JPH1146115A - Tuning slot antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the resonance frequency of an antenna in a wide range while keeping matching conditions of the antenna by providing an island-shaped conductor that is isolated from a conductor box in a slot and connecting a circuit that can change a capacitance between both conductors between the island-shaped conductor and a wall surface of the conductor box. SOLUTION: An island-shape conductor 20 is provided in a slot 2. A variable capacity circuit 16 connects one of a pair of terminals in which inter-terminal capacity changes to the conductor 20, the other to a wall surface of a flat conductor box 1, and one end of a control line 30 to a terminal to which a control signal to change inter-terminal capacity is applied. The other end of the line 30 is connected to a control circuit 50, and a capacity value between the conductor 20 and the box 1 can be changed by changing a control signal that is supplied from the circuit 50. This makes it possible to equivalently change band-shaped conductor length and slot length which are just under the slot at the same time and to change an impedance matching center frequency (resonance frequency) of an antenna in a wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna suitable for use in a portable radio terminal, and more particularly, to a slot antenna using a coaxial resonator.

[0002]

2. Description of the Related Art Portable wireless terminals have been reduced in size and thickness from the viewpoint of improving portability, and at the same time, various types of small antennas to be mounted on such terminals have been developed. Among them, a slot antenna using a coaxial resonator has a feature that it can be built in without a protrusion, and in particular, its center conductor (band-shaped conductor) is insulated from a resonator outer box (flat conductor box). Japanese Patent Application No. 7-227959 proposes a coaxial resonance type slot antenna which is miniaturized by a contacting structure.

[0003] Since the antenna includes a resonator structure,
The volume and the impedance matching band are directly proportional. Therefore, when the present invention is applied to a terminal of a broadband wireless communication system having a large capacity using a plurality of carrier frequencies, there is a problem that an impedance matching frequency band to be provided for the antenna is expanded and the volume of the antenna is increased.

[0004] Usually, the frequency used for communication between a specific base station and a terminal is extremely narrower than the frequency band of the entire system. Therefore, by changing the impedance matching center frequency of the antenna adaptively to the frequency used at the time of a call each time a call is made, the frequency band to be provided for the antenna can be reduced and the volume of the antenna can be reduced. As such an antenna, in a slot antenna using a coaxial resonator, a variable capacitance is provided between a point near the end including a far end of the band-shaped conductor from which a high-frequency power is supplied and a wall surface of the flat conductor box. Japanese Patent Application No. 9-5482 discloses a tuned slot antenna which can change the impedance matching center frequency of an antenna by connecting elements and changing the capacitance value of a variable capacitance element.
Proposed by five applications. FIG. 10 shows an example of the structure.
Shown in

[0005] The antenna comprises a flat conductor box 1 which is a rectangular parallelepiped as a whole, and an elongated strip-shaped conductor 3 disposed along the resonance axis direction of the internal space of the conductor box and insulated from the flat conductor box 1. A coupling portion 10 provided in the band-shaped conductor 3 and a slot 10 for transmitting and receiving radio waves formed on the upper surface of the flat-shaped conductor box 1 so as to intersect with the band-shaped conductor 3.
High-frequency power is supplied from the high-frequency power supply circuit 7 to the wall surface. A variable capacitance element 6 is connected between a point near the end of the band-shaped conductor 3 farther from the coupling portion 10 and the wall surface of the flat conductor box 1, and an element 8 for preventing outflow of high frequency and A variable DC power supply 9 is connected via the belt-shaped conductor 3.
To apply a DC voltage to the variable capacitance element 6. In the antenna, the capacitance value of the variable capacitance element 6 is changed by a DC voltage applied from the variable DC power supply 9 to the variable capacitance element 6,
Thus, by changing the current phase on the strip conductor immediately below the slot and equivalently changing the length of the strip conductor 3 related to the resonance frequency of the coaxial resonance type slot antenna, the impedance matching center frequency of the antenna, that is, , It is possible to change the resonance frequency.

[0006]

SUMMARY OF THE INVENTION The aforementioned Japanese Patent Application No. 7-227 is disclosed.
The matching conditions of the coaxial resonance type slot antenna proposed in the 959 application and the conventional tuned slot antenna proposed in the above-mentioned Japanese Patent Application No. 9-54825 are based on the current phase and the slot length on the strip conductor immediately below the slot. Determined by both parties. Therefore, by changing the capacitance value of the variable capacitance element connected between the vicinity of the antenna including the end farthest from the coupling portion of the strip conductor and the wall surface of the flat conductor box, the current on the strip conductor immediately below the slot is changed. When the phase is changed, the matching condition changes along with the change in the resonance frequency, and it becomes impossible to supply effective high-frequency power to the antenna. In this antenna, since the absolute value and the amount of change of the capacitance value of the variable capacitance element that suppresses the change range of the matching state to a level that can supply effective high-frequency power to the antenna are very small, the effective high-frequency power However, there is a problem that the resonance frequency cannot be changed over a wide range in a state where the power can be supplied.

