JP4922339B2 - Broadband antenna - Google Patents

Description

  The present invention relates to a broadband antenna.

For example, in the case of an antenna for a car, a plurality of antennas having different target frequencies such as AM / FM radio, VICS (registered trademark) (Vehicle Infomation and Communication System), GPS, television (VHF / UHF band), ETC, etc. It was necessary to install inside or outside the car.
These antennas are preferably arranged as compactly as possible. However, when the antennas are brought close to each other, they may interfere with each other due to interference between the antennas and may not function normally as an antenna. was there.

Therefore, in order to avoid interference of each antenna, it is necessary to consider an appropriate interval and layout for each antenna. Or, since a lead-in wire from each antenna to each device is attached, there is a problem that wiring is complicated when a plurality of wireless devices using different antennas coexist.
On the other hand, various frequency bands are used in wireless communications such as mobile phones and wireless LANs, and in particular, UWB (Ultra Wide Band) communications proposed in recent years are very wide ranging from 3.1 to 10.6 GHz. Since a frequency band is used, a broadband antenna that can cover such a wide frequency band has been demanded.

  Conventionally, in Patent Document 1, as a UWB antenna, two corners of a square antenna element such as a rhombus, a square, or a rectangle are made close to each other and arranged symmetrically, and the corner is fed as a feeding point. A lead wire or the like was connected so that the other end of the lead wire was connected to the electronic circuit unit.

JP 2005-277501 A

However, the conventional UWB antenna disclosed in Patent Document 1 may not have a wide frequency band in which the performance of return loss of −10 dB or less (corresponding to a voltage standing wave ratio of 2.0 or less) that is generally required for an antenna is obtained. As a result of experiment, it became clear.
That is, as shown in FIG. 13, antenna elements 30 and 30 made of two square thin metal plates are arranged symmetrically with respect to a straight line 31, and the corner portions 32 and 32 of the antenna elements 30 and 30 are close to each other. In addition, the strip-like leg pieces 33 and 33 are extended in parallel from the corner portions 32 and 32 so as to form the minute gap K along the straight line 31. A lead wire 35 is connected to the outer end 33 a of the leg piece 33. That is, the outer end 33a is set as a feeding point Q. Reference numeral 36 denotes an electronic circuit unit.

Each antenna element 30 in FIG. 13A is a square with a side of 25 mm (referred to as a 25 mm square) and has a total length W ₀ of 75 mm. Each antenna element 30 in FIG. 13B has a square with a side of 50 mm (a 50 mm square). It is said). FIG. 14 is a graph showing an actual measurement result of the return loss measured by stretching the two antennas 40A and 40B of FIGS. 13A and 13B on a 3 mm thick glass plate. The horizontal width indicates the frequency (GHz), and the vertical axis indicates the return loss (dB). From this graph, it has been found that the frequency bands F _A and F _B at which return loss of −10 dB or less can be obtained are narrow and lack practicality.

Therefore, the present invention provides a wideband antenna that can provide a practical return loss sufficient as an antenna in a sufficiently wide frequency band than the return loss shown in FIG. Objective. Another object is to remarkably improve the directivity of circular polarization at a specific frequency as an antenna.
Another object of the antenna according to the present invention is to integrate many antennas necessary for each of a plurality of conventional wireless communication systems to simplify complicated wiring.

In order to achieve the above object, a wideband antenna according to the present invention includes a pair of conductive material thin-plate antenna elements arranged in line symmetry with respect to a straight line, and further with a minute gap as line symmetry with respect to the straight line. A planar feeding leg piece made of a pair of conductive materials is formed so as to protrude from the mutually adjacent portion of the antenna element, and each leg piece gradually has a width dimension in the outer end direction. An outward widening shape that increases, and the wavelength of the target wave is λ (where λ is the wavelength in the space λ ₀ and the equivalent dielectric constant around the antenna is εr, λ ₀ / √ is the electrical length indicated by εr), and a short slit having a length of λ / 4 is located at a position separated by one wavelength λ along the outer peripheral edge of the antenna element from the close proximity portion. It is the arrangement | positioning.

In addition, the thin planar antenna elements made of a pair of conductive materials are arranged in line symmetry with respect to a straight line, and are further arranged in line symmetry with respect to the straight line so as to be close to each other with a minute gap and are made of a planar feed made of a pair of conductive materials. The leg pieces are formed so as to protrude from the adjacent parts of the antenna element, and each leg piece has an outwardly widened shape in which the width dimension gradually increases in the outer end direction, and the center piece When a substantially small circular divided loop slit composed of a pair of arcs having an angle of less than 180 ° is disposed in the close proximity portion of the antenna element, and the wavelength of the target wave is λ, the antenna is connected from the close proximity portion to the antenna. In this configuration, an obtuse small protrusion is provided at a position separated by (1/2 · λ) along the outer peripheral edge of the element and only on one of the pair of antenna elements .

