JP2007128985A - Variable inductor and antenna using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the reduction of resonant frequency or the reduction of upper-limit frequency as an inductor, to stabilize potential of an adjusting coil in a variable inductor, and to appropriately reduce a change in potential or the generation of noises in a main coil. <P>SOLUTION: A switch 22 is opened or closed to change inductance between terminals 10 and 12. In this case, a terminal 20 of an adjusting coil 16 is connected to the ground through a choke coil 24 or a choke resistor 26. Therefore, current necessary to stabilize potential runs to the ground through the choke coil 24 or the choke resistor 26. Consequently, the potential on the side of the adjusting coil 16 is made stable when viewed from the side of the main coil 14. Thus, current generated due to the unstable potential is suppressed, and noises generating in the main coil 14 according to the current can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable inductor capable of changing an inductance value and an antenna device using the same.

  As a variable inductor capable of varying the inductance value, for example, there is one described in the following patent document. First, the variable inductor described in Patent Document 1 has a variable inductance value and is intended to be incorporated in a semiconductor integrated circuit or a microwave integrated circuit. FIG. As shown, a plurality of loop-like wiring layers 4 having an open end below the spiral inductor 1, field effect transistors Q1 to Q4 as switches for opening / shorting the open end, the spiral inductor 1, An insulating film is provided between the wiring layer 4 and the switches Q1 to Q4 are opened and closed to vary the inductance value.

The frequency switching device disclosed in Patent Document 2 is intended to widen the oscillation frequency range of a voltage controlled oscillation circuit formed of a semiconductor integrated circuit, and to be small and low phase noise. As shown in FIG. 1 of the same document 2, the main inductors L1 and L2 of the resonance circuit of the voltage controlled oscillation circuit are formed on the silicon substrate by wiring, and are magnetically coupled to the outer periphery of these main inductors L1 and L2. It is described that the sub inductors L3 and L4 are formed by wiring, the switches SW1 and SW2 are turned ON / OFF, and the inductances of the main inductors L1 and L2 are switched by switching the inductances of the sub inductors L3 and L4. .
Japanese Patent Laid-Open No. 08-162331 JP 2002-151953 A

  In the background art described above, a closed circuit (coil ring or coil ring) of an inductance adjusting sub-coil (hereinafter referred to as “adjusting coil”) is connected to the ground directly or via only a switch. This is because if the adjustment coil is not connected to the ground (GND), the potential becomes unstable, and noise may occur on the main coil (main coil) side. By connecting the adjustment coil to the ground, the potential is stabilized and noise generation in the main coil is reduced.

However, if the ground direct connection as described above is performed, the following inconvenience may occur.
(1) The parasitic capacitance between the main coil and the adjustment coil is directly connected to the ground. For this reason, the self-resonance frequency seen from the main coil side falls, and the inconvenience that the upper limit frequency which functions as an inductor falls arises.
(2) Comparing the parasitic capacitance generated between the main coil and the adjustment coil and the ground connection position, the parasitic capacitance near the ground connection is more grounded than the opposite parasitic connection. Will be strongly connected to. For this reason, directionality arises in the electrical characteristics of the main coil.

  The present invention pays attention to the above points, and while stabilizing the potential of the adjustment coil while satisfactorily suppressing the decrease in the self-resonance frequency and the upper limit frequency as the inductor viewed from the main coil side, The object is to satisfactorily reduce potential fluctuations and noise generation in the main coil.