An object of the present invention is to provide a novel antenna capable of changing the resonance frequency of the antenna over a wide range while maintaining the matching condition of the antenna by simultaneously and equivalently changing the length of the strip conductor immediately below the slot and the length of the slot. A tuned slot antenna is provided.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a conductor box, a slot provided on a main surface of the conductor box, and an inside of the conductor box which is insulated from the conductor box and intersects with the slot. And a conductor that is provided with the conductor box, and supplies AC power between the coupling portion connected to the conductor and the conductor box, wherein an island insulated from the conductor box in the slot is provided. This can be effectively solved by forming a conductor and connecting a circuit capable of changing the capacitance value between the conductors between the island-shaped conductor and the wall surface of the conductor box. . More specifically, a flat conductor box that is a rectangular parallelepiped as a whole, an elongated strip-shaped conductor arranged along the resonance axis direction of the internal space of the conductor box and insulated from the flat conductor box, and a flat conductor Coaxial resonance, which consists of slots for transmitting and receiving radio waves formed on the upper surface of the box so as to intersect with the band-shaped conductor, and in which high-frequency power is supplied between the coupling portion set in the band-shaped conductor and the wall surface of the flat conductor box. In the type slot antenna, an elongated island-shaped conductor is provided in the slot insulated from the flat conductor box, and the capacitance between the two conductors is changed between the island-shaped conductor and the wall surface of the flat conductor box. The problem can be solved effectively by connecting a variable capacitance circuit that can perform the operation.

If such a means is adopted, the capacitance between the island-shaped conductor and the wall surface of the flat conductor box is changed by the variable capacitance circuit, so that the antenna can be widely used without affecting the matching condition of the antenna. This is because the impedance matching center frequency can be changed.

A technique for changing the resonance frequency of the coaxial resonance type antenna by equivalently changing the length of the strip-shaped conductor is proposed in Japanese Patent Application No. 9-54825. On the other hand, in the present invention, instead of directly connecting the variable capacitance element between the end of the strip-shaped conductor and the conductor box wall, the island-shaped conductor provided in the slot and capacitively coupled to the strip-shaped conductor is connected to the conductor box wall. And a variable capacitance circuit capable of changing the capacitance value between the two. As a result, even when the capacitance value is largely changed by the variable capacitance circuit, a small change in the capacitance value can be generated between the end of the strip-shaped conductor and the wall of the conductor box. It is possible to vary the accuracy.

To achieve at least the task of changing the equivalent slot length, a first conductor, a slot provided in the first conductor, and a second conductor are provided. In a slot antenna to which AC power is supplied between the first conductor and the second conductor, a third conductor is provided in the slot insulated from the first conductor, and the third conductor is provided in the slot. It is sufficient that a circuit capable of changing the capacitance value between the first and third conductors is connected between the first conductor and the first conductor.

[0012] It is to be noted that a small capacitance value change is caused at least between the wall surface of the conductor box and the conductor disposed inside the conductor box, thereby achieving the object of changing the impedance matching center frequency of the antenna with high accuracy. Therefore, the island-shaped conductor capacitively coupled to the conductor does not need to be provided in the slot, and the conductor box, the slot provided on the main surface of the conductor box, A slot antenna having a conductor insulated from the conductor box and disposed to intersect with the slot therein, and in which AC power is supplied between a coupling portion connected to the conductor and the conductor box. ,
An island-shaped conductor capacitively coupled to the conductor, and a circuit connected between the island-shaped conductor and a wall surface of the conductor box, capable of changing a capacitance value between the two conductors. Good.

Further, the present invention is not limited to the slot antenna, and generally has a first conductor and a second conductor, and supplies AC power between the first conductor and the second conductor. An antenna having a third conductor disposed opposite to the second conductor, wherein the first and third conductors are connected between the first conductor and the third conductor. If a circuit capable of changing the capacitance value between the first and second conductors is connected, the problem of causing a minute change in the capacitance value between the first conductor and the second conductor is achieved.

