JP2010045649A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device capable of correcting a frequency deviation of vertical in-plane directivity of a collinear array antenna of series feeding type. <P>SOLUTION: The collinear array antenna device of the series feeding type have band-shaped parasitic elements extended linearly or in a curved shape in the direction orthogonal to the axial direction of a radiation element. In the collinear array antenna device, slots extended in the longitudinal direction are formed to the parasitic elements, and the length of each slot extended in the longitudinal direction is formed in half-wave length when the band-shaped parasitic elements are developed in planes. The parasitic elements are shifted and arranged in the direction of the end section of the radiation element from a central position in the axial direction of the radiation element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna device having a collinear array antenna structure of a series (series) feeding system.

  2. Description of the Related Art Conventionally, an antenna apparatus having a collinear array antenna structure of a series feeding system is known as a PHS (Personal Handy-phone System) base station antenna or trunk lid antenna. As shown in FIG. 6, the series-fed collinear array antenna is realized with a simple structure by alternately repeating the coaxial line at half wavelength (λ / 2) by the radiation elements 1a, 1b, and 1c arranged in series. It has the feature that it can.

As a prior art, there is a series feed antenna device including a parasitic element for the purpose of impedance matching (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 07-202563 Japanese Patent No. 3444079

  By the way, the collinear array antenna of the series feeding system has a narrow frequency band, and if it deviates from the target frequency, an electric tilt is applied in the direction of the main beam having directivity in the vertical plane. Therefore, at present, it is limited to a PHS base station antenna having a narrow frequency band in a TDD (Time Division Duplex) system having the same transmission / reception frequency.

  In the frequency arrangement used for mobile phone mobile communication, the center frequency of transmission and reception is 55 MHz in the 800 MHz band and 190 MHz in the 2 GHz band. FIG. 7 is a diagram illustrating vertical in-plane directivity when designed for a 2-GHz band mobile communication base station using a four-element series feed antenna. As shown in FIG. 7, in the series-feed antenna, the tilt is 0 degrees in the 1920 MHz band used for upstream communication, and the tilt is 3 degrees in the sky direction in the 2025 MHz band, and in the 2130 MHz band used for downstream communication. A phenomenon occurs in which the tilt is applied to the sky direction by 8 degrees. Specifically, when the operating frequency is higher than the design frequency, tilt occurs on the sky side, and when the operating frequency is lower than the design frequency, tilt occurs on the ground side.

  In the case of the FDD (Frequency Division Duplex) system in which the frequency is different between transmission and reception, there is a problem that if the transmission is used in a tilted state, an area where communication cannot be performed occurs because the formation zone differs between transmission and reception. . Even in the case of the TDD scheme, if the frequency band is wide, the area differs between the channel using the low frequency and the channel using the high frequency. It becomes a factor which degrades. In this way, when the frequency band is distant between transmission and reception, there is a problem that a frequency deviation occurs in the collinear array antenna of the series feeding method, and specifically, there is a problem that the beam direction in the vertical plane is different between transmission and reception.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an antenna device capable of correcting a frequency deviation of directivity in a vertical plane of a collinear array antenna of a series feed system.

  The present invention is a series-fed collinear array antenna device, which includes a strip-shaped parasitic element extending in a straight line or a curved line in a direction intersecting the axial direction of a radiating element, and extends in the longitudinal direction of the parasitic element. A slot is formed.

  The present invention is characterized in that the parasitic element is shifted from the center position in the axial direction of the radiating element toward the end of the radiating element.

  The present invention is characterized in that the shift amount of the parasitic element is changed in accordance with the frequency deviation in the beam direction.

  The present invention is characterized in that the strip-shaped parasitic element is formed in a cylindrical shape.

  The present invention is characterized in that the band-shaped parasitic element is formed in an arc shape in accordance with directivity in a plane orthogonal to the axis of the radiating element.

  The present invention is characterized in that, when the strip-shaped parasitic element is developed on a plane, the length of the slot extending in the longitudinal direction is a half wavelength.

  The present invention is characterized in that a dielectric is inserted between the radiating element and the parasitic element.