  In order to achieve the above object, the present invention includes a main coil, at least one adjustment coil magnetically coupled to the main coil, and a switch connected between terminals of the adjustment coil to open and close the terminals. In the inductor, a closed circuit including the adjustment coil and the switch is connected to a ground of a circuit in which the main coil is used via a choke coil and / or a choke resistor. One of the main forms is that the switch is an electrical switch element or a mechanical switch element, and the electrical switch element corresponds to at least a PIN diode, FET, or junction transistor, and the mechanical switch element includes At least a mechanical relay is applicable. In another embodiment, when the switch is a switch element that allows a current to flow in one direction in the closed circuit, the switch element is connected in antiparallel. Still another embodiment is characterized in that at least one other adjustment coil is connected in series and / or in parallel to the main coil. The antenna device of the present invention is characterized in that any one of the variable inductors is used in a received signal matching circuit. The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

  According to the present invention, a switch is connected between terminals of at least one adjustment coil that is magnetically coupled to the main coil, and the main coil is used via a choke coil or choke resistor as a closed circuit formed thereby. By connecting to the circuit ground, it is possible to satisfactorily reduce potential fluctuations and noise generation in the main coil while satisfactorily suppressing a decrease in resonance frequency and occurrence of directionality of electrical characteristics.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

  First, Embodiment 1 of the present invention will be described with reference to FIG. 1A and 1B, a main coil 14 and a circuit (hereinafter simply referred to as “circuit body”) 15 in which an inductance of the main coil 14 is used are connected between terminals 10 and 12. The main coil 14 is provided with an adjustment coil 16 for electromagnetic coupling. Both terminals 18 and 20 of the adjustment coil 16 are connected to a switch 22, and one terminal 20 side of the adjustment coil 16 is connected to a choke coil 24 (see FIG. 1A) or a choke resistor or high resistance element 26. It is connected to the ground of the circuit body 15 through (see FIG. 5B).

  Of the above portions, the main coil 14 and the adjustment coil 16 are electromagnetically coupled as described above, thereby generating mutual inductance. The switch 22 may of course be a normal mechanical device, but may be a switch element that is electrically switched on and off. Examples of the switch element include a diode and a transistor.

  Next, the operation of this embodiment will be described. First, when the switch 22 is “OFF”, no current flows through the adjustment coil 16. For this reason, the interaction between the main coil 14 and the adjustment coil 16 does not occur, and the inductance viewed from the terminals 10 and 12 becomes the inductance of the main coil 14. On the other hand, when the switch 22 is turned “ON”, the terminals 18 and 20 of the adjustment coil 16 are short-circuited and a current flows. For this reason, a mutual inductance is generated between the main coil 14 and the adjustment coil 16, and the inductance viewed from the terminals 10 and 12 changes. In this way, the inductance between the terminals 10 and 12 can be varied by opening and closing the switch 22.

  By the way, in this embodiment, the terminal 20 side of the adjustment coil 16 is connected to the ground by the choke coil 24 or the choke resistor 26. For this reason, the current necessary for stabilizing the potential flows to the ground by the choke coil 24 and the choke resistor 26. Therefore, when viewed from the main coil 14 side, the potential on the adjustment coil 16 side becomes stable. For this reason, the current flowing due to potential instability is suppressed, and noise generated in the main coil 14 based on this current is reduced. The parasitic capacitance generated between the main coil 14 and the adjustment coil 16 is connected to the ground via the choke coil 24 or the choke resistor 26. Thereby, the connection between the parasitic capacitance and the ground is suppressed, and the lowering of the upper limit frequency at which the main coil 14 functions as an inductor can be suppressed.

  FIGS. 1C and 1D show a modification of the above-described embodiment. In this example, the main coil side and the adjustment coil side are directly connected by a choke coil or a choke resistor. In other words, a choke coil 28 (see FIG. 1C) or a choke resistor 30 (see FIG. 1D) is connected between the terminal 12 side of the main coil 14 and the terminal 20 side of the adjustment coil 16. ing.

  As described above, the choke coil 28 and the choke resistor 30 also function to flow a current for stabilizing the potential. For this reason, the potential difference between the main coil side and the adjustment coil side is eliminated, and the same effect as in the above embodiment can be obtained.

  FIG. 2 shows an example in which the inductance is varied in multiple stages. As shown in the figure, adjustment circuits 40 a, 40 b,..., 40 n including adjustment coil 16, switch 22 and choke coil 24 (or choke resistor 26) are provided so as to be electromagnetically coupled to main coil 14. It has been. If an inductance increase of ΔL occurs when the switch 22 of any one of the adjustment circuits is turned on with respect to the inductance LM of the main coil 14, the whole is in the range of ML to ML + n · ΔL, with ΔL as a unit. The inductance can be varied.

