JP2002151953A - Frequency changeover device for voltage controlled oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized frequency changeover device for a voltage controlled oscillator circuit consisting of a semiconductor integrated circuit that extends an oscillated frequency range of the voltage controlled oscillator circuit and has an excellent phase noise characteristic. SOLUTION: Main inductors L1, L2 of a resonance circuit of the voltage controlled oscillator circuit are formed on a silicon substrate by wires. Sub- inductors L3, L4 magnetically coupled with the main inductors L1, L2 are formed on outer circumferences of the main inductors L1, L2 respectively by wires. By turning ON/OFF switches SW1, SW2 to switch the inductance of the sub inductors L3, L4, the inductance of the main inductors L1, L2 is switched. Since no switch is directly connected to the main inductors L1, L2, deterioration in the Q of a resonance circuit due to the parasitic resistance of the switch is avoided to improve the phase noise characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency switching device for a voltage controlled oscillator, and more particularly to a frequency switching device for increasing the oscillation frequency range of a voltage controlled oscillator having a resonance circuit integrated with an active element circuit.

[0002]

2. Description of the Related Art In a conventional voltage controlled oscillation circuit having a wide oscillation frequency range, a resonance circuit capable of changing the oscillation frequency and an active element circuit for driving the resonance circuit include:
Oscillation circuits are configured by being integrated together on one semiconductor substrate. In recent years, this type of voltage-controlled oscillation circuit has been used as a PLL in a local oscillation circuit of a wireless device represented by a mobile phone.
It is used for frequency synthesizers and the like. The performance required of a local oscillator configured using such a voltage controlled oscillator circuit includes high stability, a wide oscillation frequency range,
Low noise, low phase noise, and the like.

As an example of a conventional voltage controlled oscillator circuit, reference 1 ["RF-CMOS Oscillators with Switched Tuning" Cus
tom IC Conference, Santa Clara, CA., May 1998, p55
5-p558.] Shown in Fig. 6. This oscillation circuit is shown in FIG. This oscillation circuit is equivalent to a circuit in which a plurality of voltage-controlled oscillation circuits as shown in FIG. 11 are connected in parallel.

The configuration and operation of the voltage controlled oscillator shown in FIG. 11 will be described. A first transistor (M1) 1 and a second transistor (M1) for amplification and feedback of an oscillation circuit
2) 2 is a differential pair cross-coupling configuration. The first main inductor (L1) 5, the parasitic capacitance of the first variable capacitance type MOS transistor (M3) 3 connected in parallel thereto, the second main inductor (L2) 6, and the second main inductor (L2) 6 connected in parallel thereto. Variable capacitance type MOS transistor (M4) 4
A resonance circuit is constituted by the parasitic capacitance of First variable capacitance type M
OS transistor (M3) 3 and second variable capacitance type MOS
The parasitic capacitance is changed by changing the voltage Vc applied between the gate and the drain and source of the transistor (M4) 4. The oscillation frequency changes according to the change in the capacitance. At the top of this circuit is an S consisting of select transistors M5 and M6.
The W gate is connected. Switching to select one of a plurality of voltage controlled oscillator circuits using this gate,
A desired circuit can be oscillated. Further, by switching the inductors L1 and L2, the F
As shown in the graph of FIG. 7 (FIG. 12), a wide oscillation frequency range can be realized.

However, in this circuit, a plurality of identical circuits must be prepared, so that a large integrated circuit is required, and a chip area is required, resulting in an increase in chip cost. In particular, an inductor is formed in the shape of a spiral inductor to be realized on an integrated circuit. In a general silicon substrate, even an inductor having a value of several nH requires an area of at least about 100 μm ^2. .

Therefore, in this oscillation circuit, an oscillation circuit shown in FIG. 4 of Document 1 realizes a method of switching the frequency by switching only the capacitance without using a plurality of inductors. This oscillation circuit is shown in FIG. FIG.
In the oscillation circuit shown in (1), by switching the gate voltage VG of the RF switches M7 and M8 from High (power supply voltage Vdd) to Low (GND voltage), the fixed capacitance connected in parallel to the resonance circuit is switched from ground to open. Thus, the resonance frequency can be switched. In order to secure a wide frequency range, a plurality of variable capacitance MOS transistors are connected in parallel to the same circuit as a frequency switching circuit of the resonance circuit.

