KR101328134B1 - Low voltage lc voltage controlled oscillator - Google Patents

Abstract

An LC voltage controlled oscillator is disclosed. According to an embodiment of the present invention, an LC resonant circuit including at least one inductor connected at both ends to an output node and at least one capacitor connected in parallel with the inductor, and an amplifier circuit including at least one pair of switching transistors, And the drains of the paired switching transistors are each connected to the output node, and each gate and drain are interconnected through a variable capacitance block having different characteristics according to the input signal. do.

Description

LOW VOLTAGE LC VOLTAGE CONTROLLED OSCILLATOR}

The present invention relates to an LC voltage controlled oscillator, and more particularly, to an LC voltage controlled oscillator capable of mitigating a limitation of a power supply voltage magnitude required for oscillation, and capable of oscillation without a varactor element.

The present invention is derived from a study performed as part of the original technology development project of the Ministry of Knowledge Economy [Task management number: 2008-S-006-04, Task name: ubiquitous terminal component module].

Voltage-controlled oscillator (VCO) is a circuit that can change the frequency of oscillation signal according to externally applied voltage and is used as an important component in wireless transceiver.

Among these voltage-controlled oscillators, the LC-type voltage-controlled oscillator is an oscillator using negative resistance according to the positive feedback of the circuit. In such an oscillator, the oscillation frequency can be controlled by controlling the capacitance value of the varactor element existing on the circuit through a control signal.

As an LC type voltage controlled oscillator, a negative conductance LC oscillator using negative resistance characteristics according to positive feedback by a transistor is widely known.

1 is a circuit diagram showing the configuration of a conventional LC voltage controlled oscillator.

As shown in FIG. 1, a typical LC voltage controlled oscillator includes at least one inductor L ₁ , a capacitor C ₁ connected in parallel with the inductor L ₁ , and a variable capacitor C included in at least one varactor element. _2, C _3), the LC resonance circuit including the 110, the gate and the two transistors having a drain connected to each other (M _1, M ₂₎ amplification comprising a positive feedback circuit formed of the circuit 120 and the current source (I ₁ It may be configured to include a current source circuit 130 having a).

In addition, both ends of the inductor L ₁ and the variable capacitors C ₂ and C ₃ connected in series are connected to the output nodes outp and outn of the transistors M ₁ and M ₂ included in the amplifying circuit 120. The drain is also connected to the output nodes outp and outn respectively.

The LC voltage controlled oscillator oscillates when the absolute value | R _in | of the input impedance R _in = -2 / g _m of the positive feedback circuit constituting the amplifier circuit 120 is equal to or less than the equivalent resistance value of the LC resonant circuit 110. do. On the other hand, the oscillation frequency of the output signal can be represented by the following equation (1). Here, C _T is a combined capacitance value of the capacitor C ₁ and the variable capacitors C ₂ and C ₃ .

As can be seen from Equation 1, the oscillation frequency of the output signal of the voltage controlled oscillator is dependent on the inductance value or the synthesized capacitance value C _T of the inductor L ₁ included in the LC resonance circuit 110. Typically the inductor (L ₁₎ as is used the wire and the lead wire spiral inductor formed of a wire of the spiral shape, the transistors (M _1, M ₂₎ there is to be formed on the same substrate with the element, this inductor (L ₁₎ inductance The value can only be changed discretely. Therefore, it is difficult to adjust the oscillation frequency by adjusting the value. Accordingly, a fixed value is used as the inductance value of the inductor L ₁ , and the variable capacitor C ₂ constituting the varactor element is used. , C ₃ ) has been widely used to control the oscillation frequency by applying the control signal vc to adjust the capacitance values of the variable capacitors C ₂ and C ₃ . At this time, the variable range of the capacitance value of the varactor element soon corresponds to the variable range of the oscillation frequency.

