JP3839393B2 - Dual frequency antenna device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna device for a mobile station in, for example, a mobile communication system, and more particularly to a dual-frequency antenna device composed of a dipole antenna and a whip antenna that requires shared characteristics in two frequency bands.
[0002]
[Prior art]
Conventionally, this type of dual-frequency antenna device includes, for example, a whip antenna type as shown in FIG.
In FIG. 6, the dual-frequency antenna device 1 includes a trap circuit 3 using a coil or the like inserted in series in the middle of the antenna element 2, and a dual-frequency common antenna at the feeding point of the antenna device 1. And a power feeding matching circuit 4. Reference numeral 5 denotes a feed line.
[0003]
The feeding matching circuit 4 includes a loading coil L1 and a capacitor C1 of the matching circuit. In this case, the structure of the feeding point is the loading coil L1, and in order to perform impedance matching at two frequencies, the capacitor C1 functioning to reduce the inductance of the loading coil L1 in the desired high frequency band is replaced with the coil L1. Many of them are arranged in parallel from the middle and resonate at two frequencies.
[0004]
When the frequency of the loading coil L1 is low, the impedance can be matched without requiring the coil L1 and its manufacturing accuracy so much, but when the frequency becomes 1 GHz or more, in order to realize dual frequency sharing. The joining accuracy of the coil L1 and the capacitor C1, the loss of the coil L1 portion, and the like cannot be ignored.
[0005]
[Problems to be solved by the invention]
In recent mobile communication systems, mobile communication terminals capable of receiving a plurality of frequencies within the same area have become widespread. In this system, when a certain frequency band is crowded, it is distributed to a different frequency band.
Along with this, the existence of a place where a small antenna that shares two frequencies is required as an auxiliary antenna of the mobile terminal has been expected or awaited.
[0006]
In addition, since the frequency band of mobile phones is higher than in-vehicle antennas of 500 MHz band or lower, it is difficult to share the frequency with a normal whib antenna, and even if it is realized, the cost is increased and it is not realistic There was a problem. Therefore, there has been a need for an antenna that has good and stable return loss characteristics in a high frequency band and is inexpensive.
[0007]
The present invention has been made in view of the above points, and the object thereof is to solve the above-mentioned problems, the return loss characteristic in a high frequency band is good and stable, the gain is high, and even a normal whib antenna is a mobile communication system. Another object of the present invention is to provide an inexpensive dual-frequency antenna device that can share the same frequency.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the dual-frequency antenna apparatus according to the present invention is configured by a metal foil or a metal flat plate having an arbitrary width on one surface of a dielectric substrate in order to share two frequency bands. The radiating element includes a plurality of radiating elements, and forms a dipole that resonates at a first frequency f1, and extends from the geometric center between both ends of the two radiating elements in the length direction of the radiating element. The position shifted from the end to a point that becomes 1/4 of the wavelength of the second frequency f2 (f2> f1) is set as the central feeding point of the dipole, and power is fed from one of the feeding lines through the feeding point and the balun. The two radiating elements include one radiating element whose length is ¼ of the wavelength of the second frequency f2 and the other radiating element having a length longer than the one radiating element. A first dipole is formed and the feed point U formed of a metal foil or a metal flat plate having an arbitrary width on both sides of a slit having a length of ¼ of the wavelength of the second frequency f2 provided in a direction perpendicular to the two radiating elements. A U-shaped balun portion, wherein each end is formed by connecting to each end of the two radiating elements, and the other end of the feeder line is connected to a U-shaped bottom. A second dipole comprising a balun portion and the first dipole and resonating at the second frequency f2 is formed, and the balun is a metal having an arbitrary width on the other surface of the dielectric substrate. It is formed from a foil or a metal flat plate, one of which is formed along one side of the slit, and reverses a reverse “U” shape near the feeding point, and again on the other side of the slit. And formed along Connected to said one other end of the feed line, out of the second dipole, the shorter the one radiating element of said two radiating elements of the first dipole, the second This is a dual-frequency antenna device that resonates at the frequency f2 and operates as a whip antenna.
[0010]
In the dual-frequency antenna apparatus, a plurality of pairs of dipole elements of the dipole antenna are formed on the same dielectric substrate to operate as a diversity antenna.
