JP2004048367A - Composite antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable composite antenna which is constituted by combining a circular polarization wave antenna with a vertical polarization antenna and is suitably miniaturized and made thin. <P>SOLUTION: A flat antenna 11 being a vertical polarization antenna for a ground wave is fixed on a printed board 10, and a patch antenna 12 being a circular polarization wave antenna for a satellite wave is placed and fixed on a metallic plate 14 of the flat antenna 11. A power feeding pin 23 of the patch antenna 12 is connected to the power feeding line of a coaxial cable 31 by using an opening 13 of the flat antenna 11. Also, the relative positional relation of the metallic plate 14 to the patch electrode 21 is set so as to be almost uniform along the peripheral direction. Thus, it is possible to reduce the heightwise dimension or planar size of the whole composite antenna, and to prevent the collapse of non-directional properties within an azimuth face due to the electromagnetic coupling of the flat antenna 11 to the patch antenna 12. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a composite antenna mounted on a mobile body such as an automobile and capable of receiving satellite waves and terrestrial waves.
[0002]
[Prior art]
Circularly polarized waves are mainly used in systems that receive satellite broadcasts in vehicles such as automobiles, but recently, in order to increase the reception probability in blind zones such as behind buildings, similar to direct broadcast waves from geostationary satellites, A satellite broadcasting system that retransmits the contents on the ground has been considered. Conventionally, as an antenna applicable to such a satellite broadcasting system, a composite antenna as shown in FIG. 6 has been proposed.
[0003]
The conventional composite antenna shown in FIG. 6 has a 4-wire wound helical antenna 2 for receiving a circularly polarized wave and a monopole antenna 3 for receiving a vertically polarized terrestrial wave on a printed circuit board 1. Schematically configured. A ground conductor made of copper foil or the like is provided on almost the entire upper surface of the printed circuit board 1, and a microstrip line is provided on the lower surface of the printed circuit board 1. The helical antenna 2 is provided with four helical conductors 5 extending spirally on the outer peripheral surface of a cylindrical block 4 made of a dielectric material, and feeds each helical conductor 5 connected to the microstrip line with a phase difference of 90 degrees. That is. When the helical antenna 2 is excited, a circularly polarized wave is radiated upward, so that it can function as an antenna for receiving satellite waves. In addition, the monopole antenna 3 raises a linear conductor having a length of about a quarter of the wavelength of a radio wave to be used, and connects the lower end of the conductor to a microstrip line to supply power. When the monopole antenna 3 is excited, omnidirectional vertically polarized radio waves are radiated in a plane parallel to the printed circuit board 1, so that the antenna can function as an antenna for receiving ground waves.
[0004]
[Problems to be solved by the invention]
In the above-described conventional composite antenna, the height of the helical antenna 2 is about 0.55λ, where λ is the wavelength of a radio wave to be used. Therefore, when the operating frequency is, for example, 2.3 GHz (λ = 130 mm), the height is The size is increased up to about 72 mm, and there has been a problem that it is not possible to reduce the thickness suitable for an antenna mounted on a moving body such as an automobile. Further, since such a conventional composite antenna has a structure in which the helical antenna 2 and the monopole antenna 3 are arranged side by side, a large size is required in plan view, it is difficult to reduce the size, and the antennas 2 and 3 are electromagnetically coupled. Therefore, the directivity of the monopole antenna 3 tends to be distorted on the side of the helical antenna 2, and therefore, there is a problem that the reception sensitivity of the terrestrial wave at a specific azimuth angle tends to decrease.
[0005]
The present invention has been made in view of such a situation of the related art, and an object thereof is to provide a highly reliable composite antenna suitable for reduction in size and thickness by combining a circularly polarized antenna and a vertically polarized antenna. Is to do.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the composite antenna of the present invention has a metal flat plate having a circular or regular polygonal shape and having an opening at the center portion facing a ground conductor at a predetermined interval, and grounding the metal flat plate. A flat plate antenna connected to the ground conductor via a terminal and the metal flat plate connected to a first feed line via a feed terminal; a patch electrode provided on an upper surface of a dielectric substrate and a ground electrode provided on a lower surface. The dielectric substrate is placed and fixed on the metal flat plate via an insulating member, and a power supply pin connected to the patch electrode and passing through the dielectric substrate is inserted into the opening to form a second power supply. A patch antenna connected to an electric wire is provided to excite the flat plate antenna to emit a vertically polarized radio wave and excite the patch antenna to emit a circularly polarized radio wave.