Meanwhile, in order to operate the voltage controlled oscillator illustrated in FIG. 1, a voltage capable of driving the current source I ₁ of the current source circuit 130 and a voltage for operating the positive feedback circuit included in the amplification circuit 120 are required. Do. That is, for the operation of the voltage controlled oscillator of FIG. 1, a voltage equal to the sum of the two voltages is required as the minimum power supply voltage VDD. Therefore, in order to operate the voltage controlled oscillator even at the low power supply voltage VDD, it is necessary to remove the current source I ₁ .

FIG. 2 shows the removal of the current source I ₁ from the voltage controlled oscillator of FIG. 1 for this reason. However, in order to have a negative resistance by positive feedback in the amplifier circuit 120, the gate-source voltage of the transistors M ₁ and M ₂ should be greater than or equal to a threshold voltage. In the voltage controlled oscillator of FIG. VDD) the gates of the transistors (M _1, M ₂₎ -, so that the source voltage, a limit to the power supply voltage (VDD) and the transistor (have a value more than the threshold voltage of M _1, M ₂₎ and jonje.

In addition, in the voltage controlled oscillator illustrated in FIGS. 1 and 2, the oscillation frequency is adjusted through the varactor element, which may cause the characteristics of the voltage controlled oscillator to be limited by the varactor element. In addition, there is a problem in that the design of the voltage controlled oscillator itself is impossible under the process in which the varactor element is not provided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to enable an oscillation signal to be output even when a power supply voltage value is less than a predetermined threshold voltage value in an LC voltage controlled oscillator.

In addition, another object of the present invention is to enable the implementation of an LC voltage controlled oscillator even in an environment in which no varactor device is provided.

On the other hand, another object of the present invention is to minimize the 1 / f noise of the LC voltage controlled oscillator to improve the overall phase noise.

According to an embodiment of the present invention for achieving the above object, an LC resonant circuit comprising at least one inductor connected to an output node and at least one capacitor connected in parallel with the inductor, and at least one switching transistor And a drain circuit of the paired switching transistors, each of which is connected to the output node, and each gate and drain are interconnected through a variable capacitance block having different characteristics according to an input signal. An LC voltage controlled oscillator is provided.

The variable capacitance block may include a control transistor to which the input signal is applied to a gate node, and a capacitor connected in parallel with a source and a drain of the control transistor.

The variable capacitance block may further include a resistor added to a source or a drain of the control transistor.

The control transistor may be an n-type or p-type transistor.

The LC voltage controlled oscillator may further include a bias voltage supply circuit for supplying a predetermined bias voltage to the gate of the switching transistor.

The bias voltage supply circuit includes a bias voltage supply transistor, and a gate of the bias voltage supply transistor is connected to a drain and connected to a gate of the paired switching transistor through a resistor and simultaneously connected to a source through a capacitor. Can be.

The bias voltage supply circuit may further include a current source for supplying current to the drain of the bias voltage supply transistor.

The at least one inductor may be connected to a power supply terminal, the source of the switching transistor may be connected to ground, and the switching transistor may be an n-type transistor.

The at least one inductor may be connected to ground, the source of the switching transistor may be connected to a power supply terminal, and the switching transistor may be a p-type transistor.

The LC voltage controlled oscillator may further include a current source circuit having a current source connected to a source of the paired switching transistor.

The LC resonant circuit may further include one or more varactor elements connected in parallel with the one or more inductors in series connection and exhibiting different characteristics according to input signals.

According to the present invention, since the gate-source voltage of the transistor included in the LC voltage controlled oscillator is determined irrespective of the power supply voltage value, the limitation of the power supply voltage value for oscillation is eliminated, and the threshold voltage level of the transistor or higher is increased. Normal operation is possible even when a low power supply voltage is applied.

Further, according to the present invention, since the variable capacitance block including the transistor and the capacitor replaces the varactor element, the LC voltage controlled oscillator can be implemented even in an environment in which no varactor element is provided.

