KR20090040640A - Transformer-based lc tank with differential-turned structure and differential-tuned voltage controlled oscillator using the lc tank - Google Patents

Abstract

A transformer-based LC tank with differential-turned structure and the differential-tuned voltage controlled oscillator using the LC tank are provided to improve the quality factor of the resonant cavity by applying the transformer to the LC tank resonant cavity. A differential tuning voltage controlled oscillator comprises a current source portion(110), the first active portion(121), the second active portion(122), and the LC tank resonant cavity. The LC tank resonant cavity generates the resonant frequency and is located between the first active portion and the second active portion. The LC tank resonant cavity comprises the transformer and the first to fourth varactors(Cv11,Cv12,Cv21,Cv22). The first and second varactors are serially connected and the capacitance is controlled into the positive direction. The capacitance of the third and fourth varactors is controlled into the negative direction.

Description

Transformer-based LC tank with differential-turned structure and differential-tuned voltage controlled oscillator using the LC tank}

The present invention relates to a differential tuning voltage controlled oscillator (VCO). In particular, the present invention relates to a differential tuning LC tank using a transformer and a differential tuning voltage controlled oscillator using the same.

In general, a voltage controlled oscillator that varies in frequency with voltage is mainly used in analog sound synthesis apparatuses and mobile communication terminals. Such a voltage controlled oscillator typically has an LC resonator composed of an inductor (L) and one or more capacitors (C), that is, an LC tank resonator, which is a common mode generated by various causes in a chip environment. The performance is greatly affected by noise.

In general, common mode noise generated on a chip is generated in a power source, a bias circuit, low frequency noise of an active circuit, a substrate, and the like. Common-mode noise affects the potential of the common node in the voltage-controlled oscillator, causing the fixed output frequency to shake, resulting in degradation of the phase-noise performance of the voltage-controlled oscillator.

As a method for suppressing common mode noise generated in a voltage controlled oscillator, a differential varcactor tuning method has been proposed.

The differential varistor tuning method connects two pairs of variable capacitors connected in series, namely, a pair of first and second varactor diodes (hereinafter, referred to as "varactors") in parallel to form a differential tuning structure, and generates capacitance of each pair. When varying through voltage, the common capacitance noise is suppressed by adjusting the direction of the variable capacitances to be complementary to each other (ie, one pair in the negative direction and the other pair in the positive direction). In general, common mode noise degrades the phase noise in proportion to the magnitude of the increasing ratio of the tuner's tuning voltage to the varistor. It can prevent the deterioration of characteristics.

However, in order to implement differential tuning in a voltage controlled oscillator, the differential tuning varactor must be decoupled from the point of view of direct current (DC) in the active device section. Therefore, conventionally, a blocking cap is used to separate the differential tuning varactor from the active element sector by direct current (DC).

 On the other hand, as another method for achieving the differential varistor tuning method, there is a method for implementing differential tuning by using the NMOS varactor and the PMOS varactor reacting at different polarities.

However, voltage controlled oscillators designed by this method must use blocking capacitors for differential tuning, which not only increases the core area of the voltage controlled oscillator, but also increases capacitance at the resonant section. Decrease the overall Q-factor. In addition, in order for differential tuning to be effective, both ends of the differential tuning must be symmetrical, but there is a problem that the ability of suppressing common mode noise is degraded due to the asymmetry of two terminals of the varistor's anode and the cathode. .

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an LC tank having a differential tuning structure for improving phase noise and variable frequency range performance, which is one of important performance indicators of a voltage controlled oscillator, and a differential tuning voltage controlled oscillator using the same.

According to a feature of the present invention for achieving the above technical problem, the present invention provides a LC tank comprising a plurality of inductors and a plurality of varactors in a voltage controlled oscillator to generate a resonant frequency and a differential tuning voltage controlled oscillator including the same do. Here, the LC tank has a transformer having a primary coil stage and first and second secondary coil stages, a first variable capacitor pair connected in series with each other in a different direction, and a first connection type having the same connection form as the first variable capacitor pair. And a second variable capacitor pair, wherein the first variable capacitor pair is connected to the first secondary coil end to form a closed loop, and the second variable capacitor pair is connected to the second secondary coil end to form a closed loop. The first coil end is connected to both ends of the first resonant node and the second resonant node.

