WO2006097996A1

WO2006097996A1 - Antenna assembly, its frequency adjusting method, and radio communication apparatus

Info

Publication number: WO2006097996A1
Application number: PCT/JP2005/004498
Authority: WO
Inventors: Shin Watanabe; Kouji Soekawa
Original assignee: Fujitsu Limited
Priority date: 2005-03-15
Filing date: 2005-03-15
Publication date: 2006-09-21

Abstract

In an antenna assembly (4) equipped with a coil (10), a plurality of resonance frequencies and their frequency intervals are adjusted. In the antenna assembly (4) equipped with the coil (10), the coil (10) is provided with a passive conductor (16) covering a part of the coil (10) and the passive conductor (16) is arranged at a position where the primary resonance current or higher order resonance current of the coil (10) concentrates. The passive conductor (16) is brought to the vicinity of the coil (10) and coupled to the coil (10). Resonance characteristics of the coil (10) are coupled with the resonance characteristics of the passive conductor (16), thus obtaining the resonance characteristics of both of them.

Description

Antenna device, frequency adjustment method thereof, and wireless communication device

Technical field

The present invention relates to an antenna such as a multi-resonance antenna having a plurality of resonance points, and relates to an antenna device corresponding to a plurality of radio communication frequencies, a frequency adjustment method thereof, and a radio communication device.

Background art

[0002] An antenna such as a multi-resonant antenna having a plurality of resonance frequencies in order to cope with a multi-band transmission such as a dual band or a triple band using a plurality of frequencies as transmission / reception frequencies for a wireless communication device such as a cellular phone. A device is required.

[0003] With regard to wireless communication using a plurality of frequencies, a filter (for example, Patent Document 1) installed in a transmission line that transmits a multilevel signal having a binary power with a predetermined symbol period, and a plurality of frequency bands There are multiple resonant antennas that operate (for example, Patent Documents 2 and 3). Patent Documents 2 and 3 disclose an antenna used in a portable wireless communication device in which a parasitic conductor is installed inside a helical antenna element. In this case, the parasitic conductor is inserted into the antenna bobbin that supports the helical antenna element.

Patent Document 1: JP-A-6-37591 (paragraph number 0013)

Patent Document 2: Japanese Patent Laid-Open No. 2004-23430 (FIGS. 2, 7, paragraph number 0013, etc.)

Patent Document 3: Japanese Patent Application Laid-Open No. 2004-15623 (FIG. 2, paragraph number 0011, FIG. 16, etc.) Disclosure of Invention

Problems to be solved by the invention

[0004] Since an antenna device using a coil as an antenna element includes a helical coil, it is called a helical antenna and constitutes a λZ4 type antenna. Such an antenna device is called a multi-resonant antenna because its primary resonance frequency is f, and it has resonance points at odd frequencies f, 3f, 5f,.

[0005] By using such a plurality of resonance frequencies, it is possible to function as a multiband antenna. However, it is rare that each resonant frequency matches the frequency to be used. Therefore

Therefore, it is necessary to change or adjust the resonance frequency. In the antennas described in Patent Documents 2 and 3, a parasitic conductor is inserted inside the helical coil, and the resonance frequency is adjusted.

[0006] A configuration example of an antenna device in which such a parasitic conductor is inserted will be described with reference to FIG. FIG. 1 shows an antenna device 4 installed in a mobile phone 2. The cellular phone 2 is provided with a circuit board 6. The circuit board 6 is provided with a wireless unit (not shown) and a connection unit 8 for connecting the antenna device 4. The antenna device 4 is provided with a coil 10 that constitutes an antenna element, and a feeding point 12 of the coil 10 is connected to the connection portion 8.

[0007] Frequency characteristics of the antenna device 4 including the parasitic conductor 14 will be described. FIG. 2 shows the frequency characteristics of the antenna device 4. In Fig. 2, in order to explain the change in characteristics due to the insertion of the parasitic conductor 14, the characteristics when the parasitic conductor 14 is inserted and when it is 給電 (dotted line display, frequency characteristics shown in Fig. 6) are superimposed. ing. In Fig. 2, regarding antenna device 4 in which parasitic conductor 14 is not inserted, al is the primary resonance characteristic, a2 is the secondary resonance characteristic, a3 is the tertiary resonance characteristic, fal is the primary resonance frequency, fa2 Is the secondary resonance frequency, f a3 is the tertiary resonance frequency, and fal 2 and fa23 are the frequency intervals. On the other hand, in the antenna device 4 with the parasitic conductor 14 inserted, bl is the primary resonance characteristic, b2 is the secondary resonance characteristic, b3 is the tertiary resonance characteristic, fbl is the primary resonance frequency, and fb2 is 2 The second resonance frequency, fb3, changes to the third resonance frequency. In this case, fbl2 and fb23 similarly indicate frequency intervals. When the parasitic conductor 14 is inserted in this way, the characteristics al, a2, and a3 (before insertion of the parasitic conductor 14) change to characteristics bl, b2, and b3 (after insertion of the parasitic conductor 14), and the resonance frequency As fal decreases by fbl, the resonance frequency fa2 decreases to fb2, the resonance frequency fa3 decreases to fb3, and the higher-order resonance frequencies fb2 and fb3 decrease significantly. As a result, frequency intervals fal2 (= fa2 -fal), fa23 (= fa3-fa2), fbl2 (= fb2-fbl), fb23 (= fb3-fb2) Has fal2> fbl2 and ia23> fb23.

[0008] As described above, when the parasitic conductor 14 is inserted, the resonance frequency of the antenna device 4 is lowered and the frequency interval of each resonance frequency is narrowed. Therefore, when the resonance frequency is increased or the frequency interval is widened. Can't respond to. [0009] Accordingly, a first object of the present invention relates to an antenna device including a coil, and is to adjust a plurality of resonance frequencies.

[0010] A second object of the present invention relates to an antenna device including a coil, and is to realize adjustment of frequency intervals of a plurality of resonance frequencies.

[0011] Further, a third object of the present invention is to realize a wireless communication device using an antenna device including a coil.

Means for solving the problem

[0012] In order to achieve the above object, the present invention is an antenna device including a coil, wherein the coil is provided with a parasitic conductor, and the parasitic conductor covers a part of the coil.