Meanwhile, according to the present invention, since the current source that caused the 1 / f noise is removed in the LC voltage controlled oscillator, the 1 / f noise can be minimized, and thus the overall phase noise can be improved.

1 and 2 are circuit diagrams showing the configuration of a conventional LC voltage controlled oscillator.
3 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a first embodiment of the present invention.
4A to 4D are circuit diagrams illustrating a configuration of a variable capacitance block according to an embodiment of the present invention.
5 is an equivalent circuit diagram illustrating the characteristics of a variable capacitance block according to an embodiment of the present invention.
6 is a graph illustrating capacitance values according to control voltages in an LC voltage controlled oscillator according to an embodiment of the present invention.
7 is a graph showing oscillation frequency according to a control voltage applied to an LC voltage controlled oscillator according to an embodiment of the present invention.
8 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a second embodiment of the present invention.
9 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a third embodiment of the present invention.
10 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a fourth embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily carry out the technical idea of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

[Preferred Embodiment of the Present Invention]

First Embodiment

3 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a first embodiment of the present invention.

As shown in FIG. 3, the LC voltage controlled oscillator of the present invention may be composed of an LC resonant circuit 310, an amplifier circuit 320, and a bias voltage supply circuit 330.

First, the LC resonant circuit 310 may include one or more inductors L ₁ connected to the power supply terminal VDD and one or more capacitors C ₁ connected in parallel with the inductor L ₁ . Both ends of the inductor L ₁ and the capacitor C ₁ are connected to the output nodes outp and outn.

In addition, the amplifier circuit 320 may include a pair of transistors M ₁ and M ₂ . Gate nodes of the transistors M ₁ and M ₂ are connected to the bias voltage through the resistors R ₁ and R ₂ , respectively, and to the drain nodes of each other through the variable capacitance block 321, respectively. Specifically, the transistor gate nodes of the transistors (M ₁₎ with variable capacitance block 321, the transistor (M ₂₎ coupled to the drain node, and a transistor gate node, a variable capacitance block 321 of the (M ₂₎ of the through Is connected to the drain node of (M ₁ ). Transistor M ₁ , The drain node of M ₂ ) is connected to the output nodes outp and outn, respectively, and the source node is connected to ground. In FIG. 3, the amplifier circuit 320 includes a pair of transistors M ₁ and M ₂ , but two or more pairs of transistors may be included. A control voltage vc is applied to the variable capacitance block 321 to adjust the impedance of the overall variable capacitance block 321. This will be described later in detail.

On the other hand, in the bias voltage supply circuit 330, the current source I ₁ , the drain node, and the gate node are formed as common nodes, and the gate nodes of the transistors M ₁ and M ₂ are formed through the resistors R ₁ and R ₂ , respectively. And a gate node connected to the source node through a capacitor C ₂ , and may include a transistor M ₃ . In the bias voltage supply circuit 330, the gate node of the transistor M ₃ has a constant DC voltage value by the current source I ₁ . In FIG. 3, the bias voltage supply circuit 330 including the current source I ₁ and the transistor M ₃ as described above has been described as an example, but is not limited thereto. The transistors M ₁ and M _{2 are} described. The bias voltage supply circuit for applying a constant DC voltage to the gate node of may be modified in various forms according to the needs of those skilled in the art.

On the other hand, the variable capacitance block 321 included in the amplifier circuit 320 can be implemented in various forms, the implementations are shown in Figures 4a to 4d.

As shown in FIGS. 4A to 4D, the variable capacitance block 321 basically includes a transistor M ₄ to which a control voltage vc is applied to a gate node, and a drain node and a source node of the transistor M ₄ . Capacitor C ₃ may be connected. However, this is only one example, and the variable capacitance block 321 can be implemented as long as the circuit is embodied in another kind of lumped element or a different kind of element and can exhibit different electrical characteristics according to the applied control voltage vc. ) Can be applied.

