JP2000183644A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna system of a small size with a low posture that copes with a plurality of frequencies with a broadband. SOLUTION: This antenna system is provided with a radiation element 2 connected to ground via a ground place 6 at a grounding point 7, a radiation element 3 that has an electric length different from that of the radiation element 2 and connected to the ground plate 6 at a grounding point 8, a feeding point F1 through which power is supplied to the radiation element 2, and a feeding point F2 through which power is supplied to the radiation element 3. Furthermore, the antenna system is constituted so that the distance between the grounding point 7 and the feeding point F1 differs from a distance between the grounding point 8 and the feeding point F2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device having frequency sharing characteristics.

[0002]

2. Description of the Related Art In recent years, mobile satellite communication using a mobile object such as an aircraft, a ship, an automobile and the like and a communication satellite has been spreading.
With the spread of this, the demand for a small and high-performance antenna has been further increased. As is well known, a meander type antenna has been proposed which is formed of a linear conductor having a structure in which a radiation element of an antenna is bent for miniaturization. For example, an antenna described in JP-A-6-90108 is one of them.

Conventionally, the frequency bandwidth of an antenna is generally about several percent in a fractional band, and there is a problem that the band is further narrowed if the length of the radiating element is further reduced to make it smaller. When the transmission band and the reception band are larger than the ratio band, there is a problem that a plurality of antennas are required for transmission and reception. In the conventional antenna shown in FIG. 17, since the resonance frequency of the antenna is single resonance, 137 of the frequency assigned in the mobile satellite communication system for performing data communication between the ground and the satellite using the low orbit satellite is used. .0
It is not possible to cope with the two frequency bands of the downlink from 148.0 MHz to 150.05 MHz, that is, the resonance frequency fr is determined by the length L of the radiating element. However, there is a problem that resonance occurs only for a single frequency.

[0004] Further, in consideration of mounting on a moving body such as a vehicle,
In consideration of a reduction in wind pressure applied to the antenna opening surface, breakage due to contact with other objects, and the like, an antenna with a low antenna height and a low attitude is desired. In particular, considering that the antenna is mounted on a container, the height of the antenna becomes about 0.5 m even if the above-mentioned quarter-wavelength grounded antenna is used by stacking the containers, and mounting is impossible. However, when the conventional antenna shown in FIG. 17 is vertically mounted on the vehicle body as shown in FIG. 18, in addition to the above-mentioned bandwidth problem, problems such as further reduction in wind pressure and damage due to contact with other objects occur. Further, when the antenna of the related art is horizontally mounted on the vehicle body as shown in FIG. 19, the impedance of the antenna decreases as the antenna approaches the conductor plate of the vehicle body,
The resonance frequency shifts, the impedance matching between the antenna and the feed line is lost, and there is a major problem that reception or transmission cannot be performed. Further, the antenna gain versus frequency characteristic of this antenna has a bandwidth of only a few percent in a fractional band as shown in FIG.

[0005]

As described above, the conventional antenna has a narrow bandwidth and cannot obtain a sufficient gain in a satellite communication system in which the reception frequency band and the transmission frequency band are separated from each other.

[0006] In addition, in consideration of mounting on a moving body such as a vehicle, and when vertically mounted on a vehicle body, problems such as damage due to wind pressure and contact with other objects occur.

Further, when the antenna is mounted horizontally on the vehicle body, the problem of damage due to wind pressure or contact with other objects is solved, but the impedance of the antenna decreases as the antenna approaches the conductor plate of the vehicle body, and the impedance of the antenna and the feed line is reduced. Matching is lost, the resonance frequency is shifted, and reception or transmission cannot be performed. There were two problems.

SUMMARY OF THE INVENTION In view of the above, the present invention has been made to solve the above two problems, and an object of the present invention is to provide a small-sized and low-profile antenna device which supports a plurality of frequencies and has a wide band. It is in.

[0009]

According to the present invention, a first radiating element grounded to a ground plate at a first ground point and an electric length different from the first radiating element are provided. A second radiating element having a second grounding point and connected to the ground plate at a second grounding point; a first feeding point for feeding the first radiating element;
A second feeding point for feeding the second radiating element;
And the distance between the second ground point and the second power supply point is made different from the distance between the ground point and the first power supply point.

[0010]

The first aspect of the present invention is directed to a first radiating element and a second radiating element having a different electrical length from the first radiating element.
, A first feeding point for feeding the first radiating element, a second feeding point for feeding the second radiating element, the first radiating element and the second radiating element A first radiating element is grounded to the ground plate at a first ground point, and the second radiating element is grounded to the ground plate at a second ground point. Grounded, and the distance between the first grounding point and the first feeding point is different from the distance between the second grounding point and the second feeding point. Impedance matching can be accurately performed.

According to a second aspect of the present invention, the width of the first radiating element and the width of the second radiating element are made constant and the lengths thereof are made different, so that the electrical length of the first radiating element and the electric length of the first radiating element are different from each other. By making the electrical length of the second radiating element different,
Transmission and reception of a plurality of wavelengths becomes possible.

According to a third aspect of the present invention, the electrical length of the first radiating element and the second radiating element are made constant by making the lengths of the first radiating element and the second radiating element different from each other. By making the electrical length of the second radiating element different,
Transmission and reception of a plurality of wavelengths becomes possible.

According to a fourth aspect of the present invention, by loading an impedance element near the open end of the radiation element and selecting an impedance value thereof to a desired value, the voltage standing wave ratio can be broadened. I can plan.

