JP2004007510A - Antenna and electronic apparatus employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized antenna with a broadband and small reduction in a radiation efficiency and to provide an electronic apparatus employing the same. <P>SOLUTION: The antenna is provided with: a ground plate electrode; a radiation plate electrode opposed to the ground plate electrode with a prescribed space inbetween; a ground lead wire interconnecting the ground electrode and the radiation electrode; and a feed lead wire connected to the radiation electrode. A magnetic body 31 is provided in the vicinity of the ground lead wire 28 and a space without the magnetic body 31 is provided between the radiation electrode 27 and the ground electrode 26. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an antenna and an electronic device using the same.
[0002]
[Prior art]
The configuration of this type of conventional antenna is as follows. That is, a plate-shaped ground electrode, a plate-shaped radiating electrode arranged to face the ground electrode with a predetermined space, a ground lead wire connecting the radiating electrode and the ground electrode, and a power supply lead connected to the radiating electrode. And a line. In this configuration, a ground electrode and a radiation electrode are connected to each other by a ground lead wire to create a λ / 4 mode resonance, and a radio wave is radiated by the resonance electrode. The λ / 4 mode referred to here is a resonance mode in which the current is maximum at the ground lead and the current is minimum and the voltage is maximum at the open end furthest from the ground lead.
[0003]
As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
[0004]
[Patent Document 1]
JP-A-1-228303
[Problems to be solved by the invention]
In this type of conventional antenna, attempts have been made to insert a dielectric or magnetic material between a ground electrode and a radiation electrode in order to reduce the size. As a result, the wavelength of the electromagnetic field between the ground electrode and the radiation electrode is shortened, and thereby the size of the antenna is reduced.
[0006]
The λ / 4 mode resonance can be equivalently represented by a parallel resonance circuit of a capacitor and an inductor. If the wavelength of the λ / 4 resonator is shortened by using a dielectric, the capacitor value (hereinafter referred to as “capacitance”) equivalently increases, and the frequency characteristic of the impedance becomes steep to narrow the band. On the other hand, when a magnetic material is used, the frequency characteristic of the impedance is moderated by equivalently increasing the inductance value (hereinafter, inductive), and the band can be widened. Therefore, the use of a magnetic material is effective for obtaining a broadband antenna. However, magnetic materials generally also have the characteristics of a dielectric, so from the viewpoint of loss, when a dielectric is used, there is only dielectric loss, but when a magnetic material is used, magnetic Both loss and dielectric loss occur, which causes a problem of lowering radiation efficiency.
[0007]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an antenna that suppresses a loss and prevents a decrease in radiation efficiency while using a magnetic material to achieve a small size and a wide band, and an electronic device using the antenna.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the present invention provides a magnetic body near the ground lead wire, and provides a space where no magnetic body is provided between the ground electrode and the radiation electrode. In other words, by providing a magnetic material near the grounding lead wire where current concentration occurs most in λ / 4 mode resonance, the effect of shortening the wavelength and increasing the inductivity due to the magnetic material is effectively exerted, realizing miniaturization and broadening of the band. On the other hand, by providing a space where the magnetic material is not installed at a place where the current concentration between the radiation electrode and the ground electrode is low, the occurrence of magnetic loss and dielectric loss at that part is eliminated, and the radiation efficiency is reduced. It is to prevent.
[0009]
The invention according to a second aspect of the present invention is the antenna according to the first aspect, wherein the grounding lead wire passes through the through-hole portion of the columnar magnetic body. When the grounding lead wire passes through the through hole of the columnar magnetic body, it is possible to create a state in which the magnetic body exists so as to cover the periphery of the grounding lead wire. Since a magnetic field is generated around the current flow around it, providing a magnetic material around the ground lead wire where current concentration occurs increases the effect of shortening the wavelength and increasing the inductivity in this part. Thus, the configuration is effective for reducing the size and bandwidth of the antenna.
[0010]
Next, an antenna according to a third aspect of the present invention is the antenna according to the first aspect, wherein the grounding lead wire is drawn out from the outer peripheral portion of the radiation electrode. By drawing the ground lead from the outer peripheral portion of the radiation electrode, the length of the resonator can be increased, and the resonance frequency can be reduced. In other words, if the resonance frequency is the same, the antenna can be downsized.