For example, as shown in FIG. 4A, an n-type transistor M ₄ and a capacitor C ₃ connected between the drain node and the source node of the n-type transistor M ₄ may be included. As shown, the source node of the n-type transistor M ₄ may be connected to one end of the capacitor C ₃ through one or more resistors R ₃ . On the other hand, is replaced with, n-type transistors in the structure of the variable capacitance block 321 shown in Fig. 4a and 4b (M ₄₎ is a p-type transistor (M ₄₎ as shown in Figure 4c and Figure 4d be implemented It may be. In the present specification, the variable capacitance block 321 having the configuration illustrated in FIGS. 4A to 4D has been described as an example. However, as long as the circuit has a configuration in which the impedance may vary depending on elements such as the control voltage vc, the variable capacitance may be used. Block 321 may be.

In the LC voltage controlled oscillator according to the present invention, the oscillation frequency of the output signal can be expressed by Equation 2 below. Here, the case where the variable capacitance block 321 is implemented by the circuit shown in FIG. 4C is taken as an example.

Here, the C _T value is determined according to a capacitance value present in the entire circuit and which may vary according to a specific control voltage vc condition. The C _T value may be expressed as Equation 3 below.

Here, C _gm is obtained by the following process, and an equivalent circuit for explaining the characteristics of the variable capacitance component included in the amplifier circuit 320 is obtained as shown in FIG. 5 to obtain this value.

In the equivalent circuit shown in Fig. 5, C _P1 and C _P2 are controlled by the nodes (P1 or P2) and the output node will represent the parasitic capacitance at (outn or outp), R _M4 has a channel resistance and off of the transistor (M ₄₎ ( off).

The C _gm value can be obtained from the left half circuit of FIG. 5. The admittance seen by the output node outn can be represented by the following equation (4).

When R _M4 approaches 0 in Equation 4, since Y _gm becomes sC _P1 + sC _P2 , C _gm = C _P1 + C _P2 . On the other hand, if R _M4 approaches infinity, Y _gm becomes sC _P1 C ₃ / (C _P1 + C ₃ ) + sC _P2 , so C _gm = C _P1 C ₃ / (C _P1 + C ₃ ) + C _P2 is obtained.

Approaching the value of R _M4 to 0 is when the control voltage vc is 0V, and approaching to infinity is when the control voltage vc is the power supply voltage. When the control voltage vc is a value between 0V and the power supply voltage, the C _gm value is changed according to the value.

6 is a graph illustrating a change in the C _gm value according to the control voltage vc. Here, it is assumed that the control voltage vc varies between 0V and 1.0V. Meanwhile, as the control voltage vc is changed, the values of C _P1 and C _P2 also vary. In this case, the graph of FIG. 6 may be maintained as a monotonic reduction form according to the size of the control voltage vc. As the C _gm value is changed according to the magnitude of the control voltage vc, the C _T value is changed and the oscillation frequency can be adjusted. That is, the transistor M ₄ is turned on or off according to the control voltage vc input to the gate node of the transistor M ₄ included in the variable capacitance block 321. In this case, the resonance frequency of the LC voltage controlled oscillator can be adjusted to a desired value.

FIG. 7 is a graph showing the oscillation frequency of the output signal according to the control voltage vc as an operating characteristic of the LC voltage controlled oscillator circuit shown in FIG. Here, it is also assumed that the power supply voltage is 0.5V, and it is assumed that the control voltage vc varies between 0V and 1.0V. The LC voltage controlled oscillator of FIG. 3 was implemented using a CMOS model of a commercial company (TSMC) to obtain the graph of FIG. 7.

Referring to FIG. 7, it can be seen that the oscillation frequency varies according to the control voltage vc applied to the variable capacitance block 321. Accordingly, an output signal having a desired oscillation frequency can be obtained by appropriately adjusting the control voltage vc applied to the variable capacitance block 321 without using a varactor element.