  According to the present invention, by providing the parasitic element, it is possible to correct the frequency deviation of the directivity within the vertical plane of the collinear array antenna device of the series feeding system. In addition, by arranging the parasitic element so as to be shifted in the axial direction of the radiating element, it is possible to adjust the amount of frequency deviation of directivity in the vertical plane.

  Hereinafter, an antenna apparatus having a collinear array antenna structure of a series feeding system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a parasitic element in the same embodiment. In this figure, the same parts as those of the conventional apparatus shown in FIG. The apparatus shown in this figure is different from the conventional apparatus in that a parasitic element 2 is provided in the radiating element 1a. In FIG. 1B, the radiating elements 1b and 1c are omitted, but the parasitic element 2 is similarly provided for these elements.

  FIG. 1A is a development view of the parasitic element 2. The parasitic element 2 is made of an aluminum or iron conductor plate having a short dimension (2a + b) and a long dimension (d + c), and is a slot (hole) having a length d and a width b extending in the longitudinal direction. ) Is provided. Here, assuming that the wavelength is λ, the dimensions of each part of the developed view are as follows. That is, a = 0.02λ-03λ, b = 0.015λ-0.05λ, c = 0.015λ-0.05λ, and d = λ / 2. The parasitic element 2 is processed into a cylindrical shape and arranged so as to be concentric with the cylindrical radiating element 1a (see FIG. 1B). Then, a dielectric such as styrene foam is inserted between the radiating element 1a and the parasitic element 2, and the parasitic element 2 is fixed to the radiating element 1a by a known method.

  Next, a method of correcting the frequency deviation in the beam direction by changing the arrangement relationship of the parasitic element 2 with respect to the radiating element 1a shown in FIG. 1 will be described. Regarding the problem that the beam peak direction varies depending on the frequency, the arrangement position of the parasitic element 2 is shifted from the axial center of the radiating element 1a toward the end of the radiating element along the axial direction, and the collinear array of the series feeding system is used. The tilt can be corrected by giving a frequency characteristic opposite to the frequency characteristic of the antenna device having the antenna structure. The conventional parasitic element has a length of about a half wavelength in the vertical direction (the axial direction of the radiating element 1a) in order to resonate, but it is adjacent when shifted in the vertical direction (the direction along the axial direction) as it is. Therefore, the amount of shift is limited. In the present invention, by providing a slot having a length of about half a wavelength in the circumferential direction of the parasitic element 2, vertical polarization can be excited and the height direction can be suppressed. The shift amount in the axial direction can be increased.

  FIG. 2 shows a case where the parasitic element 2 shown in FIG. 1 is provided in each of the three radiating elements 1a, 1b, and 1c constituting the antenna device having the collinear array antenna structure of the series feed type shown in FIG. It is a figure which shows the state which shifted the electric power feeding element 2 to the edge part direction (upward direction) along the axial direction of radiation element 1a, 1b, 1c. FIG. 2A shows a state in which the parasitic element 2 is arranged at the axial center of the radiating elements 1a, 1b, and 1c (the axial center of the radiating element coincides with the slot position of the parasitic element 2). State), and the shift amount is 0 (no shift). FIG. 2C is a diagram illustrating a state in which the parasitic element 2 is shifted in the axial direction along the axial direction until the end of the parasitic element 2 and the end of the radiating element coincide with each other. The state shown in FIG. 2C is a state where the shift amount of the parasitic element 2 is the maximum. FIG. 2B shows a state where the shift amount is between 0 and the maximum (the shift amount is ½ of the maximum value).

  Next, how the beam peak changes for each shift amount (no shift, shift amount 1/2, shift amount maximum) shown in FIG. 2 will be described. FIG. 3 shows a vertical plane for each frequency (parallel to the axial direction of the radiating element) for each shift amount (no shift, ½ shift amount, maximum shift amount) using a computer simulation model in which the radiating element is one element. FIG. 6 is a diagram showing the result of obtaining the surface directivity. FIG. 4 is a diagram in which the beam peak direction is plotted for each frequency for each shift amount.