The differential tuning voltage controlled oscillator basically has two tuning voltage nodes, and a first tuning voltage node for adjusting the capacitance of the first variable capacitor pair in a positive direction is connected to a common node of the first variable capacitor pair. And a second tuning voltage node that adjusts the capacitance of the second variable capacitor pair in the negative direction, between the third and fourth inductors at the second secondary coil end.

Each variable capacitor constituting the first and second variable capacitor pairs has the same capacitance, and the first and second variable capacitor pairs have the anodes connected to each other in common.

According to another aspect of the present invention for achieving the above technical problem, the present invention provides an LC tank and a differential tuning voltage controlled oscillator comprising the same consisting of one or more inductors and one or more capacitors in the voltage controlled oscillator to generate a resonant frequency do. Here, the LC tank includes a transformer having a primary coil stage and a secondary coil stage, a first variable capacitor pair connected in series in different directions, and a second variable capacitor pair having the same connection form as the first variable capacitor pair. The first variable capacitor pair is connected in series with the primary coil stage, the second variable capacitor pair is connected in series with the secondary coil stage, and the primary coil stage and the first variable capacitor pair The first resonant node and the second resonant node are connected to both contacts.

Here, the present invention further includes a switch connected to the primary coil end to determine whether mutual inductance is generated between the primary coil end and the secondary coil end.

The secondary coil stage is composed of first and second inductors connected in series, and the first and second inductors have the same inductance.

A first tuning voltage node for adjusting capacitance in a positive direction is connected to a common node of the first variable capacitor pair, and a second tuning voltage node for adjusting capacitance in a negative direction is disposed between the first and second inductors. Connected.

In addition, the first and second variable capacitor pairs have a form in which nodes of the variable capacitors are connected to each other in common, and each variable capacitor constituting the first and second variable capacitor pairs has the same capacitance.

According to an embodiment of the present invention, the present invention improves the structure of the LC tank resonator so that the differential tuning structure, that is, the differential varactor at both output stages is completely symmetrical structure while the differential varactor is DC separated from the active part. .

Accordingly, the present invention eliminates the problem of transition to the resonant frequencies of common noise and low frequency noise that can occur in a voltage controlled oscillator, and improves the phase noise characteristics.

In addition, by applying the transformer to the LC tank resonator, the present invention improves the quality factor of the resonator unit, and thus has a strength in low power operation of the voltage controlled oscillator and has a wide band output.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. .

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, etc. described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. have.

Hereinafter, a differential tuning voltage controlled oscillator according to an embodiment of the present invention will be described with reference to the accompanying drawings.

Prior to the description, the concept of the present invention will be briefly described.

The present invention DC-separates at least one varactor from the active element section without using a blanking cap when forming a plurality of varactors in a differential tuning structure. To this end, the present invention applies a transformer to the LC tank resonator, and forms a varactor at the secondary stage of the transformer, which is DC-separated into the active element section (same as the "first and second active sections" described below). do.

In order for the differential tuning to be effective, both ends of the differential tuning must be symmetrical. To achieve this, the present invention provides a first varactor pair in which the negative tuning is adjusted and a second varactor pair in which the tuning in both directions is controlled. When viewed from two differential outputs, they form symmetrical to each other.

1 to 3, an exemplary description will be made of an LC tank of a differential tuning structure and a differential tuning voltage controlled oscillator using the same according to a first embodiment of the present invention.

1 is a circuit diagram of a differential tuning voltage controlled oscillator according to a first embodiment of the present invention. As shown in FIG. 1, the differential tuning voltage controlled oscillator according to the first embodiment of the present invention includes a current source unit 110, a first active unit 121, a second active unit 122, and an LC tank resonator unit. 130.

The current source unit 110 is for supplying power to the first active unit 121 and includes a current source I1. The current source unit 110 may be configured of a power supply source and a transistor connected between the power supply source and the first active unit 121 in place of the current source I1. In this case, the transistor is configured such that a source is connected to a power supply source, a drain is connected to the first active part 121, and a bias voltage is input to the source.

The first active part 121 and the second active part 122 continue oscillation of the LC tank resonator 130, and the first active part 121 is composed of two PMOS transistors to generate negative resistance. The second active part 122 is composed of two NMOS transistors to generate a negative resistance.

In detail, the first active part 121 includes a first PMOS transistor M1 and a second PMOS transistor M2 having emitters connected in common and gates connected to drains of each other, and a current source unit 110 is connected. The second active part 122 includes a first MNOS transistor M3 and a second NMOS transistor M4 having emitters connected in common and gates connected to drains thereof, and a common emitter connected to a ground terminal. do.