[0007]

However, in the conventional voltage controlled oscillator circuit, a MOS transistor for switching the frequency is provided in the resonance circuit, and the parasitic resistance component of the MOS transistor deteriorates the Q of the resonance circuit. However, there is a problem that the phase noise characteristic is deteriorated.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a voltage-controlled oscillation circuit having a wide oscillation frequency range and low phase noise characteristics. It is another object of the present invention to provide a voltage controlled oscillator circuit that does not require a large chip area when integrated.

[0009]

In order to solve the above problems, the present invention provides an oscillation circuit, a resonance circuit comprising an inductor and a variable capacitor connected to the oscillation circuit, Electrical connection between the main inductor, the sub-inductor magnetically coupled to the main inductor, and the sub-inductor And switching means for changing the inductance of the main inductor.

With this configuration, the Q of the resonance circuit is not degraded by the means for switching the inductance, and the voltage controlled oscillation circuit can have low phase noise characteristics.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS.

(First Embodiment) In a first embodiment of the present invention, the oscillation of the main inductor is changed by opening and closing a loop of a sub-inductor magnetically coupled to the main inductor. Is a voltage-controlled oscillation circuit for switching the voltage.

FIG. 1 is a circuit diagram of a voltage controlled oscillation circuit according to a first embodiment of the present invention. In FIG. 1, a first transistor (M1) 1 and a second transistor (M2) 2
Is a cross-coupled transistor that constitutes an oscillation amplifier. First variable capacitance type MOS transistor (M
3) 3 and second variable capacitance type MOS transistor (M4) 4
Is a transistor in which the capacitance between the gate and the source / drain changes depending on the applied voltage.

The first main inductor (L1) 5 and the second main inductor (L2) 6 are inductors forming a resonance circuit. The first auxiliary inductor (L3) 7 is an inductor that changes the inductance by changing the connection state, thereby changing the inductance of the first main inductor (L1) 5 that is magnetically coupled. Second sub inductor (L
4) Reference numeral 8 denotes an inductor that changes the inductance by changing the connection state to change the inductance of the magnetically coupled second main inductor (L2) 6.

The first main switch (SW1) 9 is a switch that changes the connection state of the first sub inductor (L3) 7 to change the inductance. Second main switch (SW
2) Reference numeral 10 denotes a switch for changing the connection state of the second sub inductor (L4) 8 to change the inductance. The first sub switch (SW3) 11 is a switch for grounding the first sub inductor (L3) 7. Second sub switch (SW4) 12
Is a switch for grounding the second auxiliary inductor (L4) 8.

FIG. 2 is a plan view showing the wiring configuration of the inductor of the voltage controlled oscillation circuit according to the first embodiment of the present invention. The first main inductor (L1) 5 is a square inductor forming a resonance circuit. The first sub inductor (L3) 7 is a square inductor formed outside the first main inductor (L1) 5. The first main inductor (L
1) 5, a first sub inductor (L 3) 7, a first main switch (SW 1) 9, and a first sub switch (SW 3) 11 are schematically shown. Second main inductor (L2) 6
The same applies to the second sub-inductor (L4) 8, the second main switch (SW2) 10, and the second sub-switch (SW4) 12.

FIG. 3 is a plan view showing another configuration of the voltage-controlled oscillation circuit according to the first embodiment of the present invention in which the sub-inductor of the inductor is wired inside. A first main inductor (L1) 5, a first sub inductor (L3) 7,
Main switch (SW1) 9 and first sub switch (SW3) 11
Is schematically shown. The second main inductor (L
2) The same applies to 6, the second sub inductor (L4) 8, the second main switch (SW2) 10, and the second sub switch (SW4) 12.

The operation of the voltage controlled oscillator according to the first embodiment of the present invention will be described.
First, the function of each element of the voltage controlled oscillation circuit will be described.
In the voltage controlled oscillation circuit shown in FIG.
1) The gates of 1 and the transistor (M2) 2 are connected to the drains of the transistors. Further, the sources of the transistors M1 and M2 are grounded. A first variable capacitance MOS transistor (M3) 3 for frequency change is provided between the drains of the transistors M1 and M2 and GND;
The second variable capacitance type MOS transistor (M4) 4 is connected. Further, a first main inductor (L1) 5 and a second main inductor (L2) 6 are connected between the drains of the transistors M1 and M2 and the power supply, respectively. The configuration so far is the same as that of the conventional oscillation circuit.