On the other hand, the oscillation signal amplitude (V _OSC ) in the oscillation state of the LC voltage controlled oscillator may be expressed by Equation 5 below.

Here, Z _total = (1 / g _m ) / / Z _tank , 1 / g _m is the negative resistance according to the positive feedback of the circuit, Z _tank is the impedance value of the LC resonant circuit (310). Meanwhile, the g _m value and the I ₁ value have a relationship as shown in Equation 6 below.

Here, β value is a value that changes according to transistor characteristics, and is a constant value, k is a width / length (W / L) and a bias voltage supply circuit of the transistors M ₁ and M ₂ included in the amplifier circuit 320. The ratio of the width / length (W / L) of the transistor M ₃ included in 330 is shown.

In the control voltage range, the negative resistance characteristic due to the positive feedback can be obtained, so that the oscillation according to Equation 5 can be maintained at all times.

Meanwhile, the gate-source voltage of the transistors M ₁ and M ₂ included in the amplifier circuit 320 is determined by the bias voltage supply circuit 330. That is, in the bias voltage supply circuit 330, the gate node of the transistor M ₃ has a constant DC voltage value by the current source I ₁ , which is a transistor through the resistors R ₁ and R ₂ . therefore connected to the gate node of the (M _1, M _2), the gate node voltage of transistor (M _1, M ₂₎ can be said to be determined by the bias voltage supply circuit (330). Therefore, when the bias voltage provided by the bias voltage supply circuit 330 is properly controlled, the gate-source voltage of the transistors M ₁ and M ₂ included in the amplifier circuit 320 can be adjusted. In order to have a negative resistance for oscillation in the amplifier circuit 320, the gate-source voltage of the transistors M ₁ and M ₂ should have a value greater than or equal to a threshold voltage. The bias voltage supply circuit 330 causes the transistors M ₁ ,. Since the gate-source voltage of M ₂ ) is determined, oscillation can be maintained even if the power supply voltage VDD is set lower than that used in the conventional LC voltage controlled oscillator structure. Furthermore, if the guarantee the minimum current needed by the transistors (M _1, M ₂₎ for the oscillation, it is under the transistors (M _1, M ₂₎ the supply voltage (VDD) of less than or equal to the threshold voltage conditions can do the oscillation.

That is, in the LC voltage controlled oscillator as shown in FIG. 2, since the power supply voltage VDD corresponds to the gate-source voltage of the transistors M ₁ and M ₂ , the power supply voltage VDD is the transistor ( M ₁ , M ₂ ) should be above the threshold voltage. According to the LC voltage controlled oscillator of the present invention, since the gate-source voltage of the transistors M ₁ , M ₂ is independent of the power supply voltage VDD, Even when the voltage VDD is equal to or less than the threshold voltage values of the transistors M ₁ and M ₂ , oscillation is possible. However, since the current value flowing in the circuit varies according to the drain-source voltages of the transistors M ₁ and M ₂ , the minimum current for oscillation must of course be guaranteed.

Meanwhile, the phase noise L (Δf) index of the LC voltage controlled oscillator may be expressed as Equation 4 below.

Here, P _sig (f _o ) is a power value of the oscillation frequency, and P _noise (Δf) is a power value at a position separated by a specific offset frequency. That is, the phase noise indicator is defined as the difference between P _sig (f _o ) and P _noise (f), and can improve phase noise performance by increasing the signal size of the oscillation frequency or reducing the power value at a specific offset frequency. have. One of the factors that aggravate phase noise by increasing the power value P _noise (Δf) at a specific offset frequency is flicker noise, or 1 / f noise, of the current source, which is caused by the Up Conversion mechanism. Moving near the oscillation frequency, the phase noise deteriorates. The voltage controlled oscillator shown in FIG. 1 includes a current source circuit 130 between the amplifying circuit 120 and the ground, thereby generating a large 1 / f noise. In the voltage controlled oscillator of FIG. 1 / f noise can be improved because a pair of transistors (M ₁ , M ₂ ) are provided and operate as an amplifier together with the function as a current source, thereby reducing the P _noise (Δf) value and thus the overall phase. Noise can be improved.