[0011]
Next, an antenna according to a fourth aspect of the present invention is the antenna according to the first aspect, wherein a magnetic body is provided on an outer peripheral portion of the radiation electrode. When current concentration also occurs in the outer peripheral portion of the radiation electrode due to the edge effect, by providing a magnetic material also in that portion, the effect of shortening the wavelength and increasing the inductivity can be enhanced, and the antenna can be reduced in size and bandwidth.
[0012]
Next, an antenna according to a fifth aspect of the present invention is the antenna according to the first aspect, wherein a spacer is provided at a portion other than a portion where the ground lead wire extends between the outer peripheral portion of the radiation electrode and the ground electrode. By providing the spacer on the outer peripheral portion of the radiation electrode, the distance between the radiation electrode and the ground electrode can be kept uniform, and the characteristic hardly fluctuates.
[0013]
Next, the invention according to claim 6 of the present invention is the antenna according to claim 5, wherein the spacer is formed of an insulator. By using an insulator having almost no dielectric and magnetic properties for the spacer, the occurrence of dielectric loss and magnetic loss can be suppressed, and a decrease in radiation efficiency can be prevented.
[0014]
Next, the invention according to claim 7 of the present invention is the antenna according to claim 1, wherein the upper and lower surfaces of the magnetic material are provided so as to be in contact with the radiation electrode and the ground electrode, respectively. With this configuration, the grounding lead wire connecting the radiation electrode and the grounding electrode is entirely covered with a magnetic material, which further enhances the effect of shortening the wavelength and increasing the inductive property of the magnetic material. That is, a broadband antenna can be obtained.
[0015]
Next, the invention according to claim 8 of the present invention is the antenna according to claim 2, wherein the antenna is configured to have the same shape as a grounding lead wire passing through a through hole of a magnetic body. With this configuration, the magnetic material is closely located on the outer periphery of the ground lead wire, and the size and the bandwidth can be effectively reduced.
[0016]
Next, an antenna according to a ninth aspect of the present invention is the antenna according to the second aspect, wherein the grounding lead wire and the through-hole portion of the columnar magnetic body are formed without a gap. With this configuration, the magnetic field generated on the outer periphery of the grounding lead wire can be made to act on the magnetic material without leaking, and further downsizing and a wider band can be achieved.
[0017]
Next, an antenna according to a tenth aspect of the present invention is the antenna according to the second aspect, wherein the through-hole is provided in a central portion of the columnar magnetic body. With this configuration, it is possible to create a state in which the magnetic material is uniformly present on the outer periphery of the ground lead wire, and the magnetic material can be made to act effectively.
[0018]
Next, an antenna according to an eleventh aspect of the present invention is the antenna according to the second aspect, wherein the through hole is provided so as to be eccentric to the radiation electrode and the ground electrode. With this configuration, it is possible to provide a configuration in which a magnetic material also exists near the connection portion between the radiation electrode and the ground electrode to which the ground lead wire where the current is concentrated is connected. It can be obtained effectively.
[0019]
Next, the invention according to claim 12 of the present invention is the antenna according to claim 1, wherein the grounding lead wire has a meandering shape. With this configuration, the line length of the ground lead wire portion can be increased, so that the radiation electrode can be downsized. That is, a smaller antenna can be obtained.
[0020]
Next, the invention according to claim 13 of the present invention is the antenna according to claim 1 provided with a plurality of grounding leads. With this configuration, the area of the radiation electrode is larger than that of a single ground lead, but the bandwidth is increased. That is, a low-profile antenna can be obtained without reducing the bandwidth.
[0021]
Next, an antenna according to a fourteenth aspect of the present invention is the antenna according to the thirteenth aspect, wherein at least one of the plurality of grounding leads is penetrated through the through-hole portion of the columnar magnetic body. According to this configuration, the radiation electrode area enlarged by increasing the number of grounding leads can be reduced by the effect of the magnetic material, and as a result, a small and low-profile antenna can be obtained. Things.
[0022]
Next, the invention according to claim 15 of the present invention is the antenna according to claim 1, wherein a slit is provided in the radiation electrode. By providing the slit, the paths through which the current flows are separated, and a resonance mode can be obtained for each flow. As a result, since resonance can be performed in a plurality of frequency bands, a small multi-band antenna can be obtained.