With such a configuration, when a parasitic conductor is provided in the coil and a part of the coil is covered with the parasitic conductor, electromagnetic coupling is obtained between the coil and the parasitic conductor. The degree of this coupling depends on the distance and area between the two. In addition, the portion covered with the parasitic conductor affects the electromagnetic field due to the antenna current flowing in the coil, and the function as a coil is affected by the parasitic conductor. Therefore, the resonant frequency of the antenna device is adjusted by the parasitic conductor provided in the coil, that is, by the area of the parasitic conductor, the distance between the parasitic conductor and the coil, and the frequency interval of the resonant frequency is adjusted. It is.

[0014] In order to achieve the above object, the parasitic conductor may be arranged at the concentrated portion of the primary resonance current or the high-order resonance current of the coil in the antenna device. .

[0015] When a parasitic conductor is installed in a concentrated portion of the primary resonance current of the coil, the coil function of the portion covered with the parasitic conductor is reduced, and as a result, the coil length is shortened. The resonance frequency increases. In this case, since the higher order resonance frequency is not affected, the frequency interval between the first order resonance frequency and the higher order resonance frequency is narrowed. In addition, when a parasitic conductor is installed at a concentrated part of the higher-order resonance current of the coil, the coil function of the portion covered with the parasitic conductor is reduced, and as a result, the coil length is shortened. Higher order resonance frequency increases. In this case, since the primary resonance frequency is not affected, the frequency interval between the primary resonance frequency and the higher order resonance frequency is widened. Therefore, installation of the parasitic conductors The resonance frequency is adjusted, and the frequency interval of the resonance frequency is narrowed or enlarged depending on the installation position of the parasitic conductor.

[0016] In order to achieve the above object, the parasitic conductor may be a cylindrical body over the antenna device, and may be configured to cover the coil. The parasitic conductor may take any form that covers the coil, but if it is a cylinder, it can be placed on the coil and set at any position, and the resonance frequency of the antenna device can be adjusted and the frequency of the resonance frequency can be set. The interval can be adjusted.

In order to achieve the above object, the antenna device may be configured such that the parasitic conductor is coupled to the coil by bringing the parasitic conductor closer to the coil. As described above, since the distance between the coil and the parasitic conductor changes the degree of electromagnetic coupling between the two, the coupling between the two can be strengthened by bringing them closer together.

[0018] In order to achieve the above object, in the antenna device, a resonance characteristic of the parasitic conductor is coupled to a resonance characteristic of the coil to obtain a resonance frequency of the coil and the parasitic conductor. Moyo! Since the coil and the parasitic conductor each have individual resonance characteristics, by combining them, the resonance frequency of the parasitic conductor is added to the resonance frequency of the antenna device obtained by the coil. Functionalization is planned.

In order to achieve the above object, the parasitic conductor may be installed on the feeding point side of the coil in the antenna device. With such a configuration, it becomes possible to cover the concentrated portion of the primary resonance current described above, and the above-described operation can be obtained.

[0020] In order to achieve the above object, the parasitic conductor may be installed on the open end side of the coil in the antenna device. With such a configuration, it is possible to cover the concentrated portion of the high-order resonance current described above, and the above-described operation can be obtained.

[0021] In order to achieve the above object, in the antenna device, the parasitic conductor includes a slit that exposes the coil. If the coil is exposed from the slit, the electromagnetic coupling between the coil and the parasitic conductor becomes rough, so that the specific resonance frequency can be adjusted to a desired frequency by adjusting the slit. [0022] In order to achieve the above object, the present invention provides a method of adjusting the frequency of an antenna device including a coil, wherein a parasitic conductor is provided along with the coil, and a part of the coil is covered with the parasitic conductor. Thus, the resonance frequency of the coil is adjusted.

[0023] In order to achieve the above object, the present invention provides a frequency adjustment method for an antenna device including a coil, wherein a parasitic conductor is provided in the coil, and a part of the coil is provided by the parasitic conductor. A specific resonance frequency may be set by covering, and a resonance frequency other than the resonance frequency may be adjusted by adjusting a range of the coil covered by the parasitic conductor.

In this antenna device, when a parasitic conductor is provided along with the coil, a part of the coil is covered with the parasitic conductor, so that electromagnetic coupling is obtained between the coil and the parasitic conductor. The degree of this coupling depends on the distance and area between the two. In addition, the portion covered with the parasitic conductor affects the electromagnetic field due to the antenna current flowing in the coil, and the function as a coil is affected by the parasitic conductor. Therefore, the resonant frequency of the antenna device is adjusted by the parasitic conductor provided in the coil, that is, the area of the parasitic conductor, the distance between the parasitic conductor and the coil, and the frequency interval of the resonant frequency is adjusted. .

[0025] In order to achieve the above object, the present invention provides a wireless communication device using an antenna device including a coil, wherein a parasitic conductor is attached to the coil, and the parasitic conductor includes a part of the coil. It is the structure which covered. According to such a configuration, a plurality of resonance frequencies adjusted to a desired frequency by installing a parasitic conductor can be used for wireless communication.

[0026] In order to achieve the above object, in the wireless communication apparatus, the parasitic conductor is arranged at a portion where the primary resonance current or the high-order resonance current of the coil is concentrated. Also good.

In order to achieve the above object, in the wireless communication apparatus, the parasitic conductor is formed of a cylindrical body that covers the coil, and the outer peripheral portion of the coil is covered with the parasitic conductor. It is good also as a structure to be called.

[0028] In order to achieve the above object, in the wireless communication apparatus, the parasitic conductor may be installed on the feeding point side of the coil.

[0029] In order to achieve the above object, the wireless communication device is! It is good also as a structure installed in the position most distant from the feeding point of the said coil.

In order to achieve the above object, the wireless communication apparatus may be configured such that the parasitic conductor includes a slit that exposes the coil.

The invention's effect

[0031] According to the present invention, the following effects can be obtained.

[0032] (1) Regarding an antenna device including a coil, the resonance frequency can be adjusted to a desired frequency by providing a parasitic conductor in the coil and covering a part of the coil with the parasitic conductor. In addition, the frequency interval of the plurality of resonance frequencies can be adjusted to an arbitrary frequency interval.

