JP2015185853A - Multifrequency monopole antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small size multifrequency monopole antenna capable of reducing the height and width thereof by optimizing the clearance among elements depending on the frequency band.SOLUTION: Radiation elements are disposed at the center of a base 5. Defining a wavelength at frequency fn as λn, the multifrequency monopole antenna includes: a f1 element 2a which is set to a height H1 smaller than 0.2λ1; four f2 elements 2b which are disposed being branched in a diameter direction within a range of 0.05λ1 of element storage diameter R including the f1 element 2a at an element branch point 7 at a height Y of 0.05λ1 from a power supply point 4; two f3 elements 2c; and two f4 elements 2d. The f2 element 2b is disposed at a height H2 of 0.2λ2 from the element branch point 7; the f3 element 2c is disposed at a height H3 of 0.2λ3 from the element branch point 7; and the f4 element 2d is disposed at a height H4 of 0.19λ4 from the element branch point 7. The open angle S between the f2 element 2b and the f3 element 2c is set to 60 degree.

Description

  The present invention relates to a multi-frequency monopole antenna used for mobile communication, local area network, TV broadcasting, and the like.

  When an antenna is installed, an antenna with a protruding length and a small wind receiving area is generally required. Conversely, from the electromagnetic field theory, the optimum size is determined by the wavelength of the operating frequency. In the case of configuring a multi-frequency antenna corresponding to a plurality of bands, it is easily realized by operating each frequency independently by separating the distance between a plurality of radiating element portions corresponding to each frequency.

Japanese Patent No. 5275418

  In a multi-frequency monopole antenna, it is generally difficult to make the antenna small and operate at multiple frequencies. For example, in the “multi-frequency antenna device” of Patent Document 1, when the form is the smallest, the size has a height of 0.21 times the wavelength of the lowest operating frequency and a width of 0.14 times.

  The present invention has been made paying attention to the above circumstances, and its purpose is to reduce the height and width, and by optimizing the element spacing according to the frequency band, a compact multi-frequency monopole antenna can be obtained. It is to provide.

  An aspect of one aspect of the present invention is a radiating element corresponding to four frequencies set to f2 = 1.8f1, f3 = 2.4f1, and f4 = 3.1f1 with respect to the minimum operating frequency f1, and a GND plate. And a radiating element is a multi-frequency monopole antenna supported from the pedestal through an element support, and has a wavelength λn with respect to the frequency fn. The radiating element is arranged at the center of the base and is an f1 element set at a height H1 of 0.2λ1 or less, and an element having a height Y from the feeding point of 0.05λ1 It has four f2 elements, two f3 elements, and two f4 elements, which are arranged to be branched in the radial direction from the f1 element in the range where the element storage diameter R is 0.05λ1 at the branch point. , The f2 element is the element branch The height H2 from the point is 0.2λ2, the f3 element has a height H3 from the element branch point of 0.2λ3, and the f4 element has a height H4 from the element branch point of 0.19λ4, respectively. The multi-frequency monopole antenna is set and the opening angle S between the f2 element and the f3 element is set to 60 degrees.

  According to the present invention, a small multi-frequency monopole antenna can be provided by optimizing the element spacing according to the frequency band for the purpose of reducing the height and width.

1 is a perspective view showing an overall schematic configuration of a multifrequency monopole antenna according to a first embodiment of the present invention. The side view which shows the schematic structure of the whole multifrequency monopole antenna of 1st Embodiment. The top view of the multifrequency monopole antenna of 1st Embodiment. The top view which shows the arrangement | positioning state of the radiation element of the multifrequency monopole antenna of 1st Embodiment. The VSWR characteristic figure of the multifrequency monopole antenna of 1st Embodiment. The characteristic view which shows the vertical surface directivity of the multifrequency monopole antenna of 1st Embodiment. The schematic block diagram which shows a 2 frequency monopole antenna. The VSWR characteristic figure which shows the characteristic at the time of changing only element spacing d with the 2 frequency monopole antenna of FIG. The schematic block diagram which shows a 4 frequency monopole antenna. FIG. 10 is a VSWR characteristic diagram showing characteristics when only the element spacing d is changed in the four-frequency monopole antenna of FIG. 9.

[First Embodiment]
(Constitution)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 6 show a first embodiment of the present invention. FIG. 1 is a perspective view showing an overall schematic configuration of a multi-frequency monopole antenna 1 according to a first embodiment, and FIG. 2 is a side view. The multi-frequency monopole antenna 1 of the present embodiment is a radiating element (corresponding to four frequencies respectively set to f2 = 1.8f1, f3 = 2.4f1, and f4 = 3.1f1 with respect to the minimum operating frequency f1). f1 element 2a, f2 element 2b, f3 element 2c, f4 element 2d), and GND plate 3. Note that the wavelength is described as λn with respect to the frequency fn.