  As is apparent from FIGS. 3 and 4, it is understood that the beam peak direction can be adjusted by shifting the parasitic element 2. For example, when the shift amount of the parasitic element 2 is ½ of the maximum value (FIG. 2B), adjustment of 8 degrees is possible, and 17 when the shift amount of the parasitic element 2 is maximum. The degree can be adjusted.

  Thus, by arranging the parasitic element 2 so as to be shifted in the end direction along the axial direction of the radiating elements 1a, 1b and 1c, the direction of the beam peak can be adjusted.

  The parasitic element 2 shown in FIG. 1A may be processed into an arc shape in accordance with the required horizontal directivity (plane orthogonal to the axial direction of the radiating element). FIG. 5 is a diagram showing an example in which the processing method of the parasitic element 2 shown in FIG. 1 is changed. FIG. 5 shows an example in which the parasitic element 2 shown in FIG. 1 (a) is processed into a cylindrical shape as shown in FIG. 1 (b). By processing in this way, the directivity in the horizontal plane can be made omnidirectional. 5B and 5C are examples in which the parasitic element 2 shown in FIG. 1 is processed into an arc shape. By processing in this way, directivity can be given in the horizontal plane. Furthermore, when narrowing the directivity in the horizontal plane, the parasitic element 2 shown in FIG. 1 may be used as it is without being processed into a cylindrical shape or an arc shape. As described above, an antenna device having directivity in a horizontal plane can be realized by changing the processing method of the parasitic element 2 shown in FIG.

  As described above, by using the parasitic element shifted in the axial direction of the radiating element, it is possible to correct the frequency deviation in the antenna apparatus having the collinear array antenna structure of the series feeding type. Since the structure of the collinear array antenna of the series feeding system is simple, an inexpensive omnidirectional antenna can be realized only by including a cylindrical parasitic element. Further, by using an arc-shaped parasitic element with respect to the beam direction, an antenna having directivity as well as non-directivity can be realized. As described above, since the tilt direction does not change even when the frequency band is widened, the wireless communication system in which the antenna apparatus having the collinear array antenna structure of the conventional series feeding system with a wide band cannot be used. Even so, a well-balanced communication area can be configured.

It is the expanded view and perspective view which show the structure of one Embodiment of this invention. It is explanatory drawing which shows the state which changed the shift amount of the parasitic element 2 shown in FIG. It is a figure which shows the directivity in a vertical plane according to the shift amount shown in FIG. It is a figure which shows the relationship between the beam peak direction according to the shift amount shown in FIG. 2, and a frequency. It is a figure which shows the modification of the parasitic element 2 shown in FIG. It is a perspective view which shows the collinear array antenna apparatus of the serial feed system by a prior art. It is a figure which shows the vertical in-plane directivity of the collinear array antenna apparatus of the serial feed system shown in FIG.

Explanation of symbols

  1a, 1b, 1c ... Radiation element, 2 ... Parasitic element

Claims (7)

A collinear array antenna device of a series feeding method,
A strip-shaped parasitic element extending linearly or curvedly in a direction intersecting the axial direction of the radiating element;
An antenna device, wherein a slot extending in a longitudinal direction is formed in the parasitic element.   The antenna device according to claim 1, wherein the parasitic element is arranged by being shifted from a center position in the axial direction of the radiating element toward an end of the radiating element.   The antenna device according to claim 2, wherein a shift amount of the parasitic element is changed in accordance with a frequency deviation in a beam direction.   4. The antenna device according to claim 1, wherein the belt-shaped parasitic element is formed in a cylindrical shape.   4. The antenna device according to claim 1, wherein the band-shaped parasitic element is formed in an arc shape according to directivity in a plane orthogonal to the axis of the radiating element. 5.   6. The antenna device according to claim 1, wherein when the band-shaped parasitic element is developed on a plane, the length of the slot extending in the longitudinal direction is a half wavelength.   The antenna device according to claim 1, wherein a dielectric is inserted between the radiating element and the parasitic element.

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