JP2009021716A - Tunable antenna and radio terminal equipment having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin tunable antenna easily built in radio terminal equipment, and having radiation gain equal to that of a conventional antenna. <P>SOLUTION: The antenna comprises: a ground substrate 1; first and second short stubs 2, 3; first and second variable-capacitance diodes 4, 5; and a power feed section 6. One end of the power feed section 6 is connected to the ground substrate 1, and each one end of the two short stubs 2, 3 is connected to the other end of the power feed section 6. One end of the first variable-capacitance diode 4 is connected to the other end of the first short stub 2, and the ground substrate 1 is connected to the other end of the variable-capacitance diode 4. One end of the second variable-capacitance diode 5 is connected to the other end of the second short stub 3, and the ground substrate 1 is connected to the other end of the variable-capacitance diode 5. The capacitance values of the first and second variable-capacitance diodes 4, 5 are controlled by a voltage control circuit 12, and the operating frequency of the antenna is tuned to a desired one. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tuning antenna that tunes the operating frequency of an antenna to a desired frequency using a variable capacitance element, and a wireless terminal device that includes the tuning antenna.

  In recent years, a radio system that is composed of a plurality of narrowband channels such as terrestrial digital broadcasting and uses a wide frequency band as a whole system has become widespread, and the development of radio terminal devices corresponding to this has been activated.

  The antenna corresponding to the wireless system as described above does not always need to transmit and receive all electromagnetic waves in a wide frequency band used as the entire system, and may operate only at individual channel frequencies depending on the situation.

  For this reason, a method is widely used in which the operating frequency of an antenna is varied using a variable capacitance element or a switch and is tuned only to a desired channel frequency. By using the tuning method in this way, it is possible to reduce the size and gain of the antenna.

As typical examples of the tuning antenna, there are methods described in Patent Documents 1 and 2, for example.
JP 2006-041840 A JP 2002-335117 A

  In Patent Document 1, a variable tuning circuit and a band switching circuit are connected to a loop element that operates as an antenna. The loop element is arranged so that the loop opening surface thereof is orthogonal to the substrate surface of the circuit board of the telephone. The operating frequency of the antenna is changed by the variable tuning circuit and the band switching circuit.

  In Patent Document 2, a radiation electrode is formed on a rectangular parallelepiped base, and a resonance frequency adjusting means is added. The resonance frequency adjusting means has a capacity or inductance, and the operating frequency of the antenna is changed by changing the capacity or inductance.

  The tuning antenna described in Patent Document 1 is arranged so that the loop opening surface of the loop element is orthogonal to the substrate surface of the circuit board of the telephone, and the antenna has a thickness of 10 mm. Therefore, when this antenna is mounted on a wireless terminal device, there is a problem that it is difficult to reduce the thickness of the wireless terminal device.

  In addition, the tuning antenna described in Patent Document 2 has a rectangular parallelepiped base, and the thickness of the antenna needs to be about 5 mm in order to obtain a good radiation gain of the antenna. Therefore, when this antenna is mounted on a wireless terminal device, there is a problem that it is difficult to reduce the thickness of the wireless terminal device.

  In view of the above, a thin tuned antenna is desired to reduce the thickness of the wireless terminal device.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a tuned antenna that is thin and has a radiation gain equivalent to that of a conventional product.

  The operating frequency of the antenna is a frequency at which the input impedance of the antenna and the impedance of the power supply unit are complex conjugate, that is, the frequency at which the input impedance of the antenna is most matched to the impedance of the power supply unit.

  The input impedance of the antenna is determined by the inductive reactance of the transmission line and the capacitive reactance of the variable capacitance element. That is, when the capacitive reactance of the variable capacitance element changes, the input impedance of the antenna changes and the operating frequency of the antenna also changes.

  As an example, a case where a variable capacitance diode is used as the variable capacitance element will be described. As the reverse voltage applied to the variable capacitance diode increases, the capacitance value of the variable capacitance diode decreases and the capacitive reactance increases. This is because the capacitive reactance is defined by 1 / ωc (ω is the angular frequency, and c is the capacitance value of the variable capacitance diode).

  That is, when the reverse voltage applied to the variable capacitance diode is changed, the capacitive reactance is changed and the input impedance of the antenna is also changed, so that the operating frequency of the antenna can be tuned to a desired frequency.

