JP2005286384A - Voltage controlled oscillator and its variable LC series resonator - Google Patents

Abstract

A variable LC series resonator constituting a voltage-controlled oscillator and its tuning circuit has a desired tuning sensitivity even when the operating frequency is increased.
A variable capacitance diode, an open-ended stub (capacitive stub) having a capacitive characteristic near a tuning frequency, an open state near a resonance frequency, and a barrier potential of the variable capacitance element are provided. And a reference voltage applying circuit. One end of the capacitive stub 15 is connected to a terminal on the opposite side to the terminal to which the inductance of the variable capacitance element is connected.
[Selection] Figure 1-1

Description

  The present invention relates to a voltage-controlled oscillator and its variable LC direct resonator, and more particularly to a voltage-controlled oscillator that can cope with a higher oscillation frequency and its variable LC series resonator.

  A voltage-controlled oscillator according to the prior art is generally composed of a tuning circuit section and an oscillator circuit section. A loop gain is obtained by connecting a resonator in the tuning circuit section to an active element in the oscillator circuit section. The oscillation operation is performed by superimposing the loop phases in the same phase, and the output of the predetermined oscillation frequency is obtained by changing the resonance frequency of the variable LC series resonator in the tuning circuit section. (For example, Non-Patent Document 1).

  Further, as a capacitive element for configuring a variable LC series resonator, a variable capacitance diode whose anode side is grounded as close as possible through a through hole or the like is generally used.

  On the other hand, in order to change the output signal frequency of the oscillator, it is necessary to change the resonance frequency of the variable LC series resonator. However, in Non-Patent Document 1, the potential difference between the cathode and the anode is determined by the applied voltage applied from the cathode side. The barrier capacitance of the variable capacitance diode is changed, and as a result, the resonance frequency of the variable LC series resonator is changed.

  In addition to Non-Patent Document 1, there are Patent Documents 1 and 2 shown below as related art related to a tuning circuit of a voltage controlled oscillator.

JP-A-4-40079 (FIG. 4 etc.) JP-A-8-1660 (FIG. 1 etc.) H. Ikematsu, M .; Inoue, K .; Kawakami, T .; Katoh, K .; Itoh, Y. et al. Isota, O .; Ishida, “A V-Band MMIC VCO with a Sub-Resonator Coupled by a 90-Degree Inverter”, The 10th Asia Pacific Microconference (Dec 19).

  However, in the conventional technology described above, when the frequency used is increased, the influence of the parasitic inductance component and the additional inductance component due to the distance to the through hole, the lead length of the diode chip, the wire length at the time of chip mounting, etc. increases. The resonance point at which the maximum sensitivity of tuning change is obtained moves from the short-circuit side to the open side, and there is a problem that desired tuning sensitivity that can be expected from the capacitance change ratio of the variable capacitance diode cannot be obtained.

  The present invention has been made in view of the above, and even when the influence of the parasitic inductance component and the additional inductance component increases as the oscillation frequency increases, the influence is reduced, and a desired tuning sensitivity is obtained. An object of the present invention is to obtain a voltage controlled oscillator having the same and a variable LC series resonator thereof.

  In order to solve the above-described problems and achieve the object, the variable LC series resonator according to the present invention is a capacitive that is capacitive in the vicinity of the resonance frequency in the variable LC series resonator composed of a variable capacitance element and an inductor. A stub and a reference voltage application circuit that is open near a resonance frequency and that provides a barrier potential of the variable capacitance element, and one end of the capacitive stub is connected to a terminal to which the inductor of the variable capacitance element is connected It is connected to the terminal on the opposite side.

  According to the present invention, for example, the canceling capacity of the capacitive stub connected to the anode of the variable capacitance element acts to cancel the inductance component such as the transmission line, the wire, or the lead. The resonance frequency change, that is, the tuning sensitivity of the variable LC series resonator can be improved.

  The voltage controlled oscillator and its variable LC series resonator according to the present invention operate so that the canceling capacity of the capacitive stub connected to the anode of the variable capacitance element cancels the inductance component such as a transmission line, a wire, or a lead. Therefore, a variable LC direct resonator with high sensitivity can be configured even in a high-frequency region where the influence of parasitic / load inductance is significant, and as a result, an effect of being able to cope with a higher oscillation frequency is achieved.

  Embodiments of a voltage controlled oscillator and its variable LC series resonator according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  1-1 is a top view showing a configuration of a variable LC series resonator provided in the voltage controlled oscillator of the present invention, and FIG. 1-2 is an X-type of the variable LC series resonator shown in FIG. 1-1. It is X sectional drawing. Hereinafter, the configuration of the variable LC series resonator according to this embodiment will be described with reference to FIGS. 1-1 and 1-2.