In this case, the drains of the first PMOS transistor M1 and the first NMOS transistor M3 are connected to each other so that the first PMOS transistor and the NMOS transistors M1 and M3 act as a first inverter. The drains of the second PMOS transistor M2 and the second NMOS transistor M4 are connected to each other so that the second PMOS transistor and the NMOS transistors M2 and M4 act as a second inverter.

Here, the resonant node Vout (+) is connected to the common drain of the first PMOS and NMOS transistors M1 and M3, and the resonant node Vout (-) is connected to the second PMOS and NMOS transistors M2 and M4. It is connected to the common drain.

Thus, the resonant nodes Vout (+) and Vout (−) represent the input and output of the first inverter and the input and output of the second inverter, respectively. Thus, the first and second inverters are cross coupled, and the resonant nodes Vout (+) and Vout (-) represent the differential outputs of the differential tuning voltage controlled oscillator.

The LC tank resonator 130 generates a resonant frequency and is positioned between the first active part 121 and the second active part 122. The LC tank resonator 130 has a transformer having three ports and a differential tuning structure in which differential varactors are formed at two ports forming second stages among the three ports.

Specifically, the LC tank resonator 130 may include first and second inductors connected in series to a common drain of the first PMOS and NMOS transistors M1 and M3 and a common drain of the second PMOS and NMOS transistors M2 and M4. L11 and L12 are connected to form a first port, that is, a primary coil end of a transformer. Here, the first and second inductors L11 and L12 have the same inductance.

In addition, in accordance with the primary coil stage of the transformer, the present invention forms a second port, that is, the first secondary coil stage of the transformer, with the third and fourth inductors L21 and L22 connected in series, and the fifth and Sixth inductors L31 and L32 form a third port, that is, a second secondary coil end of the transformer. Here, the third to sixth inductors L21, L22, L31, and L32 have approximately the same inductance.

In the structure of such a transformer, the present invention forms a closed loop by connecting the first and second varactors Cv11 and Cv12 connected in series to the second secondary coil stage for the differential tuning structure, and the third and third connected series. The fourth varactors Cv21 and Cv22 are connected in series with the first secondary coil to form a closed loop.

Here, the first and second selectors Cv11 and Cv12 are connected in opposite directions to each other, and the third and fourth selectors Cv21 and Cv22 are also connected in opposite directions to each other. However, the connection of the first and second collectors Cv11 and Cv12 and the connection of the third and fourth collectors Cv21 and Cv22 have the same form. For example, if the series connection of the first and second varactors Cv11 and Cv12 is a form in which the anodes are commonly connected, the series connection of the third and fourth varactors Cv21 and Cv22 and the form in which the anodes are commonly connected Has The first to fourth varieties Cv11 to Cv22 have approximately the same capacitance.

On the other hand, in order to adjust the capacitance of the varactor in the negative and positive directions for differential tuning, the tuning node Vc (-) which adjusts the capacitance in the direction of decreasing frequency includes the third and fourth inductors L21 and L22. The tuning node Vc (+), which is formed at the common node of and adjusts the capacitance in the direction of increasing frequency, is formed at the common node of the first and second varactors Cv11 and Cv12. The bias node VB is formed at the common node of the fifth and sixth inductors L31 and L32 and the common node of the third and fourth varactors Cv21 and Cv22.

As a result, since the differential varactors Cv11, Cv12, Cv21, and Cv22 of the LC tank resonator 130 shown in FIG. 1 are formed at the secondary coil ends of the transformer, the first and second active parts 121 and 122 are formed. Are DC isolated for.

Also, in the differential tuning structures at each resonant node (Vout (+), Vout (-)), the differential tuning structure is perfectly symmetrical with the same connection structure with the resonant node.

Hereinafter, the frequency characteristics of the LC tank resonator 130 shown in FIG. 1 will be described with reference to FIG. 2. FIG. 2 is a circuit diagram for describing an operation of the LC tank resonator illustrated in FIG. 1.

In FIG. 2, L1 is an equivalent representation of the primary coils L11 and L12 of the transformer, and L2 is an equivalent representation of the first secondary coils L21 and L22 of the transformer, and L3 is an equivalent representation of the transformer's first coils L11 and L12. Secondary coils L31 and L32 are equivalently displayed. And n1 and n2 represent turn ratios between the primary coil L1 and the first and second secondary coils L2 and L3. N22 represents the turn ratio between secondary coil stages.