In addition, the thin planar antenna elements made of a pair of conductive materials are arranged in line symmetry with respect to a straight line, and are further arranged in line symmetry with respect to the straight line so as to be close to each other with a minute gap and are made of a planar feed made of a pair of conductive materials. the Yoashihen from mutual proximity site of the antenna element, formed on the protruding shape, moreover, each leg is a outwardly widening shape gradually width at the outer end direction is increased, moreover, the purpose When the wavelength of the wave is λ, a short slit having a length of λ / 4 is disposed at a position separated by 1 wavelength λ along the outer peripheral edge of the antenna element from the above-mentioned close proximity portion. If the wavelength of the wave is λ, the obtuse angle shape is located at a position (1/2 · λ) away from the above-mentioned close proximity portion along the outer peripheral edge of the antenna element and only in one of the pair of antenna elements. It is the structure which provided the small processus | protrusion.

Alternatively, the thin planar antenna elements made of a pair of conductive materials are arranged line-symmetrically with respect to a straight line, and are further made to be line-symmetric with respect to the straight line and close to each other with a minute gap so as to have a planar power supply made of a pair of conductive materials. The leg pieces are formed so as to protrude from the adjacent parts of the antenna element, and each leg piece has an outwardly widened shape in which the width dimension gradually increases in the outer end direction, and the center piece A substantially small circular divided loop slit composed of a pair of arcs with an angle of less than 180 ° is disposed in the mutually adjacent portion of the antenna element, and the wavelength of the target wave is λ, and the length is λ / 4. A short slit having a size is disposed at a position separated by one wavelength λ along the outer peripheral edge of the antenna element from the adjacent portion, and when the wavelength of the target wave is λ, the antenna is moved from the adjacent portion to the antenna. Outside the element In accordance with (1/2 · λ) apart positions on edge, and only one of the pair of antenna elements, a configuration in which an obtuse angle-shaped small projections.

The outermost edge of the antenna element farthest from the adjacent portion has a smooth arc shape, and the adjacent portion of the antenna element touches the arcuate virtual arc as a smooth arc shape. The leg pieces are joined from the tangential direction to form a joined portion.
Further, in each of the antenna elements, a plurality of the short slits are juxtaposed on the outer peripheral edge with an interval pitch of the one wavelength λ in the clockwise direction and the counterclockwise direction.
Each of the antenna elements is substantially oval, and the major axis intersects with the straight line at an angle of about 90 °. The antenna elements are arranged orthogonal to each other, and the substantially small circular divided loop slits are arranged on the major axis. It is arranged above .

  It exhibits excellent return loss characteristics and good directivity in an extremely wide frequency band. And it is suitable as an antenna for ETC, and moreover, it is possible to cope with not only UWB communication but also a lower digital terrestrial television with one type of antenna.

It is a front view which shows the 1st Embodiment of this invention. It is a principal part enlarged view. It is a front view which shows a reference example . It is a principal part enlarged view. It is a front view which shows 2nd Embodiment. It is a principal part enlarged view. It is a front view which shows 3rd Embodiment. It is a front view which shows 4th Embodiment. It is a graph which shows the actual measurement result about the Example corresponding to FIG. 1 of this invention. It is a front view which shows a comparative example. It is a graph which shows the measurement result of the Example of FIG. 1, and the comparative example of FIG. It is a graph which shows the cross polarization discrimination | determination degree measurement result about the Example of FIG. It is a front view which shows a prior art example. It is a graph which shows the actual measurement result of a prior art example. It is a graph which shows the actual measurement result about the Example corresponding to FIG. 8 of this invention. It is a graph which shows the cross polarization discrimination | determination degree measurement result about the Example of FIG.

Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
The first embodiment shown in FIGS. 1 and 2, the reference example shown in FIGS. 3 and 4, the second embodiment shown in FIGS. 5 and 6, and the third embodiment shown in FIG. The basic configuration will be described. The pair of thin-sided antenna elements 1 and 1 are arranged symmetrically with respect to the straight line L, and the pair of thin-sided feeding legs 2 and 2 are connected to the antenna element 1. , 1 projecting from the mutually adjacent portions 5, 5 and integrally. As shown in FIG. 1, when the total length is W ₀ , W ₀ ≈1 / 2λ _L when the wavelength of the lowest frequency f _{L to be} applied is λ _L.

The pair of leg pieces 2 and 2 are line-symmetric with respect to the straight line L and are close to each other with a minute gap G.
Moreover, each leg piece 2 has an outwardly widened shape in which the width dimension W gradually increases in the outer end direction C.
Further, the outwardly widened leg piece 2 and the antenna element 1 are preferably constituted by a single thin metal plate. Specifically, the antenna element 1 and the leg piece 2 can be made of a thin metal plate (metal foil) such as Cu, Al, Ag, or Au, and is stretched on a glass, a resin sheet and a resin film, an electronic substrate, or the like. Can be used.
In addition, a metal film, a transparent conductive film and a conductive paint film can be used by directly forming them on glass and an electronic substrate, or a film once formed on a resin sheet, a resin film, etc. is further stretched on the glass and the electronic substrate. Can also be used.