[0011]
In the dual-frequency antenna apparatus, the feeding line is configured by a balanced circuit, a balanced / unbalanced conversion circuit, a microstrip line or a balun of the unbalanced circuit.
[0012]
Since the dual-frequency shared antenna apparatus of the present invention is configured as described above in order to share two frequency bands, it is made to resonate and operate as a dipole antenna at a low first frequency f1, and each length is Of the two dipole elements having different lengths, the shorter dipole element length is used to resonate at a higher second frequency f2 (f2> f1) and operate as a whip antenna.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the drawings. 1 and 2 are diagrams showing an embodiment of a dual-frequency antenna device according to the present invention. FIG. 1 is a front configuration diagram showing the configuration of the dual-frequency antenna device. FIG. 2 is the antenna device. FIG. 6 is a diagram showing a current distribution with dotted lines when resonance occurs at a low first frequency f1 and a high second frequency f2 of the two frequencies.
[0014]
In FIG. 1, the dual-frequency antenna device 1 is made of a metal foil having an arbitrary width formed on one surface of a dielectric substrate 11, and the first frequency f1 is in the 0.8 GHz band (its wavelength is λ1), and a case where the second frequency f2 is an antenna for two frequencies used in a 1.5 GHz band (having a wavelength of λ2), and two linearly-shaped antennas constituting the first dipole 12 are formed. The dipole elements 12a and 12b are formed so that the length between both ends thereof is about (λ1) / 2 so as to resonate at the frequency f1.
[0015]
One dipole element 12a extends in the length direction of the dipole elements 12a and 12b from the geometric center point C0 of the frequency f1 of about (λ1) / 2 of the length between both ends of the dipole elements 12a and 12b. The position shifted from the end of the antenna device 10 to a point at about (λ2) / 4 of the frequency f2 is defined as the feeding center point C of the antenna device 10, and the shorter one of the dipole elements 12a and 12b has a length of about (λ2 ) / 4 of the dipole element 12a is resonated at the frequency f2.
[0016]
On the both sides of the slit 19 having a length L provided on the center line C1 perpendicular to the dipole elements 12a and 12b (downward vertical direction in FIG. 1) from the feeding center point C of the antenna device 10, A U-shaped dipole U-shaped balun portion 13a made of a metal foil having a width is formed, and each end 13b, 13c is formed to be connected to each end of the dipole elements 12a, 12b. .
[0017]
Accordingly, the second dipole 13 is formed by the dipole elements 12a and 12b and the dipole U-shaped balun portion 13a, and resonates the dipole element 12a at the frequency f2.
Further, the total length of the dipole elements 12a and 12b and the dipole U-shaped balun portion 13a forming the second dipole 13 is about 1.5 times the wavelength λ2 of the frequency f2, as shown in FIG. The length L of the slit 19 is about (λ2) / 4 or more of the frequency f2 and is determined by impedance matching with the balun 14 described later, or the wavelength f2 from the central feeding point 20 described later. It is set to about 1/4 of λ2.
[0018]
The feed lines for feeding power to the first and second dipoles 12 and 13 are a feed line 15a formed on the other surface side of the dielectric substrate 11 and a U-shaped bottom portion of the dipole U-shaped balun portion 13a. Forms the feed line 15b.
[0019]
One of the feed lines 15a formed on the other surface (back side in FIG. 1) of the dielectric substrate 11 is on one side (left side in FIG. 1) of the slit 19 provided on the center line C1. In the vicinity of the central feeding point 20, the direction is reversed to an inverted “U” shape, and the balun 14 is formed again along the other side (right side in FIG. 1) of the slit 19. One side is connected to a feeding end at the lower end of the dielectric substrate 11.
[0020]
The length of the balun 14 is adjusted by forming its length from the central feeding point 20 to about (λ2) / 4 of the second frequency f2. The dipole elements 12a, 12b; 12a, 12b, 13a as the radiating elements of the first and second dipoles 12, 13 are fed from the feed lines 15a, 15b to the central feed point 20, respectively. Thus, power of the predetermined frequency is supplied.
[0021]
Thus, the structure of the balun 14 is an open structure. In addition, the part which surrounds the said balun 14 containing the said electric power feeding lines 15a and 15b with the chain line of FIG. 1 as the electric power feeding balun part 17 is shown.