In the structure of the LC tank resonator 130 illustrated in FIG. 2, the capacitance of the pair of varactors formed at the first secondary coil end is called C1, and the capacitance of the varactor pairs formed at the second secondary coil end is referred to as C2. The values of the capacitances C1 and C2 may be represented by Equation 1 below.

[Equation 1]

Here, Co is the capacitance when the control voltage is 0, and Kv is the frequency sensitivity versus control voltage of the oscillator with respect to the control voltage Vc (+) or Vc (-).

The capacitance C _T seen from the resonant nodes Vout (+) and Vout (−) together with the common mode noise Vncm is represented by the sum of the capacitances C1 and C2. However, if the differential tuning structures of the LC tank resonator 130 are perfectly symmetrical structures, that is, equal to n1 = n2, the value of the total variable capacitance C _T viewed from the resonator may be represented by Equation 2 below. have.

[Equation 2]

Where Vc is ⁺ Vc - Vc ^- a.

Therefore, according to Equation 2, the common mode noise can be eliminated by symmetrical differential tuning.

Hereinafter, with reference to Figure 3 will be described an L tank of a differential tuning structure and a differential tuning voltage controlled oscillator using the same according to a second embodiment of the present invention.

3 is a circuit diagram of a differential tuning voltage controlled oscillator according to a second embodiment of the present invention. As shown in FIG. 3, the differential tuning voltage controlled oscillator according to the second embodiment of the present invention includes a current source unit 110, a first active unit 121, a second active unit 122, and an LC tank resonator unit. 131.

Here, the same reference numerals are given to the same components as those of the first embodiment among the configurations of the differential tuning voltage controlled oscillator according to the second embodiment.

The current source unit 110 and the first and second active units 121 and 122 are the same as in the first embodiment of the present invention. The resonant nodes Vout (+) and Vout (-) are also configured in the same manner as in the first embodiment.

The LC tank resonator 131 according to the second embodiment of the present invention generates a resonant frequency like the LC tank resonator 130 according to the first embodiment. The first active part 121 and the second Located between the active portion 122, it has a transformer having two ports and a differential tuning structure having a differential varactor formed on a port forming a second stage of the two ports.

However, the LC tank resonator 131 according to the second embodiment of the present invention has a structure different from that of the LC tank resonator 130 of the first embodiment.

In detail, the LC tank resonator 131 may include first and second inductors connected in series to a common drain of the first PMOS and NMOS transistors M1 and M3 and a common drain of the second PMOS and NMOS transistors M2 and M4. L11 and L12 are connected to form a primary coil end of the transformer. Here, the first and second inductors L11 and L12 have the same inductance.

Corresponding to the primary coil stage of the transformer, the present invention forms the secondary coil stage of the transformer with third and fourth inductors L21 and L22 connected in series. Here, the third and fourth inductors L21 and L22 have the same inductance.

In the structure of such a transformer, the present invention uses the first and second varactors Cv11 and Cv12 connected in series for the differential tuning structure to the common drain of the first PMOS and NMOS transistors M1 and M3 and the second PMOS and NMOS transistors. To the common drain of (M2, M4). In addition, the third and fourth varactors Cv21 and Cv22 connected in series are connected in series to the secondary coil to form a closed loop.

Here, the first and second selectors Cv11 and Cv12 are connected in opposite directions to each other, and the third and fourth selectors Cv21 and Cv22 are also connected in opposite directions to each other. However, the connection of the first and second collectors Cv11 and Cv12 and the connection of the third and fourth collectors Cv21 and Cv22 have the same form. For example, if the series connection of the first and second varactors Cv11 and Cv12 is a form in which the anodes are commonly connected, the series connection of the third and fourth varactors Cv21 and Cv22 and the form in which the anodes are commonly connected Has

On the other hand, in order to adjust the capacitance of the varactor in the negative and positive directions for differential tuning, the tuning node Vc (-) which adjusts the capacitance in the direction of decreasing frequency includes the third and fourth inductors L21 and L22. The tuning node Vc (+), which is formed at the common node of and adjusts the capacitance in the direction of increasing frequency, is formed at the common node of the first and second varactors Cv21 and Cv22.

As a result, since the differential varactors Cv21 and Cv22 of the LC tank resonator 130 shown in FIG. 3 are formed at the secondary coil ends of the transformer, the first and second active parts 121 and 122 may be used. DC isolated.