  Furthermore, the multi-frequency monopole antenna 1 of the present embodiment has a base 5 having a feeding point 4 provided at the center, and the f1 element 2a to f4 element 2d are passed through an element support base 6 made of an insulator. It is supported from the base 5 using screws or the like.

  The f1 element 2a is a radiating element corresponding to the lowest operating frequency f1, and has a rod-shaped element body 2a1 arranged in the center of the base 5 in the vertical direction. The height H1 of the element body 2a1 is set to 0.2λ1 or less.

  The f2 element 2b is a radiating element corresponding to f2 = 1.8f1, and has four rod-shaped f2 element bodies 2b1 to 2b4 with a width of about 0.01λ1 arranged in the vertical direction. Here, the lower end portions of the two of the four f2 element main bodies 2b1 and 2b3 are connected via a bar-shaped first connecting portion 2b5 extending in the horizontal direction. The lower ends of the remaining two f2 element bodies 2b2 and 2b4 are connected via a bar-like second connecting portion 2b6 extending in the horizontal direction.

  The f3 element 2c is a radiating element corresponding to f3 = 2.4f1, and has two rod-shaped f3 element bodies 2c1 and 2c2 having a width of about 0.01λ1 arranged in the vertical direction. The lower ends of the two f3 element bodies 2c1 and 2c2 are connected via a bar-like third connecting portion 2c3 extending in the horizontal direction.

  The f4 element 2d is a radiating element corresponding to f4 = 3.1f1, and has two rod-shaped f4 element bodies 2d1 and 2d2 having a width of about 0.01λ1 arranged in the vertical direction. The lower ends of the two f4 element bodies 2d1 and 2d2 are connected via a bar-like fourth connecting portion 2d3 extending in the horizontal direction.

  As shown in FIG. 2, an element branching point 7 is provided at a position where the height Y from the feeding point 4 in the f1 element 2a is 0.05λ1. As shown in FIG. 4, the four f2 element bodies 2b1 to 2b4, the two f3 element bodies 2c1 and 2c2, and the two f4 element bodies 2d1 and 2d2 have a diameter from the f1 element 2a at the element branching point 7. Branched in the direction. That is, the element branching portion 7 includes a first connecting portion 2b5 between the lower end portions of the two f2 element main bodies 2b1 and 2b3, and a second portion between the lower end portions of the two f2 element main bodies 2b2 and 2b4. The second connection portion 2b6, the third connection portion 2c3 between the lower ends of the two f3 element bodies 2c1 and 2c2, and the fourth connection portion 2d3 between the lower ends of the two f4 element bodies 2d1 and 2d2. Are radially branched in a state where the center is superimposed on the f1 element 2a. These four f2 element main bodies 2b1 to 2b4, the two f3 element main bodies 2c1 and 2c2, and the two f4 element main bodies 2d1 and 2d2 are in the range where the element storage diameter R is 0.05λ1 from the f1 element 2a. Has been placed.

  The four f2 element bodies 2b1 to 2b4 have a height H2 from the element branch point 7 set to 0.2λ2. In the two f3 element bodies 2c1 and 2c2, the height H3 from the element branch point 7 is set to 0.2λ3. The two f4 element bodies 2d1 and 2d2 have a height H4 from the element branch point 7 set to 0.19λ4. Further, the opening angle S between the f2 element 2b and the f3 element 2c is set to 60 degrees.

  In addition, a rectangular flat plate-shaped wide portion 2a2 is provided on the upper portion of the element body 2a1 of the f1 element 2a. On the wide portion 2a2, a flat top plate 2a3 is extended in a direction orthogonal to the axial direction of the f1 element 2a as shown in FIG. The top plate 2a3 has a width L in the direction orthogonal to the axial direction of the f1 element 2a set to 0.04λ1.

  Furthermore, first folding elements 8a and 8b extending downward are bent at both sides of the upper portion of the wide portion 2a2. The heights Ha1 of the first folding elements 8a and 8b are set to 0.04λ1. Second folding elements 9a and 9b extending downward are bent at both sides of the top plate 2a3. The heights Hb1 of these second folding elements 9a and 9b are set to 0.01λ1.