[0033] (2) If an antenna device capable of adjusting a resonance frequency by providing a parasitic conductor in the coil and adjusting a frequency interval of a plurality of resonance frequencies to an arbitrary frequency interval is used for a radio communication device, The resonance frequency can be matched with a plurality of radio communication frequencies, antenna loss can be reduced, and the efficiency of radio communication can be improved.

[0034] Other objects, features, and advantages of the present invention will become clearer with reference to the accompanying drawings and each embodiment.

Brief Description of Drawings

FIG. 1 is a diagram showing a conventional antenna device.

FIG. 2 is a diagram showing frequency characteristics of the antenna device.

FIG. 3 is a perspective view showing an antenna device. (First embodiment)

FIG. 4 is a diagram showing an antenna device.

FIG. 5 is a diagram showing a configuration of an antenna device.

FIG. 6 is a perspective view showing the configuration of the antenna device.

FIG. 7 is a diagram showing frequency characteristics of the antenna device.

FIG. 8 is a diagram showing an antenna current distribution at the time of primary resonance.

FIG. 9 is a diagram showing an antenna current distribution during secondary resonance.

FIG. 10 is a diagram showing frequency characteristics of the antenna device.

FIG. 11 is a diagram showing the relationship between the distributed constant line and the current distribution.

FIG. 12 is a circuit diagram showing an equivalent circuit of a distributed constant line. FIG. 13 is a diagram showing a coil.

FIG. 14 is a diagram showing a magnetic field distribution of a coil.

FIG. 15 is a diagram showing an antenna device. (Second embodiment)

FIG. 16 is a diagram showing an antenna device. (Third embodiment)

[17] FIG. 17 shows an antenna device. (Fourth embodiment)

FIG. 18 is a diagram showing frequency characteristics of the antenna device.

[19] FIG. 19 is a diagram showing an antenna device. (Fifth embodiment)

FIG. 20 is a diagram showing frequency characteristics of the antenna device.

FIG. 21 shows an antenna device.

圆 22] A diagram showing an antenna device. (Sixth embodiment)

FIG. 23 is a diagram showing coupling by a parasitic conductor between coil conductors.

FIG. 24 is a diagram showing frequency characteristics of the antenna device.

FIG. 25 shows an antenna device.

[26] FIG. 26 is a plan view showing a mobile phone equipped with an antenna device. (Seventh embodiment)

FIG. 27 is a diagram showing an internal configuration.

FIG. 28 is a plan view showing a PDA equipped with an antenna device.

[29] FIG. 29 is a perspective view showing a PC on which an antenna device is mounted.

圆 30] A diagram showing an internal configuration. (Other embodiments)

Explanation of symbols

2 Mobile phone (wireless communication device)

4 Antenna device

10 coils

12 Feed point

16 Parasitic conductor

34 Slit

38 PDA (wireless communication equipment)

40 PC (wireless communication device) BEST MODE FOR CARRYING OUT THE INVENTION

[0037] First embodiment

A first embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a perspective view illustrating an outline of the antenna device 4 in the mobile phone 2, and FIG. 4 is a diagram illustrating a configuration of the antenna device 4.

[0039] In this embodiment, the primary resonance frequency of the antenna device 4 is increased and, for example, the frequency interval between the secondary resonance frequency and the primary resonance frequency is narrowed as a resonance frequency on the higher order side. It is.

[0040] The mobile phone 2 is shown in a simplified manner and is an example of a wireless communication device using a plurality of transmission / reception frequencies. The cellular phone 2 is provided with a circuit board 6, on which a radio unit (not shown) is mounted, and a connection unit 8 for connecting the antenna device 4 is formed. The connecting portion 8 is formed of a conductor pattern formed on the surface of the circuit board 6 by printing or the like, for example.

In this antenna device 4, a helical coil 10 is installed as an antenna element, and a parasitic conductor 16 is provided alongside the coil 10. The parasitic conductor 16 is configured to cover the feeding point 12 side on the outer peripheral side of the coil 10. One end of the coil 10 is set as an open end 18, and the base end 20 side of the other end is set as a feeding point 12. The feed point 12 is connected to the connection portion 8 of the circuit board 6 by a connection method such as soldering, and the antenna device 4 is electrically coupled to a radio unit or the like (not shown) to be fed. The parasitic conductor 16 is made of a conductor and is maintained in a parasitic state. Here, the parasitic state is a state in which the conductor constituting the parasitic conductor 16 is not connected to either the coil 10 or the ground conductor (GND) and is maintained in an electrically floating state. is there.

Regarding the parasitic conductor 16, the material of the parasitic conductor 16 is a conductor for achieving electromagnetic coupling with the coil 10, and is made of a conductive material such as silver, copper, or aluminum.

Further, the parasitic conductor 16 may have any shape such as a cylindrical body, a rectangular tubular body, a cylindrical body, a casing, or the like. In this embodiment, the parasitic conductor 16 is a cylindrical body. For example, a conductor pattern is formed by printing on the surface of a cylindrical body that also has a dielectric strength by placing a conductor in a cylindrical body made of an insulator, and the parasitic conductor 16 is formed as a parasitic conductor 16. Also good. [0044] Regarding the position of the parasitic conductor 16 with respect to the coil 10, the parasitic conductor 16 is any of the proximal end 20 side near the feeding point 12 of the coil 10, the intermediate portion of the coil 10, and the open end 18 side of the coil 10. However, in this embodiment, as shown in FIG. 3 and FIG. 4, it is located near the feed point 12 and on the base end 20 side.

Next, the relationship of the parasitic conductor 16 with respect to the coil 10 will be described with reference to FIG. FIG. 5 shows the configuration of the antenna device 4 according to the first embodiment.

A part of the coil 10 is covered with a parasitic conductor 16 provided alongside the coil 10.

In this embodiment, a part of the coil 10 is covered by the length of the parasitic conductor 16 starting from the base end 20 side of the coil 10 of the parasitic conductor 16. Here, the outer diameter of the coil 10 is D, the distance between the outer surface of the coil 10 and the parasitic conductor 16 is d, the coil length of the coil 10 is Lc, the length of the parasitic conductor 16 is Ln (the parasitic conductor of the coil 10). 16), if the exposed length of the coil 10 exposed from the parasitic conductor 16 is Le, the relationship between Le, Ln, and Lc is

Ln = Lc— Le * · · (1)

It becomes. The exposure length Le is the coil function part of the coil 10, the length Ln of the parasitic conductor 16 is the part that reduces the coil function, and the distance d is the electromagnetic coupling between the coil 10 and the parasitic conductor 16. Affect. In this antenna device 4, when Ln = 0, the equation (1) force Lc = Le is obtained, and as shown in FIG. 6, the antenna device 4 without the parasitic conductor 16 is configured.

