KR20040093407A - Apparatus for antenna - Google Patents

Abstract

PURPOSE: An antenna apparatus is provided to change an antenna resonance frequency in accordance with a received frequency by arranging a variable capacity element on a surface of a dielectric block. CONSTITUTION: An antenna apparatus comprises a radiation electrode(19) and a variable capacity element(16) arranged on a surface of a dielectric block(18). A high frequency feeder voltage is supplied to the radiation electrode, and a DC bias voltage is supplied to the variable capacity element. The variable capacity element has a capacitance value changing in accordance with the bias voltage. The variable capacity element is electrically connected to the radiation electrode in such a manner that the capacitance value of the variable capacity element becomes an additional capacitance value for changing an antenna resonance frequency. The antenna resonance frequency changes in accordance with a received frequency by using the DC bias voltage as a control signal.

Description

Antenna device {APPARATUS FOR ANTENNA}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an antenna device suitable for a small antenna used in a portable information terminal device and the like and having a tuning control function for changing an antenna resonance frequency in accordance with a reception frequency.

As an antenna device used in a portable television receiver or the like, a stretchable rod antenna is generally used. However, in order to obtain an optimal reception sensitivity in the rod antenna, the user may add or decrease the length according to the reception channel (reception frequency), or change the angle or direction. The complicated sensitivity adjustment must be performed. In addition, since the rod antenna is elongated and used, it is easy to be regarded as a cumbersome projection and easily bends. Therefore, although it is possible to consider using a variety of antenna devices that can be easily miniaturized compared to the rod antenna, since the small antenna has a narrow resonance frequency bandwidth, in order to correspond the small antennas to a plurality of reception frequencies, the antenna resonant frequency is set to the reception frequency. Accordingly, there is a need for a tuning control function that changes appropriately.

As a small antenna device having such a tuning control function, a variable capacitance element for changing the additional capacitance value of the antenna element on a circuit board on which an antenna element such as an inverted F-type antenna or a loop antenna is conventionally provided. And a DC bias voltage (control voltage) are supplied to this variable capacitor, and is proposed (see Patent Document 1, for example). The variable capacitance element and its bias control circuit are inserted in series in the feed line of the circuit board side connected to the feed point of the antenna element, and the capacitance value of the variable capacitance element is determined by the DC bias voltage supplied from the bias control circuit. Varies with size When the capacitance value of the variable capacitance element is changed, the additional capacitance value of the antenna element is changed to change the antenna resonance frequency. Therefore, by setting the DC bias voltage appropriately according to the reception frequency, the antenna resonance frequency is changed to the reception frequency. It is possible to adjust the tuning accordingly.

[Patent Document 1]

Japanese Patent Laid-Open No. 10-107671 (second to third page, Fig. 1)

In the above conventional proposal, in order to realize an antenna device having a tuning control function, a configuration is provided in which a variable capacitance element and a bias control circuit are provided in a feed line on the circuit board side. Since a space for arranging the variable capacitor and the bias control circuit must be secured on the side, there is a problem in that desired miniaturization is difficult to be achieved. In other words, in a portable information terminal device such as a portable television receiver, a high installation density is required for the circuit board, and the space on the circuit board that can be used for the antenna is also limited. The arrangement disposed in an area different from that of the tuner portion is a factor that impairs the miniaturization. For example, in the case of terrestrial digital television broadcasting, which is expected to be introduced in recent years, reception not only from a dedicated television receiver but also from a PDA (Personal Digital Assistant) or a mobile phone is assumed, but in this type of portable information terminal equipment, a television is used. It is essential to design the antenna device for broadcast reception very compactly.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation of the prior art, and an object thereof is to provide an antenna device which can change the antenna resonant frequency according to the reception frequency, and at the same time have a simple configuration and can be easily miniaturized.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic configuration diagram of a card for receiving television equipped with an antenna device according to a first embodiment of the present invention;

2 is an explanatory diagram showing a state in which the card shown in FIG. 1 is mounted on a portable information terminal device;

3 is a perspective view of an antenna element incorporated in the card shown in FIG. 1;

4 is a bottom view of the antenna element shown in FIG. 3;

5 is a characteristic diagram showing a relationship between a control voltage supplied to a varactor diode of the antenna element shown in FIG. 3 and a resonance frequency;