According to the fifth aspect of the invention, the impedance element is loaded near the feeding point, and the impedance value is selected to a desired value, so that the voltage standing wave ratio can be widened.

According to a sixth aspect of the present invention, a power supply line for supplying power to both the first power supply point and the second power supply point includes a ground plate, a first radiating element, and a second power supply line. Between the radiating element and the ground plate, the first radiating element, and the second radiating element, so that the antenna device can be made thinner. it can.

According to the seventh aspect of the present invention, since the power supply line is formed of a coaxial cable, it is possible to prevent noise from being mixed into the supplied high-frequency power.

[0018] The invention according to claim 8 is the present invention, wherein the connection part of the power supply line, the first ground line connecting between the first ground point and the first power supply point, and the second ground point to the second ground point. A second ground line that connects to the second power supply point and a second ground line integrally formed by one connection member, and the connection member is electrically connected to the ground plate, so that the power supply line 13 is connected to the second ground line. And the ground line that grounds the radiating element to the ground plate can be integrated, improving the productivity by reducing the number of parts and simplifying the assembling process, and improving the reliability by reducing the number of joining and processing parts. be able to.

According to the ninth aspect of the present invention, the first ground point and the second ground point are grounded to the ground plate via the common conductive member, so that the ground area is increased and noise is reduced. Stable electrical operation can be ensured, and mechanical mechanical strength can be improved.

According to the tenth aspect of the present invention, since the first radiating element and the second radiating element are provided on the same antenna substrate, the configuration of the antenna device is simplified as compared with the case where they are provided separately. In addition, the productivity can be improved and the antenna can be reduced in size and thickness.

According to an eleventh aspect of the present invention, both the first radiating element and the second radiating element are constituted by meander line elements, and the element length of the meander line element is set to about １ ／ of the corresponding line wavelength. By setting the length of each wavelength, optimal transmission / reception corresponding to each wavelength becomes possible, and the polarization characteristics of the antenna device can be improved.

According to a twelfth aspect of the present invention, a first radiating element, a second radiating element having an electrical length different from that of the first radiating element, and a first feeding point are provided to the first radiating element. Power,
Feeding means for feeding the second radiating element at a second feeding point; and a feeding means provided apart from the first radiating element and the second radiating element, wherein the first radiating element is provided at a first ground point. Grounded,
The second radiating element includes a ground plate grounded at a second ground point, and a value obtained by dividing a distance (h) between the radiating element and the ground plate by a wavelength (λ) is 1 ÷ 250. ≤h ÷
λ ≦ 1 ÷ 80, preferably 1 ÷ 200 ≦ h ÷ λ ≦ 1 ÷ 10
0, wherein the distance between the first ground point and the first feed point is different from the distance between the second ground point and the second feed point, resulting in radiation loss And the copper body loss can be suppressed to a minimum, so that it is possible to realize an antenna device having excellent antenna characteristics with a small loss as a whole. In addition, since the thickness of the antenna device is extremely thin, the antenna device can be more easily mounted on a device that is used on the premise of stacking containers and the like.

(Embodiment 1) Next, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the antenna device according to the first embodiment of the present invention, FIG. 2 is a perspective view of the antenna device according to the first embodiment of the present invention,
FIG. 3 is a diagram showing a configuration of the radiating element according to the first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an antenna substrate, and the antenna substrate 1 is often mainly made of a dielectric material.
It is often composed of a printed board or a PET film board provided with a conductor layer on one or both sides thereof.

Reference numerals 2 and 3 denote radiating elements.
Is formed on one or both surfaces of the antenna substrate 1 by a method such as etching, photolithography, or sputtering. In this embodiment, in order to enable transmission and reception of a plurality of wavelengths, one radiating element corresponds to one wavelength, and the radiating element 2 corresponds to the long wavelength (λg1). The radiating element 3 corresponds to λg2).

Here, the electrical lengths of the radiating elements 2 and 3 shown in FIG. 3 are set such that the line widths W1 and W2 of the radiating elements 2 and 3 are the same and the respective line lengths L21 and L22 are different. Alternatively, the line lengths L21 and L22 of the radiating element may be the same length, and the line widths W1 and W2 may be different lengths.
In each case, the element line length is set to about ４ of each of a plurality of line wavelengths λg1, λg2,... Λgn corresponding to a plurality of desired frequencies f1, f2,. It is preferable to adopt the configuration described above.

The radiating elements 2 and 3 having different corresponding wavelengths as described above
Are formed on the same antenna substrate 1, the configuration of the antenna can be simplified, the productivity can be improved, and the antenna can be reduced in size and thickness as compared with the case where they are separately provided.

Further, by making the line length or line width different, transmission and reception of a plurality of wavelengths becomes possible. In particular, by setting the line length to 25% of the corresponding wavelength, optimal transmission / reception corresponding to each wavelength becomes possible, and the polarization characteristics of the antenna can be improved.

The transmission line 4 is connected to the end 2a of the radiating element 2.
Are connected, and a transmission line 5 is connected to the end 3 a of the radiating element 3. The transmission lines 4 and 5 connect the radiating elements 2 and 3 to ground points 7 and 8 of a ground plate 6 provided substantially parallel to the radiating elements 2 and 3 and have ends 2a and 3a. Is preferably connected near the center because antenna characteristics can be improved. Here, the ground plate 6 may be provided on the surface of the antenna substrate 1 opposite to the surface on which the radiating elements 2 and 3 are formed.
It may be separately provided substantially parallel to zero. Also, the ground plate 6
Often formed of a metal conductor such as aluminum, stainless steel, or plated steel.