As the metal film, Au, Ag, Cu, Al, Pd, Pt and alloys containing them can be used. As the transparent conductive film, metal oxides such as ITO, zinc oxide and tin oxide can be used. It can be manufactured by sputtering, plating, electrodeposition or the like.
As the conductive paint film, a metal paste or a carbon paste can be used, and it can be manufactured by screen printing, roll coating, transfer or the like.
When it is stretched and used on a glass surface such as an automotive windshield, rear glass or window glass, it is desirable to have a visible light transmittance of 70% or more. In applications where such transparency is required, metal It is preferably composed of a mesh type, an extremely thin (for example, 0.05 μm) metal foil, or a transparent conductive film or a metal translucent film. As the metal translucent film, Ag-Cu, Ag-Pd, Ni-Au, or the like can be used.
In addition, tensioning or tensioning means tensioning the outer surface of the glass surface with an adhesive or pressure-sensitive adhesive, etc., or baking and laminating, or otherwise sandwiching or sandwiching between glass layers. In the present invention.

The minute gap G between the pair of leg pieces 2 and 2 is preferably formed in a tapered shape that gradually increases from the outer end 2A side toward the adjacent portion 5 side (of the antenna element 1). In other words, the minute gap G gradually decreases in the outer end direction C from the proximity portion 5 side.
The shape of the antenna element 1 is substantially elliptical.

In FIG. 1, 6 shows an electronic circuit part (amplifier or filter), and is connected to the outer end 2A of the leg piece 2 by a conducting wire (lead wire) 7, and E indicates a feeding point. This feeding point E is preferably arranged at a position (corner) close to the minute gap G. 3, 5, and 7, although the electronic circuit unit 6 and the conductive wire 7 are not shown, they are similarly connected.
Further, the outer edge of the leg piece 2 is formed in a concave arc shape with a large curvature radius.
More specifically, the outermost edge 10 that is farthest from the adjacent portion 5 of the antenna element 1 has a smooth arc shape, and the adjacent portion 5 also has a smooth arc shape. (In FIGS. 1-7, since the external shape of the antenna element 1 is a substantially ellipse, naturally, it can be said that the outermost edge part 10 and the adjacent part 5 are formed in circular arc shape.)

The inner end of the leg piece 2 from the tangential direction in contact with the arcuate virtual arc (the virtual curve indicated by the dotted line) of the adjacent portion 5 ---- that is, the substantially elliptical small curvature radius part (curved part) --- 9 is joined to form a joint S (shown by a dotted line).
In particular, the antenna element 1 has a substantially elliptical shape, and an angle θ at which the major axis L ₁ intersects the straight line L is set to 90 °. Therefore, the leg piece 2 is joined to the adjacent portion 5 of the antenna element 1 from the direction orthogonal to the long axis L ₁ to form a smooth joint S, and the length of the arc of the joint S is: It is set sufficiently larger than the minimum value of the width dimension W of the leg piece 2.

  Further, the outermost edge portion 10 farthest from the adjacent portion 5 of the antenna element 1 has a smooth arc shape, and the adjacent portion 5 of the antenna element 1 has a circular arc shape as a smooth arc shape. Since the leg piece 2 is joined to form the joined portion S from the tangential direction in contact with the virtual arc, a part of the return loss curve below the −10 dB line is partially shown in FIG. Only draws a steep mountain and no longer shows the characteristic of penetrating above the -10 dB line. Therefore, a stable return loss characteristic is shown in a wide frequency band.

The antenna element 1 is substantially elliptical, and has a simple shape with a configuration in which the angle θ is about 90 ° and the major axis L ₁ is arranged so as to be orthogonal to the straight line L. The present invention shows excellent return loss characteristics in a very wide frequency band, and can be applied to communications that require a very wide frequency band such as UWB communications.
If the antenna elements 1 and 1 and the leg pieces 2 and 2 are configured to have a visible light transmittance of 70% to 95%, they can be seen with the naked eye and are stretched on a transparent glass surface such as an automobile or a window. Can be used.
In addition, since the antenna is stretched on the glass surface of the automobile, even if the antenna is made of a thin metal piece (foil), it is sufficiently reinforced and durable, and further, automobiles such as ETC, GPS, and wireless LAN are provided. It is possible to realize various kinds of communication essential for an unobtrusive antenna.

Next, each embodiment will be described. In the first embodiment shown in FIGS. 1 and 2, the center angle β is less than 180 ° --preferably 160 ° ≦ β ≦ 175 ° — —A substantially small divided loop slit 11 composed of a pair of arcs 12 and 12 is formed in the mutually adjacent portions 5 and 5 of the antenna elements 1 and 1. Moreover, the divided loop slit 11 is in contact with the joint S indicated by a dotted line. The center point 13 of the split loop slit 11 is on the long axis L ₁ , and the angles α ₁ and α ₂ formed by the straight line L ₁₄ connecting the connecting remaining portions 14 and 14 on the opposite side of 180 ° and the straight line L are (see FIG. 2) The difference between right and left, the right angle α ₁ is set smaller than the left angle α ₂ , and 5 ° ≦ α ₁ ≦ 40 ° and 5 ° ≦ α ₂ ≦ 40 ° and α ₁ <α ₂ The formula holds.