6 is an explanatory diagram showing a radiation pattern of the antenna element shown in FIG. 3;

7 is a perspective view of an antenna element showing a modification of the first embodiment;

Fig. 8 is a schematic structural diagram of a card for receiving television equipped with an antenna device according to the second embodiment of the present invention;

9 is a perspective view of the antenna element incorporated in the card shown in FIG. 8;

10 is a bottom view of the antenna element shown in FIG. 9;

11 is a perspective view of an antenna element showing a modification of the second embodiment;

Fig. 12 is a schematic configuration diagram of a card for receiving television equipped with an antenna device according to the third embodiment of the present invention;

13 is a perspective view of an antenna element incorporated in the card shown in FIG. 12;

14 is a bottom view of the antenna element shown in FIG. 13;

FIG. 15 is a perspective view of an antenna element showing a modification of the third embodiment. FIG.

※ Explanation of codes for main parts of drawing

1: portable information terminal device 2: liquid crystal display

3: slot 11, 31, 41: card for receiving television

12, 28, 32, 33, 42, 43: antenna element

13 tuner 14 circuit board

15: outer case

16 varactor diode (variable capacitor) 17 resistor

18 dielectric substrate 19 radiation electrode

20: earth electrode 21: feed terminal

22: control terminal 23: ground conductor

24: Capacitor 25: Earth terminal

26, 27: empty

In order to achieve the above object, in the antenna device of the present invention, a variable electrode having a radiation electrode supplied with a high frequency feed voltage and a direct current bias voltage supplied to a surface of a dielectric substrate, and at the same time the capacitance value changes according to the bias voltage. A capacitance element is provided, and the variable capacitance element is electrically connected to the radiation electrode so that the capacitance value of the variable capacitance element is an additional capacitance value that changes the antenna resonance frequency, and the DC bias voltage is used as a control signal for the antenna resonance. It is configured to change the frequency according to the receiving frequency.

The dielectric antenna provided with the radiation electrode on the surface of the dielectric body is suitable for miniaturization since the wavelength shortening effect by the dielectric is obtained, but the variable capacitance element serving as the tuning control means is provided by using the empty space on the surface of the dielectric body. By doing so, the space for the antenna required on the circuit board side can be reduced, and the circuit for the antenna can be simplified. When the DC bias voltage supplied to the variable capacitor is increased, the capacitance value of the variable capacitor decreases, and the antenna resonance frequency increases as the additional capacitance decreases. Therefore, the magnitude of the DC bias voltage is appropriately adjusted according to the reception frequency. By setting, the tuning control for appropriately changing the antenna resonance frequency in accordance with the reception frequency is possible. Therefore, it is possible to manufacture a small antenna device to be subjected to tuning control at low cost, and can be used as an antenna device for receiving terrestrial digital television broadcasting with a portable information terminal device.

In addition, the antenna device includes an inverted F-type antenna formed by providing a radiation electrode on a ceiling surface of a dielectric substrate provided on a ground conductor, or a radiation electrode provided on a side surface of a dielectric substrate provided in an area where no ground conductor is present. If it is constituted as a loop antenna which is formed as a loop, further miniaturization can be achieved. In the case of the inverted F-type antenna, it is preferable to install the variable capacitive element on the side of the dielectric body, and in the case of the loop type antenna, it is preferable to install the variable capacitive element on the side or the ceiling surface of the dielectric body. desirable.

In addition, when the chip-shaped varactor diode is employed as the variable capacitance element, it can be installed on the surface of the dielectric body relatively simply, so that stable performance can be expected and the price is low, which is preferable.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, embodiments of the invention will be described with reference to the drawings. 3 is a perspective view of an antenna element embedded in the card, FIG. 4 is a bottom view of the antenna element, and FIG. 5 is a resonance with the control voltage supplied to the varactor diode of the antenna element. 6 is an explanatory diagram showing a radiation pattern of the antenna element.

The television receiving card 11 shown in FIG. 1 is a card type electronic device for receiving signal waves (horizontal polarization waves) of terrestrial digital television broadcasting having a frequency of 470 to 770 MHz. The portable information terminal device shown in FIG. 1) It is used for mounting. The card 11 is roughly configured by storing the circuit board 14 provided with the antenna element 12, the tuner portion 13, and the like inside the outer case 15, and on the side of the antenna element 12 The chip-shaped varactor diode 16 and the resistor 17 (refer FIG. 3) are provided.

