JP5853883B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device having a stop band.

  Conventionally, as one of antennas having a frequency characteristic such that a stop band exists in the pass band, a slit having a length substantially equal to a quarter wavelength of the center frequency of the stop band is provided in a fan-shaped plate-shaped radiating element. Are known (for example, see Patent Document 1).

JP 2008-228165 A

  However, since the conventional antenna device described in Patent Document 1 is based on a plate-shaped radiating element, this technique cannot be applied to a loop antenna or a half-loop antenna configured by linear radiating elements. There was a problem.

  In order to solve the above-described problems, an object of the present invention is to provide an antenna device that is composed of linear radiating elements and has one or more element bands.

  The antenna device of the present invention, which has been made to solve the above problems, is grounded at one end and grounded at the other end through the same feeding point, and has a half wavelength of a frequency within a preset designated band. The radiating element section is composed of N (N is an integer of 2 or more) linear radiating elements corresponding to each other and having different lengths. That is, each linear radiating element that constitutes the radiating element portion constitutes a so-called half-loop antenna.

  Then, any two radiating elements arranged adjacent to each other are used as adjacent radiating element pairs, and the closed loop formed by the adjacent radiating element pair corresponds to the wavelength of the center frequency of the stop band set in the designated band. The element length of each linear radiating element constituting the radiating element unit is set so as to be the length to be tuned.

  In the antenna device of the present invention configured as described above, N-1 linear radiating element pairs are formed as the linear radiating elements of the radiating element section, and the length of the closed loop formed by each of the linear radiating element pairs is small. By setting them to be different from each other, it is possible to easily realize frequency characteristics having N-1 stop bands.

  In the antenna device of the present invention, it is desirable that the distance between the pair of adjacent linear radiating elements be arranged so as to have a constant width. That is, for example, when the linear radiating elements have a linear shape, the linear radiating elements are arranged in parallel to each other. In this case, each linear radiating element has a shape similar to each other.

  In the antenna device of the present invention, a shared line shared by all the linear radiating elements may be provided on at least one of the feeding end and the grounding end of each linear radiating element constituting the radiating element portion. Good.

  In this case, by adjusting the length of the shared line, it is possible to make the stop band steep, and in particular, when there are multiple stop bands, the characteristics of the pass band sandwiched between the stop bands are flattened. Can be.

It is explanatory drawing which shows the structure of the antenna device 1 of 1st Embodiment. It is a graph which shows the result of having calculated | required the VSWR characteristic and gain characteristic of the antenna apparatus 1 by simulation. It is explanatory drawing which shows the coordinate system used when calculating | requiring a gain characteristic. It is a circuit diagram which shows the structure of the receiving circuit to which the antenna apparatus 1 is applied. It is explanatory drawing which showed the characteristic of the antenna device 1 single-piece | unit and the band pass filter 8 single-piece | unit, and the characteristic which synthesize | combined both with the comparative example. It is explanatory drawing which shows the structure of the antenna apparatus 2 of 2nd Embodiment. It is a graph which shows the result of having calculated | required the VSWR characteristic and gain characteristic of the antenna apparatus 2 by simulation. It is explanatory drawing which shows the structure of the antenna apparatus 3 of 3rd Embodiment. It is explanatory drawing which shows the other example of arrangement | positioning of the linear radiation element which comprises a radiation element part. It is explanatory drawing which shows the structure of other embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
<Overall configuration>
The antenna device 1 according to the present embodiment is based on a half-loop antenna used in the 700 MHz band (UHF band), and is configured such that two stop bands exist within the use band of the basic half-loop antenna. It is.

  As shown in FIG. 1, the antenna device 1 is composed of a power feeding unit 10 grounded to a ground plane G made of flat metal and a metal wire, and receives electric power from the power feeding unit 10 to radiate radio waves. The radiating element unit 20 is included.

<Configuration of radiation element>
The radiating element unit 20 includes three linear radiating elements 21, 22, and 23 wired in the same plane orthogonal to the ground plane G, and each has a shape that forms a rectangular loop together with the ground plane G. ing.