The main inductors L1 and L2 are connected to a first sub inductor (L3) 7 and a second sub inductor (L4) 8, respectively.
Magnetically coupled. The first sub inductor L3 is connected to the first main switch (SW1) 9 and the first sub switch (SW3) 11. The second sub inductor L4 is connected to the second main switch (SW2) 10 and the second sub switch (SW4) 12. The sub-inductors L3 and L4 are coils formed on a semiconductor substrate by wiring so as to be inductors in an actual wiring pattern. The sub inductors L3 and L4 are
When the main switches SW1 and SW2 are turned on, they function as inductors, and when turned off, they simply become stray capacitances. The sub switches SW3 and SW4 are means for connecting the sub inductors L3 and L4 to GND.

Second, the operation principle of switching the oscillation frequency of the voltage controlled oscillation circuit will be described. When the sub inductors L3 and L4 are magnetically coupled to the main inductors L1 and L2 of the resonance circuit,
Coupled by mutual inductance M. The sub-inductors L3 and L4 are switched by the main switches SW1 and SW2 so as to become inductors or stray capacitances, so that the inductance of the main inductors L1 and L2 is reduced by the switches SW1 to SW4.
It can be switched by SW4. Main switch S
The inductance L1on when W1 and SW2 are on and the inductance L1off when it is off have a relationship of L1on> L1off. Therefore, by switching the inductance, the oscillation frequency fosc of the voltage controlled oscillation circuit becomes fosc = 1 / (2 × π × (L × C) ^ (1/2)) (1). Here, L is the inductance of the main inductors L1 and L2 of the voltage controlled oscillation circuit, and C is the capacitance value of the variable capacitance type MOS transistors M3 and M4. When the main switches SW1 and SW2 are turned ON / OFF, the inductance of the main inductors L1 and L2 changes, so that the frequency can be switched.

Third, the operation of switching the oscillation frequency of the voltage controlled oscillation circuit will be described based on a specific configuration. The first main inductor L1 and the first sub inductor L3 are specifically realized by a wiring pattern as shown in FIG.
The first main inductor L1 is formed by an inner wiring. This inductance can be approximated as follows: L = 8.5 × (A ^ (1/2)) × (n ^ (5/3)) (2) Here, A is the area of the first main inductor L1, and n is the number of turns of the wiring. The first sub-inductor L3 of the outer wiring is separated by the first main switch SW1, and operates as an inductor when the first main switch SW1 is turned on. When the first main switch SW1 is off, the outer wiring operates as a mere stray capacitance, and does not affect the first main inductor L1 of the inner wiring.

When the first main switch SW1 is turned on, the first sub switch SW3 is turned on at the same time, and the first sub inductor L3 is grounded. By this operation, the first main inductor L1 and the first sub inductor L3 are coupled by mutual induction, and the inductance of the first main inductor L1 changes. By using a voltage-controlled oscillation circuit in which a plurality of such inductance-switchable inductors are connected in series or in parallel, a frequency-switching voltage-controlled oscillation circuit having characteristics as shown in FIG. 12 can be realized.

Furthermore, as compared with the conventional method of switching the capacitance, since the Q of the resonance circuit is not degraded due to the parasitic resistance, there is no adverse effect on the inductance at the time of switching the frequency, and a voltage having good phase noise characteristics is obtained. A controlled oscillation circuit can be realized.

Further, as shown in FIG.
3, L4 may be arranged inside the main inductors L1, L2. With such a configuration, the inductance of the main inductors L1 and L2 can be increased. If the inductances of the main inductors L1 and L2 are the same as those in the example of FIG. 2, the area of the inductor can be reduced.

As described above, in the first embodiment of the present invention, the voltage controlled oscillation circuit changes the inductance of the main inductor by opening and closing the loop of the sub inductor magnetically coupled to the main inductor. Since the oscillation frequency is switched, the oscillation frequency can be switched without lowering the Q of the resonance circuit.

(Second Embodiment) A second embodiment of the present invention is a voltage controlled oscillation circuit in which a ground shield layer is provided below a wiring layer of an inductance switching type inductor.

FIG. 4 is a plan view showing a wiring configuration of an inductor of a voltage controlled oscillation circuit according to a second embodiment of the present invention. In FIG. 4, a ground shield 17 is a ground shield made of polysilicon or the like. The ground switch (SW5) 23 is a switch for grounding the ground shield 17. First main inductor (L1) 5, first sub inductor (L3) 7, first main switch (SW1)
9 and a first sub-switch (SW3) 11 are schematically shown as in FIG. Second main inductor (L2) 6
The same applies to the second sub-inductor (L4) 8, the second main switch (SW2) 10, and the second sub-switch (SW4) 12.