  Next, Embodiment 2 of the present invention will be described with reference to FIGS. The second embodiment is an example in which a PIN diode is used as a switching element. In the example of FIG. 3A, the anode of the PIN diode 52 is connected to the terminal 18 of the adjustment coil 16 via the coupling capacitor 50, and the cathode is connected to the terminal 20 of the adjustment coil 16. ing. Further, a driving power supply 60 is connected to both ends of the PIN diode 52 via choke resistors 54 and 56 and a switch 58. The negative side of the power supply 60 is connected to the ground. That is, the terminal 20 of the adjustment coil 16 is connected to the ground via the choke resistor 56 as in the above embodiment. When the switch 58 is OFF, the PIN diode 52 is also OFF. For this reason, no current flows through the adjustment coil 16. However, when the switch 58 is turned on, the voltage of the power source 60 is applied to the PIN diode 52 via the choke resistors 54 and 56, the PIN diode 52 becomes conductive, and both ends of the adjustment coil 16 are connected via the coupling capacitor 50. Short circuit. As a result, the inductance viewed from the terminals 10 and 12 of the main coil 14 changes.

  FIG. 3B shows an example in which a plurality of adjustment coil circuits 62a to 62n are electromagnetically coupled to the main coil 14, and the operation of each adjustment coil 16 is the same as that shown in FIG. It is the same. According to this example, by combining ON / OFF of the switch 58, the inductance viewed from the terminals 10 and 12 of the main coil 14 can be varied in multiple stages.

  FIG. 4 shows a modification of FIG. In FIG. 3B, the adjustment coil circuits 62a to 62n are provided independently for each coil, but are connected by a subordinate coupling capacitor 64, and the coupling capacitors 50 in the second and subsequent stages. And the coupling capacitor 64 for subordinate connection. The basic operation is the same as the example of FIG.

  In FIG. 5, the connection polarity of the PIN diodes 70 and 72 is reversed every other so that the subordinate coupling capacitor 64 is omitted, and among the choke resistors 74, 76, and 78, the central choke resistor 76 is replaced. This is a combined example. A switch 80 and a power source 84 are connected between the choke resistors 74 and 76, and a switch 82 and a power source 86 are connected between the choke resistors 78 and 76. A centrally connected choke resistor 76 is connected to the ground. FIG. 6 is a modification of FIG. 5, and the adjustment coil circuit shown in FIG. 5 is connected in multiple stages by a coupling capacitor 90.

  Next, the example of FIG. 7 will be described. In the examples of FIGS. 3 to 6 described above, the polarity of the power supply corresponds to the direction of the control current flowing through the PIN diode, and the connection polarity of the power supply is limited. However, in this example, the PIN diodes 52a and 52b are connected in reverse parallel. For this reason, even if any of the power supplies 60a and 60b having opposite polarities is connected, either one of the PIN diodes 52a and 52b becomes conductive. Thus, since the polarity of a power supply is not chosen, it is convenient.

  Next, Embodiment 3 of the present invention will be described with reference to FIG. The third embodiment is an example in which a MOSFET is used as a switch element. The example of FIG. 1A is an example in which the terminals 18 and 20 of the adjustment coil 16 are connected between the drain and source of the N-channel MOSFET 100, respectively, and the source is connected to the ground via the choke coil 24. ing. By applying a voltage to the gate 102, ON / OFF of the MOSFET 100 is controlled, and a switching operation is performed. In this example, when there is a risk of shorting in high frequency with the ground due to the parasitic capacitance between the main coil 14 and the adjustment coil 16, a coil or a resistor is connected between the source and gate of the MOSFET 100, Try to separate high frequency components.