  Specifically, the radiating element unit 20 is erected vertically with respect to the ground plane G, and one end (hereinafter also referred to as “feeding end”) is connected to the feeding unit 10, and the first site 20 a. The end of the second part 20b extending from the end opposite to the power supply end so as to be substantially parallel to the ground plane G and the end of the second part 20b opposite to the connection end of the first part 20a And a third portion 20 c that extends perpendicularly to the ground plane G and whose tip (hereinafter also referred to as “grounding end”) is connected to the ground plane G.

  Moreover, the distance between the linear radiating elements 21 and 22 (the width between the lines) is set to be a constant width, and the linear radiating elements 21 and 22 are parallel to each other at the respective portions 20a, 20b, and 20c. It is configured. Similarly, the distance between the linear radiating elements 22 and 23 (the width between the lines) is also set to a constant width, and the linear radiating elements 22 and 23 are also parallel to each other at the respective portions 20a, 20b, and 20c. It is configured.

  That is, the linear radiating elements 21, 22, and 23 have shapes similar to each other as a whole, and the bending points (vertices) of the linear radiating elements 21, 22, and 23 are arranged substantially in a straight line. ing. Note that the line width of the linear radiating elements 21 and 22 is D1, and the line width of the linear radiating elements 22 and 23 is D2. Both may be the same size (D1 = D2) or different sizes. (D1 ≠ D2).

Thus, the linear radiation elements 21, 22, and 23 wired in the same plane have a longer element length as they are located on the outer side (the side farther from the ground plane G). That is, the element length of the outermost linear radiating element 21 is L ₁ , the element length of the linear radiating element 22 positioned in the middle is L ₂ , and the element length of the innermost linear radiating element 23 is L ₃ If you, the _{L 1> L 2> L 3} .

Further, the linear frequencies 21, 22, and 23 are set such that the center frequencies of the two stop bands are f _i (i = 1, 2), and the wavelength of the center frequency (hereinafter also referred to as “center wavelength”) is λ _i. The element lengths L ₁ , L ₂ and L ₃ are set so as to satisfy the following relational expression (1).

Specifically, assuming that the center frequency of the use band is f ₀ (where f ₁ <f ₀ <f ₂ ) and the wavelength at the center frequency f ₀ is λ ₀ , first, the element length L _{2 is set} to (2 ) Set according to the formula.

However, the device length L ₂ is exactly lambda ₀ / need not be 2, it is possible to be transmitted and received at high efficiency under the half-loop antenna length (usually about 10% larger) it is sufficient that.
The element lengths L ₁ and L ₃ of the linear radiating elements 21 and 23 are set according to the following equations (3) and (4) based on the element length L ₂ and the center wavelengths λ ₁ and λ ₂ .

<Simulation>
FIG. 2 shows the results obtained by simulating the VSWR characteristics and the gain characteristics of the antenna device 1 configured as described above.

Here, the center frequency (center wavelength) of the used band is f ₀ = 760 MHz (λ ₀ = 395 mm), and the center frequencies (center wavelengths) of the two stop bands are f ₁ = 750 MHz (λ ₁ = 400 mm) and f _{2, respectively.} Assuming = 770 MHz (λ ₂ = 389 mm), the element lengths of the linear radiating elements 21, 22 and 23 were determined as L ₁ = 203 mm, L ₂ = 197 mm, and L ₃ = 192 mm.

  Further, as shown in FIG. 3, the coordinate system of the gain characteristic is that the ground plane G is disposed on the XY plane, and is symmetrical with respect to the Z axis on the YZ plane (however, the feeding end is the negative side of the Y axis and the grounding end is It is assumed that the radiating element unit 20 is disposed so as to be located on the plus side of the Y axis. The gain in the plane (that is, the XY plane) where the angle with respect to the Z axis (normal direction of the ground plane G) is θ = 90 ° (that is, the XY plane) is φ = 0 in the XY plane where the X axis direction is 0 °. 4 (+ direction of X axis), φ = 90 ° (positive direction of Y axis), φ = 180 ° (negative direction of X axis), φ = 270 ° (negative direction of Y axis) The result calculated | required about the location is shown.

<Effect>
As described above, according to the antenna device 1, by using the linear radiating element, not only can a frequency characteristic having one or more element bands be realized, but also a closed loop formed by a radiating element pair. The center frequency of the stop band can be adjusted to a desired value by appropriately setting the length of.

  FIG. 4 shows a configuration in which the above-described antenna device 1 is applied to a receiving circuit used in an on-board unit or the like of an intelligent road traffic system (ITS) using a 10 MHz-wide frequency band whose center frequency is 760 MHz. Is.