  Also, the number of transmission lines, topology, length, and number of variable capacitance elements so that good matching with the power feeding unit can be realized at a desired operating frequency, and the operating frequency of the antenna can be changed within a desired frequency range. It is necessary to select a combination of capacitance values.

  In order to achieve the above object, the invention of claim 1 includes a ground substrate, a first transmission line made of a short stub, a second transmission line made of a short stub, a first variable capacitance element, and a second In the tunable antenna including the variable capacitance element and the power feeding unit, one end of the power feeding unit and the ground substrate are electrically connected, and the other end of the power feeding unit and each one end of the two transmission lines are connected to each other. Electrically connected in parallel, the other end of the first transmission line and one end of the first variable capacitor are electrically connected, and the other end of the first variable capacitor and the ground substrate Are electrically connected, the other end of the second transmission line and one end of the second variable capacitance element are electrically connected, and the other end of the second variable capacitance element and the ground substrate are Tuned antenna characterized by being electrically connected It is.

  According to a second aspect of the present invention, there is provided a tuning antenna including a ground substrate, a first transmission line composed of an open stub, a second transmission line composed of a short stub, a variable capacitance element, and a power feeding unit. One end of the first part and the ground substrate are electrically connected, one end of the first and second transmission lines is electrically connected in parallel to the other end of the power feeding part, and the second transmission line The tuning antenna is characterized in that the other end and one end of the variable capacitance element are electrically connected, and the other end of the variable capacitance element and the ground substrate are electrically connected.

  The invention of claim 3 includes a ground substrate, a first transmission line made of a short stub, a second transmission line made of a short stub, a third transmission line made of a coupling line, and a first variable capacitance element. And a second variable capacitance element and a power feeding unit, wherein one end of the power feeding unit and the ground substrate are electrically connected, and the other end of the power feeding unit and the third transmission line One end of the third transmission line, and the other end of the third transmission line and each one end of the first and second transmission lines are electrically connected in parallel. One end of the first variable capacitance element is electrically connected, the other end of the first variable capacitance element and the ground substrate are electrically connected, and the other end of the second transmission line. Are electrically connected to one end of the second variable capacitance element, and the second variable capacitance element is electrically connected. It is a tunable antenna, wherein a the other end and the ground board of the capacitor are electrically connected.

  According to a fourth aspect of the present invention, the electrical length of the transmission line and the capacitance value of the variable capacitance element are determined so that the voltage standing wave ratio of the tuned antenna is 3 or less for a predetermined frequency. The tunable antenna according to any one of claims 1 to 3.

  According to a fifth aspect of the present invention, the transmission line is a conductor pattern formed on a printed board or a flexible board, and the ground board, the variable capacitance element, and the power feeding unit are installed on the printed board or the flexible board. The tunable antenna according to any one of claims 1 to 4, wherein the tunable antenna is provided.

  A sixth aspect of the present invention is a wireless terminal device including the tuning antenna according to any one of the first to fifth aspects.

The tuned antenna according to the present invention has the following effects.
(1) The tuned antenna of the present invention can use a conductor pattern formed on a printed circuit board as a transmission line, and can also install a ground substrate, a variable capacitance element, and a power feeding unit on the printed circuit board. Thus, the antenna can be thinned by using the transmission line functioning as a radiating element as the conductor pattern of the printed circuit board. Further, since the tuning antenna can be formed integrally with a high-frequency circuit such as a control device for a variable capacitance element, it can be easily incorporated in a wireless terminal device.
(2) The tunable antenna of the present invention can use a flexible substrate instead of the printed circuit board. That is, the tuned antenna of the present invention can use a conductor pattern formed on a flexible substrate as a transmission line, and can also install a ground substrate, a variable capacitance element, and a power feeding unit on the flexible substrate. As described above, by using the transmission line functioning as a radiating element as the conductor pattern of the flexible substrate, the antenna can be thinned and bent. In addition, since such an antenna can be bent and incorporated in a gap of the case of the wireless terminal device, it is very easy to incorporate it in the wireless terminal device.
(3) When a transmission line functioning as a radiating element is produced as a conductor pattern of a printed circuit board or a flexible substrate, and an antenna peripheral circuit such as a variable capacitance element is mounted on the printed circuit board or the flexible substrate, a conventional printed circuit board Alternatively, a flexible substrate manufacturing process can be used. Therefore, it becomes possible to produce a tuning antenna at low cost and in large quantities.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram illustrating a structure of an antenna A1 according to the present embodiment.