A transmission line 9 is connected to the transmission line 4 at a feed point F1.
2, a transmission line 10 is connected. The transmission lines 9 and 10 are connected to a power supply unit 12 via common transmission lines 11 provided from the ground plate 6 side, respectively. High-frequency power is supplied to the radiating elements 2 and 3 by matching.
Here, the transmission line 11 is connected to the ground plate 6 and the antenna substrate 1.
Are formed substantially perpendicular to both of the transmission lines 1
1, both the power supply unit 12 may be formed on the antenna substrate 20.

Here, each of the feeding points F1,
Distances L1 and L2 to F2 are different lengths. By adopting such a configuration, the impedance matching can be accurately performed, so that the resonance frequency does not deviate in any of the radiating elements 2 and 3, and an antenna device that can surely share two wavelengths is provided. Can be supplied. Further, when L1 and L2 each have a length L and a corresponding wavelength λg, λg {30 ≦ L ≦ λg}.
120, the impedance Z0 at the feeding points F1 and F2 with respect to the impedance Z0 of the feeding line.
Since the values of 1, Z2 can be kept within ± 20%, the matching loss can be kept within an allowable limit. Therefore, it is preferable for accurate impedance matching.

Further, by making the lengths of the transmission lines 9 and 10 different, it is possible to adjust the feeding phase more easily.

As the transmission lines 4, 5, 9, 10, and 11, a coaxial cable or a microstrip transmission line can be used.

Although only one power supply unit is provided in the present embodiment, it may be provided separately.

Although only two radiating elements are provided here, it is naturally possible to provide three or more radiating elements.

The radiating elements 2 and 3 may be formed in a meander line as shown in FIG. 2, or may have other configurations. In this case, the radiation elements 2 and 3 have a line width w 幅 λ / 200 to λ / 400 and an element interval d 間隔 λ / 1, respectively.
It is formed of a meander line that is periodically bent with a range of 00 to λ / 200 and an element width l ≒ λ / 10 to λ / 20.
Here, the radiation element 2 and the radiation element 3 are formed with different line lengths.

The radiation elements 2 and 3 having different corresponding wavelengths as described above.
Are formed on the same antenna substrate 1, the configuration of the antenna device can be simplified, the productivity can be improved, and the antenna can be reduced in size and thickness as compared with the case where they are separately provided. In addition, radiating elements 2 and 3
The transmission / reception of a plurality of wavelengths is made possible by making the line lengths different. In particular, by setting the line length to 25% of the corresponding wavelength, optimal transmission / reception corresponding to each wavelength becomes possible, and the polarization characteristics of the antenna can be improved.

Since the radiating elements 2 and 3 are configured as shown in FIG. 1, the length of the radiating elements 2 and 3 in the short direction can be further reduced, so that the short direction of the antenna can be reduced. Thus, an elongated antenna device can be realized. Further, since the radiating elements 2 and 3 are configured as shown in FIG. 2, the length of the radiating elements 2 and 3 in the longitudinal direction can be further reduced, and a small antenna device having a smaller projected area can be realized. it can.

Next, a method of supplying power to the power supply unit 12 in the present embodiment will be described with reference to the drawings. FIG. 4 is a perspective view showing a configuration of the power supply unit according to Embodiment 1 of the present invention. In FIG. 4, reference numeral 13 denotes a power supply line, and the power supply line 13 is connected to the transmission line 11 at the power supply unit 12 and supplies high-frequency power to the antenna device. It is preferable that the power supply line 13 be arranged between the ground plate 6 and the antenna substrate 1 substantially in parallel. Thereby, compared with the case where the connection plug (connector) is taken out from the back surface of the ground plate 6,
The antenna device can be made thinner. In addition, it is preferable to use a unit having a configuration in which noise is not superposed as much as possible, such as a coaxial cable, for the power supply line 13 because the frequency shift of the supplied high-frequency power can be minimized.

In this way, the transmission line 1
1 and a plurality of radiating elements 2, 3 via transmission lines 9, 10.
With this configuration, the area occupied by the power supply equipment on the antenna substrate 1 and the antenna device can be reduced, and the antenna substrate 1 and the entire antenna device can be reduced in size. Also, the radiation elements 2 and 3
To the radiating elements 2 and 3 can be made the same by feeding the same power to the power supply line 12 to each of the radiating elements 2 and 3.
It is possible to provide a highly reliable antenna having excellent antenna characteristics with respect to any of f1 and f2.

Further, since the power supply unit 12 and the power supply line 13 connected to the power supply unit 12 are provided as one, compared with the case where one power supply line 13 is provided for each of the radiating elements 2 and 3, the antenna device has Since the configuration can be simplified, the productivity of the antenna can be improved. In addition, since the number of entrances of the transmission line penetrating the outside of the antenna can be reduced, entry of water or foreign matter from the entrances can be minimized. Can be suppressed, and a highly reliable antenna can be realized.

Here, the radiating elements 2, 3 and the feeding section 12, the transmission lines 9, 10, 11 may be formed on the same surface on the antenna substrate 1, or the radiating elements 2, 3 may be formed on one side. And
The power supply unit 12 and the transmission lines 9, 10, 11 may be formed on other surfaces. At this time, by forming the radiating elements 2 and 3, the feeding unit 12, and the transmission lines 9, 10, and 11 on the same surface,
Since the configuration of the antenna substrate 1 can be simplified,
The processing and forming steps of the antenna substrate 1 can be shortened, and the productivity of the antenna substrate 1 can be improved. Further, since various circuits formed on the antenna substrate 1 can be formed at the same time, productivity can be similarly improved.