  In the example of FIG. 8B, the terminals 18 and 20 of the adjustment coil 16 are connected to the source and drain of a P-channel MOSFET 110 via capacitors 112 and 114, respectively. A power source 118 is connected to the source of the MOSFET 110 via a coil 117, and the terminal 20 of the adjustment coil 16 is connected to the ground via a choke resistor 26. The coil 117 between the power source 118 and the source is inserted in order to isolate the power source in terms of high frequency. By applying a voltage to the gate 116, ON / OFF of the MOSFET 110 is controlled, and a switching operation is performed. The capacitors 112 and 114 are for reducing the leakage current flowing through the choke resistor 26, but the capacitor 114 may be omitted when the resistance value of the choke resistor 26 is large.

  Next, Embodiment 4 of the present invention will be described with reference to FIG. The fourth embodiment is an example in which another adjustment coil is connected to the main coil. In the example of FIG. 1A, a series circuit of other adjustment coils 200 and 202 is additionally connected to the main coil 14 in parallel, and between the terminals of the adjustment coils 200 and 202, respectively. Switches 204 and 206 are connected. According to this example, three adjustment coils 16, 200, and 202 are provided as a whole, and the inductance between the terminals 10 and 12 is multistaged by changing the combination of 0N / OFF of the switches 22, 204, and 206. Can be varied. The example of FIG. 5B is an example in which another adjustment coil 210 is connected in series to the main coil 14, and a switch 212 is connected between the terminals of the adjustment coil 210. According to this example, two adjustment coils 16 and 210 are provided as a whole, and the inductance between the terminals 10 and 12 can be varied in multiple stages by changing the combination of 0N / OFF of the switches 22 and 212. Can do.

  Next, Embodiment 5 of the present invention will be described with reference to FIG. The fifth embodiment is an example of an antenna device using the variable inductor described above. In the figure, an antenna unit 300 is connected to a circuit body 320 via a matching circuit unit 310. The matching circuit unit 310 is a circuit for extracting a signal having a desired frequency from the signal received by the antenna unit 300, and includes a tuning circuit including capacitors 312 and 322 and a variable inductor 314. The circuit body 320 performs amplification, detection, reproduction, and the like of a signal having a predetermined frequency extracted by the matching circuit unit 310. For example, a mobile phone is a suitable example.

  The variable inductor 314 has the same configuration as that shown in FIG. 3A described above, and the inductance between the terminals of the main coil 14 is changed by switching the switch 58 ON / OFF. Therefore, the tuning frequency of the entire circuit including the capacitor 312 changes, and only a signal having a desired frequency is supplied to the circuit body 320.

  In addition, this invention is not limited to the Example mentioned above, A various change can be added in the range which does not deviate from the summary of this invention. For example, the following are also included.

  (1) Although the ground connection is performed using one choke coil 24 or choke resistor 26 in the above embodiment, they may be connected in series and parallel. FIG. 11 shows some examples. 11 (A) and 11 (B) are modified examples of FIGS. 1 (A) and 1 (B). FIG. 11A shows an example in which a choke coil 24A and a choke resistor 26A are connected in series. FIG. 11B shows an example in which a choke coil 24B and a choke resistor 26B are connected in parallel. 11 (C) to 11 (F) are modified examples of FIGS. 1 (C) and 1 (D). First, FIG. 3C shows an example in which a choke resistor 30A is connected in parallel to the choke coil 28A. FIG. 4D shows an example in which a choke resistor 30B is connected in series to the choke coil 28B. FIG. 4E shows an example in which choke coils 28C and 28D are connected to both ends of the main coil 14 and the adjustment 16. FIG. 2F shows an example in which choke resistors 30C and 30D are connected to both ends of the main coil 14 and the adjustment 16. As shown in FIGS. 11 (C) to 11 (F), the embodiment shown in FIGS. 1 (A) to (B) may be combined with the embodiment shown in FIGS. 1 (C) to (D).

  (2) The number of connection stages of the adjustment coil may be appropriately increased or decreased as necessary. It is also optional to add other circuit elements such as coupling capacitors so as to achieve the same effect.