  As shown in FIG. 4, the receiving circuit includes a bandpass filter (BPF) 8 that extracts a signal in a predetermined frequency band from a received signal supplied from the antenna device 1, and a low-noise amplifier (LNA) that amplifies the signal extracted by the BPF 8. 9).

  That is, assuming that a band where VSWR is 3 or less is a pass band, the frequency characteristic of the antenna device 1 alone shown in FIG. 2 is not only a frequency band (760 MHz to 770 MHz) sandwiched between two stop bands, but also a stop band. The frequency band outside the band (735 MHz to 750 MHz or 785 MHz or more) also becomes a pass band, but by combining with BPF8, the characteristic that only the narrow frequency band sandwiched between the two stop bands is a pass band is realized. Can do.

  Here, FIG. 5A shows the frequency characteristics of the antenna device 1 alone and the BPF 3 alone, and the combined characteristics, and FIG. 5B uses an antenna device having no stopband. This is a comparative example.

  That is, by applying the antenna device 1 to such a receiving circuit, a steep attenuation characteristic outside the passband can be realized without using an expensive filter or a filter with a large circuit scale. Thereby, interference from a frequency close to the pass band (for example, the LNA 9 is saturated by noise) can be effectively suppressed.

[Second Embodiment]
A second embodiment will be described.
<Configuration>
The antenna device 2 of the present embodiment is different from the antenna device 1 of the first embodiment only in a part of the configuration, and therefore, the difference will be mainly described.

  As shown in FIG. 6, in the antenna device 2, the feeding ends of the linear radiating elements 21, 22, and 23 constituting the radiating element unit 20 are connected to each other, and the connected feeding ends (hereinafter referred to as “feeding side connection”). Part ”) is connected to the power feeding unit 10 via the shared line 31.

That is, the antenna device 2 is configured such that the power feeding side connection portion in the radiating element portion 20 is located at a location separated from the ground plane G by the length H1 of the shared line 31.
<Effect>
In the antenna device 2 configured as described above, the frequency characteristics (VSWR characteristics, gain characteristics) can be changed by appropriately adjusting the length H1 of the shared line 31 (here, H1 = 15 mm).

  Specifically, as shown in FIG. 7 (a), the center frequency of the pass band sandwiched between the two stop bands can be adjusted to the center of both stop bands, as shown in FIG. 7 (b). As described above, the gain in the pass band can be set to a substantially constant value, that is, the frequency characteristic in the pass band can be improved.

Moreover, according to the antenna apparatus 2, since only the shared line 31 should just be connected to the electric power feeding part 10, the effort required for the connection of an electric power feeding end can be reduced.
[Third Embodiment]
A third embodiment will be described.

<Configuration>
The antenna device 3 according to the present embodiment is different from the antenna device 2 according to the second embodiment only in a part of the configuration, and thus the description will focus on the differences.

  As shown in FIG. 8, in the antenna device 3, not only the feeding ends of the linear radiating elements 21, 22, and 23 constituting the radiating element unit 20, but also the ground ends are connected to each other, and the connected ground ends (Hereinafter referred to as “grounding side connection portion”) is connected to the ground plane G via the shared line 32.

  That is, in the antenna device 3, the ground side connection portion in the radiating element portion 20 is also configured to be located at a place away from the ground plane by the length H <b> 2 of the shared line 32, similarly to the power feeding side connection portion.

<Effect>
In the antenna device 3 configured as described above, the frequency characteristics (VSWR characteristics, gain characteristics) are adjusted by appropriately adjusting the lengths H1, H2 of the shared lines 31, 32 (here, H1 = H2 = 8 mm). Therefore, the same frequency characteristic as that of the antenna device 2 of the second embodiment can be obtained, and the same effect can be obtained.

Moreover, according to the antenna device 3, since only the shared line 32 has to be connected to the ground plane G, it is possible to reduce the labor required for connection of the ground end.
In addition, although the structure provided with both the shared lines 31 and 32 was shown here, the shared line 31 may be omitted and the structure provided with only the shared line 32 may be used. Even in this case, the same effect as that of the antenna device 2 of the second embodiment can be obtained.

[Other Embodiments]
Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented in various modes.