If the wavelength of the target wave is λ, the arc length of each arc 12 is set to ½ · λ, and the entire circumference of the divided loop slit 11 is set to be equal to about λ.
Then, 15 and 16, as shown in FIGS. 1, 2 and 6, when the wavelength of interest wave lambda, an elongated part length slits of length L ₁₅ of lambda / 4, the mutually adjacent site 5 along the outer peripheral edge of the antenna element 1 by 1 wavelength λ at equal intervals and sequentially away from each other.

Specifically, in the antenna element 1 on the right side, a circle having a radius of 1 wavelength λ and a wavelength of 2 λ is drawn from the above-described center point 13 and crosses the outer peripheral edge. Short slits 15 and 16 (arc-shaped) having a length L ₁₅ are notched. FIG. 1 and FIG. 2 illustrate the case where two are provided clockwise and two are provided counterclockwise from the adjacent portion 5 along the outer peripheral edge. Each of the two short slits 15 and 16 may be one of the above-mentioned one wavelength λ, or conversely, three of one wavelength λ, two wavelengths 2λ, and three wavelengths 3λ. Is possible.
In the antenna element 1 on the left side, the short slits 15 and 16 are arranged symmetrically with respect to the straight line L, and the same can be said. As described above, in each of the right and left antenna elements 1, a plurality of short slits 15 and 16 are arranged side by side in the clockwise direction and the counterclockwise direction with an interval pitch of one wavelength λ.

  Further, as shown in FIGS. 1 and 2, only one of the pair of antenna elements 1 and 1 (right side in the example) is provided with a triangular small protrusion 18 having an obtuse apex angle at a position close to each other. 5 along the outer peripheral edge of the antenna element 1 at a position separated by ½ · λ. In other words, in FIG. 2, in the antenna element 1 on the right side, two short slits 15 and 16 are arranged clockwise from the adjacent portion 5 with an interval of one wavelength λ along the outer peripheral edge. A small protrusion 18 having an obtuse angle isosceles triangle is disposed at a position where the half dimension of this interval--1 / 2 · λ-- is returned to the adjacent portion 5.

Next, the reference example shown in FIGS. 3 and 4 will be described. The short slits 15 and 16 and the small protrusions 18 are omitted from the first embodiment shown in FIGS. is there. That is, the configuration has only the divided loop slits 11 and 11. The configuration of the divided loop slits 11, 11 such as shape, size, arrangement, angle, and the like is the same as that described in FIGS. 1 and 2 (the same reference numerals are the same), and the description thereof is omitted.

Then, At a second embodiment shown in FIGS. 5 and 6, the same reference numerals as Figures 1 and 2 is the duplicated description thereof is omitted have the same configuration, the second embodiment The wideband antenna has short slits 15 and 16 but does not have the split loop slits 11 and 11 and the small protrusions 18 shown in FIGS. The shapes and dimensions of the short slits 15 and 16, the arrangement interval (pitch), and the like are the same as those in the first embodiment shown in FIGS. 1 and 2.

Then, At a third embodiment shown in FIG. 7, the same reference numerals as in FIG. 1 and FIG. 2 is the duplicated description thereof is omitted have the same configuration, the antenna of the third embodiment In this configuration, the split loop slits 11 and 11 and the small protrusions 18 are provided, but the short slits 15 and 16 shown in FIGS. 1 and 2 are omitted. Other configurations are the same as those in FIGS. 1 and 2.

Next, in the fourth embodiment shown in FIG. 8, the same reference numerals as those in FIG. 1 and FIG. 2 have the same configuration, and different points will be described. This is cut from the center point 13 of the loop slit 11 with a radius of one wavelength λ. Each of the pair of left and right antenna elements 1 and 1 has a rugby ball shape, and the (long) axis of the rugby ball is a straight line L. Arranged in the parallel direction (longitudinal direction), the overall width dimension W ₀ ′ (full length dimension in the direction of the horizontal axis L ₁ ′) is significantly shortened compared to the horizontally long ellipse shown in FIGS. . Further, the short slits 15 and 16 shown in FIGS. 1 and 2 are not provided, but the divided loop slits 11 and 11 and the small protrusions 18 are provided. The dimensions of the divided loop slits 11 and 11 and the crossing angles α ₁ and α ₂ with the straight line L are as described with reference to FIG.

  The other configurations are the same as those in FIGS. 1 and 2, but to be careful, as shown in FIG. 8, the broadband antenna has a rugby ball shape with respect to the straight line L except for the small protrusion 18. The antenna elements 1, 1 are symmetrically arranged in line symmetry, and the outwardly widened leg pieces 2, 2 whose width dimension W gradually increases in the outer end direction C are also line symmetric with respect to the straight line L, They are arranged close to each other with a minute gap G.