The matching condition of the tuned slot antenna is determined by both the current phase on the strip conductor immediately below the slot and the slot length. When the capacitance value between the island-shaped conductor and the conductor box wall that is the ground potential is changed by the variable capacitance circuit, for example, when the capacitance value is sufficiently large, the potential of the island-shaped conductor is the potential of the conductor box wall that is the ground potential. The potential is almost equal to the potential, and the width of the island-shaped conductor slot is equivalently reduced. Since a partial decrease in the width of the slot corresponds to an increase in the length of the slot, it is possible to change the equivalent slot length by changing the capacitance value of the variable capacitance circuit as a result. It becomes possible. By increasing the capacitance value, both the band-shaped conductor length and the slot length seem to be equivalently longer, so that the matching condition of the antenna is maintained.

As the variable capacitance circuit used in the tuned slot antenna of the present invention, an element whose capacitance changes when a DC voltage is applied, for example, a variable capacitance diode can be used. When an element whose capacitance value changes by applying such a DC voltage is used, one end of the element is connected to an island-shaped conductor and the other end is connected to a conductor box wall which is a ground potential, and a DC voltage is applied to the island-shaped conductor. By applying the voltage, the capacitance value between the island-shaped conductor and the wall surface of the flat conductor box can be changed.

A control signal is supplied to the variable capacitance circuit by arranging a control line inside the flat conductor box insulated from the flat conductor box,
One end of the control line is connected to the variable capacitance circuit through a small hole in the flat conductor box wall, and the other end is pulled out from another small hole in the flat conductor box wall and connected to the control circuit. can do.

By using such an antenna in a terminal of a wireless communication system, it is possible to tune the resonance frequency of the antenna to a radio frequency set each time a call is made. In this case, the frequency band of the antenna is extremely narrow as compared with the frequency band of the wireless communication system, as long as there is a band required for communication. Therefore,
The volume can be reduced as compared to an antenna covering the entire frequency band, thereby facilitating the incorporation of the antenna into the terminal. Further, since the antenna of the present structure has a wide change range of the resonance frequency, it can be applied to a portable wireless terminal used in a wireless communication system having a wide system frequency band.

The variable capacitance circuit used in the tuned slot antenna of the present invention may be a circuit capable of switching between two or more capacitance values by a control signal applied to a certain terminal, for example, a combination circuit of a high-frequency switch and a capacitance element. it can. In this case, if one end of the input / output terminal of the high-frequency switch is connected to, for example, a flat conductor box, the other end is connected to one end of the capacitive element, and the other end of the capacitive element is connected to the island-shaped conductor, a control signal is applied to the control terminal of the high-frequency switch. To control on / off between the input and output terminals to change the capacitance value between the island-shaped conductor and the wall surface of the flat conductor box.

Further, by providing a plurality of input / output numbers of the capacitive element and the high frequency switch, a multi-valued change in the capacitance value can be realized. In order to realize multi-value capacitance value change, not only using the multiple elements as described above, but also using an integrated circuit integrating multiple high-frequency switches with multiple capacitance elements and multiple inputs and outputs it can.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a tunable slot antenna according to the present invention will be described below in more detail with reference to some embodiments shown in the drawings. 1 to 3
, The same symbol indicates the same or similar.

<Example 1> FIG. 1 shows a tuned slot antenna in which a variable capacitance circuit is arranged on the upper surface of a flat conductor box and an island-shaped conductor is provided on the bottom surface of the box for drawing out a coupling portion outside the box.
Shown in FIG. 1a is a perspective view thereof, and FIG. 1b is a sectional view taken along line BB. In FIG. 1, reference numeral 20 denotes an island-shaped conductor provided in the slot 2, 16 denotes a variable capacitance circuit, 30 denotes a control line for supplying a DC voltage to the variable capacitance circuit, and 14 denotes a bottom surface of the flat conductor box 11 immediately below the coupling portion 10. The island-shaped conductor 13 formed in
A through-hole conductor (hereinafter, simply referred to as a through-hole in the present application) for electrically connecting the island-shaped conductor 14 to the zero is shown. The inside of the flat conductor box 1 is filled with an insulator for fixing the strip-shaped conductor 3, but illustration of the insulator is omitted.

The island-shaped conductor 14 formed in a small hole formed in the wall surface of the flat conductor box 1 so as not to contact the wall surface serves as a feeding point of the antenna, and high-frequency power is supplied from the feeding circuit 7 to this feeding point. Supply.

The variable capacitance circuit 16 is configured such that one of the terminal pairs whose terminal-to-terminal capacitance changes is connected to the island-shaped conductor 20 and the other is connected to the flat conductor box 1.
One end of the control line 30 is connected to a terminal to which a control signal for changing a capacitance between terminals is applied. By connecting the other end of the control line 30 to the control circuit 50 and changing the control signal supplied from the control circuit 50,
The capacitance value between the island-shaped conductor 20 and the flat conductor box 1 can be changed.