[0022]
The dipole element 12a is operated as a whip antenna. In this case, the whip antenna by the dipole element 12a of the antenna device 10 is an antenna that does not require grounding such as a ground plate.
As shown in FIG. 2, the whip antenna whose current distribution by the second frequency f2 has a length of 3/2 of the wavelength λ2 does not require grounding such as a grounding plate below the antenna, Nevertheless, it is an antenna that can radiate in the horizontal direction in the directivity of the vertical plane.
[0023]
The antenna device 10 is a deformed dipole antenna device that is asymmetrical when viewed from the central feeding point 20.
The antenna device 10 can be operated as a dual-frequency diversity antenna by forming a plurality of pairs of the dipole elements 12a, 12b, and 13a on the same dielectric substrate 11 in the vertical direction.
[0024]
In the present embodiment, the example in which the first and second dipoles 12 and 13 are formed of metal foil on one surface of the dielectric substrate 11 has been described, but instead of this, formed from a metal flat plate. You may let them.
In the present embodiment, one frequency f1 used is 0.8 GHz band and the other frequency f2 is 1.5 GHz band. However, the present invention is not limited to this, and other frequencies may be used. Of course, the frequency f2 is preferably about twice the frequency f1.
[0025]
With respect to the dual frequency antenna apparatus 10 as described above, the frequency versus return loss characteristics in each frequency band, that is, in the first frequency f1 = 0.8 GHz band and the second frequency f2 = 1.5 GHz band, As shown in FIG. 3, a broadband characteristic is obtained.
[0026]
The dual-frequency antenna apparatus 10 is a horizontal plane directivity characteristic diagram when the dipole element 12a is operated as a whip antenna, and the first frequency f1 = 0.8 GHz band, the second frequency f2 = 1. The magnetic field in-plane directivity characteristics in the 5 GHz band are shown in FIGS.
Similarly, in the vertical in-plane directivity characteristic diagrams, the in-plane directivity characteristics in the electric field in the first frequency f1 = 0.8 GHz band and the second frequency f2 = 1.5 GHz band are shown in FIGS. Shown in b).
[0027]
The dual-frequency antenna apparatus 10 can be configured by connecting a balanced circuit, a balanced / unbalanced conversion circuit, a micro-slip line of an unbalanced circuit, a balun, or the like to the feed lines 15a and 15b.
[0028]
Note that the technology of the present invention is not limited to the technology in the above-described embodiment, and may be implemented by means of other modes that perform the same function. Addition is possible.
[0029]
【The invention's effect】
As is apparent from the above description, according to the dual-frequency antenna device of the present invention, in order to share two frequency bands, a metal foil or metal flat plate having an arbitrary width on one surface of the dielectric substrate is used. One radiating element is formed of two radiating elements and forms a dipole that resonates at a first frequency f1 and extends in the longitudinal direction of the radiating element from the geometric center between both ends of the two radiating elements. Is fed from one of the feed lines through the feed point and the balun, with the position shifted from the end of the point to a point that becomes 1/4 of the wavelength of the second frequency f2 (f2> f1) as the central feed point of the dipole. with that, the two radiating elements is composed of a one radiating element a quarter wavelength of the length the second frequency f2, the length from the one radiating element said that the longer the other radiating element A first dipole is formed and the feed point U formed of a metal foil or a metal flat plate having an arbitrary width on both sides of a slit having a length of ¼ of the wavelength of the second frequency f2 provided in a direction perpendicular to the two radiating elements. A U-shaped balun portion, wherein each end is formed by connecting to each end of the two radiating elements, and the other end of the feeder line is connected to a U-shaped bottom. A second dipole comprising a balun portion and the first dipole and resonating at the second frequency f2 is formed, and the balun is a metal having an arbitrary width on the other surface of the dielectric substrate. It is formed from a foil or a metal flat plate, one of which is formed along one side of the slit, and reverses a reverse “U” shape near the feeding point, and again on the other side of the slit. And formed along Connected to said one other end of the feed line, out of the second dipole, the shorter the one radiating element of said two radiating elements of the first dipole, the second Resonates at the frequency f2 and operates as a whip antenna, so that the return loss characteristic in the high frequency band is good and stable, the gain is high, and the frequency of the mobile communication system can be shared even with a normal whib antenna, and downsizing Therefore, there is an excellent effect that an inexpensive two-frequency shared dipole antenna device can be obtained.