FIG. 5 is an enlarged perspective view of the power supply unit according to the first embodiment of the present invention. As shown in FIG. 5, the crimped portion 14 of the feed line 13 and the ground lines 15 and 16 for grounding the radiating elements 2 and 3 via the transmission lines 4 and 5 are formed of one conductive material. The connecting member 17 is integrally formed, and the connecting member 17 is electrically connected to the ground plate 6 by a joining method such as soldering or welding. Here, the ends of the ground lines 15 and 16 on the antenna substrate 1 side are
Protrusions 15a and 16a used for connection with the transmission lines 4 and 5 are formed on the antenna substrate 1, and the transmission lines 4 and 5 are formed.
5 and a bonding material such as solder or conductive resin.

With this configuration, a structure for inserting the biasing of the feeder line 13 between the braided crimping portions 14 and crimping with a tool such as pliers, and a ground for grounding the radiating elements 2 and 3 to the ground plate 6 Since the lines 15 and 16 can be integrated, the productivity can be improved by reducing the number of parts and simplifying the assembling process, and the reliability can be improved by reducing the number of joining and processing parts.

FIG. 6 is a perspective view showing a grounding form of the radiating element according to the first embodiment of the present invention. As shown in FIG. 6, grounding points 7 and 8 are made of a material such as metal or resin having electrical conductivity. The ground plate 18 may be configured to be grounded to the ground plate 6. As a result, the ground area is increased, stable electrical operation against noise can be ensured, and mechanical mechanical strength can be improved.

FIG. 7 is a perspective view showing the configuration of the antenna device according to the first embodiment of the present invention. As shown in FIG. 7, the radiating elements 2 and 3 are formed on the same antenna substrate 1, and a space between the antenna substrate 1 and the ground plate 6 is secured by a spacer 19 formed of resin, ceramic, or the like. And With this spacer 19, the space between the antenna substrate 1 and the ground plate 6 can be secured at a predetermined height, and an antenna device having stable antenna characteristics can be provided. Although a plurality of spacers 19 are discretely provided here, a configuration in which a dielectric substrate larger than the spacers 19 is inserted may be adopted.

The operation of the antenna configured as described above will be described. First, the high-frequency power supplied from the power supply unit 12 is transmitted to the transmission line 11, the transmission lines 9 and 10,
Radiation elements 2 and 3 are supplied via feed points F1 and F2, transmission lines 4 and 5, and end faces 2a and 3a. Then, by selecting the distances L1 and L2 from the grounding points 7 and 8 to the feeding points F1 and F2 to different desired lengths, matching feeding can be performed so as to have a desired impedance.

By appropriately selecting the dimensions of each part of the radiating elements 2 and 3, the radiating elements 2 and 3 radiate radio waves into the air at desired resonance frequencies f1 and f2. in this case,
The electrical length of the radiating element 2 is Le1, and the electrical length of the radiating element 3 is L.
Assuming that e2, Le1 ≒ C / 4f1 (Equation 1) is approximated by Le2 ≒ C / 4f2 (Equation 2), and FIG. 8 (Embodiment 1 of the present invention) Of the radiating element in FIG. 2) shows a plurality of resonance characteristics (in this case, two frequencies) shown by a line a.

The operation of the current distribution I of the antenna configured as described above will be described with reference to FIGS. 9 (a) and 9 (b). FIGS. 9A and 9B are diagrams showing the current distribution of the antenna according to the first embodiment of the present invention. FIG.
, The electrical lengths Le1 and Le2 of the radiating elements 2 and 3
Is set to about １ ／ of the length of each of the two line wavelengths λg1 and λg2 corresponding to the desired frequencies f1 and f2, so that at the desired frequencies f1 and f2, the vicinity of the center of the feeding unit has the maximum current amplitude, The current is distributed in a substantially semi-sinusoidal waveform such that the tip of the radiating element has a minimum current amplitude. As shown by an arrow (→) in the figure, the direction of the current running in the horizontal direction on the paper is horizontal, Horizontally polarized radio waves resulting from this current are emitted. In this case, as shown in FIG. 9B, the voltage distribution V has the minimum potential at the ground point, and has the maximum voltage distribution V at the open end of the radiating element. Therefore, when the impedance at the feeding point F is Z, it is expressed as Z = V ÷ I. As shown in FIG. 9B, assuming that the distance between the ground plate and the radiating element is h, from the ground points 7, 8, Feeding point F
By adjusting the distance to F1 and F2, that is, by changing L1 and L2, the values of the voltage distribution V and the current distribution I at that point (position) change with the change of the distance, that is, the voltage distribution V and the current distribution Impedance Z which is the ratio of I
Are the distances L1 from the grounding points 7 and 8 to the feeding points F1 and F2.
By changing L2, adjustment becomes possible. When resonance occurs at the two frequencies f1 and f2, respectively, the feeding points F1 and F1 are supplied from the ground points 7 and 8 for each of the frequencies f1 and f2.
2, the impedances Z1 and Z2 can be adjusted for each of the frequencies f1 and f2, and the impedance Z0 of the feed line such as a coaxial line can be adjusted.
Can be matched. In particular, when L1 and L2 are L and the corresponding wavelength is λg, both are λg
By satisfying {30 ≦ L ≦ λg} 120, the impedance matching can be accurately achieved while shortening the lengths of the transmission lines 4 and 5 formed on the antenna substrate 1, which is preferable.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described with reference to the drawings. Note that the configuration of the antenna device not mentioned in the present embodiment has substantially the same configuration as that shown in the first embodiment.
FIGS. 10A and 10B show Embodiment 2 of the present invention.
FIG. 3 is a plan view showing a configuration of a radiating element in FIG. FIG.
As shown in (a) and (b), by loading the impedance elements 20a and 20b on the open ends 2b and 3b of the radiation elements 2 and 3, and selecting their impedance values to desired values, FIG. As shown by the line b, the voltage standing wave ratio (V
SWR) can be broadened. Note that a desired result can be obtained if only one of the impedance elements is formed. Thereby, even if a slight variation occurs in the finish during mass production, the antenna characteristics can be kept within a predetermined range, and an antenna device with a low process failure rate can be realized, and the surface of the antenna device can be realized. Even if snow, raindrops, dust, or the like adheres, a highly reliable antenna device with very little deterioration in antenna characteristics can be realized.