The combined capacitance of the capacitance between the island-shaped conductor 20 and the flat conductor box 1 and the capacitance between the band-shaped conductor 3 and the island-shaped conductor 20 includes an end of the band-shaped conductor 3 that is farther from the coupling portion 10. In order to play a role of adding a capacitance between the nearby point and the conductor box wall surface that is the ground potential, the density of the electric flux lines at the nearby point including the end far from the coupling portion 10 is reduced by the island-shaped conductor 20. And the current density induced on the strip-shaped conductor 3 increases so as to compensate for the increase in the electric flux density. As a result, as if the length of the strip-shaped conductor 3 has changed, the impedance matching center frequency, that is, the resonance frequency changes. Since the combined capacitance is a series combined capacitance, the band-shaped conductor 3 and the island-shaped conductor 2
By reducing the capacitance value between 0 and 0, the island-shaped conductor 2
Even when the capacitance value between 0 and the flat conductor box 1 is greatly changed by the variable capacitance circuit 16, a minute change in the capacitance value can be caused, so that the resonance frequency of the antenna can be changed with high accuracy. It is possible.

Further, since the island-shaped conductor 20 provided in the slot 2 is capacitively coupled to the wall surface of the flat conductor box 1, a part of the current generated around the slot depends on the capacitance value. The route is also taken on the island-shaped conductor. Therefore, by changing the capacitance value between the island-shaped conductor 20 and the flat conductor box 1 by the variable capacitance circuit 16, the path of the current generated around the slot is changed, that is, the equivalent slot length is changed. be able to.

According to this embodiment, as described above, the capacitance between the island-shaped conductor 20 and the flat conductor box 1 is changed by the variable capacitance circuit 16 so that the length of the strip-shaped conductor 3 and the length of the slot 2 are changed. The length can be changed simultaneously and equivalently. The matching condition of the coaxial resonant antenna is
This structure, which is determined by both the current phase on the strip conductor immediately below the slot and the slot length, allows both of these to be changed at the same time. That is, it is possible to change the resonance frequency.

Since the capacitance value between the island-shaped conductor 20 and the flat conductor box 1 can be changed by the variable capacitance circuit 16, a control circuit for supplying a control signal for changing the capacitance value to the variable capacitance circuit 16 50 allows the resonance frequency to be changed. Therefore, by changing the control signal from the control circuit 50 according to the radio frequency set for each call, the radio frequency can be made to match the resonance frequency. As a result, the band at a certain resonance frequency of the antenna can be limited to the band required for communication, which is extremely narrower than the entire band required by the system, and the volume of the antenna can be reduced. Further, since the antenna of the present structure has a wide change range of the resonance frequency, it can be applied to a portable wireless terminal used in a wireless communication system having a wide system frequency band.

This structure can be a flat thin plate flat structure like a conventional coaxial resonance type slot antenna, and can be mounted on a high-frequency circuit board of a portable radio terminal or the like so as to have no built-in projection. It can be in the form of an antenna.

It should be noted that in the antenna of this structure, the antenna dimensions can be shortened by filling the inside of the flat conductor box with a dielectric material as compared with the case where no dielectric material is used. This is the same as the case of the conventional tuned slot antenna proposed by the application.

<Embodiment 2> FIG. 2 shows an embodiment in which a variable DC power supply circuit is used as the control circuit in the embodiment 1.
In FIG. 2, reference numeral 9 denotes a variable DC power supply circuit. In this configuration, the variable capacitance circuit 16 changes the capacitance value between the island-shaped conductor 20 and the flat conductor box 1 by a DC voltage applied from the variable DC power supply circuit 9 via the control line 30.

According to the present embodiment, since the potential of the control line 30 provided near the antenna becomes constant with time (DC), unnecessary noise is not given to the antenna, and the transmission / reception characteristics are improved. Is done.

The variable DC power supply circuit 9 changes the voltage under the control of a voltage control circuit (not shown). The voltage control circuit generates a control signal indicating a voltage value corresponding to the radio frequency, and the variable DC power supply 9 generates a predetermined DC voltage according to the control signal. The variable DC power supply 9 has a control signal terminal (not shown) for inputting a control signal.

<Embodiment 3> FIG. 3 shows an embodiment using a variable capacitance element whose capacitance value changes continuously by applying a DC voltage as the variable capacitance circuit in Embodiment 2. In FIG. 3, reference numeral 6 denotes a variable capacitance element, such as a varicap diode. One end of the variable capacitance element 6 is connected to the island-shaped conductor 20, and the other end is connected to the wall surface of the flat conductor box 1, which is a ground potential, and a DC voltage is applied from the variable DC power supply circuit 9 to the island-shaped conductor 20 via the control line 30. By applying the voltage, the island-shaped conductor 20 and the flat conductor box 1
Can be changed.