[0030]
Further, according to the present invention, the dielectric substrate can be used without using a matching element or the like in the trap circuit and the feeding point, that is, without requiring an inductance portion (the coil) and a capacitance portion, as compared with the conventional one. Since the dipole element can be formed on the top, the manufacturing accuracy is high and it is very efficient for mass production. Since there is no loss in the coil, there is an effect that a high gain can be obtained stably.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a dual frequency antenna device according to the present invention, and is a front configuration diagram showing a configuration of the dual frequency antenna device.
2 is a diagram showing a current distribution by dotted lines when the dipole of the antenna apparatus of FIG. 1 resonates at a first frequency f1 which is lower than two frequencies and a second frequency f2 which is higher.
3 is a frequency vs. return loss characteristic diagram of the dual-frequency antenna device of FIG. 1;
4 is a horizontal plane directivity characteristic diagram of the dual-frequency antenna device of FIG. 1. FIG. 4 (a) is a magnetic field in-plane directivity chart at the first frequency f1 = 0.8 GHz, and FIG. FIG. 6 is a magnetic field in-plane directivity characteristic diagram at the second frequency f2 = 1.5 GHz.
5 is a vertical in-plane directivity characteristic diagram of the dual-frequency antenna device of FIG. 1. FIG. 5 (a) is an electric field in-plane directivity diagram at the first frequency f1 = 0.8 GHz, and FIG. 5 (b). These are electric field in-plane directivity characteristics diagrams at the second frequency f2 = 1.5 GHz.
FIG. 6 is an explanatory diagram showing a configuration of a whip antenna type antenna device as an example of a conventional dual-frequency antenna device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Dual frequency antenna apparatus 11 Dielectric board | substrate 12 1st dipole 12a, 12b Dipole element 13 2nd dipole 13a Dipole U-shaped balun part 13b, 13c End 14 Baluns 15, 15a, 15b Feed line 17 Feed balun part 19 Slit 20 Center feed point C Feed center point C0 Geometric center point C1 Center lines f1, f2 Frequency

Claims (3)

In order to share the two frequency bands, a dipole that resonates at the first frequency f1 is formed of two radiating elements of a metal foil or a metal plate having an arbitrary width on one surface of the dielectric substrate. , From the geometric center between both ends of the two radiating elements in the length direction of the radiating element, and from one end of the radiating element to ¼ of the wavelength of the second frequency f2 (f2> f1). A position shifted to a certain point is set as the central feed point of the dipole, and power is fed from one of the feed lines via the feed point and the balun, and the two radiating elements have a length of the second frequency f2. A first dipole composed of one radiating element that is ¼ of the wavelength of the first radiating element and the other radiating element that is longer than the one radiating element ,
A metal foil or metal flat plate having an arbitrary width on both sides of a slit having a length ¼ of the wavelength of the second frequency f2 provided in a direction perpendicular to the two radiating elements from the feeding point. A U-shaped balun portion, each of which is formed by connecting each end to each end of the two radiating elements, and the other end of the feed line is connected to the U-shaped bottom. A second dipole consisting of a U-shaped balun portion and the first dipole and resonating at the second frequency f2 is formed,
The balun is formed of a metal foil or a metal flat plate having an arbitrary width on the other surface of the dielectric substrate, and one of the baluns is formed along one side of the slit and in the vicinity of the feeding point. Reversing the direction into an inverted “U” shape, again formed along the other side of the slit, and the one end connected to one of the feed lines,
The second of the dipole, the shorter the one of the radiating elements of said two radiating elements of the first dipole, is resonated in the second frequency f2, characterized in that to operate as a whip antenna A dual frequency antenna device. 2. The dual-frequency antenna device according to claim 1, wherein a plurality of pairs of the dipole elements are formed on the same dielectric substrate and operate as a diversity antenna . 2. The dual-frequency antenna apparatus according to claim 1, wherein a balanced circuit, a balanced / unbalanced conversion circuit, a microstrip line of an unbalanced circuit, or a balun are connected to the feed line. Dual frequency antenna device.

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