The outermost edge 10 that is farthest from the adjacent portion 5 of the antenna element 1 has a smooth arc shape, and the adjacent portion 5 has a smooth arc shape (as indicated by a dotted phantom line). The leg pieces 2 are joined from the tangential direction in contact with the virtual arc to form the joined portion S (the configuration is the same as that in FIGS. 1 and 2). A horizontal axis L ₁ ′ crossing the antenna element 1 as a vertical center line intersects (is orthogonal to) the straight line L with a 90 ° crossing angle, and has a center point 13 on the horizontal axis L ₁ ′. That is, the split loop slit 11 is on the horizontal axis L ₁ ′.

Next, the graph shown in FIG. 9 is the first embodiment shown in FIG. 1, and the material is Cu, the thickness dimension is 35 μm, and the length along the elliptical long axis L ₁ of the antenna element 1 is shown. is 100mm dimensions, 70 mm elliptical minor axis dimensions, 50 mm dimension from the long axis L ₁ to the outer end 2A of the leg 2, the side length of the outer end 2A 35 mm, the curvature of the outer edge portion 8 a radius Is the measured data when the antenna of the embodiment of the present invention is stretched on a glass plate of 3 mm thickness with the value near the outer end 2A of the minute gap G being 0.5 mm, and the horizontal axis represents the frequency (GHz), The vertical axis represents the return loss (dB).

In FIG. 9, it can be seen that the frequency band F _c showing the return loss (dB) below the ₋₁₀ dB line N ₋₁₀ (described above) is sufficiently wide. That is, a return loss of −10 dB or less of the line N ₋₁₀ was obtained in a wide band from the frequency f _L to the high frequency f _H. Specifically, f _L = 0.4 GHz and f _H = 7.9 GHz. Assuming that the center frequency (average frequency) of both is f ₀ , in the present invention, a case where the following Equation 1 is satisfied is defined as a “wideband” antenna.
[Equation 1]
(F _H −f _L ) / f ₀ ≧ 1.0
Then, in the embodiment shown in FIG. 9, since (f _H −f _L ) = 7.9−0.4 = 7.5, f ₀ = (7.9 + 0.4) ÷ 2 = 4.15, (f _H −f _L ) / F ₀ = 7.5 ÷ 4.15 = 1.81, indicating a preferable return loss characteristic of −10 dB or less in a sufficiently wide frequency band.
In FIG. 1, by optimizing the shape and size of the leg piece 2 and the minute gap G, 10.6 GHz for UWB communication is also covered as shown by a two-dot chain line M in FIG. Is possible. This point has been confirmed by the present inventor.

  Further, FIG. 9 will be described. The symbols “i”, “i”, “b”, “ha”, “d”, “e”, and “f” to “h” on the horizontal axis indicate main frequencies currently used in our country. It is as Table 1.

  From Table 1 and FIG. 9, if the broadband antenna according to the embodiment of the present invention is used, only one type of antenna integrating terrestrial digital television, GPS, wireless LAN, ETC, etc. is sufficient. For example, it can be seen that it is extremely useful when it is attached to a windshield of an automobile and the wideband antenna of the present invention is used. Compared with the graph of FIG. 14 showing the conventional example, it can be seen how the graph of FIG. 9 showing the embodiment of the present invention covers a wide frequency band. As indicated by a two-dot chain line M in FIG. 9, an antenna that exhibits wideband characteristics applicable to UWB communication can also be used.

In any of the embodiments of FIGS. 1 to 8 according to the present invention, the pair of thin-sided antenna elements 1 and 1 are arranged symmetrically with respect to the straight line L, and further symmetrical with respect to the straight line L. A pair of planar feeding leg pieces 2 and 2 are formed in close proximity to each other with a minute gap G so as to protrude from the mutually adjacent portions 5 and 5 of the antenna elements 1 and 1, and each leg piece 2. , 2 is an outwardly widened shape in which the width dimension W gradually increases in the outer end direction C. Therefore, the leg pieces 2, 2 constitute a broadband impedance matching circuit in which the characteristic impedance gradually changes, It is possible to deal with a wide frequency band, and it is possible to integrate a plurality of antennas of a wireless communication system (which conventionally required many antennas). As a result, complicated wiring can be simplified, and the contribution to communication that requires a very wide frequency band, such as UWB communication, is significant. In addition, since it is a thin single-sided shape, it can be easily attached to a windshield of an automobile and has high practicality.
In addition, there are many disaster prevention radio systems in underground shopping malls, mobile phones and terrestrial digital TVs in high-rise buildings and apartment buildings, convenience stores, gas stations, DSRC (narrow area radio communication) systems in parking lots, etc. It is also useful as a broadband antenna that shares a frequency band.