[0023]
Next, the invention according to claim 16 of the present invention is the antenna according to claim 1, wherein a parasitic electrode is provided between the radiation electrode and the ground electrode. By utilizing the mutual electromagnetic coupling between the radiation electrode, the parasitic electrode, and the ground electrode, it is possible to efficiently obtain impedance characteristics corresponding to a desired frequency band and to broaden the band, thereby enabling a compact, wideband multiband antenna. Can be obtained.
[0024]
Next, an antenna according to a seventeenth aspect of the present invention is the antenna according to the first aspect, wherein a magnetic body having a relative permeability having a frequency characteristic is used. If a magnetic material having a frequency characteristic such that the relative permeability is large at a low frequency and becomes smaller as the frequency becomes higher is used, the effect of shortening the wavelength of the magnetic material in a low-frequency band having a longer wavelength is increased, and as a result, That is, a small antenna can be obtained.
[0025]
Next, an invention according to claim 18 of the present invention is an electronic device in which the power supply lead wire of the antenna according to any one of claims 1 to 17 is connected to at least one of a transmission line and a reception line, By connecting an extremely miniaturized antenna to at least one of the transmission line and the reception line, the miniaturization of the electronic device itself can be achieved.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the accompanying drawings.
[0027]
1 to 7 show one embodiment of the present invention, and show a mobile phone as an example of an electronic apparatus.
[0028]
That is, FIG. 3 shows an electric circuit of the mobile phone. As shown in FIG. 3, the antenna 1 is connected to the transmission line 3 and the reception line 4 via the antenna duplexer 2. The duplexer 2 includes a transmission filter 5 and a reception filter 6. The radio wave received by the antenna 1 is transmitted to the reception line 4 via the antenna sharing device 2, and the transmission signal such as voice is transmitted from the antenna 1 via the transmission line 3 and the antenna sharing device 2. ing. Since the electric circuit shown in FIG. 3 shows a general example of a mobile phone, the detailed description will be simplified, but an amplifier 7, an interstage filter 8, a mixer 9, an IF filter 10, a demodulator 11 The speaker 12 is connected via the. Further, a modulator 14, a mixer 15, an interstage filter 16, an amplifier 17, and an isolator 18 are provided on the transmission line 3 in order from the microphone 13, and are connected to the antenna duplexer 2. Further, a voltage controlled oscillator (VCO) 19 is connected to the mixers 9 and 15 via filters 20 and 21, respectively.
[0029]
FIG. 1 specifically shows this electric circuit as a configuration diagram. In FIG. 1, the components of the transmission line 3 and the reception line 4 from the antenna duplexer 2 to the demodulator 11 or the modulator 14 shown in FIG. The transmission / reception circuit unit 23 of FIG. A signal line 24 is provided from the transmission / reception circuit unit 23, and a power supply terminal 25 is connected to the signal line 24. The power supply terminal 25 is provided between the antenna 1 and the antenna duplexer 2 in FIG.
[0030]
The antenna 1 is provided on the printed circuit board 22 in addition to the transmission / reception circuit unit 23 as shown in FIG. The antenna 1 has a structure as shown in FIG. That is, for example, a ground electrode 26 formed of a copper plate, a radiation electrode 27 of the same copper plate facing the ground electrode 26 with a predetermined space therebetween, a ground lead wire 28 drawn from the radiation electrode 27, It is composed of a lead wire 29, a spacer 30, and a magnetic body 31. As shown in FIG. 2, the ground lead wire 28 is drawn outward from a corner portion of the plate-shaped radiation electrode 27 and then bent downward to form a plate-shaped or meander-shaped ground. The lead wire 28 penetrates through the through hole 31a of the prismatic magnetic body 31 as shown in FIG. 1, and its lower end is electrically and mechanically connected to the ground electrode 26. The through hole 31 a is configured to have the same shape as the ground lead wire 28, and is eccentric so that the central portion of the magnetic body 31 or the magnetic body 31 exists more on the ground electrode 26 and the radiation electrode 27 side. It is assumed that it is provided at such a position. It is desirable that the ground lead wire 28 and the magnetic body 31 be formed as closely as possible by a simultaneous firing method or the like.