  In the present embodiment, the first short stub 2 as the first transmission line, the second short stub 3 as the second transmission line, the first variable capacitance diode 4 as the first variable capacitance element, and the second The second variable capacitance diode 5 was used as the variable capacitance element. In addition, MEMS (Micro Electro Mechanical Systems) can also be used as the first and second variable capacitance elements.

  This transmission line functions as a radiating element, and the variable capacitance element is for changing the operating frequency of the antenna.

  The antenna A1 is formed of a ground substrate 1, a first short stub 2, a second short stub 3, a first variable capacitance diode 4, a second variable capacitance diode 5, and a power feeding unit 6. The first and second short stubs 2 and 3 were formed of strip conductors.

  The power feeding unit 6 is for supplying high frequency power to the metal conductor to which the power feeding unit 6 is electrically connected, or for receiving high frequency power from the metal conductor. In the antenna A1, the ground substrate 1, the first short stub 2, and the second short stub 3 are metal conductors.

  The ground substrate 1 is electrically connected to one end of the power supply unit 6, and one end of the first short stub 2 and one end of the second short stub 3 are electrically connected in parallel to the other end of the power supply unit 6. Yes.

  One end of the first variable capacitance diode 4 is electrically connected to the other end of the first short stub 2, and the ground substrate 1 is electrically connected to the other end of the first variable capacitance diode 4. Yes.

  One end of the second variable capacitance diode 5 is electrically connected to the other end of the second short stub 3, and the ground substrate 1 is electrically connected to the other end of the second variable capacitance diode 5. Yes.

  The antenna A1 receives the electromagnetic waves near 470 MHz used in terrestrial digital broadcasting, and the electric lengths of the first and second short stubs 2 and 3 and the capacities of the first and second variable capacitance diodes 4 and 5. The value is optimized. These optimization methods are described in detail below.

First, the input impedance Z _in of the antenna A1 is shown in the following formula 1.

  Here, Z1 is an impedance in the first short stub 2, Z2 is an impedance in the second short stub 3, j is an imaginary unit, β is a propagation constant, ω is an angular frequency, and L1 is an electrical length of the first short stub 2. , L2 is the electrical length of the second short stub 3, C1 is the capacitance value of the first variable capacitance diode 4, and C2 is the capacitance value of the second variable capacitance diode 5.

  The range of L1 is 50 mm to 150 mm (allocation at 5 mm intervals), the range of L2 is 50 mm to 150 mm (allocation at 5 mm intervals), the range of C1 is 1 pF to 3 pF (allocation at 0.5 pF intervals), and C1 = C2 Z1 is calculated for all combinations of L1, L2, C1, and C2, and L1, L2, and C1 are set so that the VSWR (voltage standing wave ratio) calculated by the following formula (2) is 3 or less. , C2 combination was derived. Here, the purpose of setting the VSWR to 3 or less is to realize an antenna having good transmission / reception characteristics by matching the input impedance of the antenna and the input impedance of the power feeding unit 6 well.

  As a result of derivation, in the antenna A1, the electrical length of the first short stub 2 is 85 mm, the electrical length of the second short stub 3 is 115 mm, the capacitance value of the first variable capacitance diode 4 is 1.5 pF, and the second variable. It was found that when the capacitance value of the capacitive diode 5 was 1.5 pF, the VSWR was 3 or less.

  FIG. 2 is a diagram showing the radiation gain of the antenna A1 of the present embodiment. The radiation gain with respect to the horizontal polarization in the YZ plane in FIG. 1 was measured, and the average value was calculated. Specifically, the horizontally polarized wave radiated from the transmitting antenna was received by the antenna A1. At this time, the antenna A1 is rotated in the YZ plane (rotated around the X axis), the received power (in dBm unit) is measured every 1 degree from 0 to 359 degrees, and the obtained 360 received powers are measured. Averaged. Furthermore, the average received power was compared with the received power of the reference antenna (isotropic antenna), and expressed in dBi units. As an example, the radiation gain of −8 dBi indicates that the gain of 10.15 dB is lower than the peak radiation gain (+2.15 dBi) of the dipole antenna.

  In the low frequency band of 400 to 500 MHz, the average radiation gain of the conventional built-in antenna is -10 to -8 dBi. However, the antenna A1 of this embodiment also has an average radiation gain of about -8 dBi with a peak at around 470 MHz. It has been obtained and achieves the same reception performance as conventional products.