Another installation position of the impedance element will be described with reference to FIGS. 11 (a) and 11 (b). FIG.
(A), (b) is a plan view showing a configuration of a radiating element according to Embodiment 2 of the present invention. As shown in FIG. 11, impedance elements 20c and 20d are provided near feed points F1 and F2.
The same effect can be obtained by loading on one side or both sides. That is, generally, the values of the voltage distribution V and the current distribution I near the feeding points F1 and F2 are such that the voltage distribution V is small and the current distribution I is large, and the impedance Z, which is the ratio of the voltage distribution V to the current distribution I, is small. (Usually: several tens of ohms, Z
≒ 5 to 75Ω). Therefore, by loading the impedance elements 20c and 20d near the feeding points F1 and F2 and selecting the impedance value to a desired value, it is possible to widen the VSWR. Also, by setting the values of the impedance elements 20c and 20d to desired values,
The radiated power can be changed arbitrarily. FIG. 12 shows how the radiation power changes. FIG. 12 is a diagram showing a relationship between radiated power and frequency according to Embodiment 2 of the present invention.
In the solid line a shown in the figure, the impedance elements 20c, 20c
d indicates the radiated power when the impedance element ratios are substantially the same, and the broken line b indicates the impedance elements 20c, 2
The case where the impedance element ratio of 0d is not the same is shown. Thus, depending on the requirements of the radio system, the frequency f
The radiation power at 1 and f2, in other words, the antenna gain can be adjusted. Also, by combining each configuration,
It is also possible to provide an antenna device capable of adjusting the antenna gain in a wider band.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a perspective view showing the configuration of the antenna according to the third embodiment of the present invention, and the same members as those of the antenna shown in the drawings of the first embodiment are denoted by the same reference numerals.

The antenna shown in the present embodiment has an antenna substrate 1 on which radiating elements 2 and 3 and transmission lines 4, 5, 9 and 10 are formed, and a ground plate 6 and the like are basically the same as those in the first embodiment. It has a configuration.

The spacer 19 is formed of a material having elasticity such as rubber or resin, and is inserted between the antenna substrate 1 and the ground plate 6 as a support member, so that the distance between the antenna substrate 1 and the ground plate 6 can be accurately determined. At a height h. As the mounting position of the spacer 19,
It is preferable that the radiating elements 2 and 3 are not formed on the antenna substrate 1 because a change in the dielectric constant between the ground plate 6 and the antenna substrate 1 that affects the antenna characteristics can be minimized.

Although not shown, at least one of the ground plate 6 and the antenna substrate 1 is provided with a mounting recess so that the mounting position can be easily determined, and the spacer 19 is fitted into the recess. Preferably, it is formed. With such a configuration, the spacer 19
Is not displaced at the time of attachment, and there is almost no change in antenna characteristics due to the insertion of the spacer 19 in the portion where the radiating elements 2 and 3 are formed, so that a highly reliable antenna can be realized.

A protrusion may be provided on at least one of the ground plate 6 and the antenna substrate 1 and a recess may be provided in the spacer 19 to fit therewith, or a through hole may be provided in at least one of the ground plate 6 and the antenna substrate 1. It may be provided and screwed.

In this embodiment, the spacer 19 is provided between the antenna substrate 1 and the ground plate 6. However, the spacer 19 is provided between the antenna substrate 1 and the ground plate 6 and between the ground plate 6 and the radome 21. You may provide in both. In this case, the height of the spacer 19 provided between the antenna substrate 1 and the ground
It is preferable to make the height higher than the height of the spacers 19 provided between the first and second spacers, because the antenna substrate 1 can be further distant from the ground plate 6 to improve antenna characteristics.

Even when a plurality of spacers 19 are not used, for the same reason, the antenna substrate 1 is connected to the ground plate 6.
It is preferable to dispose it closer to the radome 21 than to.

It is preferable that the elasticity of the spacer 19 be different depending on whether the contact surface is the front surface or the back surface of the antenna substrate 1. Specifically, the elasticity is increased on the side of the antenna substrate 1 where the radiating element 2 is formed, and reduced on the side of the antenna substrate 1 where the radiating elements 2 and 3 are not formed. This is preferable because the possibility that the radiating element 2 is damaged by the spacer 19 when the antenna substrate 1 is displaced by vibration or the like can be reduced.

For the same reason, when the antenna substrate 1 is brought into direct contact with the radome 21, the surface on which the radiating elements 2 and 3 are formed preferably faces the ground substrate 6.