[0047] Therefore, referring to Figs. 7, 8, and 9 for antenna device 4 (Fig. 6) without parasitic conductor 16 as antenna device 4 when Ln = 0 and Lc = Le, The frequency characteristics, antenna current distribution of the coil 10 and the like will be described. Fig. 6 is a perspective view showing the antenna device 4 without the parasitic conductor 16, Fig. 7 shows the frequency characteristics of the antenna device 4 without the parasitic conductor 16, and Fig. 8 shows the antenna at the primary resonance. Fig. 9 shows the current distribution, and Fig. 9 shows the antenna current distribution during the secondary resonance.

In the frequency characteristics shown in FIG. 7, the horizontal axis represents the frequency f, the vertical axis represents the voltage standing wave ratio VS WR (Voltage Standing Wave Ratio), al is the primary resonance characteristic, and a2 is the secondary resonance. Characteristics, a3 is the third-order resonance frequency, fal is the first-order resonance frequency, fa2 is the second-order resonance frequency, and fa3 is the third-order resonance frequency. This type of antenna has an odd multiple when the primary resonant frequency fal = f If there are resonance points at the frequencies f, 3f, 5f ···, which are expressed in terms of wavelength, 1 · λ Z4, 3 · λ Z4, 5 · λ Ζ 4 ···.

[0049] Then, in the antenna device 4 in which the parasitic conductor 16 is not installed, the antenna current distribution is obtained in the coil 10 at the primary resonance, as shown in Fig. 8, and the antenna current is generated at the portion ilmax surrounded by the broken line. Become the strongest. In this case, the antenna current exhibits a maximum value in the range of about λ Ζ4 from the feed point 12. Further, the location where the antenna current is concentrated is a point away from the open end 18 of the coil 10 by λ 4. That is, the current concentration is maximized at that point.

Further, at the time of secondary resonance, an antenna current distribution is obtained in the coil 10 as shown in FIG. During secondary resonance, the coil 10 resonates at 3 · λ Ζ4, so the frequency 3'fal, which is three times the primary resonance frequency fal, becomes the secondary resonance frequency fa2 (= 3'fal). At this secondary resonance frequency, the maximum current occurs at a location that is λ Ζ4 away from the open end 18 and current concentration occurs at a location that is 2 λ Ζ4 away from the open end 18, but from the open end 18 The emission of electromagnetic waves with the highest current density is dominant at λ Ζ4. The part i2max surrounded by the broken line is the maximum antenna current during secondary resonance.

Next, in this antenna device 4, when the length Ln of the parasitic conductor 16 is Ln> 0, the antenna device 4 (FIGS. 3 and 4) is provided with the parasitic conductor 16. The frequency characteristics of the antenna device 4 (FIGS. 3 and 4) provided with the parasitic conductor 16 will be described with reference to FIG. In Fig. 10, the horizontal axis represents the frequency f, the vertical axis represents the voltage standing wave ratio VSWR, and as indicated by the broken line, the frequency characteristics al, a2, a 3 of the antenna device 4 without the parasitic conductor 16 installed. (Fig. 7) and the frequency characteristics bl, b2, and b3 of the antenna device 4 with the parasitic conductor 16 installed as shown by the solid line, al and bl are the primary resonance characteristics, a2 and b2 Are secondary resonance characteristics, a3 and b3 are tertiary resonance characteristics, fal and fbl are primary resonance frequencies, fa2 and fb2 are secondary resonance frequencies, and fa3 and fb3 are tertiary resonance frequencies.

[0052] As can be seen from the comparative power of these frequency characteristics, when the parasitic conductor 16 is installed (Figs. 3 and 4), the resonance frequency increases compared to the case without the parasitic conductor 16. The Comparing each resonance frequency with respect to this increase in frequency, the primary resonance frequency fal is increased to the primary resonance frequency fbl, and the increase width Δ ίΐ is Afl = fbl-fal---(2)

It is. In addition, the secondary resonance frequency fa2 slightly rises to the secondary resonance frequency fb2, and the increase width Δί2 is

Af2 = fb2-fa2 = 0---(3)

It is. Accordingly, the magnitude relationship between these rising widths Δί1 and Δί2 is Δί1> Δί2. Therefore, the frequency interval fal2 (= fa2− fal) between the primary resonance frequency fal and the secondary resonance frequency fa2 and the frequency interval fbl2 (= fb2− fbl) between the primary resonance frequency fbl and the secondary resonance frequency fb2 are small or large. The relationship is fbl2 and fal2 from the above described Δί1> Δί2. Therefore, in the antenna device 4 (FIGS. 3 and 4) in which the parasitic conductor 16 is installed, the force that raises both the primary resonance frequency fbl and the secondary resonance frequency fb2 is as follows: Δί1> Δί2 The frequency interval fal2 is adjusted to a narrow frequency interval fbl2.

[0053] The effect of adjusting the frequency interval of each resonance frequency such as the resonance frequency, primary resonance frequency, and secondary resonance frequency of the antenna device 4 will be described in detail.

As shown in FIG. 8, at the time of primary resonance, the antenna current of the coil 10 becomes the strongest on the feeding point 12 side, but this portion ilmax is covered with the parasitic conductor 16. The location where the current concentrates is the maximum at a location away from the open end 18 of the coil 10 by λ 4, but the exposed length Le of the coil 10 exposed from the parasitic conductor 16 is the total length Lc of the coil 10. Since it is shorter, the wavelength at which the coil 10 resonates becomes shorter. For this reason, the primary resonance frequency fbl rises.

