JP2008017426A - Antenna assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna assembly from which excellent reception sensitivity can be obtained over a broadband without losing downsizing and a gain. <P>SOLUTION: The antenna assembly 1 is configured such that a pattern antenna 4 is provided to other side of a circuit board (e.g. antenna board) 3 on one side of which a chip antenna 2 is mounted and the pattern antenna 4 is tuned to a high frequency part of a required frequency band and the chip antenna 2 is turned to the remaining band. Since varactor elements 7 are interposed to discontinuous parts 6a of a belt-like radiation conductor 6 wound on an outer circumferential face of a base body 5 and the capacitance of the varactor elements 7 is changed with a tuning voltage V(TUNE), the chip antenna 2 can be acted as a tunable antenna. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna device including a chip antenna in which a strip-shaped radiation conductor is wound around a base made of a dielectric material or a magnetic material, and in particular, a variable capacitance element is attached to the radiation conductor of the chip antenna to provide a wide band. The present invention relates to an antenna device that can be tuned to a frequency.

2. Description of the Related Art Conventionally, chip antennas are known in which a radiating conductor is wound in a strip shape (many spirals) around a substantially columnar base made of a dielectric material or a magnetic material so as to be tuned to a desired frequency. In addition, in order to be able to tune to a wide band frequency with this kind of chip antenna, a discontinuous portion is provided in the strip-shaped radiation conductor, and a variable capacitance element is provided in the discontinuous portion, and a tuning voltage based on a bias control signal is provided. Conventionally, an antenna device has been proposed in which the resonance frequency of the radiating conductor is changed in accordance with the tuning voltage by supplying a variable capacitance element to the capacitance element to change the capacitance value (see, for example, Patent Document 1). In such a conventional proposal, the chip antenna is mounted on a circuit board on which a feeding circuit, a bias circuit, and the like are disposed, and the feeding portion of the radiation conductor of the chip antenna is connected to the feeding circuit, and the variable capacitance element is biased. A DC tuning voltage is supplied from the circuit. Such a chip antenna that can be tuned to a wideband frequency can be easily built in a portable wireless device such as a cellular phone, and can be used as a receiving antenna for the UHF band of TV broadcasting. It is expected to increase more and more.
Japanese Patent Laying-Open No. 2005-210564 (page 4-6, FIG. 1)

  However, since the above-described conventional proposal in which the variable capacitance element is attached to the radiation conductor is a one-band antenna device, if the number of variable capacitance elements is increased to widen the frequency band with good reception sensitivity, the size must be increased. There was a problem of being. For example, if such a conventional antenna device attempts to receive all UHF bands of television broadcasting, it becomes difficult to reduce the size that can be built into a mobile phone or the like, and the number of variable capacitance elements increases undesirably, resulting in a gain. It will get worse.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide an antenna device capable of obtaining good reception sensitivity over a wide band without reducing the size and gain. .

  In order to achieve the above object, in the antenna device of the present invention, a radiating conductor is wound in a strip shape on the outer peripheral surface of a base made of a dielectric or magnetic material, and a variable capacitance element is provided at a discontinuous portion of the radiating conductor. A chip antenna, a circuit board on which the chip antenna is mounted on one side, and a pattern antenna formed on the other side of the circuit board as a conductor pattern having an electrical length shorter than that of the radiating conductor. A transmission line for supplying a power supply signal to the radiation conductor of the chip antenna and the pattern antenna on the circuit board; and a bias line for changing a capacitance value by supplying a tuning voltage based on a bias control signal to the variable capacitance element. The pattern antenna is tuned to a relatively high and narrow frequency band, and the chip antenna is relatively low and wide frequency Configured to tune to the band.

