WO2006062215A1

WO2006062215A1 - Antenna device

Info

Publication number: WO2006062215A1
Application number: PCT/JP2005/022712
Authority: WO
Inventors: Kenichi Mitsugi; Ryo Horie; Fusao Sekiguchi; Tetsuya Shimazaki
Original assignee: Yokowo Co., Ltd.
Priority date: 2004-12-06
Filing date: 2005-12-05
Publication date: 2006-06-15
Also published as: JP2006165834A

Abstract

An antenna device employing an inverted-F antenna capable of resonating in a plurality of frequency bands and having an antenna efficiency scarcely degrading even in a low frequency band. The antenna device comprises an inverted-F antenna where a radiation electrode (12) is disposed generally parallel with an earth conductor (10), spaced apart therefrom, and provided with an open end and one earth end short-circuited to the earth conductor (10) and a feeding electrode (20) is connected with a feeding point (16) provided between the open end and the earth end, and a switching circuit means (18) formed by connecting an inductive circuit (24) parallel with a switch means (22) the conduction of which is controlled. The switching circuit means (18) is interposed between the feeding point (16) of the radiation electrode (12) and the feeding electrode (20). When the antenna device resonates in a low frequency band, the switch means (22) does not conduct so that the inductive circuit (24) is connected to the radiation electrode (12) and the insertion loss is not caused by the switch means (22).

Description

Description Antenna Device Technical Field

The present invention relates to an antenna device that is small and can be used in a plurality of frequency bands and can be used for multimedia so that it can be incorporated in a portable radio such as a cellular phone or a mobile radio. . Background art

In recent years, mobile radios such as mobile phones and mobile radios have made remarkable progress. In particular, the miniaturization has been remarkable, and it has been rapidly becoming multimedia T such as being able to handle sound, image, data communication, and multiple carriers. ing. Therefore, it is desirable that the antenna built in these devices is small and can be used in a plurality of frequency bands to be compatible with multimedia. Inverted F antennas are known as antennas suitable for such miniaturization. In addition, various techniques have been proposed for making the inverted F antenna multiband by switching the frequency band that resonates with the switch means.

For example, in the prior art disclosed in Japanese Patent No. 3 1 1 2 8 1 5, the shape of the short-circuit electrode that electrically short-circuits the radiating electrode of the inverted F antenna to the ground conductor is substantially changed by switching the switch means. The frequency band that resonates is switched by switching the frequency. In addition, the technology disclosed in Japanese Patent No. 3 4 8 2 0 8 9 uses a capacitive coupling between the radiating electrode and the feeding electrode at the feeding point of the inverted F antenna, and this coupling capacitance is switched using a switching means. By switching, the resonant frequency band is switched. The technology disclosed in Japanese Patent No. 3 4 3 0 1 4 0 resonates by switching the position where the radiation electrode is conductively short-circuited to the ground conductor, or by switching the impedance of the ground point. The frequency band is switched. Technical issues In the above-described conventional technology, the frequency band in which the inverted F antenna resonates can be switched by the switch means, which is suitable for downsizing and multibanding. However, a major problem is that the antenna efficiency is lowered due to the insertion loss caused by the switching means interposed to switch and control the resonating frequency band. In particular, the antenna efficiency in the low frequency band is reduced. .

The present invention has been made in order to improve the problems of the prior art as described above, and uses an inverted-F antenna that can resonate in a plurality of frequency bands and can alleviate a decrease in antenna efficiency in a low frequency band. The purpose is to provide an antenna device. Disclosure of the invention