[0055] In addition, at the time of secondary resonance, the coil 10 resonates at a wavelength (3 · λ Ζ4), so that three times the primary resonance frequency becomes the secondary resonance frequency fb2. However, since the higher-order resonance frequency of the coil 10 changes due to the coupling between the lines, the secondary resonance frequency fb2 is fb2 = 2.1 [GHz] in the frequency characteristics shown in FIG. The antenna current during resonance at the wavelength (3 · λ Ζ4) of the coil 10 has the current distribution shown in Fig. 9. At the secondary resonance frequency fb2, the open end 18 force of the coil 10 is also the wavelength (1 · λ Ζ4) The current is maximized at a location separated by a distance of, and further, the current is concentrated at a location separated from the open end 18 of the coil 10 by a distance of wavelength (2 · λ Ζ4). Therefore, at the time of secondary resonance, the radiation of electromagnetic waves with the highest current density at the point moved to the feeding point 12 side by the distance of the wavelength (1 · λ Ζ4) from the open end 18 of the coil 10 is dominant. . This Therefore, when the base end 20 side (feeding point 12 side) of the coil 10 is covered with the parasitic conductor 16, there is no influence on the secondary resonance frequency fb2, and the secondary resonance frequency fb2 has little fluctuation. Therefore, by covering the vicinity of the feeding point 12 of the coil 10 with the parasitic conductor 16, it is possible to raise only the primary resonance frequency fbl without causing a change in the secondary resonance frequency fb2. As a result, the frequency interval fbl2 between the primary resonance frequency fbl and the secondary resonance frequency fb2 is narrowed.

Next, the principle of adjusting the resonance frequency of the antenna device 4 and the frequency interval of the resonance frequency will be described with reference to FIG. 11, FIG. 12, FIG. 13, and FIG. Fig. 11 is a diagram showing the relationship between the distributed constant line and the current distribution, Fig. 12 is a circuit diagram showing an equivalent circuit of the distributed constant line, and Fig. 13 is a diagram showing a coil (helical coil) with a line length λλ4. 14 is a diagram showing the magnetic field distribution of the coil.

[0057] As shown in Fig. 11 (Α), the circuit board 22 made of an insulator has a signal line 24 having a conducting force on one side and a ground conductor (GND) having a conducting force on the other side. ) 26 is installed, and these lengths are set to λ 4, and the signal line 24 and GND 26 are set to open ends. In such a signal line 24, as shown in FIG. 12, a distributed constant circuit including an inductor L (= signal line 24) and a capacitor C (= circuit board 22) is formed. Therefore, from the theory of the distributed constant circuit, as shown in FIG. 11B, the electric field is maximum at the open end 28 of the signal line 24 and no current flows, but the wavelength (λ The impedance is zero (short-circuited) at a location separated by Ζ4), and the current is maximum. As a result, the signal line 24 adjusted to the length of the wavelength (λ / 4) functions as a resonator.

Therefore, in the coil 10 shown in FIG. 13, the ground of the circuit board 6 is kept away, but the electrical length of the coil 10 is set to a length that resonates at a length of λ 4, so the coil 10 If the left end is the open end 18 and the right end is the base end 20 and the feed point 12 is set, the impedance is short-circuited and the coil 10 resonates at λ Ζ4.

[0059] When an antenna current flows through the coil 10, as shown in FIG. 14, with respect to the magnetic field generated in the coil 10, the magnetic field density that passes through the inside of the coil 10 (Η and the magnetic field outside the coil 10). Comparing with the density φ ο, φ i> φ o and the magnetic field density of the magnetic field passing through the inside and outside of the coil 10 is different, that is, when the parasitic conductor 16 is installed outside the coil 10, Magnetic field density φ ο acts on parasitic conductor 16 and is not supplied inside coil 10. The degree of influence on the magnetic field distribution of the coil 10 is different from the case where the conductor 14 (FIG. 1) is installed, and the change in the resonance frequency is thereby different.

Therefore, as a method of adjusting the frequency of the antenna device 4, as shown in FIGS. 3, 4 and 5, a parasitic conductor 16 is installed near the feeding point 12 of the coil 10, thereby providing a parasitic conductor. Compared to the case where 16 is not installed, the primary resonance frequency fbl can be increased. Then, with only the coil 10 without the parasitic conductor 16, the secondary resonant frequency fa2 (fb2) is set to the target frequency, for example, fb2 = 2.1 [GHz], and then the parasitic conductor 16 is added. If the length Ln is adjusted, the primary resonance frequency fbl can be set to a desired frequency, for example, fbl = 900 [MHz].

[0061] Further, if the shape of the parasitic conductor 16 installed around the coil 10 is changed, a function of shielding a part of the coil 10 by the parasitic conductor 16 and the electromagnetic of the coil 10 and the parasitic conductor 16 can be obtained. The state of the field coupling can be changed. As a result, the adjustment of the primary resonance frequency and the frequency interval between the primary and secondary resonance frequencies can be arbitrarily varied and set.

[0062] As described above, in the antenna device 4 in which the parasitic conductor 16 is provided on the feeding point 12 side of the coil 10, the primary resonance frequency fbl is increased, and the frequency interval fbl2 between the primary and secondary resonance frequencies is narrowed. Since the function is obtained, such an antenna device 4 can be used for a wireless communication device such as a mobile phone using a plurality of radio frequencies, and the radiation loss of the wireless communication device can be reduced, thereby improving efficiency. be able to.

[0063] Second Embodiment

[0064] A second embodiment of the present invention will be described with reference to FIG. FIG. 15 is a diagram showing an antenna device 4 in which a parasitic conductor 16 is installed together with an insulating cylinder. The same parts as those in the first embodiment (FIGS. 3, 4, and 5) are denoted by the same reference numerals.

This embodiment is a specific configuration example for holding the parasitic conductor 16. In this antenna device 4, for example, a part of the coil 10 is closely attached to the outer peripheral portion thereof. Insulating tube 30 is installed, and parasitic conductor 16 is installed on the outer surface of insulating tube 30. The insulating cylinder 30 is made of an insulating material such as an insulating synthetic resin. Corresponding to the length Ln of the parasitic conductor 16 described above, the insulation cylinder 30 is also set to the same length. The length of the insulation cylinder 30 is different from the length Ln of the parasitic conductor 16. May be. Insulation cylinder 30 If the length is longer than the length Ln of 16, the holding of the parasitic conductor 16 to the coil 10 is stabilized. Further, if the thickness of the insulating cylinder 30 is the above-mentioned distance d, the distance between the outer surface of the coil 10 and the inner surface of the parasitic conductor 16 is regulated by the insulating cylinder 30 so that the uniform distance d can be maintained. it can.