[0007]
In the composite antenna configured as described above, if the flat antenna is excited in the TM01 mode having the lowest resonance frequency, omnidirectional vertically polarized radio waves are radiated to the surroundings in a plane parallel to the metal flat plate. The flat antenna can function as a vertically polarized antenna for terrestrial waves. When the patch antenna is excited in the TM11 mode, a circularly polarized wave is radiated upward, so that this patch antenna can function as a circularly polarized wave antenna for satellite waves. A laminated structure is adopted in which a patch antenna for satellite waves is placed and fixed on a flat antenna for terrestrial waves, and the feed pin of the patch antenna is connected to the feed line using the opening of the flat antenna. Therefore, this composite antenna has a small height dimension and can be reduced in planar size, and therefore, it is easy to reduce the thickness and size. In addition, since the relative positional relationship between the metal plate and the patch electrode can be set substantially uniformly along the circumferential direction, this composite antenna has no azimuth plane in the azimuthal plane due to electromagnetic coupling between the plate antenna and the patch antenna. It is easy to avoid the loss of directivity, and therefore stable performance with little variation in reception sensitivity depending on the azimuth can be expected.
[0008]
In the composite antenna having such a configuration, a printed circuit board provided with the ground conductor on the upper surface and insertion holes at a plurality of locations is provided on the upper surface, and the ground terminal, the power supply terminal, and the power supply pin inserted into each of the insertion holes are respectively printed by the printed circuit board. By fixing the power supply terminal and power supply pin to the power supply line and connecting the ground terminal to the corresponding land on the lower surface of the printed circuit board, the terminal fixed to the printed circuit board can be used to easily fix the metal plate. Also, it is preferable because the dielectric substrate can be easily held in a stable posture. In this case, if both the ground terminal and the feed terminal of the flat antenna are formed of bent pieces extending from the metal flat plate to the printed circuit board side, a single metal plate is press-cut and bent. The metal plate, the ground terminal, and the power supply terminal can be easily formed only by itself, and the mechanical strength of the flat plate antenna is greatly improved.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an exploded perspective view of a composite antenna according to a first embodiment of the present invention, FIG. 2 is a perspective view of the composite antenna, and FIG. FIG. 4 is a top view of the antenna, and FIG. 4 is a sectional view taken along line AA of FIG.
[0010]
The composite antenna shown in these figures includes a printed circuit board 10 having insertion holes 10a at a plurality of locations, a terrestrial flat plate antenna 11 held on the printed circuit board 10, and a satellite held on the flat plate antenna 11. It mainly comprises a patch antenna 12 for waves.
[0011]
The flat plate antenna 11 has an annular metal flat plate 14 having an opening 13 in the center, four ground terminals 15 bent downward with the inner edge of the flat metal plate 14 as a base end, and a cut inside the flat metal plate 14. This is an antenna generally constituted by one feed terminal 16 raised and bent downward, and a ground conductor 17 such as copper foil provided on substantially the entire upper surface of the printed circuit board 10. A high-frequency signal is supplied.
[0012]
The ground terminals 15 and the power supply terminals 16 are formed by pressing and bending the metal flat plate 14, and the terminal groups 15, 16 and the metal flat plate 14 are formed of a single metal plate. The four ground terminals 15 are arranged at equal intervals, and each ground terminal 15 and the power supply terminal 16 are formed to have the same length. As shown in FIG. 4, on the lower surface of the printed circuit board 10, a land 18 to which the lower end of each ground terminal 15 penetrating the insertion hole 10a is soldered, and a lower end of the power supply terminal 16 penetrating another insertion hole 10a. A land 19 to which the portion is soldered is provided. The lands 18 are electrically connected to the ground conductor 17 on the upper surface, and the power supply lines (inner conductors) of the coaxial cable 30 are soldered to the lands 19. Since the terminal groups 15 and 16 are fixed to the printed circuit board 10 in this manner, the metal flat plate 14 is securely supported on the printed circuit board 10 in a stable posture with a certain interval between the metal plate 14 and the ground conductor 17. The formation position of the power supply terminal 16 in the metal plate 14 is determined by selecting an appropriate position where the impedance is matched.