In the antenna device of the present invention, a radiation electrode is disposed substantially in parallel with the ground conductor and spaced apart, and an open end is provided on the radiation electrode and one ground end that is electrically short-circuited to the ground conductor is provided. Switching circuit means formed by connecting an inductive circuit in parallel to a reverse F antenna having a feeding electrode connected to the grounding end connected to a feeding point and a switching means for controlling conduction and non-conduction. The switching circuit means is inserted in series with the radiation electrode at or near the feeding point, or in series with or near the feeding point and the feeding electrode. It is configured to intervene. Therefore, the switching circuit means interposed at or near the feeding point causes the inductive circuit to be interposed or short-circuited by the conduction and non-conduction of the switching means, and the antenna effective length of the radiation electrode changes, and each of the different It can resonate in the frequency band. And, when the switch means is interposed in the radiation electrode, the antenna efficiency of the relatively lower frequency band deteriorates due to the insertion loss, but in the present invention, when resonating in the lower frequency band, The switch means is non-conductive to increase the effective antenna length by interposing an inductive circuit, there is no insertion loss, and the antenna efficiency does not deteriorate. Further, in the present invention, the antenna efficiency that is most excellent from the experimental data is obtained by interposing the switching circuit means at or near the feeding point. In addition, since the inductive circuit is interposed at or near the feeding point where the value of the flowing current is relatively large, the frequency band that resonates due to the conduction and non-conduction of the switch means can change greatly. The switch means may be formed of a semiconductor switch element whose conduction and non-conduction are controlled by a control signal given from the outside, and the GND terminal of the semiconductor switch element may be connected to the radiation electrode. Since the GND terminal of the semiconductor switch element as the switch means is connected to the radiation electrode, the GND terminal line acts as a part of the radiation electrode to increase the electrical area of the antenna and increase the antenna gain accordingly. . If this GND terminal line is connected to the ground conductor, the GND terminal line acts as an unnecessary reactance and causes a decrease in antenna efficiency, but such a problem does not occur.

In addition to the inductive circuit, a second inductive circuit for eliminating the stray capacitance between the terminals when the switch means is controlled to be non-conductive is connected in parallel to the switch means. You can also. Since the stray capacitance between terminals when the switch means is non-conductive is canceled by the second inductive circuit, it is possible to prevent the deterioration of isolation due to the stray capacitance between terminals when the switch means is non-conductive.

Furthermore, the inductive circuit may be formed on the same surface as the radiation electrode by a distributed constant circuit. By forming the inductive circuit as a distributed constant circuit on the same surface as the radiation electrode, the inductive circuit and the radiation electrode can be formed in the same process.

The inductive circuit may be configured by using a surface mount element of a lumped constant circuit and being disposed on the same substrate as the semiconductor switch element. By arranging the inductive circuit on the same substrate as the semiconductor switch element using the surface mounted element of the centralized distributed constant circuit, the switching circuit means can be formed on one substrate.

In addition, a series circuit is formed by interposing a third inductive circuit, a capacitive circuit, or a resonance circuit in series with the switch means, and the switching is performed by connecting the inductive circuit in parallel to the series circuit. Circuit means can also be constructed. By interposing a third inductive circuit, capacitive circuit, or resonant circuit in series with the switch means, these circuits allow phase adjustment and matching adjustment to the frequency band in which the switch means resonates when conducting. Can be planned.

Further, the radiation electrode may be configured to have two or more open ends and one ground end having different antenna effective lengths'. The effective antenna length is different for the radiation electrode 2 By providing the above open ends, the radiation electrode itself can resonate in two or more frequency bands, and by this and switching of the resonating frequency band by the switching circuit means, it can resonate in four or more frequency bands. .

The switching circuit means can be configured such that any one of two or more inductive circuits having different constants and conduction can be selected by the switch means. One switching circuit means can be selected by appropriately selecting the circuit by enabling the switching circuit means to select any one of two or more inductive circuits having different constants and conduction by the switching means. The frequency band that resonates can be switched to a plurality. Brief Description of Drawings

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

FIG. 2 is a circuit configuration diagram of the antenna device of FIG.

FIG. 3 is a circuit diagram of the switching circuit means of FIG.

FIG. 4 is a mounting external view of the unit of the switching circuit means of FIG.

Fig. 5 shows the V S WR characteristics of the antenna device of Fig. 1.