Also, in the differential tuning structures at each resonant node (Vout (+), Vout (-)), the differential tuning structure is perfectly symmetrical with the same connection structure with the resonant node.

Hereinafter, the frequency characteristics of the LC tank resonator 131 illustrated in FIG. 3 will be described with reference to FIG. 4. FIG. 4 is a circuit diagram for describing an operation of the LC tank resonator illustrated in FIG. 3.

In FIG. 4, L1 is an equivalent display of the primary coils L11 and L12 of the transformer, and L2 is an equivalent display of the secondary coils L21 and L22 of the transformer. N represents a turn ratio between the primary coil L1 and the first and second secondary coils L2.

In FIG. 4, in order to achieve symmetrical tuning of the differential varistors P ports p1 and p2 and the S ports s1 and s2, the same frequency characteristic is obtained when the turn ratio n is 1 or not 1. The value of the first selector pairs Cv11 and Cv12 and the second selector pairs Cv21 and Cv22 should be adjusted to have a value.

Hereinafter, the transformer layout of the LC tank resonator of the voltage controlled oscillator according to the first embodiment of the present invention will be described with reference to FIG. 5.

As shown in FIG. 5, in the transformer having a three port according to the present invention, the first and second secondary coil stages L2 and L3 are independent of each other, and are referred to the nodes P1 and P2 of the primary coil stage. It is symmetrical with each other.

Accordingly, it can be seen that the differential varactors formed at the secondary coil ends L2 and L3 are DC-separated from the first and second active parts 211 and 212. And it can be seen that the present invention improves the common noise as having a completely symmetrical structure.

Now, referring to FIG. 6, it will be described that the differential tuning voltage controlled oscillator according to the present invention improves the characteristics of phase noise while having a wide frequency characteristic. FIG. 6 is a diagram illustrating a frequency tuning simulation result of the differential tuning voltage controlled oscillator shown in FIG. 1.

Where Vc ⁺ is the regulating voltage whose frequency is adjusted in the positive direction, Vc ^- is the regulating voltage where the frequency is adjusted in the negative direction, V _CM is the voltage that is commonly regulated by the connection of Vc ⁺ and Vc ^- and Vd is differential The voltage to be regulated. (V _C -V _B ⁺ = V _d, V _C ^- V _B = + V _d, Vc = Vc ^{+ -} = V _CM, V _d = (V _C ^- _C ⁺ -V) / 2), shown in Figure 6 As shown, the frequency tuning curves for the tuning voltages Vc (+) and Vc (−) are symmetrical to each other. However, the frequency tuning curve for the common voltage VCM (Vc + = Vc- = VCM) is almost unchanged. The frequency tuning curve for the differential tuning voltage Vd is expressed as the sum of the frequency adjustment ranges of the differential tuning voltages and is changed to the widest band.

Therefore, in the graph shown in FIG. 6, in general, a broadband oscillator having a high frequency output gain of a voltage controlled oscillator has a degraded phase noise characteristic, and a differential tuning voltage controlled oscillator of the present invention has a wide frequency tuning output. In addition, the phase noise characteristics of the oscillator are improved because the phase noise sensitivity is almost insensitive to the common noise and the low frequency noise.

The embodiments of the present invention described above are not implemented only through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

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

FIG. 2 is a circuit diagram for describing an operation of the LC tank resonator illustrated in FIG. 1.

3 is a circuit diagram of a differential tuning voltage controlled oscillator according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram for describing an operation of the LC tank resonator illustrated in FIG. 3.

FIG. 5 is a transformer layout diagram of the LC tank resonator shown in FIG. 1.

FIG. 6 is a diagram illustrating a frequency tuning simulation result of the differential tuning voltage controlled oscillator shown in FIG. 1.

Claims (17)