According to this embodiment, 1 is used as the variable capacitance circuit.
Since only one variable capacitance element may be used, the circuit configuration can be simplified and the cost of parts can be reduced. Also, since a variable capacitance element whose capacitance value is continuously varied by a DC voltage applied is used, the resonance frequency can be continuously changed to an arbitrary value by the DC voltage value.

The voltage control circuit (not shown) stores the relationship between the DC applied voltage of the variable capacitance element and the capacitance value, and changes the voltage value for generating the capacitance value corresponding to the radio frequency to the variable DC voltage. By instructing the power supply circuit 9, the resonance frequency of the antenna can be matched with a desired radio frequency.

<Embodiment 4> FIG. 4 shows an embodiment in which the supply site of the DC voltage applied to the variable capacitance element in the embodiment 3 is made coincident with the coupling portion of the strip conductor. In FIG. 4, 6 is a variable capacitance element, and 21 is a resistance element. One end of the resistance element 21 is connected to the island-shaped conductor 20, and the other end is connected to the island-shaped conductor 4 provided in a small hole formed on the flat conductor box 1 so as not to contact the wall surface of the flat conductor box 1. Connected. The island-shaped conductor 4 is connected to the strip-shaped conductor 3 at a nearby point 11 including an end of the strip-shaped conductor 3 farther from the coupling portion 10 through the through hole 5.
Connected to.

The resistance value of the resistance element 21 should be so large as to be negligible in view of the high-frequency impedance at the end of the strip-shaped conductor 3 remote from the coupling portion 10 and sufficiently smaller than the impedance of the DC voltage application terminal of the variable capacitance element 6. Accordingly, the DC potential of the island-shaped conductor 20 and the DC potential of the coupling portion 10 can be made substantially the same without damaging the high-frequency power supplied to the strip-shaped conductor 3. Specifically, the above condition can be realized by setting the resistance to a value of several kΩ to about 100 kΩ.

The control line 30 can be eliminated and the circuit can be simplified by matching the supply site of the DC voltage applied to the variable capacitance element 6 with the coupling portion 10 of the strip conductor 3. Further, by eliminating the control line 30 provided near the slot of the antenna, the influence on the radiation pattern of the antenna can be reduced.

The supply of the high frequency and the DC voltage to the coupling section 10 is performed by the through hole 1 having one end connected to the coupling section 10.
And an island-shaped conductor 14 insulated from the flat conductor box 1 in a small hole formed in the wall surface of the flat conductor box 1 connected to the other end of the flat conductor box 1
Done from The method of supplying power to the high-frequency power supply circuit 7, the variable DC power supply 9, and the variable DC power supply 9 by using the element 8 for preventing the outflow of the high-frequency current is disclosed in Japanese Patent Application No. 9-54.
This is the same as the case of the conventional tuned slot antenna proposed in the 825 application.

<Embodiment 5> FIG. 5 shows an embodiment using a variable capacitance circuit capable of switching a capacitance value between certain terminals by two or more values by a control signal as the variable capacitance circuit in the first embodiment. In FIG. 5, reference numeral 51 denotes a capacitance between certain terminals of 2
This is a variable capacitance circuit that can be switched over the value. The variable capacitance circuit 51 can be realized by, for example, a combination of a high-frequency switch and a capacitance element. FIG. 5 shows a configuration in which the capacitance value can be switched among three values by the switch. One end of the terminal pair where the capacitance of such a variable capacitance circuit 51 changes is connected to the island-shaped conductor 20 and the other end is connected to the wall surface of the flat conductor box 1 which is the ground potential.
By applying a control signal to the control terminal of the variable capacitance circuit 51 via 0, the capacitance value between the island-shaped conductor 20 and the flat conductor box 1 can be switched to a set value.

By setting each capacitance value such that the resonance frequency of the antenna determined by the capacitance value between the island-shaped conductor 20 and the flat conductor box 1 matches the desired antenna resonance frequency, the variable capacitance circuit can be used. By giving a control signal for generating each capacitance value, the resonance frequency of the antenna can be set to a desired frequency. In this case, there is a limitation that only a limited resonance frequency can be realized as compared with the variable capacitance circuit in which the capacitance value changes continuously by the DC applied voltage as in the second embodiment. There is no problem because the carrier frequency used for speech takes a discrete value.

The control signal supplied to such a variable capacitance circuit may be a so-called digital signal for instructing the switching of the capacitance value based on a difference in signal voltage level or a temporal pattern of the signal. , The antenna can maintain a stable resonance frequency.