FIG. 6 is an antenna efficiency characteristic graph with respect to frequency change of the antenna apparatus of FIG. Fig. 7 is an antenna efficiency characteristic diagram when the position of the switching circuit means is inserted in series with the feed electrode and the position is changed.

FIG. 8 is a characteristic diagram showing the change width of the frequency when the position of the switching circuit means is changed in series with the power supply electrode. '

Figure 9 shows the antenna efficiency characteristics for frequency changes when the GND terminal line of the switch means is connected to the radiation electrode and to the ground conductor.

FIG. 10 is a diagram showing an example of the dimensions of the antenna device of the present invention.

FIG. 11 is a diagram showing positions where the antenna device of the present invention can be disposed when used in a mobile phone.

FIG. 12 is another circuit diagram of the switching circuit means used in the antenna device of the first embodiment of the present invention.

FIG. 13 is still another circuit diagram of the switching circuit means used in the antenna device of the first embodiment of the present invention. FIG. 14 is a diagram showing another structure of the radiation electrode that can be used in the antenna device of the present invention. '

FIG. 15 is a circuit configuration diagram of the second embodiment of the antenna device of the present invention.

FIG. 16 is a structural external view of a third embodiment of the antenna device of the present invention.

FIG. 17 is a circuit configuration diagram of the antenna device of FIG.

FIG. 18 is a circuit diagram of the switching circuit means of FIG.

Fig. 19 is a circuit configuration diagram for measuring the antenna efficiency and frequency change width depending on the position of the switching circuit means by placing the switching circuit means away from the feeding point in series with the radiation electrode. .

FIG. 20 is an antenna efficiency characteristic diagram according to the position of the switching circuit means.

FIG. 21 is a characteristic diagram showing the frequency change width according to the position of the switching circuit means. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of the present invention will be described with reference to FIG. 1 to FIG. FIG. 1 is an external view of the configuration of a first embodiment of an antenna device according to the present invention. FIG. 2 is a circuit configuration diagram of the antenna device of FIG. FIG. 3 is a circuit diagram of the switching circuit means of FIG. FIG. 4 is an external view of the mounting unit of the switching circuit means of FIG. Fig. 5 shows the V S WR characteristics of the antenna device of Fig. 1. FIG. 6 is an antenna efficiency characteristic diagram with respect to frequency change of the antenna apparatus of FIG. FIG. 7 is an antenna efficiency characteristic diagram when the position of the switching circuit means is inserted in series with the feed electrode and the position thereof is changed. FIG. 8 is a characteristic diagram showing the change width of the frequency when the position of the switching circuit means is inserted in series with the feeding electrode and the position thereof is changed. Fig. 9 is an antenna efficiency characteristic diagram with respect to frequency changes when the GND terminal line of the switch means is connected to the radiation electrode and to the ground conductor. FIG. 10 is a diagram showing an example of the dimensions of the antenna device of the present invention. FIG. 11 is a diagram showing positions where the antenna device of the present invention can be disposed when used in a mobile phone.

1 to 4, the antenna device according to the first embodiment of the present invention includes a radiation electrode made of a flat conductive metal plate or a conductive metal film with an interval substantially parallel to the flat ground conductor 10. 1 2 is arranged. This radiation electrode 1 2 is made of a dielectric material. The rear (not shown) is appropriately supported and arranged. Then, the grounding conductor 10 is short-circuited to the grounding conductor 10 by the short-circuit electrode 14 at one ground end at the edge of the radiation electrode 12, and the feeding point 16 force S and the switching circuit means 18 provided at another part of the edge are connected in series. And connected to one end of the feeding electrode 20. The other end of the power feeding electrode 20 is connected to an antenna input / output terminal (not shown) such as a wireless transmission / reception circuit. As shown in FIG. 2, the switching circuit means 18 is configured in parallel with the switch means 22 composed of a semiconductor switch element or the like in which conduction and non-conduction are appropriately controlled by a control signal given from the outside. It is formed by connecting inductive circuits 24 of centralized constant circuit elements. More specifically, as shown in FIG. 3, the switch means 22 and the inductive circuit 24 are connected in parallel, one end of which is connected to the feeding point 16 of the radiation electrode 12 and the other end is connected to one end of the feeding electrode 20. Connected. Further, the line 26 of the control terminal of the switch means 22 is connected to the control signal terminal via the high impedance element 28. Further, the line 30 of the GND terminal of the switch means 22 is connected to the feeding point 16.