[0066] The parasitic conductor 16 may be formed on the surface of the insulating cylinder 30 by printing or applying a conductive material.

[0067] Third Embodiment

[0068] A third embodiment of the present invention will be described with reference to FIG. FIG. 16 is a diagram showing the antenna device 4 in which the coil 10 and the parasitic conductor 16 are fixed by insulating grease. The same parts as those in the first embodiment (FIGS. 3, 4, and 5) are denoted by the same reference numerals.

This embodiment is a specific configuration example for holding the coil 10 and the parasitic conductor 16. In the antenna device 4, the coil 10 and the parasitic conductor 16 are covered with an exterior part 32. The exterior part 32 is made of an insulating material such as an insulating synthetic resin. The exterior portion 32 is, for example, integral molding (insert molding) using an insulating material, and the coil 10 and the cylindrical parasitic conductor 16 are held therein. In this case, not only the shape of the coil 10 but also the distance d between the outer surface of the coil 10 and the inner surface of the parasitic conductor 16 is firmly held by the exterior portion 32.

[0070] Fourth embodiment

[0071] A fourth embodiment of the present invention will be described with reference to FIG. FIG. 17 is a diagram showing the antenna device 4. In FIG. 17, the same or corresponding parts as those in the first embodiment (FIGS. 3, 4, and 5) are denoted by the same reference numerals.

[0072] This embodiment is an example in which the frequency interval between the primary resonance frequency and the secondary resonance frequency is expanded. Therefore, in this antenna device 4, the parasitic conductor 16 is installed on the open end 18 side of the coil 10, and a part of the coil 10 is the parasitic conductor 16 with the length Ln of the parasitic conductor 16 from the open end 18. Covered and shielded. In this case, if the length Ln of the parasitic conductor 16 is the length of the coil 10, the portion where the intermediate partial force of the coil 10 reaches the base end portion 20 is exposed, and the exposed length is. The installation form of the parasitic conductor 16 may be the second or third embodiment.

The frequency characteristics of the antenna device 4 (FIG. 17) will be described with reference to FIG. Figure In Fig. 18, the horizontal axis represents the frequency f, the vertical axis represents the voltage standing wave ratio VSWR, and the frequency characteristics al, a2, and a3 are the characteristics when the parasitic conductor 16 is not installed (Fig. 7), the frequency characteristics bl , B2 and b3 are characteristics in the case of the antenna device 4 according to this embodiment. In this characteristic, parts corresponding to the characteristics shown in FIG.

As is clear from the comparison power of each frequency characteristic, when the parasitic conductor 16 is installed (FIG. 17), each resonance frequency rises compared to the case where the parasitic conductor 16 is not provided. Comparing each resonance frequency with respect to this increase in frequency, the primary resonance frequency fal is slightly increased to the primary resonance frequency fbl, and the increase width Δ ίΐ is

A fl = fbl-fal = 0

It is. Also, the secondary resonance frequency fa2 has risen significantly to the secondary resonance frequency fb2, and its rise width Δ ί2 is

A f2 = fb2— fa2 >> A fl · '· (5)

It is. In other words, in this antenna device (FIG. 17), the fluctuation of the primary resonance frequency fbl is suppressed and the secondary resonance frequency fb2 is increased, so that the frequency interval fb 12 between the primary resonance frequency fbl and the secondary resonance frequency fb2 is increased. Can be enlarged.

In this antenna device (FIG. 17), the parasitic conductor 16 is installed on the open end 18 side of the coil 10 and the base end 20 side of the coil 10 is exposed. The concentrated part is not affected by the parasitic conductor 16 The change of the primary resonance frequency fbl is suppressed. In addition, at the secondary resonance, the part where the antenna current of the coil 10 is the strongest is covered with the parasitic conductor 16, that is, the current concentrated part at λ Ζ4 of the secondary resonance frequency fb2 is covered with the parasitic conductor 16. Therefore, it is covered with the parasitic conductor 16! /, N! /, The exposed length Le of the coil 10 is short, and the current distribution in that portion is shortened, so the secondary resonance frequency fa2 is set to 2 It can be raised to the next resonance frequency fb2 (Fig. 18). As a result, the frequency interval fbl2 between the primary resonance frequency fbl and the secondary resonance frequency fb2 is widened.

In this case, the third-order resonance frequency fb3 is slightly lower than the third-order resonance frequency fa3, and the frequency interval fb23 is narrower than the frequency interval fa23. The fluctuation range is slight and can be regarded as fb3 = fa3.

[0077] By providing such frequency characteristics, the frequency adjustment method of the antenna device 4 (Fig. 17) As a method, after the primary resonance frequency is set to a target frequency of 900 [MHz] in the coil 10 without the parasitic conductor 16, for example, the parasitic conductor 16 is connected to the open end 18 side of the coil 10. By adjusting the length Ln, the secondary resonance frequency fb2 can be adjusted to, for example, 2.2 [GHz] as a desired frequency.

[0078] Fifth Embodiment

A fifth embodiment of the present invention will be described with reference to FIG. FIG. 19 shows an antenna device.

This embodiment provides a frequency adjustment method for the antenna device 4 by coupling the resonance of the coil 10 and the resonance of the parasitic conductor 16. In this antenna device 4, a parasitic conductor 16 is provided so as to cover the intermediate portion side of the coil 10 from the base end portion 20 of the coil 10. In this case, the parasitic conductor 16 may be installed in the second or third embodiment.

[0081] The relationship between the coil length Lc, the length Ln of the parasitic conductor 16 and the exposed length Le of the coil 10 is as described in the equation (1), and in this case, for example, Ln≥Le is set.

With such a configuration, the frequency characteristics shown in FIG. 20 are obtained. As shown by the solid line in Fig. 20, the horizontal axis is frequency f, the vertical axis is voltage standing wave ratio VSWR, bl (primary resonance characteristic), b2c (secondary resonance characteristic) and b3 (third resonance characteristic). Become. As indicated by the broken line, al (primary resonance characteristic), a2 (secondary resonance characteristic), and a3 (third resonance characteristic) are frequency characteristics of only the coil 10 when the parasitic conductor 16 is not installed. It is. In each characteristic, portions corresponding to the characteristics shown in FIG. Fb2c is the secondary resonance frequency.