[0031]
A power supply lead wire 29 extending outward from the outer peripheral portion of the plate-like radiation electrode 27 and bent downward is also provided with a notch 26a provided in the plate-like ground electrode 26 shown in FIG. The power supply terminal 25 is electrically and mechanically connected to the power supply terminal 25 shown in FIG.
[0032]
The spacer 30 has a U-shape as shown in FIG. 2 and is provided so as to support the outer peripheral portion of the radiation electrode 27 between the radiation electrode 27 and the ground electrode 26. The spacer 30 is formed of, for example, an insulator such as an ABS resin. The magnetic body 31 is made of, for example, a ferrite-based material having frequency characteristics such that the relative magnetic permeability increases at low frequencies and decreases with increasing frequency. It is configured to have the same length as the ground lead wire 28 so as to be in contact with the ground electrode 27 and the ground electrode 26. Subsequently, the ground electrode 26 is configured to be electrically and mechanically connected to the printed circuit board 22 at the four ground terminals 32 shown in FIG.
[0033]
In the above configuration, the radiation electrode 27 basically functions as an antenna as shown in FIG. 3, and the radiation electrode 27 is connected to the plate-like ground electrode 26 via the ground lead 28. Accordingly, the antenna functions as an antenna in the λ / 4 resonance mode.
[0034]
The most characteristic feature of the present embodiment in such a situation is that the grounding lead wire 28 is disposed so as to penetrate through the prismatic magnetic body 31. With this configuration, it is possible to create a state in which the magnetic body 31 exists around the ground lead wire 28 where the current is most concentrated in the resonance in the λ / 4 mode. Since the magnetic field is generated so as to orbit around the current flow, the magnetic body 31 provided around the ground lead wire 28 acts most effectively on the magnetic field, thereby exhibiting the wavelength shortening effect. While increasing the inductive property, the frequency change of the impedance can be moderated, and as a result, the antenna 1 shown in FIG. 2 has a small size and a wide band. Specifically, the radiation electrode 27, the ground electrode 26, and the like can be made smaller. Of course, this makes it possible to reduce the size of an electronic device using the mobile phone shown in FIG. 3 as an example.
[0035]
The spacer 30 shown in FIG. 2 is provided on the outer peripheral portion of the radiation electrode 27. The spacer 30 is made of an insulator as described above. Originally, if all of the space between the radiation electrode 27 and the ground electrode 26 is made of a magnetic material, the antenna 1 can be reduced in size and a wider band, but in such a case, the dielectric loss and magnetic property of the magnetic material are reduced. The adverse effect that a radiation loss causes a decrease in radiation efficiency occurs. Therefore, in the present embodiment, as described above, the magnetic body 31 is effectively disposed only at the outer peripheral portion of the ground lead wire 28 where current concentration occurs, and the other portion where the current concentration is small is The space is defined as an existing space, and is only mechanically supported by the spacer 30. Further, an insulator having almost no dielectric and magnetic properties is used for the spacer 30, thereby suppressing occurrence of dielectric loss and magnetic loss.
[0036]
With the above-described configuration, it is possible to obtain an antenna having stable characteristics by suppressing a decrease in radiation efficiency while reducing the size and the bandwidth of the antenna 1 and further suppressing a change in the interval between the radiation electrode 27 and the ground electrode 26. You can do it.
[0037]
In the present embodiment, the magnetic body 31 is arranged only in the vicinity of the ground lead 28, but may be arranged in other parts in addition to the magnetic body 31. Particularly, depending on the form of the antenna, a current concentration may occur around the radiation electrode 27 due to the edge effect. In such a case, a magnetic material may be provided around the radiation electrode 27 or a part thereof in addition to the vicinity of the ground lead wire 28.
[0038]
Further, as shown in FIG. 4, a plurality of ground lead wires 28 may be provided like ground lead wires 28a and 28b, and may be penetrated through the through holes 31a and 31b of the magnetic body 31. The use of a plurality of ground leads 28 increases the size of the radiation electrode 27, thereby increasing the bandwidth. Further, since the radiation electrode 27 enlarged by the magnetic body 31 can be reduced in size, the configuration is effective for reducing the height of the antenna.
[0039]
Further, as shown in FIG. 5, the radiation electrode 27 may be provided with a slit 27a. By providing the slit 27a, it is possible to resonate in a plurality of frequency bands, so that an antenna compatible with multiple bands can be obtained.