Second Embodiment

8 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a second embodiment of the present invention.

Referring to FIG. 8, the LC voltage controlled oscillator according to the second embodiment of the present invention includes all the n-type transistors included in the LC voltage controlled oscillator according to the first embodiment of the present invention as shown in FIG. 3. It has been replaced, and the positions of the power supply terminal (VDD) and the ground are reversed.

Specifically, referring to the configuration of the LC voltage controlled oscillator according to the second embodiment of the present invention, the LC voltage controlled oscillator of the second embodiment also includes the LC resonant circuit 810, the amplifier circuit 820, and the bias voltage supply circuit 830. It is configured to include.

First, referring to the configuration of the LC resonant circuit 810, except that one or more inductors (L ₁ ) is connected to the ground instead of being connected to the power supply terminal (VDD) LC resonant circuit of the LC voltage controlled oscillator shown in FIG. 810 is the same as the configuration.

In addition, the amplifier circuit 820 is a pair of transistors (M ₁ , M ₂ ) are all composed of a p-type transistor, the source terminal of the transistors M ₁ , M ₂ is connected to the power supply terminal (VDD) The configuration is the same as that of the amplifier circuit 820 of the LC voltage controlled oscillator shown in FIG. The variable capacitance block 821 may also be a circuit of the type shown in FIGS. 4A to 4D or a separate circuit showing other characteristics according to the size of the control voltage vc.

Meanwhile, the bias voltage supply circuit 830 is illustrated in FIG. 3 except that the transistor M ₃ included in the bias voltage supply circuit 830 is formed of a p-type transistor, and the source node of the transistor M ₃ is connected to the power supply terminal VDD. The configuration of the bias voltage supply circuit 330 of the LC voltage controlled oscillator is the same.

The LC voltage controlled oscillator of FIG. 8 may also adjust the oscillation frequency or amplitude of the output signal to a desired value by controlling the control voltage vc applied to the variable capacitance block 821.

Third Embodiment

9 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a third embodiment of the present invention.

The LC voltage controlled oscillator shown in FIG. 9 is an improvement on the conventional LC voltage controlled oscillator shown in FIG.

Referring to FIG. 9, the LC voltage controlled oscillator according to the third embodiment of the present invention may include an LC resonant circuit 910, an amplifier circuit 920, and a current source circuit 930.

First, the LC resonant circuit 910 may include one or more inductors L ₁ connected to the power supply terminal VDD and one or more capacitors C ₁ connected in parallel with the inductor L ₁ .

In addition, the amplifying circuit 920 may include one or more pairs of transistors M ₁ and M ₂ , and the gate node and the drain node of the transistors M ₁ and M ₂ may form a variable capacitance block 921. Connected through. In detail, the gate node of the transistor M ₁ is connected to the drain node of the transistor M ₂ through the variable capacitance block 921, and the gate node of the transistor M ₂ is connected to the drain node of the transistor M ₁ through the variable capacitance block 921. M ₁ ) is connected to the drain node. The variable capacitance block 921 may also be a circuit of the type shown in FIGS. 4A to 4D or a separate circuit showing other characteristics according to the magnitude of the control voltage vc.

Meanwhile, the current source circuit 930 including the current source I ₁ is provided between the amplifier circuit 920 and the ground. That is, the current source I ₁ included in the current source circuit 930 is disposed between the source and the ground of the transistors M ₁ and M ₂ of the amplifier circuit 920.

Fourth Embodiment

10 is a circuit diagram showing the configuration of an LC voltage controlled oscillator according to a fourth embodiment of the present invention.

The LC voltage controlled oscillator shown in FIG. 10 is configured to further include a varactor element in the LC voltage controlled oscillator shown in FIG. 7.