In this antenna device 4 (FIG. 19), since the base end 20 side of the coil 10 is covered with the parasitic conductor 16, the force L1 of the parasitic conductor 16 is increased by the force that increases the primary resonance frequency fbl. In other words, the resonance point of the parasitic conductor 16 can be provided in the vicinity of the secondary resonance frequency fb2 by adjusting the length of the resonator composed of the parasitic conductor 16.

Therefore, if the electromagnetic coupling between the parasitic conductor 16 and the coil 10 is strengthened, the resonance of the parasitic conductor 16 can be coupled to the resonance of the coil 10. When these two resonances are combined, the characteristics of both are combined, and the characteristics b2c and b3 are obtained by combining the resonance characteristics of the parasitic conductor 16 with the secondary resonance characteristics of the coil 10. It is. Therefore, the secondary resonance frequency fb 2c is a frequency adjusted by adding resonance of the parasitic conductor 16. In the frequency characteristics shown in FIG. 20, the secondary resonance frequency fb2c is, for example, fb2c = 2 [GHzW resonance point. In order to strengthen the electromagnetic coupling between the coil 10 and the parasitic conductor 16 for obtaining such characteristics, for example, the distance d between the coil 10 and the parasitic conductor 16 may be reduced.

With such a configuration, in this antenna device 4 (FIG. 19), resonance at the feeding point 12 is obtained with a secondary resonance frequency of 2 = 2 [01¾], and the bending force is also not fed. By adjusting the length Ln of the conductor 16, the secondary resonance frequency fb2c can be adjusted to an arbitrary value in the vicinity of 2 [01¾], for example. In the primary resonance, the exposed length Le of the coil 10 is shortened in accordance with the length Ln of the parasitic conductor 16, and therefore the primary resonant frequency fbl is increased by shortening the exposed portion.

Thus, in such an antenna device 4, by using the resonance of the parasitic conductor 16, the secondary resonance frequency fb2c can be set to a desired frequency, and the primary resonance can be achieved by installing the parasitic conductor 16. The frequency fbl can be increased. In addition, even if the length Ln of the parasitic conductor 16 is increased or decreased, the primary resonant frequency fbl does not change, so after setting the primary resonant frequency fb 1 to fbl = 900 [MHz], for example By adjusting the length Ln of the parasitic conductor 16, the secondary resonance frequency fb2c can be adjusted to, for example, around ^ 2 = 2 [01¾], and the resonance point matches the desired two bands. Can be made.

For such a frequency adjustment method, the parasitic conductor 16 is divided into a plurality of parasitic conductors 161, 162... 16η having a short length Li as shown in FIG. A number of parasitic conductors 161, 162 ... 16η are installed in the base, and the length of the parasitic conductor 16 Ln (= Li X n, where n is the parasitic conductor 161, 162 If the number of installations (16η) is adjusted, the secondary resonance frequency fb2c can be adjusted to the desired frequency.

[0088] Sixth Embodiment

A sixth embodiment of the present invention will be described with reference to FIGS. 22 and 23. FIG. 22 is a diagram showing the antenna device 4, and FIG. 23 is a diagram showing the relationship between the coil 10 and the parasitic conductor 16.

This embodiment is achieved by coupling the resonance of the coil 10 and the resonance of the parasitic conductor 16. Thus, a method for adjusting the frequency of the antenna device 4 is provided. In this antenna device 4, a parasitic conductor 16 is provided so as to cover the intermediate portion side of the coil 10 from the base end portion 20 of the coil 10. The parasitic conductor 16 is formed of a cylindrical body, and a plurality of slits 34 are formed in a staggered pattern in the length direction. Also in this case, the parasitic conductor 16 may be installed in the second or third embodiment.

According to such a configuration, the coil 10 covered with the parasitic conductor 16 having the slit 34 formed in the length direction is covered with the portion exposed from the slit 34 and the parasitic conductor 16. The part that has been broken is generated. In the portion exposed from the slit 34 of the coil 10, the function of the coil 10 is obtained, and in the portion partially covered by the parasitic conductor 16, for example, between the conductors 10a and 10b of the coil 10 as shown in FIG. Is obtained with the parasitic conductor 16. In the antenna device 4 (FIG. 22) in which such a parasitic conductor 16 is installed, the primary resonance frequency fbl is lowered. In this antenna device 4, the secondary resonance frequency fb2 is determined by the length Ln of the parasitic conductor 16 as in the fifth embodiment (FIGS. 19 and 20).

In such an antenna device 4 (FIG. 22), the frequency characteristics shown in FIG. 24 are obtained. As shown by the solid line in Fig. 24 (the horizontal axis is frequency f, the vertical axis is voltage standing wave ratio VSWR), bl (primary resonance characteristics), b2c (secondary resonance characteristics) and b3 (third order resonance characteristics) Become. al (l-order resonance characteristics) and a 2 (second-order resonance characteristics) are frequency characteristics of only the coil 10 when the parasitic conductor 16 is not installed. In this frequency characteristic, portions corresponding to those shown in FIG. 20 are denoted by the same reference numerals.

In such an antenna device 4 (FIG. 22), the secondary resonance frequency fb2c is fb2c ^ 2 [GHz]. If the length Ln of the parasitic conductor 16 is changed, only the secondary resonance frequency fb2c can be adjusted without changing the primary resonance frequency fbl.

[0094] As a frequency adjustment method of this antenna device 4 (Fig. 22), after setting the primary resonance frequency fbl as a desired resonance frequency, for example, fbl = 900 [MHz], the length L n of the parasitic conductor 16 Can be adjusted to fb2c = 2 [GHz], for example, as the desired secondary resonance frequency fb2c. Further, as described above, by adjusting the area of the slit 34, for example, adjusting the width, length, or number of the slits 34, and adjusting the degree of coupling between the coil 10 and the parasitic conductor 16, The secondary resonance frequency fbl can be adjusted. Parasitic conductor 16, for example, in Figure 25 As shown, it is possible to achieve the same exposure and shielding function of the coil 10 that are formed in a comb shape and a plurality of slits 34 may be formed.

[0095] Seventh Embodiment

The seventh embodiment of the present invention will be described with reference to FIG. 26, FIG. 27, FIG. 28 or FIG. 26 is a plan view showing the cellular phone 2 equipped with the antenna device 4, FIG. 27 is a diagram showing the interior thereof, and FIG. 28 is a personal digital assistant (PDA: Personal Digital Assistant) equipped with the antenna device 4. FIG. 29 is a perspective view showing a personal computer (PC) 40.