  In this way, in the antenna device provided with the pattern antenna on the surface opposite to the chip antenna side of the circuit board on which the chip antenna is mounted, the electrical length of the pattern antenna should be set shorter than the radiation antenna of the chip antenna. Thus, a pattern antenna that can be tuned to a high frequency portion of a required frequency band can be formed in a limited region of the circuit board. In addition, a variable capacitance element is interposed in the discontinuous portion in the radiation conductor of the chip antenna, and the capacitance value of the variable capacitance element changes according to the magnitude of the tuning voltage applied via the bias line. It is possible to tune a chip antenna that can be operated as a tunable antenna whose tuning frequency can be changed as appropriate, to a remaining band excluding the high frequency part in a required frequency band. Therefore, this antenna apparatus can realize two bands applicable over a wide frequency band without increasing the planar size. Further, since the chip antenna of this antenna device only needs to be set so as to cover the band excluding the high frequency part where the pattern antenna can be tuned, it is not necessary to increase the number of variable capacitance elements. Therefore, the antenna device having such a configuration can obtain good reception sensitivity over a wide frequency band without reducing the size and gain. For example, the antenna device for a television broadcast UHF band built in a mobile phone or the like can be obtained. It is suitable as a receiving antenna.

  In the above configuration, if the pattern antenna is formed as a meander-shaped conductor pattern, the pattern antenna having a corresponding electrical length can be formed compactly in a limited area of the circuit board, so that the antenna device can be reduced in size. It becomes easier to plan.

  In the above configuration, the circuit board includes an input terminal connected to the power supply circuit, a first output terminal connected to the power supply unit of the chip antenna, and a second output connected to the power supply unit of the pattern antenna. When a power is supplied to the chip antenna, a high-frequency switching circuit having a terminal is provided, and the high-frequency switching circuit is controlled so that the input terminal is selectively connected to the first output terminal or the second output terminal. By connecting the input terminal of the high-frequency switching circuit to the first output terminal, the pattern antenna can be set not to be supplied with a feeding signal. Similarly, when feeding power to the pattern antenna, the input terminal of the high-frequency switching circuit is connected to the second output terminal. It is possible to set the chip antenna so that no power supply signal is supplied by conducting to the end. As a result, even when any one of the chip antenna and the pattern antenna is selected and fed, there is no possibility of interference between the chip antenna and the pattern antenna, so that good antenna performance can always be expected.

  In this case, the circuit board provided with the pattern antenna includes an external connection terminal connected to a wiring pattern of an external circuit board (mother board), the high-frequency switching circuit, and a bias circuit that generates the tuning voltage. The antenna board having the antenna board can be easily mounted on the mother board by mounting a chip antenna on the antenna board to form a unit (module), so that the handleability and versatility of the antenna board is enhanced. Further, if the bias circuit is provided with a boosting means for boosting the voltage level of the bias control signal to a required level, the tuning voltage of the antenna device can be made higher than the power supply voltage even if the power supply voltage on the mother board side is low. Therefore, even when the antenna device is incorporated in a portable wireless device in which the power supply voltage is set to be low, there is no possibility of hindering the control of the capacitance value of the variable capacitance element.

  In the antenna device of the present invention, a pattern antenna that can be tuned to a high frequency portion of a required frequency band is provided on the surface opposite to the chip antenna side of the circuit board on which the chip antenna is mounted. The pattern antenna can be formed in a limited area of the circuit board. In addition, the chip antenna provided with the variable capacitance element can be operated as a tunable antenna whose tuning frequency can be changed as appropriate. Can be tuned to. Therefore, this antenna apparatus can realize two bands applicable over a wide frequency band without increasing the planar size. Further, since the chip antenna of this antenna device only needs to be set so as to cover the band excluding the high frequency part where the pattern antenna can be tuned, it is not necessary to increase the number of variable capacitance elements. Therefore, this antenna device can obtain good reception sensitivity over a wide frequency band without reducing the size and gain, and for example, a reception antenna for a television broadcast UHF band built in a mobile phone or the like. It becomes suitable as.

  1 is a perspective view of an antenna device according to an embodiment of the present invention as viewed from below, FIG. 2 is an exploded perspective view of the antenna device, and FIG. FIG. 4 is an external view showing a state where the antenna device is mounted on the mother board, and FIG. 4 is an equivalent circuit diagram of the antenna device.