Referring to FIG. 10, an LC voltage controlled oscillator according to a fourth embodiment of the present invention may also include an LC resonant circuit 1010, an amplifier circuit 1020, and a current source circuit 1030. The LC resonant circuit 1010, an inductor or more connected to the power supply terminal (VDD) (L _1), the inductor capacitor or more in parallel connected to the (L ₁₎ (C _1), an inductor (L ₁₎ and capacitor (C _1, ) And one or more varactor elements connected in parallel with each other in series. In FIG. 10, the varactor device is represented by being equivalent to the variable capacitors C ₂ and C ₃ . Since the configurations of the amplifier circuit 1020 and the current source circuit 1030 except for the LC resonant circuit 1010 are the same as those of the LC voltage controlled oscillator of FIG. 9, description thereof will be omitted.

In the LC voltage controlled oscillator of FIG. 10, the control voltages vc and vc2 are applied to the varactor elements C ₂ and C ₃ included in the LC resonant circuit 1010 and the variable capacitance block 1021 included in the amplification circuit 1020. ) Is applied. That is, by applying the control voltages vc and vc2, not only the variable capacitance block 1021 but also the capacitance values of the variable capacitors C ₂ and C ₃ included in the varactor elements may be varied, thereby changing the oscillation frequency. The range becomes wider.

In the above, only the LC voltage controlled oscillator illustrated in FIGS. 2, 8, 9 and 10 is illustrated, but various modifications of the LC voltage controlled oscillator may be implemented. For example, an embodiment in which an n-type transistor included in the LC voltage controlled oscillator shown in FIGS. 9 and 10 is replaced with a p-type transistor is also possible, and one or more varactor elements in the LC resonant circuit of FIGS. It is also possible to include an embodiment as in FIG. 10.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

310, 810, 910, 1010: LC resonant circuit
320, 820, 920, 1020: amplification circuit
330, 830: bias voltage supply circuit
730, 1030: current source circuit
321, 821, 921, 1021: variable capacitance block

Claims (11)

An LC resonant circuit including at least one inductor connected at both ends to output nodes, and at least one capacitor connected in parallel with the inductor; And
An amplifier circuit comprising a pair of switching transistors,
The drains of the paired switching transistors are each connected to the output nodes, and the respective gates and drains are interconnected through variable capacitance blocks having different characteristics so that the resonant frequency is changed to a desired value according to the input signal. LC voltage controlled oscillator. The method of claim 1,
The variable capacitance block,
A control transistor to which the input signal is applied to a gate node; And
And a capacitor connected in parallel with the source and the drain of the control transistor. 3. The method of claim 2,
The variable capacitance block,
LC voltage controlled oscillator further comprises a resistor added to the source or drain of the control transistor. The method according to claim 2 or 3,
The control transistor is an LC voltage controlled oscillator, characterized in that the n-type or p-type transistor. The method of claim 1,
And a bias voltage supply circuit for supplying a predetermined bias voltage to the gate of the switching transistor. The method of claim 5,
The bias voltage supply circuit includes a bias voltage supply transistor,
And the gate of the bias voltage supply transistor is connected to a gate of the paired switching transistors through a resistor connected to a drain and connected to a source through a capacitor. The method according to claim 6,
The bias voltage supply circuit further comprises a current source for supplying current to the drain of the bias voltage supply transistor. The method of claim 1,
The at least one inductor is connected to a power terminal,
The source of the switching transistor is connected to ground,
And said switching transistor is an n-type transistor. The method of claim 1,
The at least one inductor is connected to ground,
The source of the switching transistor is connected to the power supply terminal,
And said switching transistor is a p-type transistor. The method of claim 1,
And a current source circuit having a current source connected between the source and the ground of the paired switching transistors. The method of claim 1,
The LC resonant circuit,
And one or more varactor elements connected in parallel with the one or more inductors in series and exhibiting different characteristics according to input signals.

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