The antenna element 12 has an inverted F type formed by providing a radiation electrode 19, an earth electrode 20, a power supply terminal 21, a control terminal 22, and the like on a surface of a rectangular parallelepiped substrate 18. Dielectric antenna. The dielectric substrate 18 is made of a dielectric material such as ceramic or resin, and the electrodes 19 and 20 and the terminals 21 and 22 are each made of a conductive layer such as copper foil. On the ceiling surface of the dielectric substrate 18, the radiation electrodes 19 have capacitive coupling portions C1 and C2 at two portions, and these capacitive coupling portions C1 and C2 are used to match impedance or add capacitance value. Adjustment is performed. On the bottom surface of the dielectric substrate 18, the earth electrode 20 is connected to the ground conductor 23 on the circuit board 14 side, and the feed terminal 21 and the control terminal 22 are tuner portions 13. ) The power supply terminal 21 is supplied with a high frequency power supply voltage, and the control terminal 22 is supplied with a DC bias voltage (control voltage).

The varactor diode 16 is a variable capacitance element whose capacitance value changes in accordance with the magnitude of the applied DC bias voltage. One pole of this varactor diode 16 is connected to a resistor 17, and the other pole is connected to an earth electrode 20. The high frequency blocking resistor 17 is connected to the control terminal 22, and the direct current bias voltage is supplied to the varactor diode 16 via the resistor 17. In addition, since the DC bias voltage is blocked by the capacitive coupling portion C2, the radiation electrode 19 is not affected.

The tuner unit 13 is a tuner for receiving a television signal, and the tuner unit 13 receives a received signal (RF signal) from the antenna element 12. The tuner section 13 processes the received signal and outputs it to the liquid crystal display section 2 of the portable information terminal device 1 as an IF signal.

The portable information terminal 1 is provided with a slot 3 for detachably attaching a television reception card 11 or the like. As shown in FIG. 2, when the television reception card 11 is mounted in the portable information terminal device 1, the antenna element 12 embedded in one side of the card 11 is connected to the portable information terminal device 1. ) Is protruded to the outside. That is, when receiving terrestrial digital television broadcasting and displaying an image on the liquid crystal display unit 2, as shown in Fig. 2, the TV receiving card 11 is mounted on the portable information terminal device 1, so that the antenna element 12 ) Is operated as an inverted F antenna for reception. When the reception of terrestrial digital television broadcasting is terminated or when the portable information terminal device 1 is used for another purpose by attaching another card, the card 11 for television reception is removed from the slot 3.

Next, the operation of the antenna element 12 will be described in detail. Since the additional capacitance value of the antenna element 12 changes depending on the capacitance value of the varactor diode 16 which is the variable capacitance element, the DC bias voltage supplied from the tuner section 13 to the varactor diode 16 ( The antenna resonant frequency can be changed according to the magnitude of the control voltage). That is, as shown in FIG. 5, when the DC bias voltage is increased, the capacitance value (solid line A) of the varactor diode 16 decreases and the antenna resonance frequency (dashed line B) increases as the additional capacitance value decreases. By appropriately setting the magnitude of the DC bias voltage in accordance with the reception frequency, the antenna resonance frequency can be tuned and controlled in accordance with the reception frequency. Thereby, while setting the size of the antenna element 12 to the small size of 35 mm long side, 11 mm short side, and 5 mm height, it is possible to receive terrestrial digital television broadcasting with a frequency of 470 to 770 MHz. After the image signal received by the antenna element 12 is processed by the tuner unit 13, the image signal is output to the liquid crystal display unit 2 of the portable information terminal device 1, and an image based on the signal is displayed on the screen. .