  The antenna device 1 according to this embodiment is a unit (module) by mounting the chip antenna 2 on the antenna substrate 3 having the pattern antenna 4 provided on the lower surface, as shown in FIG. The antenna board 3 is mounted on a mother board 20 which is an external circuit board. The mother board 20 is a circuit board built in a portable wireless device such as a cellular phone, and the antenna device 1 is used as a receiving antenna for the UHF band of television broadcasting. Therefore, although not shown, the mother board 20 is provided with a tuner for the antenna device 1 and the like.

  The chip antenna 2 of the antenna device 1 includes a substantially columnar base 5 made of a dielectric, a radiation conductor 6 spirally wound around the outer surface of the base 5, and a dispersed arrangement in the line of the radiation conductor 6. It is mainly composed of a plurality of variable capacitance elements (varactor diodes) 7. The radiation conductor 6 has a power feeding part P1 on one end side, and the other end side is an open end. In addition, as shown in FIG. 2, the radiation conductor 6 has a discontinuous portion 6a in the line and is therefore divided into a plurality of divided conductor portions. However, adjacent divided conductor portions are variable via the discontinuous portion 6a. The capacitors 7 are connected in series. The chip antenna 2 is positioned on the antenna substrate 3, and an appropriate portion including the feeding portion P <b> 1 of the radiation conductor 6 is soldered to the transmission line 11 and the solder land 13 of the antenna substrate 3. The material of the substrate 4 may be a magnetic material, and the shape may be a plate shape.

  As shown in FIG. 1, the pattern antenna 4 is formed on the lower surface of the antenna substrate 3 as a meander-shaped conductor pattern having a feeding portion P <b> 2 on one end side and an open end on the other end side. The electrical length of the pattern antenna 4 is set shorter than that of the radiation conductor 6 of the chip antenna 2. On the other hand, on the upper surface of the antenna substrate 3, a high frequency changeover switch 8 for performing a switching operation for selectively connecting the input end 8a to the first output end 8b or the second output end 8c, and a tuning voltage based on a bias control signal. A bias circuit 9 is provided that supplies V (TUNE) to the variable capacitance element 7 of the chip antenna 2 to change the capacitance value. In addition, the antenna substrate 3 is connected to the power supply circuit in the tuner near the high-frequency selector switch 8 and connected to the transmission line 10 for supplying the power supply signal RF to the input terminal 8a, and to the first output terminal 8b. A transmission line 11 that supplies a feeding signal RF to the feeding portion P1 of the radiation conductor 6, and a through hole (side through) 12 that is connected to the second output end 8c and supplies the feeding signal RF to the feeding portion P2 of the pattern antenna 4. And are provided. On the upper surface of the antenna substrate 3, a plurality of solder lands 13 soldered to appropriate portions of the radiation conductor 6, a matching circuit (not shown) for impedance adjustment, and the like are further provided. Each solder land 13 plays a role of mechanically fixing the chip antenna 2 to the antenna substrate 3, but a part of the solder lands 13 has a signal path for applying the tuning voltage V (TUNE) to the variable capacitance element 7. Used as Further, external connection terminals 14 are provided at a plurality of locations on the peripheral edge of the antenna substrate 3, and these external connection terminals 14 are soldered to a wiring pattern (not shown) of the mother substrate 20.

  The power supply signal RF is supplied from the power supply circuit of the mother board 20 to the input terminal 8a of the high-frequency switch 8 via the transmission line 10, but when the input terminal 8a is electrically connected to the first output terminal 8b, When the power supply signal RF is not supplied to the second output terminal 8c and the input terminal 8a is electrically connected to the second output terminal 8c, as shown in FIG. 4, the power supply signal is supplied to the first output terminal 8b. RF is not supplied. That is, the high-frequency switch 8 performs a switching operation in which the input terminal 8a is selectively conducted to the pair of output terminals 8b and 8c. Such a switching operation is performed by the switch control signal V (CTL). Be controlled.