Next, FIG. 11 is a measurement graph showing the directivity measured for each of the example (implemented product) shown in FIG. 1 and the comparative example 50 shown in FIG. The antenna dimensions of the antenna elements 1 and 1 of the comparative example of FIG. 10, the outer dimensions of the leg pieces 2, the minute gap dimension G, etc. are exactly the same, and the divided loop slits 11, 11 and 11 shown in FIG. The short slits 15 and 16 and the small protrusion 18 are eliminated.
Fig. 11 shows the directivity measurement results in the ETC band (5.8 GHz) using right-handed circularly polarized waves, and the reception level at each measurement angle is indicated by a broken line, where 0 ° is the direction of the ETC roadside antenna. The negative angle of Eθ indicates the left direction, and the negative angle of Eφ indicates the zenith direction.

The following can be seen from FIG. That is, in the comparative example (antenna 50 in FIG. 10), the reception level in the angle range of 30 ° to the left and right around 0 ° is lower than that of the product according to the present invention (antenna in FIG. 1). . Further, it can be seen that the antenna 50 of the comparative example has a deep depression (so-called “null”) at a specific angle, which is not preferable.
On the other hand, in the embodiment of the present invention, the reception level is significantly higher (compared to the comparative example) in the range of 30 ° left and right centering on 0 ° (a highly practical angle range of 60 ° in total). It is clear that the depression is slight and that there is no problem in practical use.

  Next, FIG. 12 is a graph showing the measurement result of the cross polarization discrimination for the embodiment (practical product) of the present invention shown in FIG. 0 ° indicates the direction of the ETC roadside antenna, the Eθ minus angle indicates the left direction, and the Eφ minus angle indicates the zenith direction. From the graph of FIG. 12, the cross polarization discrimination of the example shows a difference of about 5 dB or more in the range of 0 ° ± 30 ° (total angle range of 60 °), which is particularly important in ETC. This is a practically desirable performance. That is, in the embodiment of the present invention, the right-handed circularly polarized wave from the ETC roadside antenna that transmits the right-handed circularly polarized wave is surely received, and at the same time, the left-handed circularly polarized wave reflected from the road surface, the ceiling wall, or other objects. So that it is not received.

In addition, as a result of measuring by the same method for the other examples shown in FIG. 8, as shown in FIG. 15, the return loss characteristic has a minimum frequency f _L of 1.4 GHz and a frequency band higher than that. It was -10dB or less, and was -12dB even at 5.8GHz, which was good.
Further, regarding the circular polarization directivity, as shown in FIG. 16, there was a slight drop in Eθ at −60 ° in right-handed polarization, but 0 in cross-polarization discrimination with left-handed polarization. Good data was obtained in an angle range of ° ± 30 °, which was good as an ETC antenna.

As I explained on more than a thin one-sided antenna element 1,1 having a pair of electrically conductive material disposed symmetrically with respect to straight line L, further, with a minute gap G adjacent to each other as a line symmetry with respect to the straight line L The sheet feeding leg pieces 2, 2 made of a pair of conductive materials are formed so as to protrude from the mutually adjacent portions 5, 5 of the antenna elements 1, 1, and the leg pieces 2, 2 are A substantially small circular divided loop slit 11 having a pair of arcs 12 and 12 having an outwardly widened shape in which the width dimension W gradually increases in the outer end direction C and having a center angle of less than 180 ° Since the elements 1 and 1 are disposed in the mutually adjacent portions 5 and 5 (see FIGS. 3 and 4), radio waves in a frequency band of 5.8 GHz as an ETC can be selectively excited and received reliably. In addition, it can cope with a sufficiently wide frequency band and exhibits an excellent return loss characteristic.

Further, according to the present invention, the thin-plate antenna elements 1 and 1 made of a pair of conductive materials are arranged in line symmetry with respect to the straight line L, and further close to each other with a minute gap G as line symmetry with respect to the straight line L. The planar feeding leg pieces 2 and 2 made of a pair of conductive materials are formed so as to protrude from the mutually adjacent portions 5 and 5 of the antenna elements 1 and 1, and the leg pieces 2 and 2 are When the width of the target wave is λ and the wavelength of the target wave is λ, the short slits 15 and 16 having a length L ₁₅ of λ / 4 are Since it is disposed at a position separated by one wavelength λ from the mutual proximity portion 5 along the outer peripheral edge of the antenna element 1 (see FIG. 5 and FIG. 6), it can cope with a sufficiently wide frequency band, and a plurality of wireless Communication system antennas can be integrated, and automobile Easy to stick on windshields etc. In addition, the provision of the short slits 15 and 16 can prevent a drop in directivity due to the disappearance of the function as a harmonic dipole antenna. Therefore, it can be said that the antenna is suitable for ETC and the like and has high practicality.