The switch means 22, the inductive circuit 24, and the high-impedance element 28 are all surface-mounted elements, and are mounted on a switching circuit board 32 composed of a single low-temperature fired ceramic laminated board as shown in FIG. Then, the feeding electrode side terminal 34, the radiation electrode side terminal 36 and the control signal terminal 38 are drawn out to the edge of the switching circuit board 32, respectively. Therefore, the switching circuit board 32 can be easily disposed on the side surface of the carrier that supports the radiation electrode 12 disposed on the top surface. Moreover, the feeding electrode side terminal 34, the radiation electrode side terminal 36 and the control signal terminal 38 provided on the edge of the switching circuit board 32 are arranged on the same plane as the feeding point 16 of the radiation electrode 12 and the ground conductor 10. The antenna input / output terminal and control signal output terminal (both not shown) of the wireless transmitter / receiver circuit can be easily soldered with the shortest lead. In addition to the widely used Schottky diode, the semiconductor switch element has a PIN diode when importance is placed on isolation, and FET and SW-IC when low current operation is important. If it is important, a MEMS switch can be used. The switch circuit configuration includes S PDT (S ingle Pole Double Throw), SP 3T (S ingle Pole 3 Throw), SP 4T (S ingle Pole 4 Th row) Multiple route selections such as W) may be used.

In the antenna device of the present invention, as shown in FIG. 10, the size of the ground conductor 10 is 10 Omm × 4 Omm, and one end of the rectangle is 14.5 mm.X 34.5 mm. The radiation electrode 12 is arranged at a position of 4. Omm in size and the height from the ground conductor 10. The radiation electrode 12 is set to have a length force S from the feeding point 16 to the open end, approximately 1Z4 wavelength of 95 MHz as an example of a high frequency band. The inductance value of the inductive circuit 24 is set so that the effective length of the antenna connected to is approximately 1Z4 wavelength of 89 MHz as an example of a low frequency band. Here, the length from the feed point 16 to the open end of the radiation electrode 1 2 is approximately (2 n + 1)-X / (n = 0, 1, 2 ... for the high frequency band, and λ is It may be set to the wavelength of the high frequency band to be used.

In this configuration, as shown in FIG. 5, the V S WR characteristics resonating in the two frequency bands of 9 5 OMH ζ and 8 9 OMH ζ were obtained by the conduction and non-conduction of the switch means 22. In addition, as shown in Fig. 6, a relatively high antenna efficiency of about 75% is obtained for both 95 OMH ζ and 8 9 OMH ζ. In particular, the antenna efficiency in the low frequency band of 8 9 OMH ζ is almost the same as that of the high frequency band of 9 5 OMH ζ. .

By the way, in the first embodiment, the switching circuit means 18 is interposed between the feeding point 16 of the radiation electrode 12 and the feeding electrode 20, but the inventors have changed the switching circuit means 18 to The antenna efficiency characteristics and frequency change characteristics were measured experimentally when the feed electrode 20 was inserted in series and the position was separated from the feed point 16. The antenna efficiency was almost constant as shown in Fig. 7. In addition, as shown in Fig. 8, the change width of the frequency due to conduction and non-conduction of the switch means 22 is almost constant until it is separated from the feeding point 16 by about 164 wavelengths in the high frequency band. It is recognized that it gradually decreases when the value is exceeded. From these experimental data, it is clear that the switching circuit means 18 can be located at any position on the feeding electrode 20 as long as it is within the range of 1/64 wavelength from the feeding point 16. It was.