<Embodiment 6> FIG. 6 shows an embodiment using a variable DC power supply circuit as the control circuit in the embodiment 5.
As a variable capacitance circuit that can switch the capacitance value between certain terminals by two or more values, for example, a combination of a capacitor and an element, such as a high-frequency switch, whose impedance is switched between certain terminals when a DC voltage is applied to the certain terminal. Conceivable. In FIG. 6, 22 is a capacitive element, and 23 is a high-frequency switch. One end of the capacitive element 22 is an island-shaped conductor 20
The other end is connected to one end of the input / output terminal of the high-frequency switch 23, and the other end of the high-frequency switch 23 is connected to the wall surface of the flat conductor box 1. The control terminal of the high-frequency switch 23 is connected to the control line 30, and the DC voltage applied from the variable DC power supply circuit 9 via the control line 30 causes the input / output terminals of the high-frequency switch 23 to be in a low impedance state or a high impedance state. Change to impedance state.

With this configuration, the island-shaped conductor 20 and the flat conductor box 1
When the impedance between the input and output terminals of the high-frequency switch 23 is in a high impedance state, the capacitance between the island-shaped conductor 20 and the flat conductor box 1 originally exists between the conductors. Is in a low impedance state, the value is obtained by adding the capacitance value of the capacitance element 22 to the inter-conductor capacitance value.

The variable DC power supply circuit 9 changes the voltage under the control of a voltage control circuit (not shown). The voltage control circuit generates a control signal indicating a voltage value corresponding to the radio frequency, and the variable DC power supply 9 generates a predetermined DC voltage according to the control signal. The variable DC power supply 9 has a control signal terminal (not shown) for inputting a control signal.

Therefore, the tuned slot antenna to which the present configuration is applied can be realized by switching two resonance frequencies by a DC voltage specified by the voltage control circuit and applied from the variable DC power supply circuit 9.

In this embodiment, only one series connection circuit using one capacitive element and one high-frequency switch is used.
By connecting a plurality of such series connection circuits between the island-shaped conductor 20 and the wall surface of the flat conductor box 1 in parallel, a plurality of capacitance values,
Therefore, a plurality of resonance frequencies can be realized. Similar effects can be obtained by using an integrated circuit in which a plurality of capacitive elements and a high-frequency switch having a plurality of inputs and outputs are integrated instead of using a plurality of series-connected circuits.

<Embodiment 7> The connection point of the capacitive element and the high-frequency switch in Embodiment 6 was fixed to an island-shaped conductor provided in a small hole formed in the wall surface of the flat conductor box so as not to contact the wall surface of the flat conductor box. An example is shown in FIG. In FIG. 7, 2
Reference numeral 4 denotes a flat conductor box 1 in a small hole formed in a wall surface of the flat conductor box 1.
Are island-shaped conductors provided so as not to contact the wall surfaces. One end of the capacitive element 22 is connected to the island-shaped conductor 20, and the other end is connected to the island-shaped conductor 4. One end of the input / output terminal of the high-frequency switch 23 is also connected to the island-shaped conductor 4, and the other end is connected to the wall surface of the flat conductor box 1.

With this configuration, the input / output terminals of the capacitive element 22 and the high frequency switch 23 can be fixed on the respective conductors on the upper surface of the antenna, and the reliability of the circuit is improved. Further, according to this configuration, each element can be integrally mounted on the antenna by a technique such as reflow which is usually used when mounting components on a circuit board, and the assembly cost can be reduced.

<Embodiment 8> FIG. 8 shows an embodiment in which a control line is formed in a flat conductor box except for a part of the control line in the embodiment 7. 8, reference numerals 25 and 29 denote island-shaped conductors provided in small holes formed in the wall surface of the flat conductor box 1 so as not to contact the wall surface of the flat conductor box 1, 26 and 28 are through holes, and 27 is in the flat conductor box. It is a formed control line. The control line 30 having one end connected to the control terminal of the high-frequency switch 23 is provided in a small hole formed in the wall of the flat conductor box 1 near the high-frequency switch 23 so as not to contact the wall of the flat conductor box 1. The other end is connected to the conductor 25. Island-shaped conductor 25
Is connected to a control line 27 provided in the flat conductor box 1 via a through hole 26. Further, the control line 27 is connected through a through hole 28 to an island-shaped conductor 29 provided in a small hole formed on the lower surface of the antenna on the wall surface of the flat conductor box 1 so as not to contact the wall surface of the flat conductor box 1. Island-shaped conductor 2
DC voltage is applied to 9 by the variable DC power supply circuit 9, whereby the high-frequency switch 23 is controlled.