  In FIGS. 1-1 and 1-2, the variable capacitance diode 11 is mounted on an MIC substrate such as an alumina substrate. An inductor 19 for obtaining series resonance is connected to the cathode 13 which is the cathode terminal of the variable capacitance diode 11. One end of the λ / 4 high impedance line 16b is connected to the middle of the inductor 19, and the λ / 4 tip open stub 17b is connected to the other end. The λ / 4 high impedance line 16b and the λ / 4 tip open stub 17b are configured as an RF choke circuit for applying a reference potential (cathode reference potential) to the cathode 13. Further, a resistor 18b for giving a loss in a wide band is inserted between a connection point between the λ / 4 high impedance line 16b and the λ / 4 tip open stub 17b and a power source (not shown) for providing a cathode reference potential. Yes. As described above, the λ / 4 high impedance line 16b, the λ / 4 tip open stub 17b, and the resistor 18b constitute a reference voltage application circuit 25a that applies a reference voltage to the cathode 13. Note that λ indicates the effective wavelength in the substrate at the desired frequency, and the λ / 4 high impedance line 16a and the λ / 4 tip open stub 17a are literally about ¼ of the effective wavelength. Is set.

  On the other hand, on the anode 12 side which is a terminal on the opposite side of the cathode 13 of the variable capacitance diode 11, a wire-bonding 14 is bonded to the pattern on the MIC substrate of a tip open stub (capacitive stub) 15. Here, also on the anode 12 side, similarly to the cathode 13 side, an RF choke circuit comprising a λ / 4 high-impedance line 16a and a λ / 4 tip open stub 17a for applying a reference potential (anode reference potential) to the anode 12 is provided. Is configured. One end of the λ / 4 high-impedance line 16a is connected to the pattern on the MIC substrate of the open-end stub 15. Further, a resistor 18a for giving a loss in a wide band is inserted between a connection point between the λ / 4 high impedance line 16a and the λ / 4 tip open stub 17a and a power source (not shown) for supplying an anode reference potential. Has been. Thus, also on the cathode 13 side, the λ / 4 high impedance line 16a, the λ / 4 tip open stub 17a, and the resistor 18a constitute a reference voltage application circuit 25a that applies a reference voltage to the cathode 13. .

  FIG. 2 is a diagram showing an equivalent circuit of the variable LC series resonator shown in FIG. 1-1. As shown in the figure, in the variable LC series resonator shown in FIG. 1-1, the capacitance component C of the variable capacitance diode 11 and the inductance component L due to the lead length such as the wire bond 14 and the lead wire are connected in series. It can be expressed as a configured.

  Next, the operation of the variable LC series resonator shown in FIG. 2 will be described. FIG. 3 is a diagram showing a change in impedance of the variable LC series resonator shown in FIG. An anode voltage and a cathode voltage are respectively applied to the anode and cathode of the variable capacitance diode of the variable LC series resonator from a power source (not shown). At this time, since the barrier capacitance of the variable capacitance diode is changed by changing the potential difference between the anode and the cathode, the resonance frequency of the variable LC series resonator can be changed. In FIG. 3, the impedance of the diode when the anode side is viewed from the point A in FIG. 2 shows a capacitive property as indicated by the point A on the Smith chart in FIG. In this state, the impedance in the state where the inductance components are connected in series is the impedance when the anode side is viewed from the point B in FIG. Actually, the impedance seen from the point B in FIG. 2 shows a property having a pure resistance component as shown by the point B in FIG. In addition, since the point B exists in a region close to the short-circuit point (the left region on the Smith chart), the resonance frequency change (phase change at the point B) as the variable LC series resonator is maximized, and high tuning sensitivity is achieved. Can be obtained.

  FIG. 4 is a block diagram showing a configuration example of a voltage controlled oscillator on which the variable LC series resonator shown in FIG. 1-1 is mounted. The voltage controlled oscillator includes a tuning circuit unit 20 and an oscillator circuit unit 21, and the variable LC series resonator 24 is used as an oscillation frequency control circuit. The tuning circuit unit 20 has a configuration in which a sub-resonator 22 and a main resonator 23 are connected in parallel, and is designed to be an open end at an operating frequency. The sub-resonator 22 uses the short-circuit point formed by the variable LC series resonator 24 as an open end by inverting the phase via the 90 ° inverter 33. Further, in the tuning circuit unit 20, the tuning frequency at which the tuning circuit unit itself becomes an open end changes based on the change in the resonance frequency of the variable LC series resonator 24, and the oscillation frequency of the oscillator is controlled. On the other hand, the oscillator circuit unit 21 is configured by a reflection stub 61 and a peripheral circuit (reflection phase circuit 42, gate phase circuit 63, source inductor 64, etc.) of a semiconductor element 65 such as an FET or an HBT, with appropriate reflection at the operating frequency. And performing feedback amplification at the operating frequency. The 90 ° inverter 33 functions as a band pass filter having a signal band pass characteristic with an appropriate degree of coupling, and a DC voltage is applied to the bias voltage applied to the semiconductor element 61 and the cathode voltage applied to the variable capacitance diode 11. It functions as a gap capacitor. As a configuration different from the above, for example, a similar function may be provided by a combination of a series microchip capacitor passing through a signal band and a normal transmission line.