In the first embodiment, the line 30 of the GND terminal of the switch means 22 is the feeding point. Although the antenna efficiency is compared with the case where this GND terminal line 30 is connected to the ground conductor 10, the structure of the first embodiment of the present invention is superior as shown in FIG. It is clear that This is because by connecting the GND terminal line 30 to the feeding point 16, the GND terminal line 30 acts as a part of the radiation electrode 12, and the antenna area is expanded, thereby improving the antenna efficiency. On the other hand, if the GND terminal line 30 is connected to the ground conductor 10, this GND terminal line 30 acts as an unnecessary reactance component, and it is assumed that the antenna efficiency is reduced. Is done. In the first embodiment, the GND terminal line 30 is connected to the feed point 16 in order to reduce the number of circuit connection points. However, the present invention is not limited to this, and the GND terminal line 30 is connected to the radiation electrode 12. It should be. 'And, for example, if the antenna device of the present invention is used as a built-in antenna of a mobile phone, as shown in Fig. 11, both ends 4 2 and 4 4 or a lid 4 6 of the case 40 of the mobile phone are shown. It may be arranged in one place, such as the free end part 48 of the ^.

Here, another circuit diagram of the switching circuit means used in the antenna device of the first embodiment of the present invention is shown in FIG. The switching circuit means 50 shown in FIG. 12 differs from the switching circuit means 18 shown in FIG. 3 in that, in addition to the inductive circuit 24, the second inductive circuit is connected in parallel with the switch means 22. 5 2 is connected. The second inductive circuit 52 is set to a value that cancels the inter-terminal stray capacitance Co generated between the terminals when the switch means 22 is non-conductive. Since the inductance value of the second inductive circuit 52 is extremely larger than the inductance value of the inductive circuit 24, they are arranged separately. Depending on the size of the stray capacitance between terminals, the inductive circuit 24 and the second inductive circuit 52 may be shared by one circuit.

Furthermore, FIG. 13 shows still another circuit diagram of the switching circuit means used in the antenna device of the first embodiment of the present invention. The switching circuit means 5 4 shown in FIG. 13 differs from the switching circuit means 1 8 shown in FIG. 3 in that a third inductive circuit, capacitive circuit, resonant circuit, etc. in series with the switch means 2 2 5 6 A series circuit is formed by interposing the inductive circuit 24 in parallel with this series circuit. This third inductive circuit or capacitive circuit or resonant circuit 56 is suitable for fine adjustment such as phase adjustment and matching adjustment for the frequency band that resonates when switch means 22 is conducted. so is there. In FIG. 13, the switch means 2 2 is interposed on the power feeding electrode 20 side, but the present invention is not limited to this, and may be connected in series on the power feeding point 16 side, and the third inductive circuit or Capacitive circuit or resonant circuit 5 6 may be appropriately divided and connected in series to both ends of switch means 22 respectively.

Incidentally, another structure of the radiation electrode that can be used in the antenna device of the present invention is shown in FIG. The radiation electrode 60 shown in FIG. 14 has a monopole shape. Depending on the bandwidth used, the monopole radiation electrode 60 shown in FIG. 14 and the flat radiation electrode 12 shown in FIG. 1 may be appropriately selected and used. Compared to the monopole radiation electrode 60, it is known that a flat radiation electrode 12 having a larger radiation electrode area can provide a wider band.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 15 is a circuit configuration diagram of a second embodiment of the antenna device of the present invention. In FIG. 15, the same or equivalent members as those shown in FIGS. 1 to 3 are denoted by the same reference numerals, and redundant description is omitted.

In the antenna device shown in FIG. 15, the radiation electrode 70 has two open ends 7 0 a and 70 b having different electrical lengths from the feeding point 16. A switching circuit means 72 is interposed between the feeding point 16 and the feeding electrode 20. The switching circuit means 72 is formed so that the switch means 74 can selectively connect either inductive circuits 76, 78 having different two constants. Needless to say, the switch means 72 is externally supplied with a control signal for controlling which one of the inductive circuits 76, 78 having different two constants is selected.