This embodiment is a configuration example of a wireless communication device on which the antenna device 4 is mounted. As shown in FIG. 26, in the mobile phone 2 as a wireless communication device, a plurality of frequencies having different frequencies are used for the wireless communication frequency. In the cellular phone 2, a display unit 44, a plurality of operation units 46 having a key force are installed on the front surface of the housing unit 42, and the antenna device 4 is installed on the top of the housing unit 42. As shown in FIG. 27, the antenna device 4 has the same configuration as that of the first embodiment (FIG. 3). Therefore, the feeding point 12 of the coil 10 is connected to the connection part 8 of the circuit board 6 built in the casing part 42, and the parasitic conductor 16 is installed in the coil 10. Also in this case, as described above, the installation form of the parasitic conductor 16 may be the second or third embodiment.

According to such a configuration, in the mobile phone 2 which is a radio communication device, the resonance frequency of the antenna device 4 can be set to a predetermined plurality of radio frequencies, and electromagnetic waves can be efficiently transmitted and received. it can. In this embodiment, the force coil 10 having a configuration in which the coil 10 of the antenna device 4 is protruded from the housing portion 42 may be incorporated in the housing portion 42.

In addition, as shown in FIG. 28, the PDA 38 having a wireless communication function includes a display unit 50 at the center of the casing 48 and an operation unit 52 having a plurality of key forces below it. The casing unit 48 is provided with an antenna device 4. According to such a configuration, also in the PDA 38, the resonance frequency of the antenna device 4 can be set to a predetermined plurality of radio frequencies, and electromagnetic waves can be transmitted and received efficiently.

Further, as shown in FIG. 29, in the PC 40 having the wireless communication function, the first casing portion 54 and the second casing portion 56 are configured to be openable and closable by the hinge portion 58. Multiple in body 54 A display unit 62 is installed in the operation unit 60 including the keys and the casing unit 56. The antenna device 4 is installed on a side portion of the casing unit 56 and connected to the casing unit 54 or a wireless unit built in the casing unit 56. According to such a configuration, even in the PC 40 having a wireless communication function, the resonance frequency of the antenna device 4 can be set to a predetermined plurality of wireless frequencies, and electromagnetic waves can be efficiently transmitted and received.

[0101] Other embodiments

For example, as shown in FIG. 30, the antenna device 4 may be integrally molded and fixed inside a rectangular parallelepiped exterior portion 32 made of an insulating synthetic resin by a method such as insert molding. Further, the shape of the exterior portion 32 may be a columnar shape.

Further, in the above embodiment, the force described in the case where the length Ln of the parasitic conductor 16 is increased or decreased with respect to the coil 10. The exposed length Le of the coil 10 is increased or decreased with respect to the parasitic conductor 16. Alternatively, the coil length Lc of the coil 10 may be increased or decreased.

[0104] As described above, the most preferred embodiment of the present invention has been described. However, the present invention is not limited to the above description, but is described in the claims or the invention is carried out. It goes without saying that various modifications and changes can be made by those skilled in the art based on the gist of the invention disclosed in the best mode, and such modifications and changes are included in the scope of the present invention. ,.

Industrial applicability

[0105] The present invention relates to an antenna device including a coil, and a parasitic conductor is provided in the coil, and by covering a part of the coil with the parasitic conductor, the shape, area, position of the parasitic conductor, Depending on factors such as the distance to the coil, the resonant frequency can be adjusted, the frequency interval of different resonant frequencies can be adjusted, etc., and multiple different resonant frequencies can be set and adjusted. It is suitable for a wireless communication apparatus using a frequency.

Claims

The scope of the claims

[1] An antenna device including a coil,

An antenna apparatus, wherein a parasitic conductor is provided alongside the coil, and a part of the coil is covered with the parasitic conductor.

[2] The antenna device according to claim 1, wherein the parasitic conductor is arranged at a portion where the primary resonance current or the higher-order resonance current of the coil is concentrated.

[3] The antenna device according to claim 1, wherein the parasitic conductor is a cylindrical body and is placed on the coil.

4. The antenna device according to claim 1, wherein the parasitic conductor is coupled to the coil by causing the parasitic conductor to approach the coil.

[5] The antenna device according to claim 1, wherein a resonance frequency of the parasitic conductor is coupled to a resonance characteristic of the coil to obtain a resonance frequency of the coil and the parasitic conductor.

[6] The antenna device according to claim 1, wherein the parasitic conductor is disposed on a feeding point side of the coil.

[7] The antenna device according to claim 1, wherein the parasitic conductor is disposed on an open end side of the coil.

[8] The antenna device according to claim 1, wherein the parasitic conductor includes a slit that exposes the coil.

[9] A method of adjusting the frequency of an antenna device including a coil,

The coil is provided with a parasitic conductor, and the resonance frequency of the coil is adjusted by covering a part of the coil with the parasitic conductor.

A method for adjusting the frequency of an antenna device, comprising:

[10] A method for adjusting the frequency of an antenna device including a coil,

By providing a parasitic conductor in the coil and covering a part of the coil with the parasitic conductor, a specific resonance frequency is set,

The resonance frequency other than the resonance frequency is adjusted by adjusting the range of the coil covered with the parasitic conductor. A method for adjusting the frequency of an antenna device.

[11] A wireless communication device using an antenna device including a coil,

A wireless communication apparatus, wherein a parasitic conductor is provided alongside the coil, and a part of the coil is covered with the parasitic conductor.

12. The wireless communication device according to claim 11, wherein the parasitic conductor is arranged at a portion where the primary resonance current or the high-order resonance current of the coil is concentrated.

13. The wireless communication device according to claim 11, wherein the parasitic conductor is configured by a cylindrical body that covers the coil, and an outer peripheral portion of the coil is covered by the parasitic conductor.

14. The wireless communication device according to claim 11, wherein the parasitic conductor is installed on a feeding point side of the coil.

15. The wireless communication apparatus according to claim 11, wherein the parasitic conductor is installed at a position farthest from a feeding point of the coil.

16. The wireless communication device according to claim 11, wherein the parasitic conductor includes a slit that exposes the coil.