[0040]
Further, as shown in FIG. 6, between the radiation electrode 27 and the ground electrode 26, a radiation electrode 27, a ground lead wire 28, a power supply lead wire 29, and a parasitic electrode 33 which is not in contact with the ground electrode 26 are arranged. It does not matter. Electromagnetic field coupling can be generated between the parasitic electrode 33 and the radiation electrode 27 to achieve a wider band, and a wideband multiband antenna can be obtained. In this case, it is desirable that the spacer 30 be shaped to mechanically support the parasitic electrode 33.
[0041]
FIG. 7 shows a case where a magnetic material 31 having frequency characteristics such that μ ′ = 2.6, μ ″ = 0.08, ε ′ = 10.3, and ε ″ = 0.05 at 1710 MHz is used. 5 is a graph of VSWR of FIG. The antenna using the magnetic body 31 shown by the solid line can achieve a wider band than the antenna without the magnetic body 31 shown by the dotted line.
[0042]
【The invention's effect】
As described above, the present invention provides a plate-like ground electrode, a plate-like radiating electrode arranged to face the ground electrode with a predetermined space, a ground lead wire connecting the ground electrode and the radiating electrode, A power supply lead connected to the electrode; a magnetic body provided near the grounding lead; and a space where no magnetic body is provided between the radiation electrode and the grounding electrode. Moreover, it is possible to provide an antenna and a small electronic device that prevent a reduction in radiation efficiency.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of the antenna of the present invention. FIG. 2 is an exploded perspective view of the antenna. FIG. 3 is an electric circuit diagram of a mobile phone as an example of an electronic device using the antenna. 4: Exploded perspective view of antenna part FIG. 5: Exploded perspective view of antenna part FIG. 6: Exploded perspective view of antenna part FIG. 7: Graph of change in bandwidth of antenna of the present invention
1 antenna 26 ground electrode 27 radiation electrode 28 ground lead 29 feed lead 30 spacer 31 magnetic body 31a through hole

Claims (18)

A plate-shaped ground electrode, a plate-shaped radiation electrode disposed to face the ground electrode with a predetermined space therebetween, a ground lead wire connecting the radiation electrode to the ground electrode, and a power supply lead wire connected to the radiation electrode And a magnetic body is provided in the vicinity of the ground lead wire, and a space where no magnetic body is provided is provided between the radiation electrode and the ground electrode. 2. The antenna according to claim 1, wherein the grounding lead wire passes through a through-hole portion of the columnar magnetic body. 2. The antenna according to claim 1, wherein the grounding lead wire is drawn out of an outer peripheral portion of the radiation electrode. The antenna according to claim 1, wherein the magnetic material is provided on an outer peripheral portion of the radiation electrode. 2. The antenna according to claim 1, wherein a spacer is provided at a portion other than a portion where the ground lead wire extends between the outer peripheral portion of the radiation electrode and the ground electrode. The antenna according to claim 5, wherein the spacer is formed of an insulator. 2. The antenna according to claim 1, wherein upper and lower surfaces of the magnetic material are provided so as to be in contact with the radiation electrode and the ground electrode, respectively. 3. The antenna according to claim 2, wherein the antenna is configured to have the same shape as a grounding lead wire penetrating through the through-hole of the magnetic body. 3. The antenna according to claim 2, wherein the ground lead and the through-hole portion of the columnar magnetic body are formed without a gap. 3. The antenna according to claim 2, wherein the through hole is provided in a central portion of the columnar magnetic body. 3. The antenna according to claim 2, wherein the through hole is provided so as to be eccentric to the radiation electrode and the ground electrode. 2. The antenna according to claim 1, wherein the grounding lead wire has a meandering shape. The antenna according to claim 1, wherein a plurality of grounding leads are provided. 14. The antenna according to claim 13, wherein at least one of the plurality of ground lead wires penetrates a through-hole portion of the columnar magnetic body. The antenna according to claim 1, wherein a slit is provided in the radiation electrode. The antenna according to claim 1, wherein a parasitic electrode is provided between the radiation electrode and the ground electrode. The antenna according to claim 1, wherein a magnetic material having a relative magnetic permeability having a frequency characteristic is used. 18. An electronic device, wherein a power supply lead wire of the antenna according to claim 1 is connected to at least one of a transmission line and a reception line.

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