  Moreover, the thickness of the conventional built-in antenna was about 5 to 10 mm. On the other hand, since the antenna A1 of this embodiment is only the thickness of the ground substrate 1, the short stubs 2, 3, the variable capacitance diodes 4, 5, and the power feeding unit 6, the thickness of the antenna is about 1 mm. Thinner than products.

  As described above, according to the antenna A1 of the present embodiment, the antenna thickness can be reduced to about 1 mm while having the reception performance equivalent to that of the conventional built-in antenna.

  Next, 2nd embodiment of this invention is described below based on an accompanying drawing.

  FIG. 3 is a diagram showing the structure of the antenna A2 of the present embodiment.

  In the present embodiment, the first short stub 2 as the first transmission line, the second short stub 3 as the second transmission line, the first variable capacitance diode 4 as the first variable capacitance element, and the second The second variable capacitance diode 5 was used as the variable capacitance element. In addition, MEMS (Micro Electro Mechanical Systems) can also be used as the first and second variable capacitance elements.

  This transmission line functions as a radiating element, and the variable capacitance element is for changing the operating frequency of the antenna.

  The antenna A2 is obtained by arranging all the above-described antennas A1 on one printed circuit board 7.

  That is, the antenna A2 includes the ground substrate 1, the first short stub 2, the second short stub 3, the first variable capacitance diode 4, the second variable capacitance diode 5, and the power feeding unit 6 on the printed circuit board 7, It is produced in a substantially flat plate shape. The first and second short stubs 2 and 3 are conductor patterns formed on the printed circuit board 7. The first and second variable capacitance diodes 4 and 5 are surface-mounted on the printed circuit board 7.

  The ground substrate 1 is electrically connected to one end of the power supply unit 6, and one end of the first short stub 2 and one end of the second short stub 3 are electrically connected in parallel to the other end of the power supply unit 6. Yes.

  One end of the first variable capacitance diode 4 is electrically connected to the other end of the first short stub 2, and the ground substrate 1 is electrically connected to the other end of the first variable capacitance diode 4. Yes.

  One end of the second variable capacitance diode 5 is electrically connected to the other end of the second short stub 3, and the ground substrate 1 is electrically connected to the other end of the second variable capacitance diode 5. Yes.

  The antenna A2 receives the electromagnetic waves near 470 MHz used in terrestrial digital broadcasting, and the electrical lengths of the first and second short stubs 2 and 3 and the capacitances of the first and second variable capacitance diodes 4 and 5. The value is optimized. About the optimization method, the method similar to the above-mentioned antenna A1 was used.

  As a result of derivation, also in the antenna A2, the electrical length of the first short stub 2 is 85 mm, the electrical length of the second short stub 3 is 115 mm, the capacitance value of the first variable capacitance diode 4 is 1.5 pF, and the second variable. It was found that when the capacitance value of the capacitive diode 5 was 1.5 pF, the VSWR was 3 or less.

  FIG. 4 is a diagram showing the radiation gain of the antenna A2 of the present embodiment. The radiation gain with respect to horizontal polarization in the YZ plane in FIG. 3 was measured by the same method as the antenna A1 described above, and the average value was calculated.

  The average radiation gain of the antenna A2 of this embodiment is about −8 dBi with a peak at around 470 MHz, which is a reception performance equivalent to that of the conventional product (average radiation gain −10 to −8 dBi).

  Regarding the thickness of the antenna, the thickness of the printed circuit board 7 is about 1 mm, and the thickness of the ground substrate 1, the short stubs 2 and 3, the variable capacitance diodes 4 and 5, and the power feeding unit 6 is about 1 mm. Is about 2 mm, and can be made thinner than conventional products (thickness 5 to 10 mm).

  As described above, according to the antenna A2 of the present embodiment, the antenna can be thinned to about 2 mm while having the reception performance equivalent to that of the conventional built-in antenna.

  In addition, since all of the transmission line, variable capacitance element, and power feeding section constituting the tuning antenna are installed on one printed circuit board 7, the handling is simplified and the tuning antenna can be easily mounted on the wireless terminal device. be able to.

  Next, 3rd embodiment of this invention is described below based on an accompanying drawing.

  FIG. 5 is a diagram showing the structure of the antenna A3 of the present embodiment.