(Action / Effect)
Next, the operation of the above configuration will be described. The characteristics achieved by the multifrequency monopole antenna 1 of the present embodiment will be described. FIG. 5 is a VSWR characteristic diagram of the multi-frequency monopole antenna 1 of the present embodiment, and FIG. 6 is a characteristic diagram showing vertical plane directivity of the multi-frequency monopole antenna 1 of the present embodiment. In the multi-frequency monopole antenna 1 of the present embodiment, an operation with four frequencies f1 to f4 is realized as shown in FIG. Moreover, in f2-f4, it has magnetic field surface non-directivity by arrange | positioning several elements.

  FIG. 7 shows a dual frequency monopole antenna. In FIG. 7, 11 is a GND plate, 12 is an f1 element of about ¼ wavelength corresponding to the frequency band of f1, and 13 is an f2 element of about ¼ wavelength corresponding to the frequency band of f2. . The f1 element 12 and the f2 element 13 are conductors having different lengths. At this time, the characteristics when only the element interval d between the f1 element 12 and the f2 element 13 is changed are as shown in FIG. Here, da = 20 mm, db = 40 mm, dc = 80 mm, and dd = 160 mm. As shown in FIG. 8, it can be seen that at f2, the bandwidth changes greatly depending on the element spacing. Thus, the center frequency and bandwidth of the excitation element change depending on the element spacing d.

  FIG. 9 shows a four-frequency monopole antenna. The four elements 21 to 24 having different lengths correspond to the respective frequency bands. In this example, elements with adjacent excitation frequencies are not adjacent to each other in terms of arrangement. At this time, the characteristics when only the element spacing d (= d1 = d2 = d3) is changed are as shown in FIG. Thus, although the center frequency and the bandwidth of the excitation element vary depending on the element spacing d, it can be seen that there are optimum element spacings corresponding to the four required bands even with four elements.

  In the multi-frequency monopole antenna 1 of the present embodiment, as shown in FIGS. 2 and 4, the height H1 of the entire antenna is in the range of 0.2λ1, and the element housing diameter R is in the range of 0.05λ1. That is, in the multi-frequency monopole antenna 1 of the present embodiment, a smaller antenna can be obtained as compared with the conventional method. Good magnetic field surface omnidirectional deviation characteristics. An antenna that can be manufactured at low cost. Since it is small with respect to the wavelength of the lowest frequency, it is suitable for indoor installation or advantageous in terms of wind resistance. Suitable for flame retardant and heat resistant design, suitable for environments with fire resistance regulations such as underground facilities and tunnels.

  Furthermore, this structure can be manufactured by general-purpose metal plate processing, and does not require a resin material or a flammable material. Therefore, the antenna can be made inexpensive and excellent in heat resistance and fire resistance.

  Therefore, according to the present invention, a small multi-frequency monopole antenna can be provided by optimizing the element spacing according to the frequency band for the purpose of reducing the height and width.

  Furthermore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

    2a ... f1 element, 2b ... f2 element, 2c ... f3 element, 2d ... f4 element, 3 ... GND plate, 4 ... feeding point, 5 ... base, 7 ... element branch point, S ... opening angle.

Claims (2)

For the lowest operating frequency f1, it is composed of a radiating element corresponding to four frequencies respectively set to f2 = 1.8f1, f3 = 2.4f1, f4 = 3.1f1, and a GND plate.
A multi-frequency monopole antenna having a base provided with a feeding point in the center, wherein the radiating element is supported from the base through an element support;
When the wavelength is described as λn with respect to the frequency fn, the radiating element is disposed at the center of the base and is set to a height H1 of 0.2λ1 or less,
Four f2 elements that are branched in the radial direction from the f1 element in a range where the element housing diameter R is 0.05λ1 at the element branching point where the height Y from the feeding point is 0.05λ1, and two F3 element and two f4 elements,
The f2 element has a height H2 from the element branch point of 0.2λ2, the f3 element has a height H3 from the element branch point of 0.2λ3, and the f4 element has a height from the element branch point. H4 is set to 0.19λ4,
A multi-frequency monopole antenna in which an opening angle S between the f2 element and the f3 element is set to 60 degrees. The f1 element has a rectangular flat plate-like wide portion at the top,
A flat top plate extends in the direction perpendicular to the axial direction of the f1 element on the wide portion,
A first folding element extending downward on both sides of the upper portion of the wide portion and a second folding element extending downward on both sides of the top plate are respectively bent and formed;
The multi-frequency monopole antenna according to claim 1, wherein a height Ha1 of the first folding element is set to 0.04λ1, and a height Hb1 of the second folding element is set to 0.01λ1.