The radome 21 is provided so as to cover the antenna substrate 1 on which various circuits and the like are formed, and is preferably formed of a weather-resistant material such as a resin. The antenna substrate 1 is formed by the radome 21 and the ground plate 6.
The radome 21 and the ground plate 6 are accommodated, and are fixed to each other by joining the radome 21 and the ground plate 6 with a joining material or by screwing with a bolt or the like. The boundary between the radome 21 and the ground plate 6 is sealed against moisture by a waterproof seal or an O-ring, thereby preventing deterioration of antenna characteristics and malfunction of the antenna due to entry of moisture into the antenna. It is preferable because it is possible.

More preferably, it is preferable that the inside of the antenna is completely sealed and an inert gas such as dry air or nitrogen gas is sealed. Such a configuration is preferable because it is possible to suppress the occurrence of dew condensation inside the antenna that may be used in the open state, and to prevent deterioration of antenna characteristics and malfunction of the antenna due to the dew condensation.

Reference numeral 22 denotes a mounting hole provided at an end portion of the ground plate 6. The mounting hole 22 allows the ground plate 6 of the antenna to be directly mounted on a metal housing of a car or a container. With such a configuration, since the antenna device of the present embodiment can be directly mounted on the installation target with the ground plate 6 as the bottom surface, the antenna device from the installation surface of the antenna device can be compared with the case where the antenna device is installed via an antenna installation member or the like. The height can be lower.

In this embodiment, the mounting holes 22 are provided only in the short direction of the antenna. However, the mounting holes 22 may be provided only in the long direction, or may be provided in both the short direction and the long direction so as to surround the antenna. You may.

When the ground plate 6 of the antenna and the metal housing to be installed are joined by a conductive joining material or the like, the mounting holes 22 need not be provided.

Next, the mounting of the antenna substrate 1 will be described. In the present embodiment, the antenna substrate 1 is fixed so as to be pressed against the inner surface of the radome 21 by the spacer 19 provided between the antenna substrate 1 and the ground plate 6. At this time, the spacer 19 has a certain degree of elasticity, and the inner surface of the radome 21 is configured to be substantially parallel to the ground plate 6 after the antenna assembly is completed. By attaching the radome 21 to the ground plate 6 in a state where the radome 21 is arranged at a predetermined position in advance, the spacer 19 can be mounted and fixed to the antenna substrate 1 and the ground plate 6.
Since the antenna substrate 1 can be fixed relative to the ground plate 6, an antenna with high productivity that can reduce the steps of assembling and attaching the antenna can be obtained. By pressing the antenna substrate 1 against the radome 21, the planarity of the antenna substrate 1 is improved with a simple configuration, so that the difference in distance between the antenna substrate 1 and the ground plate 6, which has a particularly large effect on antenna characteristics, is substantially constant. Can be As a result, it is possible to realize an antenna that can cope with a plurality of frequencies and has both excellent antenna characteristics and high productivity.

For fixing between the radome 21 and the ground plate 6, a mounting hole may be provided at an end of the radome 21 facing the mounting hole 22, and the mounting member may be shared. A mounting hole may be provided on the ground plate 6, and a mounting portion may be provided at a position facing the mounting hole of the radome 21 of the ground plate 6, and the ground plate 6 may be fixed with a fixing member such as a screw. In the case where the mounting portion is provided on the ground plate 6, the height of the antenna device can be further reduced by preventing the protrusion from being formed toward the outside of the antenna, and the mounting target of the antenna device can be reduced. Since the flatness of the ground plate 6 serving as the mounting surface can be ensured, the mounting operation is easy and an antenna device with good stability can be realized.

The installation of the antenna having the above-described configuration on the installation target will be described with reference to the drawings, particularly when the antenna is installed on a car (truck).

FIG. 14 is a plan view showing the mounting of the antenna device on the vehicle body according to the third embodiment of the present invention.
FIG. 9 is a cross-sectional view of an antenna device mounting portion according to Embodiment 3 of the present invention.

Reference numeral 23 denotes a vehicle body to be installed, and the above-described antenna device 24 is installed in a metal housing 23a above the vehicle body 23. Specifically, a through hole 23b is provided in the metal housing 23a facing the mounting hole 22 of the antenna device 24, and a bolt 25a used as the fixing means 25 is passed through the mounting hole 22 and the through hole 23b, and the tip of the bolt is The antenna device 24 is attached to the vehicle body 23 by tightening the nut 25b.

At this time, it is preferable that the ground plate 6 of the antenna device 24 and the metal housing 23a of the vehicle body 23 are in direct contact with each other. Hereinafter, this point will be described. The antenna device 24 described in this embodiment is often mounted parallel to a mounting surface of an installation target having a metal housing such as an automobile or a container. In general, when an antenna is installed very close to a metal housing such as a car body or container, even if the antenna characteristics are set in advance to be optimal at a predetermined frequency, the antenna characteristics will be Often gets worse. This is because the antenna impedance is reduced due to the influence of the metal housing in which the antenna is installed, and the loss increases due to a mismatch with the impedance of the feed line.