In the antenna device having the structure shown in Fig. 15, the radiation electrode 70 itself can resonate in two frequency bands, and the switching circuit means 72 can change the electrical length of the radiation electrode 70 in three ways. As a whole, it can be used for six frequency bands. Therefore, it is suitable for multiband. The number of open ends of the radiation electrode 70 is not limited to two, but may be three or more, and the number of inductive circuits having different constants that can be selected by the switching circuit means 72 is limited to two. Of course, three or more may be used.

Furthermore, a third embodiment of the present invention will be described with reference to FIGS. Figure 1 FIG. 6 is an external view of the configuration of a third embodiment of the antenna apparatus of the present invention. FIG. 17 is a circuit configuration diagram of the antenna device of FIG. FIG. 18 is a circuit diagram of the switching circuit means of FIG. FIG. 19 is a circuit configuration diagram for measuring the antenna efficiency and the frequency variation depending on the position of the switching circuit means by interposing the switching circuit means away from the feeding point in series with the radiation electrode. FIG. 20 is an antenna efficiency characteristic diagram according to the position of the switching circuit means. FIG. 21 is a characteristic diagram showing the change width of the frequency depending on the position of the switching circuit means. In FIGS. 16 to 19, the same or equivalent members as those shown in FIGS. 1 to 3 are denoted by the same reference numerals and redundant description is omitted.

In FIGS. 16 to 18, the radiation electrode 1 2 is arranged by a carrier 80 made of a dielectric material at a distance approximately parallel to the ground conductor 10, but the radiation electrode 1 is provided on the feeding point 16 side. An inductive circuit 82 consisting of a distributed constant circuit on the same plane as 2 is formed of a conductive metal plate or a conductive metal film. The inductive circuit 82 and the switch means 22 are connected in parallel to form a switching circuit means 84, which is interposed between the feeding point 16 and the feeding electrode 20. By forming the inductive circuit 8 2 as a distributed constant circuit on the same plane as the radiating electrode 12 in this way, the radiating electrode 12 and the inductive circuit '8 2 can be molded in the same process, making it suitable for mass production. It is.

By the way, the switching circuit means 8 4 is not limited to the one interposed between the feeding point 16 and the feeding electrode 20 of the radiating electrode 12 as shown in FIGS. As shown in the figure, it is conceivable that the radiating electrode 12 is interposed in series at a distance from the feeding point 16 toward the open end. Therefore, the inventors experimentally measured the structure shown in FIG. 19 by shifting the position of the switching circuit means 84 to the open end side by the distance d. Then, as shown in Fig. 20, the antenna efficiency is a good value of about 80% when it is located at the feed point 16, but it rapidly deteriorates with distance and then further away. Measurement data was obtained that gradually improved. Also, as shown in Fig. 21, the frequency change with respect to the change in distance d is almost constant until it is about 1/6 wavelength away from the feed point 16 toward the open end, but 1/6 4 A gradual decrease is observed beyond the wavelength. The reason why the antenna efficiency deteriorates suddenly when the switching circuit means 8 4 moves away from the feed point 16 to the open end side is that the antenna current and its phase change suddenly in the switching circuit means 8 4. Presumed to be. Also switch to open end side The frequency change width becomes smaller as the circuit means 84 is located, because the antenna current value becomes smaller toward the open end side, so that the effect of the inductive circuit 8 2 acting as an inductance component is reduced. Conceivable. From these experimental measurement data of FIG. 20 and FIG. 21, the switching circuit means 84 must be arranged at the feeding point 16, but when actually mounted on a mobile phone or the like, In some cases, the position of the actual feed point 16 must be moved and adjusted due to the influence of other metal parts in the housing. For example, the position of the switching circuit means 84 may be shifted from the feeding point 16 toward the open end.