  The bias circuit 9 includes a DC / DC converter 15 that constantly boosts a power supply voltage V (DD) (for example, 3 volts) to a constant operating voltage (for example, 5 volts), and an output (operating voltage) of the DC / DC converter 15. And an FET switch circuit that generates a boosted bias signal from the bias control signal (pulse width modulation signal), and a smoothing circuit that smoothes the boosted bias signal to generate a DC tuning voltage V (TUNE). ing. The bias circuit 9 can change the tuning voltage V (TUNE) within the range of 0.2 to 4.8 volts, for example, according to the pulse width of the bias control signal. Therefore, the tuning frequency of the chip antenna 2 can be appropriately changed by supplying the tuning voltage V (TUNE) to the variable capacitance element 7 to change the capacitance value.

  Next, the operation of the antenna device 1 configured as described above will be described. In the antenna device 1, when the high-frequency switch 8 connects the input terminal 8 a to the first output terminal 8 b, the power supply signal RF is supplied to the power feeding part P 1 of the radiation conductor 6 of the chip antenna 2 through the transmission line 11. Since it can be supplied, the radiation conductor 6 having a longer electrical length than the pattern antenna 4 can resonate in a relatively low frequency band. At this time, if the tuning voltage V (TUNE) applied to the variable capacitance element 7 interposed in the discontinuous portion 6a of the radiating conductor 6 is changed, the tuning frequency of the chip antenna 2 changes. In the case of the present embodiment example, the chip antenna 2 is designed so that the tuning frequency of the chip antenna 2 can be appropriately changed within a range of 470 to 700 MHz. It can be operated as a tunable antenna capable of receiving a band.

  As shown in FIG. 4, when the high frequency changeover switch 8 connects the input end 8 a to the second output end 8 c, the feed signal RF is supplied to the feed portion P <b> 2 of the pattern antenna 4 through the through hole 12. Therefore, the pattern antenna 4 having an electrical length shorter than that of the radiation conductor 6 can resonate in a relatively high frequency band. In the case of the present embodiment example, the pattern antenna 4 is designed to be tuned in the frequency band of 700 to 770 MHz, so that the high frequency part of the television broadcast UHF band can be received by the pattern antenna 4.

  Thus, in the antenna device 1 according to the present embodiment, the chip antenna 2 is mounted on the antenna substrate 3 having the pattern antenna 4 provided on the lower surface, and the high frequency part of the required frequency band is the pattern antenna 4. Since the remaining band after reception is received by the chip antenna 2, the two-band configuration applicable to a wide frequency band is realized without increasing the planar size of the apparatus. . Specifically, the chip antenna 2 operating as a tunable antenna can be tuned in a frequency band of 470 to 700 MHz, and the pattern antenna 4 having a relatively short electrical length can be tuned in a frequency band of 700 to 770 MHz. Therefore, this antenna device 1 can cover the entire UHF band (470 to 770 MHz) of television broadcasting. Since the chip antenna 2 only needs to be set so as to cover the band excluding the high frequency part where the pattern antenna 4 can be tuned, it is not necessary to increase the number of variable capacitance elements 7 in particular. In addition, since the pattern antenna 4 has a relatively short electric length and is formed in a meander shape, the pattern antenna 4 can be formed compactly in a limited area of the antenna substrate 3. Therefore, the antenna device 1 can obtain good reception sensitivity over a wide frequency band without reducing the size and gain, and is suitable as a reception antenna for a television broadcast UHF band built in a cellular phone or the like. It is.

  Further, in the antenna device 1 according to the present embodiment, the power supply to the pattern antenna 4 is cut off when the power is supplied to the chip antenna 2 by the switching operation of the high-frequency changeover switch 8. Therefore, even if either the chip antenna 2 or the pattern antenna 4 is selected and supplied with power, there is no possibility that the chip antenna 2 and the pattern antenna 4 will interfere with each other. Antenna performance can be expected.