Thus, in the example of this embodiment, the antenna element 12 incorporated in the television receiving card 11 is an inverted F-type dielectric antenna, and the antenna element 12 is located in the empty space of the dielectric body 18 of the antenna element 12. Since a varactor diode 16 is provided for changing the antenna resonance frequency in accordance with the reception frequency, the small antenna element 12 can obtain a good reception sensitivity as shown in FIG. Therefore, the antenna space required on the circuit board 14 side can be reduced, and the antenna circuit can be simplified, and the overall size of the television reception card 11 can be set compactly. 6 (a) is a radiation pattern showing directivity in the xy plane of FIG. 1, FIG. 6 (b) is a radiation pattern showing directivity in the xz plane of FIG. 1, and FIG. 6 (c) is a yz plane of FIG. It is understood that the radiation pattern indicates the directivity in s, and that the extreme gain decrease does not occur even when the antenna element 12 faces in any direction.

Moreover, since this antenna element 12 is comprised as an inverted F-type antenna which can receive both a horizontal polarization and a vertical polarization, favorable reception sensitivity can be expected also in the room etc. where polarization scattering easily occurs. Since the antenna element 12 is modularized by attaching the varactor diode 16 to the dielectric substrate 18, the antenna element 12 can be installed on the circuit board 14 simply and accurately. In addition, the chip-shaped varactor diode 16 can be installed on the surface of the dielectric substrate 18 relatively simply, so that stable performance can be expected and cost is low.

7 is a perspective view of an antenna element showing a modification of the first embodiment described above, and the same reference numerals are attached to parts corresponding to FIG. 3. In the antenna element 28 shown in FIG. 7, one pole of the varactor diode 16 is connected to the feed terminal 21 via a resistor 17, and the tuner portion 13 is connected to the feed terminal 21. From this, the supply voltage and the DC bias voltage (control voltage) are superimposed and supplied. Therefore, the control terminal 22 necessary for the antenna element 12 is omitted in this antenna element 28.

Fig. 8 is a schematic configuration diagram of a card for receiving television having an antenna device according to a second embodiment of the present invention, Fig. 9 is a perspective view of an antenna element incorporated in the card, and Fig. 10 is a bottom view of the antenna element. to be. In these FIGS. 8-10, the same code | symbol is attached | subjected to the part corresponding to FIGS.

The point of configuring the antenna element 32 as a loop antenna of the television reception card 31 shown in FIG. 8 is significantly different from that of the first embodiment. That is, the antenna element 32 shown in FIGS. 8-10 is a loop type dielectric antenna provided with the strip-shaped radiation electrode 19 along the side surface of the rectangular parallelepiped dielectric body 18, and the radiation electrode 19 ) And a feed terminal 21 are provided with a capacitor 24. The feed terminal 21, the control terminal 22, and the earth terminal 25 are provided at one end of the bottom surface of the dielectric substrate 18, and the feed terminal 21 and the control terminal 22 are the tuner portion 13. The ground terminal 25 is connected to the ground conductor 23 on the circuit board 14 side. One pole of the varactor diode 16 is connected to the resistor 17, and the other pole is connected to the earth terminal 25 via the radiation electrode 19. The high frequency blocking resistor 17 is connected to the control terminal 22, and the direct current bias voltage (control voltage) is supplied to the varactor diode 16 via the resistor 17. As shown in FIG. 8, the installation area of the antenna element 32 and its vicinity on the circuit board 14 side are areas in which the ground conductor 23 does not exist, but the basic configuration of the circuit board 14 side is shown. Is equivalent to the first embodiment described above.

Thus, in the television reception card 31 which concerns on the example of 2nd Embodiment, since the antenna element 32 is comprised as a loop type antenna, the radiation pattern of a horizontal polarization becomes non-directional. Therefore, even if the direction of the portable information terminal device equipped with the television receiving card 31 is arbitrarily rotated along the circuit board 14, it is possible to receive the signal waves of terrestrial digital television broadcasting with equal sensitivity. In addition, if the antenna element 32 is a loop antenna, there is an advantage that it is difficult to be affected by the human body.

FIG. 11 is a perspective view of an antenna element showing a modification of the above-described second embodiment, and the same reference numerals are attached to parts corresponding to FIG. 9. In the antenna element 33 shown in FIG. 11, one pole of the varactor diode 16 is connected to the feed terminal 21, and the feed voltage and the direct current bias are supplied from the tuner 13 to the feed terminal 21. The voltage (control voltage) is superimposed and supplied. Therefore, the control terminal 22 and the resistor 17 which were necessary for the antenna element 32 are omitted in this antenna element 33.

