JP2011146851A - Wideband unidirectional antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a wideband unidirectional antenna having wideband unidirectionality and a reduced size in the directivity direction. <P>SOLUTION: The wideband unidirectional antenna includes a waveguide element, a feeding element, and a reflecting element on each of the surfaces distant from one another and in parallel in order. In the waveguide element, two surface-like conductors are arranged at a predetermined distance on one surface. Especially, in the feeding element, the two surface-like conductors are arranged at a predetermined distance on one surface to perform balanced feed to the two surface-like conductors. In the reflecting element, the two surface-like conductors are arranged on one surface, and facing points of the surface-like conductors are short-circuited. In addition, the waveguide element, the feeding element, and the reflecting element are arranged in this order, which is similar to the Yagi-Uda antenna. The the surface-like conductors may at least partially have a circular or elliptical shape. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wideband unidirectional antenna that includes a director and a reflector as in the case of the Yagi-Uda antenna, but has a unidirectional characteristic in a wide band, and has a directional direction greatly shortened to a low attitude.

  In general, it is known that a highly directional antenna is advantageous in order to suppress the influence from external disturbances in communication or broadcast reception. For example, in the case of a unidirectional antenna, the gain is improved as compared with a non-directional antenna. By improving the gain in this way, in addition to expanding the communication range, it is possible to obtain the effect of reducing interference with other systems that are not desired. In addition, it is easy to cover a region in a plurality of directions by combining unidirectional antennas.

  Various antennas are known as unidirectional antennas. For example, in UHF band television broadcast reception (470-770 MHz), a Yagi-Uda antenna composed of rod-shaped elements is often used.

  In general, the Yagi-Uda antenna is characterized in that it is long in the directionality direction because it includes a reflection element, a feed element, and a waveguide element in that direction. Further, in order to cover the above 470-770 MHz frequency band with a single Yagi-Uda antenna, a special device is required.

  As a Yagi-Uda antenna whose directivity direction is significantly shortened, there is a disclosure of Patent Document 1 (Japanese Patent Application No. 2008-262172). This is an element spacing of about 0.05 wavelength or less, and the reflective element is provided with a portion corresponding to an inductor so as to achieve matching and sharp directivity.

  In addition, as a broadened frequency band suitable for use, Patent Document 2 (US Pat. No. 3,364,491) discloses a dipole antenna using two solid ellipsoids. Patent Document 3 (US Pat. No. 4,370,660) discloses a dipole antenna using a planar ellipse.

  When Patent Documents 1 to 3 are combined, the waveguide element and the reflective element have similar shapes. However, in the present invention, they are not similar, so even if these Patent Documents are combined, they are realized. Obviously it is not possible.

Japanese Patent Application No. 2008-262172 U.S. Pat. No. 3,364,491 U.S. Pat. No. 4,370,660

  In general, a low-profile, unidirectional antenna has a high degree of installation flexibility and can be applied in a wide range. In other words, a low-profile antenna can be installed so as to be attached to a device housing or the like, and if it is unidirectional, even if it is installed to be attached to a housing or the like, the influence on the antenna characteristics is small. Further, in order to be usable in a wide range of fields, it is desirable that the frequency characteristic is a broadband characteristic.

  The wideband unidirectional antenna of the present invention includes a waveguide element, a feed element, and a reflection element on respective planes that are separated from each other in parallel, and the waveguide element has two planar conductors on the same plane. It is arranged at a predetermined distance on the top. In particular, the power feeding element is configured such that two planar conductors are arranged on the same plane at a predetermined distance, and balanced power is supplied to the two planar conductors. The planar conductor is short-circuited on the same surface at opposite points of the planar conductor. Moreover, it is set as the structure similar to a Yagi-Uda antenna by arranging in order of a waveguide element, a feed element, and a reflective element.

  The two planar conductors of the waveguide element may be coupled by a capacitor. The capacitor is, for example, a parallel plate type capacitor.

  Further, at least a part of the shape of the planar conductor is circular or elliptical. The whole may be round or oval.

  The distance between the waveguide element and the reflection element is 1/10 or less of the wavelength of the high frequency signal fed to the feeding element. It is desirable to provide a feeding element in the middle.

  Each planar conductor in the waveguide element, the feeding element, and the reflecting element is formed from the same planar conductor. For example, it can be easily formed using a printed board.

  A low-profile antenna capable of obtaining unidirectionality in a wide band can be realized.

It is a figure which shows the broadband unidirectional antenna of this invention. It is a figure which shows the example of a broadband unidirectional antenna designed so that the broadcast frequency band of terrestrial digital television may be substantially covered 470-710 MHz. It is a figure which shows the example of the broadband unidirectional antenna which loaded the capacitor on the director. In the configuration of FIG. 3, the frequency of the operating gain Gw, absolute gain Ga, and mismatch loss (1 / M) when the capacitance of the capacitor is (a) 6.9 pF and (b) 0 pF (open). It is a figure which shows a characteristic. It is a figure which shows the structural example which expressed the dimension of the example of a broadband unidirectional antenna of FIG. 3 with the wavelength. It is a figure which shows the comparison of the gain and band of the wideband unidirectional antenna of this invention, and another antenna.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

  In a three-element Yagi-Uda antenna that reduces the element spacing to 0.049 wavelength, which is about 1/5 of the normal 0.25 wavelength, the element dipole is composed of two ellipses, and the waveguide is 2 By opening one ellipse and short-circuiting the reflector, it is possible to widen the ratio band with an operating gain degradation within 1 dB to about 29%.