  In addition, the antenna device 1 according to the present embodiment is a module in which the chip antenna 2 is mounted on the antenna substrate 3 as a unit, so that the antenna device 1 can be easily mounted on the mother substrate 20 and is easy to handle. It is applicable to various mother boards 20 having different circuit configurations and is excellent in versatility. However, when it is not necessary to unitize the antenna device 1 using a substrate dedicated to the antenna, the chip antenna 2 may be directly mounted on the other surface of the mother substrate 20 provided with the pattern antenna 4 on one surface.

  Further, in this antenna apparatus 1, the bias circuit 9 has the DC / DC converter 15 that boosts the voltage level of the bias control signal to a required magnitude, and the antenna apparatus even if the power supply voltage on the mother board 20 side is low. 1 tuning voltage V (TUNE) can be set higher than the power supply voltage, so that the capacitance value of the variable capacitance element 7 can be obtained even when the antenna device 1 is built in a portable wireless device in which the power supply voltage is set lower. There is no risk of disturbing the control.

  In the above embodiment, as shown in FIG. 4, a DC tuning voltage V (TUNE) applied to the variable capacitance element 7 is supplied from the tuner on the mother board side to the antenna device 1 by a dedicated wiring pattern. However, as shown in FIG. 5, the tuning voltage V (TUNE) may be supplied to the antenna device 1 by superimposing it on the feed signal RF, which can simplify the wiring pattern layout on the mother board side. it can.

It is the perspective view which looked at the antenna apparatus which concerns on the example of embodiment of this invention from the downward direction. It is a disassembled perspective view of this antenna apparatus. It is an external view which shows the state which mounted this antenna apparatus in the motherboard. It is an equivalent circuit diagram of the antenna device. It is the equivalent circuit schematic of the modification of this antenna apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna apparatus 2 Chip antenna 3 Antenna board 4 Pattern antenna 5 Base body 6 Radiation conductor 6a Discontinuous part 7 Variable capacitance element (varactor diode)
8 High-frequency switch (high-frequency switching circuit)
8a Input terminal 8b First output terminal 8c Second output terminal 9 Bias circuit 10, 11 Transmission line 12 Through hole 14 External connection terminal 15 DC / DC converter (step-up means)
20 Mother board P1, P2 Feeding part

Claims (5)

A chip antenna in which a radiation conductor is wound in a band shape on the outer peripheral surface of a base made of a dielectric or magnetic material, and a variable capacitance element is interposed in a discontinuous portion of the radiation conductor, and the chip antenna on one side And a pattern antenna formed as a conductor pattern having an electrical length shorter than that of the radiation conductor on the other surface of the circuit board,
A transmission line for supplying a feeding signal to the radiation conductor of the chip antenna and the pattern antenna, and a bias line for changing a capacitance value by supplying a tuning voltage based on a bias control signal to the variable capacitance element on the circuit board. An antenna device is provided, wherein the pattern antenna is tuned to a relatively high and narrow frequency band, and the chip antenna is tuned to a relatively low and wide frequency band.   2. The antenna device according to claim 1, wherein the pattern antenna is formed as a meander-shaped conductor pattern.   3. The circuit board according to claim 1, wherein the circuit board is connected to an input terminal connected to a power feeding circuit, a first output terminal connected to a power feeding part of the chip antenna, and a power feeding part of the pattern antenna. And a high-frequency switching circuit having a second output terminal, and the high-frequency switching circuit is controlled so that the input terminal is selectively conducted to the first output terminal or the second output terminal. An antenna device characterized by that.   4. The antenna board according to claim 3, wherein the circuit board is an antenna board having an external connection terminal connected to a wiring pattern of an external circuit board, the high-frequency switching circuit, and a bias circuit that generates the tuning voltage. A chip antenna mounting structure of a characteristic antenna device.   5. The chip antenna mounting structure for an antenna device according to claim 4, wherein boosting means for boosting the voltage level of the bias control signal to a required magnitude is provided in the bias circuit.

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