  Further, a substantially small circular divided loop slit 11 composed of a pair of circular arcs 12 and 12 having a central angle of less than 180 ° is disposed in the mutually adjacent portions 5 and 5 of the antenna elements 1 and 1, and further, a target wave Where λ is the wavelength of the antenna element 1 at a position away from the mutual proximity portion 5 along the outer peripheral edge of the antenna element 1 by (1/2 · λ) and on one of the pair of antenna elements 1, 1. Only obtuse small protrusions 18 are provided (see FIGS. 7 and 8), and by intentionally breaking the left-right symmetry, 5.8 GHz band circularly polarized waves are sufficiently excited and gained. Is remarkably improved and can be received reliably. In particular, it can be said to be a suitable antenna for ETC and the like.

In addition, the thin planar antenna elements 1 and 1 made of a pair of conductive materials are arranged in line symmetry with respect to the straight line L, and are further in close proximity to each other with a minute gap G as line symmetry with respect to the straight line L. The sheet feeding leg pieces 2 and 2 made of material are formed in a protruding shape from the mutually adjacent portions 5 and 5 of the antenna elements 1 and 1, and the leg pieces 2 and 2 are formed in the outer end direction C. When the width of the target wave is λ and the wavelength of the target wave is λ, the short slits 15 and 16 having a length L ₁₅ of λ / 4 are connected to the above-mentioned adjacent portions. 5 is disposed along the outer peripheral edge of the antenna element 1 along the outer peripheral edge of the antenna element 1 by one wavelength λ, and the wavelength of the target wave is λ. And a pair of antenna elements 1, Since the obtuse small protrusion 18 is provided on only one of the two, the loss of directivity due to the disappearance of the function as a harmonic dipole antenna is prevented, and the directivity as a broadband antenna is excellent. The reception level is also high.

In addition, the thin planar antenna elements 1 and 1 made of a pair of conductive materials are arranged in line symmetry with respect to the straight line L, and are further in close proximity to each other with a minute gap G as line symmetry with respect to the straight line L. The sheet feeding leg pieces 2 and 2 made of material are formed in a protruding shape from the mutually adjacent portions 5 and 5 of the antenna elements 1 and 1, and the leg pieces 2 and 2 are formed in the outer end direction C. The antenna element 1, 1 has a substantially small circular divided loop slit 11 composed of a pair of circular arcs 12, 12 having an outwardly widened shape in which the width dimension W gradually increases and having a center angle of less than 180 °. If the wavelength of the target wave is λ, the short slits 15 and 16 having a length L ₁₅ of λ / 4 are connected to the antenna element from the mutual proximity portion 5. 1 is disposed at a position separated by one wavelength λ along the outer peripheral edge of 1 When the wavelength of the target wave is λ, the distance from the mutual proximity portion 5 along the outer peripheral edge of the antenna element 1 is ½ · λ, and within the pair of antenna elements 1 and 1 Since only one of them has an obtuse small protrusion 18 (see FIGS. 1 and 2), it exhibits excellent return loss characteristics in an extremely wide frequency band, and lower ground waves as well as UWB communication. It is a broadband antenna that can be used with a single type of antenna, up to digital television. In addition, as described in FIG. 11, the reception level is high in a predetermined angle range (for example, ± 30 °), and shows an excellent characteristic with a slight drop, and as described in FIG. A difference in reception level between the circularly polarized wave and the left-handed circularly polarized wave is shown, and the cross polarization identification characteristic is obtained.

Further, the outermost edge portion 10 farthest from the adjacent portion 5 of the antenna element 1 has a smooth arc shape, and the adjacent portion 5 of the antenna element 1 has a circular arc shape as a smooth arc shape. Since the above-mentioned leg piece 2 is joined from the tangential direction in contact with the virtual arc and the joined portion S is formed, as shown in FIG. 9, a stable return loss characteristic can be obtained over a wide frequency band. Show.
Further, in each antenna element 1, the short slits 15 and 16 are arranged in parallel on the outer peripheral edge at intervals of 1 wavelength λ in the clockwise and counterclockwise directions. Prevents decline and shows more excellent directivity.
The antenna elements 1 are substantially elliptical, and are arranged orthogonally to each other with an angle θ at which the major axis L ₁ intersects the straight line L being approximately 90 °. Since the slits 11 and 11 are arranged on the long axis L ₁ , for example, a wide-band antenna whose excitation of 5.8 GHz band circular polarization is increased, reception level is further increased, and directivity is remarkably improved is provided. Can be provided.