FIG. 5 is a diagram schematically showing an AA 'section of the ground shield type inductor shown in FIG. In FIG. 5, the silicon oxide film 18 is an insulating layer. The silicon epi layer 19 is a layer grown epitaxially.
The silicon substrate 20 is a base silicon plate. First
Main inductor (L1) 5 'and first auxiliary inductor (L3)
7 ′ is an upper layer wiring corresponding to the first main inductor (L1) 5 and the first sub inductor (L3) 7. It is a figure showing the example which made two layers of inductors.

The operation of the voltage controlled oscillation circuit according to the second embodiment of the present invention configured as described above will be described.
The basic configuration of the inductance switching type inductor is the same as that shown in FIG. 2 except for the ground shield layer. As shown in FIG. 4, a layer of a ground shield 17 made of polysilicon or the like is provided below the wiring layer of the inductor. The ground shield 17 is grounded by a ground switch (SW5) 23. If the ground shield 17 is grounded only when switched to the side where the inductance is increased, the stray capacitance when the inductance is reduced can be reduced and the resonance frequency can be increased. As described above, when the ground shield layer is provided below the inductor layer, the inductor is electromagnetically separated from the silicon substrate, and is not affected by the resistance of the Psub substrate on the silicon substrate. Therefore, generation of noise due to the resistance of the Psub substrate can be reduced.

As shown in the cross-sectional view of FIG. 5, a plurality of inductors and a ground shield 17 are provided using a multilayer wiring to form a multilayer structure. However, the total inductance can be increased.

As described above, in the second embodiment of the present invention, the voltage-controlled oscillation circuit has a configuration in which the ground shield layer is provided below the wiring layer of the inductance switching type inductor. Noise due to noise.

(Third Embodiment) In a third embodiment of the present invention, the inductance of the main inductor is opened and closed by opening and closing the loop of the sub-inductor magnetically coupled to the main inductor, which is a multiple-turn spiral inductor. Is a voltage-controlled oscillation circuit that switches the oscillation frequency by changing the oscillation frequency.

FIG. 6 is a plan view showing the wiring configuration of the inductor of the voltage controlled oscillation circuit according to the third embodiment of the present invention. In FIG. 6, the first main inductor (L1) 5
Is a multiple-turn spiral inductor. A first main inductor (L1) 5, a first sub inductor (L3) 7,
A first main switch (SW1) 9 and a first sub switch (SW1)
3) 11 is schematically shown as in FIG. Second main inductor (L2) 6 and second auxiliary inductor (L4)
8, the second main switch (SW2) 10, and the second sub-switch (SW4) 12.

The operation of the voltage controlled oscillator according to the third embodiment of the present invention having the above configuration will be described.
The basic configuration of the inductance switching type inductor is the same as that shown in FIG. 2 except for the shape of the main inductor. As shown in FIG. 6, the inner main inductor L1 is
A spiral inductor with multiple turns instead of a single turn was used. With this configuration, the main inductor L1
Can be increased, and the main inductor L1 can be reduced in size.

As described above, in the third embodiment of the present invention, the voltage-controlled oscillation circuit opens and closes the loop of the sub-inductor magnetically coupled to the main inductor having a plurality of spiral inductors. Since the oscillation frequency is switched by changing the inductance of the inductor, the size of the resonance circuit can be reduced.

(Fourth Embodiment) In a fourth embodiment of the present invention, the loop of the sub-inductor of the main-sub-inductor which is magnetically coupled as a parallel spiral inductor having a plurality of turns is opened and closed, thereby forming the main inductor. This is a voltage-controlled oscillation circuit that switches the oscillation frequency by changing the inductance.

FIG. 7 is a plan view showing a wiring configuration of an inductor of a voltage controlled oscillation circuit according to a fourth embodiment of the present invention. In FIG. 7, the first main inductor (L1) 5
Is a multiple-turn spiral inductor. The first auxiliary inductor (L3) 7 is a multiple-turn spiral inductor wired in parallel with the first main inductor (L1) 5. A first main inductor (L1) 5, a first sub inductor (L3) 7, a first main switch (SW1) 9, and a first sub switch (SW3) 11 are schematically shown as in FIG. Things. The same applies to the second main inductor (L2) 6, the second sub inductor (L4) 8, the second main switch (SW2) 10, and the second sub switch (SW4) 12.