In order to prevent such a change in antenna characteristics, the antenna device 24 is formed such that the ground plate 6 is exposed and the metal plate 23 a of the vehicle body 23 is in direct contact with the ground plate 6. . Thereby, the antenna device 2
Since the ground plate 6 and the metal housing 23a can have the same potential, a change in antenna characteristics due to the influence of the metal housing 23a can be almost eliminated. Since the ground plate 6 of the antenna device 24 and the metal housing 23a may be in electrical contact with each other, instead of using the fixing means 25, a conductive bonding material may be used between the ground plate 6 and the metal housing 23a. May be used for bonding. In this case, the work of attaching the antenna device 24 to the vehicle body 23 can be easily performed, and the mounting hole 22 can be eliminated from the ground plate 6, so that the structure of the ground plate 6 can be simplified, and high productivity and high productivity can be achieved. It is possible to realize a low-cost and more easy-to-use antenna.

Although not shown, the antenna device 24
A cushioning material may be provided between the vehicle and the vehicle body 23. In this case, since the impact caused by the constant vibration during the movement of the car or the container loaded on the car or the like is not directly transmitted to the antenna device 24, the antenna device 24 is not damaged by the impact, and the reliability of the antenna device 24 does not occur. Can be enhanced.

It is preferable that the fixing means 25 be formed of a metal material because the ground plate 6 and the metal housing 23a can be reliably brought into electrical contact with each other. Especially when a cushioning material is sandwiched between the antenna device 24 and the vehicle body 23,
This is effective when the antenna device 24 and the vehicle body 23 are not directly in contact with each other.

Reference numeral 26 denotes a fixing means assisting member. The fixing means assisting member 26 has a certain degree of water-proof rubber or the like so as to prevent moisture from entering the installation object through the fixing means 25. It is preferable to be formed in a ring shape using a material having elasticity, because it is possible to effectively suppress entry of moisture. Specifically, a rubber washer or the like can be used.

Next, the thickness of the antenna device 24 mounted on the metal housing 23a will be discussed. FIG. 16 is a graph showing the correlation between the distance between the radiating element and the ground plate and the antenna loss according to the third embodiment of the present invention.

In the case of the antenna in which the distance between the antenna substrate 1 and the ground plate 6 is short as in this embodiment, the copper loss (loss due to heat loss of the copper, B in the figure) is radiated. If the width of the element 2 is constant, the distance h is inversely proportional to the distance h (hereinafter abbreviated as distance h) between the ground plate 6 and the radiating element 2, and the distance h
Becomes larger, the radiation loss (radiation loss, A in the figure) is proportional to the distance h between the ground plate 6 and the radiation element 2 when the width of the radiation element 2 is fixed, and the distance h The larger the value, the greater the loss. Although it varies slightly depending on the strength of the target radio wave and the corresponding frequency, the reception sensitivity of an ordinary antenna varies greatly due to external factors, so internal loss other than external factors must be maintained in order to keep it usable under any circumstances. (The sum of copper loss and radiation loss, A + B in the figure) must be kept to a minimum. The internal loss generally allowed is 1 dB or less, particularly 0.5 when transmitting or receiving weak radio waves such as satellite communications.
Considering that the distance is not more than dB, the distance h is 1 ÷ 250 ≦ h ÷ λ ≦ 1 ÷ 80, preferably 1 ÷ 2, where λ is the wavelength.
By setting 00 ≦ h ÷ λ ≦ 1 ÷ 100, the antenna efficiency can be improved, so that a highly reliable antenna that operates reliably under a wide range of use conditions can be provided.

For example, this antenna device 24 is allocated by WARC '92 (World Radio Communication Administration Council, 1992) in a mobile satellite communication system for performing ground-to-satellite-to-ground data communication using low orbit satellites. 137.0 MHz to 138.0.0 M in the specified frequency VHF band
Hz is the frequency of the downlink in the band of 148.0 MHz to the frequency of the uplink of 150.05 MHz, and if it is used for the orbcom communication, the fluctuation region of the wavelength (λ) is 2
000 ≦ λ ≦ 2190 (mm), the range of h when the shortest wavelength λ = 2000 and the longest wavelength λ
Good antenna characteristics can be realized in all wavelength bands in a range overlapping with the range of h when = 2190. The range is
8.76 ≦ h ≦ 25 (mm), preferably 10.95
It is understood that it is preferable that ≦ h ≦ 20 (mm).

By setting the distance h in the above range, the sum of the radiation loss and the copper loss can be suppressed to a minimum, so that an antenna device having excellent overall antenna characteristics with little loss can be realized. Can be. In addition, since the thickness of the antenna device 24 is extremely thin, the antenna device 24 can be more easily mounted on a device that is used on the premise of stacking containers and the like. Specifically, when used as an antenna for Orbcom, when a cargo container is loaded, the gap between the containers is at most 1-2.
Although the thickness is about an inch, the entire thickness of the antenna device 24 can easily be within this range, so that an antenna capable of stacking containers while mounted on the container can be realized, and the ground plate 6 and the metal of the container can be realized. By shorting the housing, the antenna device 2
Since the change in antenna impedance can be minimized even when containers are stacked on the antenna 4, an antenna with good antenna characteristics can be realized even when stacked.

[0079]

As described above, according to the present invention, the first radiating element, the second radiating element having an electric length different from that of the first radiating element, and the first radiating element for supplying power to the first radiating element are provided. A feed point,
A second feed point for feeding the second radiating element; and a ground plate provided apart from the first radiating element and the second radiating element, wherein the first radiating element is a second radiating element. A ground point at a first ground point, the second radiating element grounded to the ground plate at a second ground point, and a distance between the first ground point and the first feed point. And the second
Since the distance between the ground point and the second feeding point is different from each other, it is possible to accurately match the respective impedances. An antenna device that can be used for a plurality of wavelengths can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of an antenna device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the antenna device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a radiating element according to the first embodiment of the present invention.