  FIG. 1 is a diagram showing a configuration example of a wideband unidirectional antenna of the present invention for a high frequency signal wavelength λ from a high frequency signal source 5. In this example, the director is formed by arranging elliptical conductors 1A and 1B having a major axis of 0.532λ and a minor axis of 0.84λ on the same plane with a distance of about 0.001λ. In addition, the feeding elements are arranged such that elliptical conductors 2A and 2B having the same size as the conductors 1A and 1B of the director are arranged on the same plane at a distance of about 0.001λ, and the conductors 2A and 2B are balanced. A high frequency signal from the high frequency signal source 5 is applied through the feeder line 4. Further, the reflecting elements are arranged on the same plane so as to short-circuit the elliptical conductors 3A and 3B having the same size as the conductors 1A and 1B of the director. The above-mentioned waveguide, the feeding element, and the reflector are sequentially arranged with a distance of 0.049λ so as to overlap each other. The directivity direction of this broadband unidirectional antenna is a direction from the reflector toward the director.

  FIG. 2 is a diagram illustrating a configuration example of a wideband unidirectional antenna for receiving digital terrestrial television broadcasting in the UHF band. An antenna having a depth of about 5 cm, which is a 0.1 wavelength of 590 MHz, which is the center frequency of terrestrial digital, can be configured to realize an operation gain of about 5 dBi or more in a specific band of about 41% of a frequency of 470-710 MHz. . In this case, the length of the antenna is about 41 cm and the width is 26 cm.

  In the above-described director, feed element, and reflector, an elliptical conductor is used. However, a circular conductor may be used, or a part of the conductor may be an elliptical or circular conductor. Moreover, although the sizes of the director, the feeding element, and the reflector are all the same, they may be different.

  In the example of FIG. 3, the director is obtained by coupling elliptical conductors 1A and 1B having a major axis of 114 mm and a minor axis of 90 mm with a capacitor. In addition, the feeding elements are arranged such that elliptical conductors 2A and 2B having the same size as the conductors 1A and 1B of the director are arranged on the same plane at a distance of about 0.001λ, and the conductors 2A and 2B are balanced. A high-frequency signal from the high-frequency signal source 5 is applied through the mold feeder line 4. It is desirable that the distance between the conductors 2A and 2B be a value sufficiently smaller than the wavelength λ. Further, the reflecting elements are arranged on the same plane so as to short-circuit the elliptical conductors 3A and 3B having the same size as the conductors 1A and 1B of the director. The above-described waveguide, feeding element, and reflector are sequentially arranged at a distance of 10.5 mm so as to overlap.

  FIG. 4 shows the frequency of operating gain Gw, absolute gain Ga, and mismatch loss (1 / M) when the capacitance is (a) 6.9 pF and (b) 0 pF (open) in the example of FIG. Show properties. (A) When the electric capacity is 6.9 pF, a beam is obtained in the vicinity of 0.72 GHz, and the ratio band where the operating gain reduction is 1 dB is about 3.8%. In the case of the structure of Patent Document 1, it is about 1.5%, but it has a wider band than this. Further, FIG. 5 shows a dimensional diagram that is not 0.72 GHz but is a dimension with respect to a general frequency. The reactance value of the reactor 6 loaded on the director is −31Ω. On the other hand, when (b) is opened, the configuration shown in FIG. 1 of the first embodiment is obtained, and the frequency of the beam is increased to about 1.35 GHz, but the specific band is increased to about 29%.

  4A and 4B, it can be seen that the frequency at which the gain is increased and the bandwidth thereof can be adjusted by changing and adjusting the capacitor capacity in FIG.

  Each planar conductor in the waveguide element, the feeding element, and the reflecting element is formed from the same planar conductor. These can be easily formed by a well-known method using, for example, a printed board.

  FIG. 6 shows a comparison of gain and band between the broadband unidirectional antenna of the present invention and another antenna such as a microstrip antenna. The microstrip antenna has characteristics in the case where there is no dielectric between the patch and the ground plane so that the band is wide, and the interval is 0.03 wavelength, which is larger than usual. It can be seen that the broadband unidirectional antenna of the present invention has a significantly wider bandwidth than other antennas.

  As described above, the present invention can be used as an antenna requiring unidirectionality in a wide frequency band. Since it has a relatively low posture, it can be installed so as to be attached to the surface of the housing. In that case, since it is unidirectional, there is little deterioration in characteristics. For example, use as a thin antenna for terrestrial digital reception is conceivable.

1A, 1B Waveguide conductor 2A, 2B Feed element conductor 3A, 3B Reflector conductor 4 Feed line 5 High-frequency signal source 6 Reactor

Claims (5)

Including a waveguide element, a feed element, and a reflection element on respective surfaces that are spaced apart from each other in parallel;
The waveguide element has two planar conductors arranged at a predetermined distance on the same plane,
The power feeding element is one in which two planar conductors are arranged on the same plane at a predetermined distance, and the two planar conductors are balancedly fed.
2. The broadband unidirectional antenna according to claim 1, wherein the reflecting element is obtained by short-circuiting two planar conductors on the same surface at opposite points of the planar conductor.   2. The broadband unidirectional antenna according to claim 1, wherein the two planar conductors of the waveguide element are coupled by a capacitor.   The broadband unidirectional antenna according to any one of claims 1 and 2, wherein at least a part of the planar conductor is circular or elliptical.   The wideband unidirectional signal according to any one of claims 1 to 3, wherein a distance between the waveguide element and the reflective element is 1/10 or less of a wavelength of a high-frequency signal fed to the power feeding element. Sex antenna.   5. The wideband single unit according to claim 1, wherein the planar conductors in the waveguide element, the feeding element, and the reflecting element are formed from the same planar conductor. Directional antenna.

Images