[0013]
When the size of the metal plate 14 and the distance between the metal plate 14 and the ground conductor 17 are set to appropriate values and the plate antenna 11 having such a configuration is excited in the TM01 mode, which is the mode having the lowest resonance frequency, the metal plate Since non-directional vertically polarized radio waves are radiated to the surroundings in a plane parallel to the flat plate 14, the antenna can function as a terrestrial vertically polarized antenna whose reception sensitivity does not vary depending on the azimuth. In this flat antenna 11, the outer shape of the metal flat plate 14 is circular. However, even if the outer shape of the flat metal plate 14 is a regular polygon, the omnidirectionality of the flat antenna 11 does not significantly deteriorate.
[0014]
The patch antenna 12 includes a disk-shaped dielectric substrate 20, a substantially circular patch electrode 21 provided on the upper surface of the dielectric substrate 20, and a ground electrode 22 provided on substantially the entire lower surface of the dielectric substrate 20. And a feed pin 23 which is soldered to the patch electrode 21 and penetrates the dielectric substrate 20 and the opening 13. A predetermined high-frequency signal is fed to the feed pin 23. .
[0015]
The dielectric substrate 20 is placed in a concentric arrangement on the metal flat plate 14 of the flat plate antenna 11, and the lower surface side of the dielectric substrate 20 is attached to the metal flat plate 14 by an insulating double-sided tape 24 as shown in FIG. Glued. The patch electrode 21 is a radiating element having a microstrip structure, and notches 21 a (which may be protrusions) serving as degenerate separation elements are provided at two points symmetrically on the outer periphery of the patch electrode 21. The feed pin 23 selects an appropriate feed point with matching impedance and is connected to the patch electrode 21. The feed point is located above the opening 13 of the flat plate antenna 11 because the position of the feed point is near the center of the patch electrode 21. Therefore, there is no fear that the power supply pin 23 extending downward from the power supply point comes into contact with the metal plate 14 and the terminal groups 15 and 16, and the lower end of the power supply pin 23 passes through the insertion hole 10 a and is formed on the lower surface of the printed circuit board 10. It is soldered to the power supply line (inner conductor) of the coaxial cable 31.
[0016]
In the patch antenna 12 having such a configuration, when the size of the patch electrode 21 and the notch 21a is set to an appropriate value and excited in the TM11 mode, a circularly polarized radio wave is radiated upward. It can function as a wave antenna. The patch antenna 12 has a single feed point, and is provided with a degenerate separation element such as a notch 21a to generate a 90-degree phase difference between two orthogonal modes having different resonance lengths. is there.
[0017]
As described above, the composite antenna according to the first embodiment has a structure in which the terrestrial wave can be received by the flat antenna 11 and the satellite wave can be received by the patch antenna 12, and the patch antenna 12 is stacked on the flat antenna 11. The size and thickness of the entire device have been reduced. Therefore, this composite antenna is suitable as a small in-vehicle antenna that can receive both terrestrial waves and satellite waves. Further, in this composite antenna, since the relative positional relationship between the metal plate 14 and the patch electrode 21 is substantially uniform along the circumferential direction, the omnidirectionality in the azimuth plane due to the electromagnetic coupling between the plate antenna 11 and the patch antenna 12 is increased. Therefore, stable performance with little variation in reception sensitivity depending on the azimuth can be expected.
[0018]
Moreover, the flat plate antenna 11 employed in the composite antenna can easily form the flat metal plate 14, the ground terminals 15 and the feed terminals 16 simply by pressing and bending a single metal plate. Therefore, the number of parts and the number of assembling steps are small, it can be manufactured at low cost, and it is easy to secure the assembling accuracy and mechanical strength. Therefore, the metal plate 14 and the dielectric substrate 20 can be supported in a stable posture by the terminal groups 15 and 16 fixed to the printed circuit board 10, so that an inexpensive and highly reliable composite antenna can be obtained. The work of connecting the ground terminal 15 and the feed terminal 16 of the flat antenna 11 to the lands 18 and 19 and the work of connecting the feed pin 23 of the patch antenna 12 to the coaxial cable 31 are performed on the lower surface side of the printed circuit board 10. Easy to do.