The operation of the voltage controlled oscillation circuit according to the fourth embodiment of the present invention configured as described above will be described.
The basic configuration of the inductance switching type inductor is the same as that shown in FIG. 2 except for the shape of the main and sub inductors. As shown in FIG. 7, the first main inductor (L1) 5
In parallel with the spiral inductor, the first sub inductor (L3) 7 is wired as a spiral inductor. With this configuration, when the inductance is switched, the inductance ratio can be increased, so that the frequency switching width can be increased.

As described above, in the fourth embodiment of the present invention, the voltage-controlled oscillation circuit opens and closes the loop of the sub-inductor of the main-sub inductor which is magnetically coupled as a parallel spiral inductor having a plurality of turns. Since the oscillation frequency is switched by changing the inductance of the main inductor, the frequency can be significantly switched.

(Fifth Embodiment) In a fifth embodiment of the present invention, a loop of an octagonal or circular sub inductor, which is magnetically coupled to an octagonal or circular main inductor, is opened and closed. By changing the inductance of the inductor,
This is a voltage-controlled oscillation circuit that switches the oscillation frequency.

FIG. 8 is a diagram showing the configuration of the inductor of the voltage controlled oscillator according to the fifth embodiment of the present invention. FIG.
In the above, the first main inductor (L1) 5 is an octagonal inductor forming a resonance circuit. The first sub inductor (L3) 7 is an octagonal inductor that changes the inductance by changing the connection state to change the inductance of the first main inductor (L1) 5 that is magnetically coupled. A first main inductor (L1) 5;
Sub inductor (L3) 7 and first main switch (SW1) 9
And the first sub-switch (SW3) 11 schematically as in FIG. Second main inductor (L2) 6
The same applies to the second sub-inductor (L4) 8, the second main switch (SW2) 10, and the second sub-switch (SW4) 12.

FIG. 9 is a plan view showing another configuration of the voltage-controlled oscillation circuit according to the fifth embodiment of the present invention in which a sub-inductor of the inductor is a circular inductor. A first main inductor (L1) 5 and a first sub inductor (L3) 7
, A first main switch (SW1) 9 and a first sub switch (SW3) 11 are schematically shown. A second main inductor (L2) 6, a second auxiliary inductor (L4) 8,
A second main switch (SW2) 10 and a second sub-switch (SW2)
4) The same applies to 12.

The operation of the voltage-controlled oscillation circuit according to the fifth embodiment of the present invention will be described.
The basic configuration of the inductance switching type inductor is the same as that shown in FIG. 2 except for the shape of the main and sub inductors. As shown in FIG. 8, the shape of the main and sub inductors L1 and L3 is octagonal. With this configuration, the inductance can be increased even in a small area.

Further, as shown in FIG. 9, the shape of the main and sub inductors L1 and L3 may be circular. Even with such a configuration, the inductance can be increased with a small area.

As described above, in the fifth embodiment of the present invention, the voltage controlled oscillation circuit is used to open and close the loop of the octagonal or circular sub-inductor magnetically coupled to the octagonal or circular main inductor. Thus, since the oscillation frequency is switched by changing the inductance of the main inductor, the resonance circuit can be downsized.

[0046]

As is apparent from the above description, in the present invention, the inductance of the main inductor is switched by changing the electrical connection state of the sub-inductor magnetically coupled to the main inductor. As a result, there is obtained an effect that the deterioration of Q of the resonance circuit due to the above is eliminated, and the voltage controlled oscillation circuit can have low phase noise characteristics.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage controlled oscillator according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a configuration of an inductor of the voltage controlled oscillator according to the first embodiment of the present invention;

FIG. 3 is a diagram showing another configuration of the inductor of the voltage controlled oscillator according to the first embodiment of the present invention;

FIG. 4 is a diagram showing a configuration of an inductor of a voltage controlled oscillator according to a second embodiment of the present invention;

FIG. 5 is a sectional view showing a configuration of an inductor of a voltage controlled oscillator according to a second embodiment of the present invention;

FIG. 6 is a diagram showing a configuration of an inductor of a voltage controlled oscillator according to a third embodiment of the present invention;