In the above-described embodiment, the radiation electrode and the feeding electrode are shown as a flat plate or a flat plate with a notch, but are not limited to this, and the meander shape is formed in a folded shape. It may be a thing. Also, the inductive circuit 8 2 formed as a distributed constant circuit is shown as a flat plate with a notch, but is not limited to this, and is formed in a meander shape or a folded shape. There may be. Furthermore, it will be readily understood that in the above embodiments, the inductive circuit may be formed of either a lumped constant circuit or a distributed constant circuit. '' Industrial applicability

As described above, the antenna device according to the present invention has a radiation electrode provided with a radiation electrode substantially parallel to and spaced from the ground conductor, and is electrically short-circuited to the radiation electrode with an open end and the ground conductor. An inductive circuit is connected in parallel to an inverted F antenna in which a feeding electrode is connected to a feeding point provided between the open end and the grounding end, and a switching means in which conduction and non-conduction are controlled. The switching circuit means is formed, and the switching circuit means is interposed in series with the radiation electrode at or near the feeding point, or the feeding electrode between or near the feeding point and the feeding electrode. Inductive circuits can be interposed or short-circuited by switching means on and off by the switching circuit means interposed at or near the feed point. Radiant electrode Na effective length is changed, it can be resonant different in each of the frequency bands. When resonating in a low frequency band, the effective length of the antenna is increased by interposing an inductive circuit. The switch means is non-conductive, has no insertion loss, and the antenna efficiency is reduced. There is no. In addition, the best antenna efficiency is obtained from the experimental data by interposing the switching circuit means at or near the feed point. In addition, since the inductive circuit is interposed at or near the feeding point where the value of the flowing current is relatively large, the frequency band that resonates can be greatly changed by the conduction and non-conduction of the switch means.

Therefore, in the present invention, it is possible to provide an antenna device using an inverted F antenna that can resonate in a plurality of frequency bands and can alleviate a decrease in antenna efficiency for a low frequency band. It is suitable as an antenna device that can be built in a portable radio device or a mobile radio device, is small, can be used in a plurality of frequency bands, and can support multimedia.

Claims

The scope of the claims

1. A radiation electrode is disposed substantially in parallel with the ground conductor and spaced apart, and the radiation electrode is provided with one ground end that is electrically short-circuited to the open end and the ground conductor, and the open end and the ground end And a switching circuit means formed by connecting an inductive circuit in parallel to a switching means whose conduction and non-conduction are controlled. It is configured to be interposed in series with the radiation electrode at or near the feeding point, or in series with the feeding electrode between or near the feeding point and the feeding electrode. Antenna device.

2. The antenna device according to claim 1, wherein the switch means is formed of a semiconductor switch element whose conduction and non-conduction are controlled by a control signal given from the outside, and the GND terminal of the semiconductor switch element is used as the radiation electrode. An antenna device characterized by being connected.

3. The antenna device according to claim 1, wherein, apart from the inductive circuit, the switch means includes a second inductive circuit for canceling a floating capacitance between terminals when the switch means is controlled to be non-conductive. An antenna device characterized by being connected in parallel with the antenna device.

4. The antenna device according to claim 1, wherein the inductive circuit is formed on the same plane as the radiation electrode by a distributed constant circuit.

5. The antenna device according to claim 2, wherein the inductive circuit is configured by using a surface mount element of a lumped constant circuit and being disposed on the same substrate as the semiconductor switch element.

6. The antenna device according to claim 1, wherein a series circuit is formed by interposing a third inductive circuit, a capacitive circuit, or a resonant circuit in series with the switch means, and the inductive property in the series circuit. An antenna device characterized in that the switching circuit means is configured by connecting circuits in parallel.

7. The antenna device according to claim 1, wherein the radiation electrode is configured to have two or more open ends having different antenna effective lengths and one ground end.

8. The antenna device according to claim 1, wherein the switching circuit means is configured such that any one of two or more inductive circuits having different constants and conduction can be selected by a switch means. apparatus.