  In this embodiment, the open stub 8 is used as the first transmission line, the short stub 2 is used as the second transmission line, and the variable capacitance diode 4 is used as the variable capacitance element. Note that MEMS (Micro Electro Mechanical Systems) can be used as the variable capacitor.

  The antenna A3 includes a ground substrate 1, an open stub 8, a short stub 2, a variable capacitance diode 4, and a power feeding unit 6 on a flexible substrate 9, and is manufactured in a substantially flat plate shape. The open stub 8 and the short stub 2 are conductor patterns formed on the flexible substrate 9, and the variable capacitance diode 4 is surface-mounted on the flexible substrate 9.

  The ground substrate 1 is electrically connected to one end of the power supply unit 6, and one end of the open stub 8 and one end of the short stub 2 are electrically connected in parallel to the other end of the power supply unit 6.

  One end of the variable capacitance diode 4 is electrically connected to the other end of the short stub 2, and the ground substrate 1 is electrically connected to the other end of the variable capacitance diode 4.

  Nothing is connected to the other end of the open stub 8, and it is an open end.

  The antenna A3 is optimized for the electrical length of the open stub 8, the electrical length of the short stub 2, and the capacitance value of the variable capacitance diode 4 in order to receive electromagnetic waves near 470 MHz used in terrestrial digital broadcasting. . These optimization methods are described in detail below.

First, the input impedance Z _in of the antenna A3 is shown in the following equation 3.

  Here, Z1 is the impedance of the short stub 2, Z2 is the impedance of the open stub 8, j is an imaginary unit, β is a propagation constant, ω is an angular frequency, L1 is the electrical length of the short stub 2, and L2 is the electrical of the open stub 8. The length C1 is the capacitance value of the variable capacitance diode 4.

  The range of L1 is 50 mm to 150 mm (allocation at intervals of 5 mm), the range of L2 is 50 mm to 150 mm (allocation at intervals of 5 mm), the range of C1 is 1 pF to 3 pF (allocation at intervals of 0.5 pF), and L1, L2, C1 Zin was calculated for all the combinations of L1, L2, and C1 with which the VSWR (voltage standing wave ratio) derived by Equation 2 was 3 or less.

  As a result of derivation, in the antenna A3, when the electrical length of the open stub 8 is 145 mm, the electrical length of the short stub 2 is 90 mm, and the capacitance value of the variable capacitance diode 4 is 2.5 pF, the VSWR is 3 or less. I understood that.

  FIG. 6 is a diagram showing the radiation gain of the antenna A3 of the present embodiment. The radiation gain with respect to the horizontal polarization in the YZ plane in FIG. 5 was measured by the same method as the antenna A1 described above, and the average value was calculated.

  The average radiation gain of the antenna A3 of this embodiment is about −10 dBi with a peak at around 470 MHz, which is a transmission / reception performance equivalent to that of the conventional product (average radiation gain −10 to −8 dBi).

  Regarding the thickness of the antenna, the thickness of the flexible substrate 9 is about 0.1 mm, and the thickness of the ground substrate 1, the open stub 8, the short stub 2, the variable capacitance diode 4, and the power feeding unit 6 is about 1 mm. The antenna has a thickness of about 1 mm and can be made thinner than the conventional product (thickness 5 to 10 mm).

  As described above, according to the antenna A3 of the present embodiment, the antenna can be thinned and bent to about 1 mm while having reception performance equivalent to that of a conventional built-in antenna.

  In addition, since all of the transmission line, variable capacitance element, and power feeding section that make up the tuned antenna are installed on a single flexible substrate 9, handling is simplified and the tuned antenna is folded into the gap of the case of the wireless terminal device. It is easy to mount.

  Next, a fourth embodiment of the present invention will be described below based on the attached drawings.

  FIG. 7 is a diagram showing the structure of the antenna A4 of the present embodiment.

  In this embodiment, the first short stub 2 is used as the first transmission line, the second short stub 3 is used as the second transmission line, the coupling line 10 is used as the third transmission line, and the first variable capacitance element is used. The first variable capacitance diode 4 was used, and the second variable capacitance diode 5 was used as the second variable capacitance element. In addition, MEMS (Micro Electro Mechanical Systems) can also be used as the first and second variable capacitance elements.