In an LC tank consisting of one or more inductors and one or more capacitors in a voltage controlled oscillator to generate a resonance frequency, A transformer having a primary coil stage and first and second secondary coil stages; A first variable capacitor pair connected in series with each other in a different direction and having a capacitance adjusted in a positive direction; And Including a second variable capacitor pair having the same connection form as the first variable capacitor pair and the capacitance is adjusted in a negative direction, The first variable capacitor pair is connected to the first secondary coil end to form a closed loop, and the second variable capacitor pair is connected to the second secondary coil end to form a closed loop, and the primary nose A transformer-based differential tuning LC tank having one end connected to a first resonant node and a second resonant node. The method of claim 1, The first secondary coil stage is composed of first and second inductors connected in series, and the second secondary coil stage is composed of third and fourth inductors connected in series, and the first to fourth inductors have the same inductance. Transformer-based differential tuning LC tank. The method of claim 2, A first tuning voltage node for adjusting the capacitance of the first variable capacitor pair in a positive direction is connected to a common node of the first variable capacitor pair, and is configured to adjust the capacitance of the second variable capacitor pair in a negative direction. And a second tuning voltage node connected between the third and fourth inductors at the second secondary coil stage. The method of claim 3, A transformer-based differential tuning LC tank, wherein each variable capacitor constituting the first and second variable capacitor pairs has the same capacitance. The method of claim 3, The first and second variable capacitor pair is a transformer-based differential tuning LC tank in which the connection of the variable capacitors are connected to the anode in common. A power supply unit; An LC tank resonator for generating a resonant frequency; An active part connected to the power supply and the LC tank resonator to generate an output having a resonant frequency determined by the LC tank resonator; The LC tank resonator, A transformer having a primary coil stage and first and second secondary coil stages, A first variable capacitor pair connected in series with each other in a different direction, connected to the first secondary coil end, and having a capacitance adjusted in a positive direction; and And a second variable capacitor pair having the same connection form as the first variable capacitor pair and connected to the second secondary coil stage and whose capacitance is adjusted in a negative direction. The method of claim 6, A first tuning voltage node for adjusting the capacitance of the first variable capacitor pair in a positive direction is connected to a common node of the first variable capacitor pair, and is configured to adjust the capacitance of the second variable capacitor pair in a negative direction. 2 The tuning voltage node is connected to the point of dividing the inductance by half at the second secondary coil stage. The method of claim 6, And each variable capacitor constituting the first and second variable capacitor pairs has the same capacitance. The method of claim 7, wherein The first and the second variable capacitor pair is a differential tuning voltage controlled oscillator in which the connection of the variable capacitors is the form in which the anode is connected to each other in common. In an LC tank consisting of one or more inductors and one or more capacitors in a voltage controlled oscillator to generate a resonance frequency, A transformer having a primary coil stage and a secondary coil stage; A first variable capacitor pair connected in series with each other in a different direction and having a capacitance adjusted in a positive direction; And Including a second variable capacitor pair having the same connection form as the first variable capacitor pair and the capacitance is adjusted in a negative direction, The first variable capacitor pair is connected in series with the primary coil stage, the second variable capacitor pair is connected in series with the secondary coil stage, and the amount of the primary coil stage and the first variable capacitor pair is A transformer-based differential tuning LC tank having a first resonant node and a second resonant node connected to a contact point, respectively. The method of claim 10, Wherein the secondary coil stage comprises first and second inductors connected in series, the first and second inductors having the same inductance. The method of claim 11, A first tuning voltage node for adjusting capacitance in a positive direction is connected to a common node of the first variable capacitor pair, and a second tuning voltage node for adjusting capacitance in a negative direction is connected between the first and second inductors. Transformer-based differential tuning LC tank connected to. The method of claim 11, The first and second variable capacitor pairs have a form in which anodes are connected in common to each other, and each variable capacitor constituting the first and second variable capacitor pairs has the same capacitance. . A power supply unit; An LC tank resonator for generating a resonant frequency; An active part connected to the power supply and the LC tank resonator to generate an output having a resonant frequency determined by the LC tank resonator; The LC tank resonator, A transformer having a primary coil stage and first and second secondary coil stages, A first variable capacitor pair connected in series with each other in a different direction, connected to the primary coil end, and having a capacitance adjusted in a positive direction; and And a second variable capacitor pair having the same connection form as the first variable capacitor pair and connected to the secondary coil stage and whose capacitance is adjusted in a negative direction. The method of claim 14, And the secondary coil stage is composed of first and second inductors connected in series, and the first and second inductors have the same inductance. The method of claim 15, A first tuning voltage node for adjusting capacitance in a positive direction is connected to a common node of the first variable capacitor pair, and a second tuning voltage node for adjusting capacitance in a negative direction is disposed between the first and second inductors. Differential tuning voltage controlled oscillator connected. The method of claim 16, The first and the second variable capacitor pair is a form of the connection of the variable capacitors are connected to the anode in common with each other, each variable capacitor constituting the first and second variable capacitor pair is a differential tuning voltage controlled oscillator having the same capacitance.

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