According to this structure, it is possible to reduce a portion of the control line for applying a DC voltage to the variable capacitance circuit, which is present on the upper surface of the antenna, so that the influence of the control line on the antenna radiation pattern is reduced. be able to.

<Embodiment 9> An embodiment in which the strip-shaped conductor formed in the flat conductor box and the control line in the embodiment 8 are electrically connected to the outside of the antenna through end-face through holes provided on the side surface of the antenna. As shown in FIG. In FIG.
And 35 are semicircular end-face through holes provided on the side surface of the antenna so as not to contact the wall surface of the flat conductor box 1. Note that the end surface through hole is not limited to a semicircular shape, and may be, for example, a prismatic shape. Joint 10 of strip-shaped conductor 3
Are connected to the end surface through-hole 15 on the side surface of the antenna. The control line 27 provided inside the flat conductor box 1 is connected to the end face through hole 35 at the end opposite to the end connected to the through hole 26.

According to this embodiment, the end surface through hole 15
, The end face through hole 35 is the power supply destination of the control line, and the lower part of the through hole is flush with the bottom surface (ground potential) of the flat conductor box 1. Therefore, it becomes easy to mount the present antenna on the circuit board. That is,
When a circuit board on which a wiring conductor and a ground conductor surface are formed is prepared, and the antenna is mounted on the substrate with the bottom surface facing down, the ground conductor surface is brought into contact with the bottom surface and the wiring conductors are directly inserted into the through holes 15 and 35 at the end surfaces. Can be contacted. Therefore, normal automatic mounting becomes possible. The antenna of this embodiment has an effect of reducing the manufacturing cost of the portable wireless terminal to which the antenna is applied.

The tuned slot antenna of the present invention, which has been described with reference to the embodiments, is disclosed in Japanese Patent Application No. 9-548.
Like the conventional tuned slot antenna proposed in the 25th application, it can be manufactured by using a normal multilayer substrate manufacturing process. Therefore, by forming the same on the same substrate as the high-frequency circuit board, it is possible to further reduce the component cost and the manufacturing cost of the portable wireless terminal.

[0055]

According to the present invention, by simultaneously and equivalently changing the length of the strip-shaped conductor immediately below the slot and the length of the slot, the impedance matching center frequency (resonance) of the antenna can be widened without affecting the matching condition of the antenna. Frequency) can be realized. Since the present antenna has a wide resonance frequency change range, it can be applied to a portable wireless terminal used in a wireless communication system having a wide system frequency band. If this antenna is applied to a portable radio terminal, it becomes possible to make the resonance frequency of the antenna follow the radio frequency set each time a call is made, so that the frequency band to be covered by the antenna can be reduced. Thereby, the volume of the antenna can be reduced. By applying the present antenna, the portable wireless terminal can eliminate the protrusions, improve portability, and reduce the volume.

[Brief description of the drawings]

FIG. 1 is a perspective view (a) and a sectional view (b) for explaining a first embodiment of a tunable slot antenna according to the present invention.

FIG. 2 is a perspective view for explaining a second embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 3 is a perspective view for explaining a third embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 4 is a perspective view for explaining a fourth embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 5 is a perspective view for explaining a fifth embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 6 is a perspective view for explaining a sixth embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 7 is a perspective view for explaining a seventh embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 8 is a perspective view for explaining an eighth embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 9 is a perspective view for explaining a ninth embodiment of the present invention.
(a) and sectional drawing (b).

FIG. 10 is a perspective view (a) and a cross-sectional view (b) illustrating a conventional tuned slot antenna.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flat conductor box, 2 ... Slot 3 ... Strip conductor, 4, 1
4, 24, 25, 29 ... island-shaped conductor, 5, 13, 26, 2
Reference Signs List 8 through hole, 6 variable capacitance element, 7 high-frequency power supply circuit, 8 element for blocking outflow of high-frequency current, 9 variable DC power supply, 10 coupling part, 15, 35 end face through hole, 16 variable Capacitance circuit, 20: island-shaped conductor provided in slot, 21: resistive element, 22: capacitive element, 23: high-frequency switch, 27, 30: control line, 50: control circuit, 5
1. Capacitance switching type variable capacitance circuit.