DESCRIPTION OF SYMBOLS 1 Antenna element 2 Feeding leg piece 5 Mutual proximity part
10 Outermost edge
11 Split loop slit
12 arcs
15, 16 Short slit
18 the wavelength of the lowest frequency f _L to the wavelength lambda _L applied at the wavelength lambda ₀ space of the small projections C outer end direction G micro gap L line L ₁ length axis L ₁₅ length S junction W width θ angle lambda object wave

Claims (7)

The thin planar antenna elements (1) and (1) made of a pair of conductive materials are arranged in line symmetry with respect to the straight line (L), and are mutually symmetrical with a minute gap (G) as line symmetry with respect to the straight line (L). A pair of sheet feeding legs (2) and (2) made of a pair of conductive materials are formed so as to protrude from the mutually adjacent portions (5) and (5) of the antenna elements (1) and (1). Moreover, each of the leg pieces (2) and (2) has an outward widening shape in which the width dimension (W) gradually increases in the outer end direction (C), and the wavelength of the target wave is (λ). Then, the short slits (15) and (16) having a length dimension (L ₁₅ ) of λ / 4 are formed from the mutual proximity portion (5) to one wavelength (λ) along the outer peripheral edge of the antenna element (1). ) A wideband antenna characterized by being disposed at a position separated by The thin planar antenna elements (1) and (1) made of a pair of conductive materials are arranged in line symmetry with respect to the straight line (L), and are mutually symmetrical with a minute gap (G) as line symmetry with respect to the straight line (L). A pair of sheet feeding legs (2) and (2) made of a pair of conductive materials are formed so as to protrude from the mutually adjacent portions (5) and (5) of the antenna elements (1) and (1). Moreover, each of the leg pieces (2) and (2) is a pair of outer widened shapes in which the width dimension (W) gradually increases in the outer end direction (C), and the center angle is less than 180 °. A substantially small circular segmented loop slit (11) composed of a plurality of arcs (12) and (12) is disposed in the mutually adjacent portions (5) and (5) of the antenna elements (1) and (1). When the wavelength of the wave and (lambda), along the said mutual proximity site (5) to the outer peripheral edge of the antenna elements (1) To (1/2 · lambda) apart positions, and only one of the pair of the antenna elements (1) (1), wide-band antenna, characterized in that a obtuse angle small projections (18). The thin planar antenna elements (1) and (1) made of a pair of conductive materials are arranged in line symmetry with respect to the straight line (L), and are mutually symmetrical with a minute gap (G) as line symmetry with respect to the straight line (L). A pair of sheet feeding legs (2) and (2) made of a pair of conductive materials are formed so as to protrude from the mutually adjacent portions (5) and (5) of the antenna elements (1) and (1). Moreover, each of the leg pieces (2) and (2) has an outward widening shape in which the width dimension (W) gradually increases in the outer end direction (C), and the wavelength of the target wave is (λ). Then, the short slits (15) and (16) having a length dimension (L ₁₅ ) of λ / 4 are formed from the mutual proximity portion (5) to one wavelength (λ) along the outer peripheral edge of the antenna element (1). ), And when the wavelength of the target wave is (λ), the antenna element is separated from the mutual proximity portion (5). An obtuse small protrusion (18) at a position separated by (1/2 · λ) along the outer peripheral edge of the child (1) and only on one of the pair of antenna elements (1) (1). A wideband antenna characterized by comprising The thin planar antenna elements (1) and (1) made of a pair of conductive materials are arranged in line symmetry with respect to the straight line (L), and are mutually symmetrical with a minute gap (G) as line symmetry with respect to the straight line (L). A pair of sheet feeding legs (2) and (2) made of a pair of conductive materials are formed so as to protrude from the mutually adjacent portions (5) and (5) of the antenna elements (1) and (1). Moreover, each of the leg pieces (2) and (2) is a pair of outer widened shapes in which the width dimension (W) gradually increases in the outer end direction (C), and the center angle is less than 180 °. A substantially small circular segmented loop slit (11) composed of a plurality of arcs (12) and (12) is disposed in the mutually adjacent portions (5) and (5) of the antenna elements (1) and (1). When the wavelength of the wave and (lambda), short-sized slits of lambda / 4 in length (L ₁₅₎ (15) (16), the mutual Disposed from contact site (5) to one wavelength (lambda) apart locations along the peripheral edge of the antenna elements (1), and, when the target wavelength wave (lambda), the mutual proximity site ( 5) an obtuse small angle at a position separated by (1/2 · λ) along the outer peripheral edge of the antenna element (1) from only one of the pair of antenna elements (1) and (1). A broadband antenna characterized by providing a protrusion (18). The outermost edge (10) farthest from the proximity part (5) of the antenna element (1) has a smooth arc shape, and the proximity part (5) of the antenna element (1) is The broadband according to claim 1, 2, 3 or 4, wherein said leg piece (2) is joined to form a joined portion (S) from a tangential direction in contact with said arcuate virtual arc as a smooth arc shape. antenna. In each of the antenna elements (1), the short slits (15) and (16) are arranged in parallel on the outer peripheral edge with a spacing pitch of one wavelength (λ) each in the clockwise and counterclockwise directions. The broadband antenna according to claim 1, 3 or 4 . Each of the antenna elements (1) has a substantially elliptical shape, and an angle (θ) at which the major axis (L ₁ ) intersects the straight line (L) is about 90 °, and is arranged orthogonal to each other. The broadband antenna according to claim 2 or 4, wherein the substantially small circular divided loop slits (11) (11) are disposed on the major axis (L ₁ ) .

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