Fig. 12 is a schematic configuration diagram of a card for receiving television equipped with an antenna device according to a third embodiment of the present invention, Fig. 13 is a perspective view of an antenna element incorporated in the card, and Fig. 14 is a bottom view of the antenna element. to be. 12-14, the same code | symbol is attached | subjected to the part corresponding to FIGS. 8-10.

The antenna element 42 of the television receiving card 41 shown in FIG. 12 is a loop antenna that is slightly different in configuration from the second embodiment. That is, in the antenna element 42 shown in FIGS. 12 to 14, the elongated radiation electrode 19 is provided in a spiral shape along the side surface of the rectangular parallelepiped dielectric base 18, and the cloth of the dielectric base 18 is formed. The varactor diode 16 and the resistor 17 disposed at the front face are connected to the power supply terminal 21 and the control terminal 22 via vias 26 and 27 passing through the dielectric body 18, respectively. One end of the spirally extending radiation electrode 19 is connected to the varactor diode 16 on the ceiling surface of the dielectric substrate 18, and is thus connected to the feed terminal 21 via the via 26. . The other end of the radiation electrode 19 is connected to the earth terminal 25 at the bottom surface of the dielectric substrate 18. The basic configuration of the circuit board 14 side is the same as that of the second embodiment.

As described above, in the television reception card 41 according to the third embodiment, since the radiation electrode 19 of the antenna element 42 extends in a spiral shape, the antenna length 18 is not required to be enlarged even if the dielectric base 18 is not enlarged. Can be increased significantly. Therefore, it is suitable as a small antenna for receiving a signal wave with a long wavelength. Since the antenna element 42 is a loop antenna, the radiation pattern of the horizontally polarized wave is non-directional as in the second embodiment, and the direction of the portable information terminal device is arbitrarily rotated along the circuit board 14. Even if it is made, it becomes possible to receive the signal wave of terrestrial digital television broadcasting with an equal sensitivity, and it has the advantage that it is hard to be influenced by a human body.

FIG. 15 is a perspective view of an antenna element showing a modification of the above-described third embodiment, and the same reference numerals are attached to parts corresponding to FIG. 13. In the antenna element 43 shown in FIG. 15, the control terminal 22, the resistor 17, and the via 27 are omitted, and the power supply voltage and the direct current bias voltage (control) from the tuner 13 to the power supply terminal 21 are controlled. Voltage) are superimposed and supplied.

In each of the above embodiments, the case where the antenna device for receiving terrestrial digital television broadcasting is incorporated in the card has been described. However, the antenna device for receiving other signal waves or the portable terminal device, such as a portable information terminal device, has been described. It goes without saying that the present invention can also be applied to an antenna device.

This invention is implemented in the form as described above, and has the effect as described below.

By installing a variable capacitance element such as a varactor diode on the surface of the dielectric body, the antenna device allows the antenna resonant frequency to be appropriately changed in accordance with the reception frequency. The antenna space required on the circuit board side can be reduced. Since the circuit for an antenna can also be simplified, it becomes possible to manufacture the small antenna apparatus with which tuning control is performed at low cost. Therefore, it can be used as an antenna device for receiving terrestrial digital television broadcasting in a portable information terminal device, and high practicality can be expected.

Claims (4)

On the surface of the dielectric substrate, a radiation electrode supplied with a high frequency feed voltage and a variable capacitance element supplied with a direct current bias voltage and varying in capacitance according to the bias voltage are provided. Electrically connecting the variable capacitor with the radiation electrode such that the capacitance of the variable capacitor is an additional capacitance that changes the antenna resonant frequency, And the DC bias voltage as a control signal so as to change the antenna resonance frequency according to a reception frequency. The method of claim 1, And an inverted F-type antenna formed by providing the radiation electrode on the ceiling surface of the dielectric substrate provided on the ground conductor, and the variable capacitance element provided on the side of the dielectric substrate. . The method of claim 1, It is configured as a loop antenna formed by providing the radiation electrode on the side of the dielectric substrate provided in the region where no ground conductor is present, and the variable capacitance element is provided on the side or ceiling surface of the dielectric substrate. An antenna device characterized in that. The method according to any one of claims 1 to 3, And said variable capacitor is a chip-shaped varactor diode.