  In the antenna A4, the ground substrate 1, the first short stub 2, the second short stub 3, the coupling line 10, the first variable capacitance diode 4, the second variable capacitance diode 5, and the power feeding unit 6 are installed on the printed circuit board 7. It is manufactured in a substantially flat plate shape. The first and second short stubs 2, 3 and the coupled line 10 are conductor patterns formed on the printed circuit board 7, and the first and second variable capacitance diodes 4, 5 are surface-mounted on the printed circuit board 7. Yes.

  The ground substrate 1 is electrically connected to one end of the power supply unit 6, and one end of the coupling line 10 is electrically connected to the other end of the power supply unit 6.

  One end of the first short stub 2 and one end of the second short stub 3 are electrically connected in parallel to the other end of the coupling line 10.

  One end of the first variable capacitance diode 4 is electrically connected to the other end of the first short stub 2, and the ground substrate 1 is electrically connected to the other end of the first variable capacitance diode 4. It is connected.

  One end of the second variable capacitance diode 5 is electrically connected to the other end of the second short stub 3, and the ground substrate 1 is electrically connected to the other end of the second variable capacitance diode 5. It is connected.

  The antenna A4 receives the electromagnetic wave near 470 MHz used in terrestrial digital broadcasting, the electrical length of the first and second short stubs 2 and 3, the electrical length of the coupling line 10, and the first and second variable. The capacitance values of the capacitive diodes 4 and 5 are optimized. These optimization methods are described in detail below.

First, the input impedance Z _in of the antenna A3 is shown in the following equation 4.

  Here, Z1 is an impedance in the coupled line 10, Z2 is an impedance in the first short stub 2, Z3 is an impedance in the second short stub 3, j is an imaginary unit, β is a propagation constant, ω is an angular frequency, and L1 is The electrical length of the coupling line 10, L2 is the electrical length of the first short stub 2, L3 is the electrical length of the second short stub 3, C1 is the capacitance of the first variable capacitance diode 4, and C2 is the second variable capacitance. This is the capacitance of the diode 5.

The L1 range is 50 mm to 150 mm (allocated at 5 mm intervals), the L2 range is 50 mm to 150 mm (allocated at 5 mm intervals), the L3 range is 50 mm to 150 mm (allocated at 5 mm intervals), and the C1 range is 1 pF to 3 pF ( and allocation) at 0.5pF intervals, under the conditions of C2 = C1, L1, L2, L3, C1, in all combinations of C2 to calculate the _{Z in,} VSWR in the number 2 of the above (voltage standing wave ratio) The combination of L1, L2, L3, C1, and C2 in which is 3 or less was derived.

  As a result of the derivation, in the antenna A4, the electrical length of the first short stub 2 is 55 mm, the electrical length of the second short stub 3 is 100 mm, the electrical length of the coupling line 10 is 55 mm, and the first variable It was found that when the capacitance value of the capacitive element 4 was 2.5 pF and the capacitance value of the second variable capacitive element 5 was 2.5 pF, VSWR was 3 or less.

  FIG. 8 is a diagram showing the radiation gain of the antenna A4 of the present embodiment. The radiation gain with respect to the horizontal polarization in the YZ plane in FIG. 7 was measured by the same method as the antenna A1 described above, and the average value was calculated.

  The average radiation gain of the antenna A4 of the present embodiment is about −9 dBi with a peak at around 470 MHz, which is a transmission / reception performance equivalent to that of a conventional product (average radiation gain of −10 to −8 dBi).

  Regarding the thickness of the antenna, the thickness of the printed circuit board 7 is about 1 mm, and the thickness of the ground substrate 1, the short stubs 2 and 3, the variable capacitance diodes 4 and 5, and the power feeding unit 6 is about 1 mm. Is about 2 mm, and can be made thinner than conventional products (thickness 5 to 10 mm).

  As described above, according to the antenna A4 of the present embodiment, the antenna can be thinned to about 2 mm while having the reception performance equivalent to that of the conventional built-in antenna.

  In addition, since all of the transmission line, variable capacitance element, and power feeding section constituting the tuning antenna are installed on one printed circuit board 7, the handling is simplified and the tuning antenna can be easily mounted on the wireless terminal device. be able to.

  Next, a fifth embodiment of the present invention will be described below with reference to the accompanying drawings.