FIG. 4 is a perspective view illustrating a configuration of a power supply unit according to the first embodiment of the present invention.

FIG. 5 is an enlarged perspective view of a power supply unit according to the first embodiment of the present invention.

FIG. 6 is a perspective view showing a grounding configuration of the radiating element according to the first embodiment of the present invention.

FIG. 7 is a perspective view showing a configuration of the antenna device according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating characteristics of a radiating element according to the first embodiment of the present invention.

9A is a diagram illustrating a current distribution of the antenna device according to the first embodiment of the present invention. FIG. 9B is a diagram illustrating a current distribution of the antenna device according to the first embodiment of the present invention.

10A is a plan view illustrating a configuration of a radiating element according to Embodiment 2 of the present invention. FIG. 10B is a plan view illustrating a configuration of a radiating element according to Embodiment 2 of the present invention.

11A is a plan view illustrating a configuration of a radiating element according to Embodiment 2 of the present invention. FIG. 11B is a plan view illustrating a configuration of a radiating element according to Embodiment 2 of the present invention.

FIG. 12 is a diagram showing a relationship between radiated power and frequency in Embodiment 2 of the present invention.

FIG. 13 is a perspective view showing a configuration of an antenna according to a third embodiment of the present invention.

FIG. 14 is a plan view showing attachment of the antenna device to the vehicle body according to the third embodiment of the present invention.

FIG. 15 is a sectional view of an antenna device mounting portion according to a third embodiment of the present invention.

FIG. 16 is a graph showing a correlation between a distance between a radiating element and a ground plate and antenna loss according to the third embodiment of the present invention.

FIG. 17 is a plan view showing a configuration of a conventional antenna.

FIG. 18 is a plan view showing attachment of a conventional antenna to a vehicle body.

FIG. 19 is a perspective view showing attachment of a conventional antenna to a vehicle body.

FIG. 20 is a graph showing characteristics of a conventional antenna.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna board 2, 3 radiating element 4, 5 transmission line 6 ground plate 7, 8 ground point 9, 10, 11 transmission line 12 feed section 13 feed line 14 uneven crimping section 15, 16 ground line 17 connection member 18 ground plate DESCRIPTION OF SYMBOLS 19 Spacer 20 Impedance element 21 Radome 22 Mounting hole 23 Body 23a Metal housing 23b Through hole 24 Antenna device 25 Fixing means 25a Bolt 26 Fixing means auxiliary member

Claims (12)

[Claims] A first radiating element, a second radiating element having an electrical length different from that of the first radiating element, a first feeding point for feeding the first radiating element, A second feed point for feeding a radiating element, the first radiating element and the second
And a ground plate provided separately from the radiating element,
The first radiating element is grounded to the ground plate at a first ground point, the second radiating element is grounded to the ground plate at a second ground point, and the first ground point is connected to the first ground point. And a distance between the second feeding point and the second ground point is different from a distance between the second feeding point and the second feeding point. 2. An electric length of the first radiating element and an electric length of the second radiating element by making each width of the first radiating element and the second radiating element constant and different in length. 2. The antenna device according to claim 1, wherein the antenna device has a different length. 3. An electric length of the first radiating element and an electric length of the second radiating element by making each of the first radiating element and the second radiating element constant in length and different in width. 2. The antenna device according to claim 1, wherein the antenna device has a different length. 4. The antenna device according to claim 1, wherein an impedance element is loaded near an open end of the radiation element. 5. The antenna device according to claim 1, wherein an impedance element is loaded near the feeding point. 6. A power supply line for supplying power to both the first power supply point and the second power supply point is provided between the ground plate and the first radiating element and the second radiating element. The antenna device according to any one of claims 1 to 5, wherein the antenna device is disposed substantially parallel to each of the ground plate, the first radiating element, and the second radiating element. 7. The antenna device according to claim 6, wherein the feed line is constituted by a coaxial cable. 8. A power supply line connecting part and a first grounding point connected to a first grounding point.
A first ground line connecting between the first power supply point and a second ground line connecting between the second ground point and the second power supply point are integrally configured with one connection member, The antenna device according to any one of claims 1 to 7, wherein the connection member is electrically connected to a ground plate. 9. The antenna device according to claim 1, wherein the first ground point and the second ground point are grounded to a ground plate via a common conductive member. 10. The apparatus according to claim 1, wherein the first radiating element and the second radiating element are provided on the same antenna substrate.
10. The antenna device according to any one of claims 9 to 9. 11. The first radiating element and the second radiating element are both constituted by a meander line element, and the element length of the meander line element is set to about １ ／ wavelength of the corresponding line wavelength. 11. The method according to claim 1, wherein
An antenna device according to any one of the preceding claims. 12. A first radiating element, a second radiating element having an electrical length different from that of the first radiating element, and a power supply to the first radiating element at a first feeding point; Second for radiating element
And a first radiating element and a second radiating element which are provided separately from the first radiating element and the second radiating element, the first radiating element is grounded at a first ground point, and the second radiating element is A ground plate grounded at a second ground point, wherein a value obtained by dividing a distance (h) between the radiating element and the ground plate by a wavelength (λ) is 1 ÷ 250 ≦ h ÷ λ ≦ 1 $ 80 preferably 1
{200 ≦ h ÷ λ ≦ 1} 100, and the distance between the first ground point and the first feeding point and the distance between the second ground point and the second feeding point An antenna device having a different distance.