  For example, in the above-described embodiment, the linear radiating elements 21, 22, and 23 constituting the radiating element unit 20 are arranged on the same plane orthogonal to the ground plane G. However, as shown in FIG. The other linear radiating elements 21 and 22 are arranged at positions offset in the normal direction of the arrangement plane (X-axis direction in the figure) with respect to the arrangement plane (YX plane in the figure) where 23 is arranged. Also good.

  In this case, each linear radiation element 21, 22, 23 has apexes at both ends of the second part 20b (contact points between the first part 20a and the second part 20b and contact points between the second part 20b and the third part 20c). Are arranged on a substantially straight line at each end.

  In this way, by arranging the three-dimensional space, the linear radiating elements 21, 22, and 23 are brought into contact with each other even when the element length difference between the linear radiating elements 21, 22, and 23 is small. It can arrange without making it.

  In the above-described embodiment, the shape of the radiating element portion 20 is rectangular (rectangular), but may be trapezoidal like the antenna device 4 shown in FIG. The shape is not limited to these, and any shape that forms a loop together with the ground plane G may be used, such as a polygonal shape or a circular shape.

  Further, as in the antenna device 5 shown in FIG. 10B, two radiating element portions 20 (201, 202) are provided, and these radiating element portions 201, 202 are axially symmetric with respect to the axis passing through the feeding portion 10. It may be arranged. That is, the ground plate G may be omitted and a loop antenna may be formed. However, in this case, it is necessary to provide the shared line 32 so that the closed loop formed by the adjacent radiation element pair becomes independent for each of the radiation element portions 201 and 202b.

  In the above embodiment, the linear radiating elements 21, 22, and 23 constituting the radiating element unit 20 are configured by metal wires. However, as in the antenna device 6 illustrated in FIG. You may comprise by the pattern on the dielectric substrate P standingly arranged so that a pattern formation surface may become perpendicular | vertical.

  In this case, the antenna device 6 can be easily manufactured, and the wavelength is shortened by the dielectric constant of the dielectric substrate P. Therefore, the size of the linear radiating elements 21, 22, and 23, and consequently the antenna device 6. The overall size can be reduced.

  In the above-described embodiment, the case where the radiating element unit 20 is configured by the three linear radiating elements 21, 22, and 23 has been described. However, the number of the linear radiating elements is two or four or more. There may be.

  DESCRIPTION OF SYMBOLS 1-6 ... Antenna apparatus 8 ... Band-pass filter (BPF) 9 ... Low noise amplifier (LNA) 10 ... Feed part 20, 201, 202 ... Radiation element part 20a ... 1st part 20b ... 2nd part 20c ... 3rd part 21 , 22, 23 ... linear radiating elements 31, 32 ... shared line G ... ground plane P ... dielectric substrate

Claims (7)

One end is grounded and the other end is grounded through the same feeding point (10), and N (N) corresponding to a half wavelength of a frequency within a preset designated band and having different lengths. Is an radiating element section (20) composed of two linear radiating elements (21, 22, 23).
Any two linear radiating elements arranged adjacent to each other are defined as adjacent radiating element pairs (21-22, 22-23), and a closed loop formed by the adjacent radiating element pairs is set within the designated band. The element length of each linear radiating element constituting the radiating element section is set so as to be a length corresponding to the wavelength of the center frequency of the stop band, wherein the antenna device (1, 2, 3, 4, 5, 6).   2. The antenna device (1, 2, 3, 4, 5, 6) according to claim 1, wherein a space between the adjacent linear radiating elements is arranged to have a constant width.   A shared line (31, 32) shared by all the radiating elements is provided on at least one of the feeding end and the grounding end of each radiating element constituting the radiating element section. The antenna device (2, 3, 4, 5, 6) according to claim 1 or 2.   4. The antenna device according to claim 1, wherein the radiating elements constituting the radiating element unit are formed on different planes. 5.   The antenna device (1, 2, 3, 4) according to any one of claims 1 to 3, wherein each radiating element constituting the radiating element section is formed on the same plane. , 5, 6).   The antenna device (6) according to claim 5, wherein the radiating element section is configured by a pattern formed on a dielectric substrate (P).   The radiating element section (201, 202) is provided, and the radiating element section is arranged symmetrically with respect to an axis passing through the feeding point. The antenna device (5) according to claim 1.