  FIG. 9 shows a mobile phone 11 incorporating the antenna A2 of the present invention. The antenna of the present invention is built in the cellular phone 11 to receive terrestrial digital broadcasting, and a voltage control circuit 12 for supplying a control voltage determined for each reception channel to the variable capacitance diodes 4 and 5. Is mounted on the ground substrate 1. The antenna of the present invention is manufactured and mounted using a general-purpose printed circuit board process, and the voltage control circuit 12 is mounted using a general-purpose printed circuit board process. As described above, by using the tunable antenna A2 of the present invention, the antenna A2 and the peripheral circuit such as the voltage control circuit 12 can be easily integrated, and an antenna that can be easily built into a wireless terminal device can be realized. .

  The antennas A3 and A4 described above can be mounted on the mobile phone 11 in the same manner, and the antenna can be integrated with a peripheral circuit such as a voltage control circuit for controlling the operating frequency of the antenna. Can be easily built in.

1 is a structural diagram showing an antenna according to a first embodiment of the present invention. It is a characteristic view which shows the radiation gain of the antenna which concerns on 1st embodiment of this invention. It is a structural diagram showing an antenna according to a second embodiment of the present invention. It is a characteristic view which shows the radiation gain of the antenna which concerns on 2nd embodiment of this invention. It is a structural diagram which shows the antenna which concerns on 3rd embodiment of this invention. It is a characteristic view which shows the radiation gain of the antenna which concerns on 3rd embodiment of this invention. It is a structural diagram which shows the antenna which concerns on 4th embodiment of this invention. It is a characteristic view which shows the radiation gain of the antenna which concerns on 4th embodiment of this invention. FIG. 10 is a structural diagram showing a mobile phone incorporating an antenna according to a fifth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground substrate 2 Short stub 3 Short stub 4 Variable capacitance diode 5 Variable capacitance diode 6 Feed part 7 Printed circuit board 8 Open stub 9 Flexible substrate 10 Coupling line 11 Mobile phone 12 Voltage control circuit A1-A4 Tunable antenna of this invention

Claims (6)

  A tuning antenna comprising a ground substrate, a first transmission line made of a short stub, a second transmission line made of a short stub, a first variable capacitance element, a second variable capacitance element, and a feeding portion The one end of the power feeding unit and the ground substrate are electrically connected, and the other end of the power feeding unit and each one end of the two transmission lines are electrically connected in parallel, and the first transmission line The other end of the first variable capacitance element is electrically connected to the other end of the first variable capacitance element, and the other end of the first variable capacitance element is electrically connected to the ground substrate. The other end and one end of the second variable capacitance element are electrically connected, and the other end of the second variable capacitance element and the ground substrate are electrically connected. antenna.   In a tunable antenna comprising a ground substrate, a first transmission line composed of an open stub, a second transmission line composed of a short stub, a variable capacitance element, and a power feeding unit, one end of the power feeding unit and the ground substrate Are electrically connected, and one end of each of the first and second transmission lines is electrically connected in parallel to the other end of the power supply unit, and the other end of the second transmission line and the variable capacitance element. One end of the tunable antenna is electrically connected, and the other end of the variable capacitance element and the ground substrate are electrically connected.   A ground substrate, a first transmission line made of a short stub, a second transmission line made of a short stub, a third transmission line made of a coupled line, a first variable capacitance element, and a second variable capacitance In a tuned antenna including an element and a power feeding unit, one end of the power feeding unit and the ground substrate are electrically connected, and the other end of the power feeding unit and one end of the third transmission line are electrically connected. Connected, the other end of the third transmission line and each one end of the first and second transmission lines are electrically connected in parallel, the other end of the first transmission line and the first variable One end of the capacitive element is electrically connected, the other end of the first variable capacitive element and the ground substrate are electrically connected, and the other end of the second transmission line and the second variable capacitor One end of the element is electrically connected, and the other end of the second variable capacitance element Tunable antenna to a serial ground substrate is characterized by being electrically connected.   The electrical length of the transmission line and the capacitance value of the variable capacitance element are determined so that a voltage standing wave ratio of the tuned antenna is 3 or less with respect to a predetermined frequency. The tuning antenna according to any one of 1 to 3.   The transmission line is a conductor pattern formed on a printed circuit board or a flexible substrate, and the ground substrate, the variable capacitance element, and the power feeding unit are installed on the printed circuit board or the flexible substrate. The tunable antenna according to any one of claims 1 to 4.   A wireless terminal device comprising the tuning antenna according to claim 1.

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