Claims (18)

[Claims] 1. A conductor box, a slot provided on a main surface of the conductor box, and a conductor provided inside the conductor box so as to be insulated from the conductor box and to intersect with the slot. In a slot antenna in which AC power is supplied between the conductor and the conductor box, an island-shaped conductor provided insulated from the conductor box in the slot; A slot antenna comprising: a circuit capable of changing a capacitance value between the island-shaped conductor connected to a wall surface and the conductor box. 2. The slot antenna according to claim 1, wherein the circuit includes a first terminal, a second terminal, and the first terminal.
A variable capacitance element that changes a capacitance value between the first and second terminals according to a DC voltage applied to a terminal of the second terminal, wherein the first terminal is connected to the island-shaped conductor, A terminal is connected to a wall surface of the conductor box. 3. The slot antenna according to claim 2, further comprising a variable DC power supply connected to said first terminal. 4. The slot antenna according to claim 1, further comprising a control circuit for supplying a control signal to said circuit, wherein said circuit includes a first terminal connected to said island-shaped conductor, and said conductor box. A second terminal connected to a wall of the first terminal, and a third terminal connected to the control circuit, wherein the first terminal is provided based on a control signal supplied from the control circuit to the third terminal. A capacitance value between the island-shaped conductor connected to the second terminal and a wall surface of the conductor box connected to the second terminal is changed. 5. The slot antenna according to claim 4, wherein said circuit has a variable capacitance element whose capacitance value changes by applying a DC voltage, wherein said variable capacitance element is connected to said first terminal and said first terminal. 2. A slot antenna connected between the second antenna and the second terminal. 6. The slot antenna according to claim 5, wherein said variable capacitance element is a varicap diode. 7. The slot antenna according to claim 4, wherein said control circuit is a variable DC power supply circuit. 8. The slot antenna according to claim 4, wherein the circuit includes a plurality of capacitance elements having different capacities from each other, and any one of the plurality of capacitance elements and the first terminal or the first terminal. A switch for switching connection with the second terminal, wherein switching control of the switch is performed based on a control signal supplied to the third terminal. 9. The slot antenna according to claim 4, wherein the first through hole provided on the upper surface of the conductor box and the second through hole provided on the lower surface of the conductor box. 3 has a control line connecting the terminal and the control circuit, the circuit is provided on the upper surface of the conductor box,
The said control circuit is provided in the lower surface of the said conductor box, The slot antenna characterized by the above-mentioned. 10. The slot antenna according to claim 4, further comprising an end face through-hole conductor provided on a wall surface of said conductor box so as to be insulated from said conductor box, wherein said control circuit and said third terminal are connected to each other. A slot antenna connected by a through-hole conductor at an end face. 11. A slot antenna according to claim 4, further comprising an end face through-hole conductor provided on a side surface of said conductor box insulated from said conductor box, and an alternating current between said conductor and said conductor box. A slot antenna, wherein power is supplied via the through-hole conductor at the end face. 12. The slot antenna according to claim 1, wherein said circuit has a capacitance element and an impedance variable element that changes impedance according to an applied DC voltage. 13. The slot antenna according to claim 12, further comprising: an island-shaped conductor provided on the main surface of the conductor box so as to be insulated from the conductor box and provided outside the slot. A slot antenna, wherein a connection portion with the variable element is connected to an island-shaped conductor provided outside the slot. 14. The slot antenna according to claim 1, wherein said circuit has a plurality of series connections of a capacitance element and a variable element whose impedance is changed by an applied DC voltage, forming said plurality of series connections. A plurality of said capacitance elements having different capacitance values from each other. 15. A conductor box, a slot provided on a main surface of the conductor box, a conductor insulated from the conductor box inside the conductor box, interposed with the slot, and the conductor A slot antenna having a coupling portion connected to the conductor box and supplying AC power between the coupling portion and the conductor box, wherein the island-shaped conductor is provided in the slot and insulated from the conductor box. A variable capacitance element connected between the island-shaped conductor and the wall surface of the conductor box; a resistance element connected between the island-shaped conductor and the conductor; and a variable element connected to the coupling portion. A slot antenna, comprising: a DC power supply circuit, wherein a DC voltage from the variable DC power supply circuit is applied to the variable capacitance element via the coupling section, the conductor, and the resistance element. 16. The slot antenna according to claim 15, further comprising an element connected between said coupling section and said variable DC power supply circuit for preventing an AC voltage from flowing out. 17. A semiconductor device comprising: a first conductor; a slot provided in the first conductor; and a second conductor insulated from the first conductor and provided to intersect the slot. The first
In the slot antenna in which AC power is supplied between the first conductor and the second conductor, the first antenna is provided in the slot.
A third conductor provided insulated from the first conductor, and changing a capacitance value between the first and third conductors connected between the first conductor and the third conductor. A slot antenna having a possible circuit. 18. An antenna having a first conductor and a second conductor, wherein AC power is supplied between the first conductor and the second conductor. It has a third conductor arranged to face, and can change a capacitance value between the first and third conductors connected between the first conductor and the third conductor. An antenna having a simple circuit.