FIG. 7 is a diagram showing a configuration of an inductor of a voltage controlled oscillator according to a fourth embodiment of the present invention;

FIG. 8 is a diagram showing a configuration of an octagonal inductor of a voltage controlled oscillator according to a fifth embodiment of the present invention;

FIG. 9 is a diagram showing a configuration of a circular inductor of a voltage controlled oscillator according to a fifth embodiment of the present invention;

FIG. 10 is a circuit diagram of a conventional composite type voltage controlled oscillator circuit,

FIG. 11 is a circuit diagram of a conventional variable capacitance type voltage controlled oscillation circuit,

FIG. 12 is a graph showing a characteristic of a frequency change with respect to a control voltage in a conventional frequency switching type voltage controlled oscillator circuit;

FIG. 13 is a circuit diagram of a conventional capacitance switching type voltage controlled oscillation circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st transistor M1 2 2nd transistor M2 3 1st variable capacitance type MOS transistor M3 4 2nd variable capacitance type MOS transistor M4 5 1st main inductor L1 6 2nd main inductor L2 7 1st auxiliary inductor L3 8 2nd auxiliary Inductor L4 9 First main switch SW1 10 Second main switch SW2 11 First sub switch SW3 12 Second sub switch SW4 13 First selection transistor M5 14 Second selection transistor M6 15 First voltage controlled oscillator circuit output 16 Second voltage Control oscillation circuit output 17 Ground shield 18 Silicon oxide film 19 Silicon epilayer 20 Silicon substrate 21 RF switch M7 22 RF switch M8 23 Ground switch SW5

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takeshi Yasunaga 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa F-term within Matsushita Communication Industrial Co., Ltd. 5J081 AA02 CC07 CC42 DD04 DD11 DD24 EE02 EE03 EE09 EE14 FF18 FF25 JJ02 JJ12 JJ13 JJ14 KK02 KK11 KK17 KK23 LL08 MM01 MM07

Claims (12)

[Claims] 1. A semiconductor device comprising: an oscillation circuit; and a resonance circuit including an inductor and a variable capacitor connected to the oscillation circuit, and oscillating a signal having a frequency corresponding to a voltage applied to a control voltage terminal. In a voltage controlled oscillator configured with an integrated circuit, the inductor is a main inductor, a sub-inductor magnetically coupled to the main inductor, and a switching for switching an inductance of the main inductor by changing an electrical connection state of the sub-inductor. And a means for controlling the voltage. 2. The switching device according to claim 1, wherein the switching unit includes a first switch that closes a loop of the sub inductor and a second switch that grounds the sub inductor.
A voltage controlled oscillator as described. 3. Between the inductor and a semiconductor substrate,
The voltage controlled oscillator according to claim 1, further comprising a ground conductor layer. 4. The semiconductor device according to claim 1, wherein the inductor has two or more wiring layers, and a ground conductor layer is provided between the two layers and between the wiring layer and the semiconductor substrate.
A voltage controlled oscillator as described. 5. The voltage controlled oscillator according to claim 1, wherein said main inductor is a spiral inductor having one or more turns, and said auxiliary inductor is formed outside said main inductor. 6. The voltage controlled oscillator according to claim 1, wherein the main inductor is a spiral inductor having one or more turns, and the sub inductor is formed inside the main inductor. 7. The device according to claim 1, wherein the main inductor is a spiral inductor having one or more turns, and the sub inductor is a spiral inductor wired in parallel with the main inductor. Voltage controlled oscillator. 8. The voltage controlled oscillator according to claim 5, wherein the spiral inductor has a square shape. 9. The shape of the spiral inductor is 8
The voltage controlled oscillator according to any one of claims 5 to 7, wherein the voltage controlled oscillator is rectangular. 10. The shape of the spiral inductor,
The voltage controlled oscillator according to any one of claims 5 to 7, wherein the voltage controlled oscillator is circular. 11. A mobile wireless terminal device comprising a wireless transmission / reception circuit having a local oscillation circuit having a PLL circuit, wherein the PLL circuit uses the voltage-controlled oscillator according to any one of claims 1 to 10. A mobile wireless terminal device characterized by the above-mentioned. 12. A radio base station apparatus comprising a radio transmission / reception circuit having a local oscillation circuit having a PLL circuit, wherein the voltage controlled oscillator according to claim 1 is used for the PLL circuit. A radio base station apparatus characterized by the above-mentioned.