circularly polarized antenna according to Embodiment 10 of the present invention. In FIG. 10, in this circularly polarized antenna 40, four dual-loop antennas 41 to 44 are arranged every 45 degrees with the common feeding point P as the center. Each loop is circular, and the loop itself is arranged in an annular shape. And between the common feeding point P and each feeding point P41-48, it is the same line length, and becomes the same electrical length.

  The double-loop antenna 41 is not provided with a phase difference portion, and the double-loop antenna 42 is provided with 1/16 wavelength folded phase difference portions 52a and 52b to give a phase difference of 45 degrees to the double-loop antenna 41, The double loop antenna 43 is provided with ８ wavelength folded phase difference portions 53 a and 53 b to give a phase difference of 90 degrees with respect to the double loop antenna 41, and the double loop antenna 44 is provided with respect to the double loop antenna 41. In order to give a phase difference of 135 degrees, 3/16 wavelength folded phase difference portions 54a and 54b are provided. As a result, by combining the electric fields generated in the loops of the dual loop antennas 41 to 44, the combined electromagnetic field rotates counterclockwise, and a right-handed circularly polarized wave is generated in the + Z direction, and at the same time in the −Z direction. Produces a left-handed circularly polarized wave.

  FIG. 11 is a diagram for explaining a state of circularly polarized wave generation according to the fourth embodiment. 11 (a) to 11 (h) show the electric field generated in each loop sequentially at 45 degree phase intervals and the direction of the combined electric field at that time. As shown in FIG. 11, the combined electric field sequentially rotates counterclockwise by 45 degrees, and right-handed circularly polarized waves are generated in the + Z direction, and at the same time, left-handed circularly polarized waves are generated in the -Z direction.

  As described above, the circularly polarized antenna according to the present invention is effective as a relay antenna and is useful as a receiving antenna that takes advantage of the characteristics of circularly polarized waves in a room where the plane of polarization exists randomly.

It is a perspective view which shows the structure of the circularly polarized wave antenna which is Embodiment 1 of this invention. It is a top view of the circularly polarized wave antenna shown in FIG. It is the sectional view on the AA line of the circularly polarized antenna shown in FIG. It is explanatory drawing explaining the polarization plane rotation of the circularly polarized antenna shown in FIG. It is a figure which shows the directivity of the left-handed circular polarization in the -Z direction of the circularly polarized wave antenna shown in FIG. It is a figure which shows the directivity of the right-handed circularly polarized wave in the + Z direction of the circularly polarized wave antenna shown in FIG. It is a figure which shows the ratio band characteristic of the axial ratio of the circularly polarized antenna shown in FIG. It is a top view of the circularly polarized wave antenna which is Embodiment 2 of this invention. It is a top view of the circularly polarized wave antenna which is Embodiment 3 of this invention. It is a top view of the circularly polarized wave antenna which is Embodiment 4 of this invention. It is explanatory drawing explaining the polarization plane rotation of the circularly polarized wave antenna shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Band-shaped member 3, 4, 23, 24, 33, 34, 52a, 52b, 53a, 53b, 54a, 54b Phase difference part 5 Feed line 6 Dielectric substrate 7, 8 Protective film 10, 20, 30, 40 Circularly polarized antenna 11, 12, 21, 22 Double loop antenna L1-L4, L31-L34 Loop P Common feed point P1-P4, P33, P34, P41-P48 Feed point P11-P14 Connection point TH1-TH4 Through hole R1 Right-hand circular polarization R2 Left-hand circular polarization

Claims (9)

  A plurality of double-loop antenna elements having two loop-shaped elements in which linear or belt-like conductors are formed in a loop shape are on the same plane at a predetermined angle around a feeding center point where the plurality of double-loop antennas are commonly connected. A phase difference unit that is disposed and fed with the same amplitude and phase with respect to the feeding center point, and that provides a phase difference corresponding to the predetermined angle between the two loop antenna elements is provided to rotate the plane of polarization. A circularly polarized antenna.   The circularly polarized antenna according to claim 1, wherein the phase difference means is provided at a position opposite to a feeding point of each loop-shaped element.   3. The circularly polarized wave antenna according to claim 1, wherein the phase difference means is provided between a feeding point of each loop-shaped element and the feeding center point.   The plurality of twin loop antennas are two, and are arranged with an angle difference of 90 degrees from each other, and the phase difference means is a loop element of any one of the loop antenna elements or a feeding point of each loop element. The circularly polarized antenna according to claim 1, wherein the circularly polarized antenna is provided between a power supply center point and a feeding center point, and provides a phase difference of about ¼ wavelength.   The circularly polarized antenna according to claim 1, wherein the loop element is substantially rectangular.   The circularly polarized antenna according to claim 1, wherein the plurality of twin loop antenna elements are formed on a dielectric substrate.   7. The circularly polarized wave antenna according to claim 6, wherein the plus side element and the minus side element of the plurality of twin loop antenna elements are formed in different layers via a dielectric film.   The circularly polarized antenna according to claim 6 or 7, wherein a protective film is formed on an upper portion of the conductor pattern on which the plurality of twin loop antenna elements are formed.   The circularly polarized antenna according to any one of claims 1 to 8, wherein the phase difference means is formed by changing an electric length of the linear or strip conductor.

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