[0019]
FIG. 5 is a perspective view of a composite antenna according to a second embodiment of the present invention. Reference numeral 25 generally indicates a patch antenna, and portions corresponding to FIG. 2 are denoted by the same reference numerals.
[0020]
The composite antenna shown in FIG. 5 differs from the first embodiment in that the patch antenna 25 is provided with a 90-degree phase difference circuit (not shown) on the printed circuit board 10 side in a two-point feeding system. . In this patch antenna 25, a circular patch electrode 27 is provided on the upper surface of a dielectric substrate 26, and power supply pins 28 and 29 are soldered to two places of the patch electrode 27, and lower end portions of the power supply pins 28 and 29 are provided. Are connected to the 90-degree phase difference circuit. Thus, two orthogonal modes having phases different from each other by 90 degrees can be excited, so that the patch antenna 25 can function as a circularly polarized antenna for satellite waves, similarly to the patch antenna 12.
[0021]
In each of the above-described embodiments, it is preferable that the composite antenna be covered with a radome (not shown) when the antenna is actually mounted on a moving body such as an automobile. In other words, if the composite antenna is covered with a radome made of a dielectric material, adhesion of dust and the like and collision of flying objects can be prevented without adversely affecting the antenna characteristics, and the life of the composite antenna can be extended. In each of the above-described embodiments, the metal flat plate 14, the grounding terminals 15, and the power supply terminals 16 of the flat antenna 11 are formed of a single metal plate. It may be a metal pin separate from the metal flat plate 14.
[0022]
【The invention's effect】
The present invention is implemented in the form described above, and has the following effects.
[0023]
A patch antenna, which is a circularly polarized antenna for satellite waves, is mounted and fixed on a metal flat plate of a flat antenna, which is a vertically polarized antenna for terrestrial waves. Since a laminated structure in which the antenna is connected to a feeder line is employed, a composite antenna capable of receiving ground waves and circularly polarized waves and being easily reduced in size and thickness is obtained, and is particularly suitable for use in vehicles. Further, since the metal plate of the flat antenna and the patch electrode of the patch antenna can be set in a substantially uniform relative positional relationship along the circumferential direction, this composite antenna is caused by electromagnetic coupling between the flat antenna and the patch antenna. It is easy to avoid omnidirectional collapse in the azimuth plane, and therefore stable performance with little variation in reception sensitivity depending on the azimuth can be expected.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a composite antenna according to a first embodiment of the present invention.
FIG. 2 is a perspective view of the composite antenna.
FIG. 3 is a top view of the composite antenna.
FIG. 4 is a sectional view taken along line AA of FIG.
FIG. 5 is a perspective view of a composite antenna according to a second embodiment of the present invention.
FIG. 6 is a perspective view of a composite antenna according to a conventional example.
[Explanation of symbols]
Reference Signs List 10 Printed circuit board 10a Insertion hole 11 Plate antenna 12, 25 Patch antenna 13 Opening 14 Metal plate 15 Ground terminal 16 Feed terminal 17 Ground conductor 20, 26 Dielectric substrate 21, 27 Patch electrode 22 Ground electrode 23, 28, 29 Feed pin 30 , 31 Coaxial cable

Claims (3)

A metal flat plate having a circular or regular polygonal shape and having an opening at the center is opposed to a ground conductor at a predetermined interval, and the metal flat plate is connected to the ground conductor via a ground terminal, and the metal flat plate is A flat plate antenna, which is connected to a first feed line via a feed terminal,
A patch electrode is provided on the upper surface of the dielectric substrate, and a ground electrode is provided on the lower surface. The dielectric substrate is mounted and fixed on the metal flat plate via an insulating member, and the dielectric substrate is connected to the patch electrode. A patch antenna connected to a second power supply line by passing a power supply pin passing through the opening into the opening,
A composite antenna, wherein the flat antenna is excited to emit vertically polarized radio waves, and the patch antenna is excited to emit circularly polarized radio waves. 2. The printed circuit board according to claim 1, further comprising a printed circuit board provided with the grounding conductor on an upper surface and having insertion holes at a plurality of locations, wherein the ground terminal, the power supply terminal, and the power supply pin inserted into each of the insertion holes are respectively printed. A composite antenna fixed to a substrate. 3. The composite antenna according to claim 2, wherein each of the ground terminal and the power supply terminal comprises a bent piece extending from the metal plate to the printed circuit board.

Images