  (3) In the above embodiment, mechanical switches, PIN diodes, and MOSFETs are shown as the open / close switches. However, various electrical switch elements such as junction transistors and mechanical relays and mechanical switch elements may be used. .

  (4) The matching circuit shown in FIG. 10A is also an example, and various configurations such as π-type and T-type may be used. FIG. 5B shows another configuration example, in which capacitors 312A and 322A are connected in series, and the main coil 14 is connected in parallel with the ground. Comparing the two, FIG. 10A shows a configuration in which the variable inductor 314 is connected in series in a circuit, and FIG. 10B shows a configuration in which the variable inductor 314A is connected in parallel in a circuit.

  According to the present invention, a switch is provided between terminals of at least one adjustment coil that is magnetically coupled to the main coil, and the adjustment coil closed circuit is connected to the ground of the circuit body via the choke coil and / or the choke resistor. By connecting, it is possible to satisfactorily reduce potential fluctuations and noise generation in the main coil while satisfactorily suppressing lowering of the resonance frequency and lowering of the upper limit frequency as an inductor. It is.

It is a circuit diagram which shows the structure of Example 1 of this invention. It is a circuit diagram which shows the structure of Example 1 of this invention. It is a circuit diagram which shows the structure of Example 2 of this invention. It is a circuit diagram which shows the structure of Example 2 of this invention. It is a circuit diagram which shows the structure of Example 2 of this invention. It is a circuit diagram which shows the structure of Example 2 of this invention. It is a circuit diagram which shows the structure of Example 2 of this invention. It is a circuit diagram which shows the structure of Example 3 of this invention. It is a circuit diagram which shows the structure of Example 4 of this invention. It is a circuit diagram which shows the structure of Example 5 and its modification of this invention. It is a circuit diagram which shows the structure of the modification of Example 1 of this invention.

Explanation of symbols

10, 12: Terminal 14: Main coil 16: Adjustment coil 15: Circuit body 18, 20: Terminal 22: Switch 24, 24A: Choke coil 26, 26A: Choke resistors 28, 28A to 28D: Choke coils 30, 30A 30D: Choke resistors 40a, 40b,..., 40n: Adjustment circuit 50: Coupling capacitors 52, 52a, 52b: PIN diodes 54, 56: Choke resistors 58: Switches 60, 60a, 60b: Power supply 62a,. 62n: Coil circuit for adjustment 64: Coupling capacitor 70 for subordinate connection, 72: PIN diodes 74, 76, 78: Choke resistor 80, 82: Switch 84, 86: Power supply 90: Coupling capacitor 100, 110: MOSFET
102: gate 112, 114: capacitor 116: gate 117: coil 118: power source 124, 126: capacitor 128, 130: resistor 134: power source 200, 202: adjustment coil 204, 206: switch 210: adjustment coil 212: switch 300: antenna unit 310: matching circuit units 312, 312A, 322, 322A: capacitors 314, 314A: variable inductor 320: circuit body

Claims (5)

In a variable inductor including a main coil, at least one adjustment coil magnetically coupled to the main coil, and a switch connected between the terminals of the adjustment coil to open and close between the terminals,
A variable inductor, wherein a closed circuit including the adjustment coil and the switch is connected to a ground of a circuit in which the main coil is used via a choke coil and / or a choke resistor. The switch is an electrical switch element or a mechanical switch element. The electrical switch element corresponds to at least a PIN diode, an FET, or a junction transistor, and the mechanical switch element corresponds to at least a mechanical relay. The variable inductor according to claim 1. 2. The variable inductor according to claim 1, wherein when the switch is a switch element that allows a current to flow in one direction in the closed circuit, the switch element is connected in antiparallel. The variable inductor according to claim 1, wherein at least one other adjustment coil is connected to the main coil in series and / or in parallel. 5. An antenna device using the variable inductor according to claim 1 in a matching circuit for a received signal.

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