  By designing each circuit so that the output signal from the tuning circuit unit 20 and the reflected signal from the oscillator circuit unit 21 are in phase, an oscillation output at a desired oscillation frequency can be obtained. Since the oscillation frequency at this time is achieved by the change in the resonance frequency of the variable LC series resonator 24, the frequency variable range (modulation sensitivity) of the voltage controlled oscillator is the amount of change in the resonance frequency of the variable LC series resonator, that is, Depends on the tuning sensitivity. Therefore, the high-frequency operation of the variable LC series resonator is an important factor for increasing the oscillation frequency. Even if the capacitance change ratio of the variable capacitance diode is large, the variable LC series resonance depends on the chip configuration and mounting restrictions. The upper limit of the oscillation frequency is determined by the high-frequency characteristics when configured as a detector.

  By the way, the point of the present invention is that the tip open stub 15 having a predetermined capacitance value on the anode 12 side, the reference voltage application circuit 25 that operates in parallel with the tip open stub 15 so as to be an open end near the desired frequency, There is a feature in that. These portions are shown in FIG. 4 as a tip open stub 15 and a reference voltage application circuit 25. The reference voltage application circuit 25 operates so as to be an open end in the vicinity of a desired frequency, but does not become an open end in terms of direct current, so that a predetermined potential is applied to the anode and the cathode of the variable capacitance diode 11. Can do.

  Next, the effect of the open-ended stub 15 inserted in the variable LC series resonator will be described. Before the description, the configuration and operation of the conventional variable LC series resonator will be described. FIG. 5 is a cross-sectional view showing a configuration of a conventional variable LC series resonator, and corresponds to FIG. 1-2 of the present invention. FIG. 6 is a diagram showing an equivalent circuit of the conventional variable LC series resonator shown in FIG.

  In FIG. 5, in a conventional variable LC series resonator, a variable capacitance diode 100 is mounted on an MIC substrate such as an alumina substrate, and an inductor 105 for obtaining series resonance is connected to a cathode terminal 102 of the variable capacitance diode 100. Are connected to obtain the necessary inductance. The anode 101, which is the anode terminal on the opposite side, is grounded in terms of direct current by being connected to a pattern to which the through hole 104 on the MIC substrate is connected by wire bonding.

  The equivalent circuit shown in FIG. 6 is different from the ideal equivalent circuit shown in FIG. 2 in that the inductance component depends on the length of the wire bond on the anode 101 side and the height of the through hole 104 on the MIC substrate (including the pattern dimensions). Is added. Due to the effect of this additional inductance component, the impedance of the actual LC resonator deviates from the ideal LC resonance point. FIG. 7 is a diagram showing a change in impedance of the conventional variable LC series resonator shown in FIG. 5, and shows a deviation from an ideal LC resonance point.

  The point B shown in FIG. 7 is the impedance viewed from the point B in FIG. 2 (that is, including the inductance component of the inductor 105), and is an ideal point where high tuning sensitivity can be obtained. However, due to the effect of the additional inductance component described above, the impedance viewed from point D in FIG. 6 moves to the inductive region as shown by point D in FIG. As the resonance point at the desired frequency moves to the open side (the area on the right side of the Smith chart), the variable capacitance width (phase change on the Smith chart) becomes smaller, and the tuning sensitivity as a variable LC series resonator decreases. Resulting in. In particular, the influence of the additional inductance component due to the wire bond or the through hole cannot be ignored as the design frequency increases, and the tuning sensitivity deterioration becomes significant.

  FIG. 8 is a diagram showing an external pattern (back surface pattern) of a flip-chip type variable capacitance diode. The variable-capacitance diode shown in the figure is a surface-mount type variable-capacitance diode called flip-chip type that does not require wire bonding. FIG. 9 is a diagram showing an equivalent circuit of the flip-chip type variable capacitance diode, and FIG. 10 is a diagram showing a change in impedance of the variable capacitance diode shown in FIG. In FIG. 9, additional inductance other than the inherent barrier capacitance (variable capacitance portion) is generated by the lead of the back surface pattern and the parasitic inductance component inside the chip in which the semiconductor element portion is molded. As described above, at a high frequency, as shown in FIG. 10, the impedance of the variable capacitance diode including the lead is inductive. Therefore, since the impedance of the variable LC series resonator is further added with inductance components such as wire bonds and leads for connecting the anode electrode and the cathode electrode, as shown in FIG. It will move to the area on the right side of the chart. This additional inductance component cannot be ignored in the high frequency band, and is inevitably generated in manufacturing. Therefore, when constructing a series LC resonance circuit, the additional inductance component is limited to a high frequency (for example, about 15 GHz). It was thought.

  On the other hand, FIG. 11 is a diagram showing an equivalent circuit of a variable LC series resonator in which a tip open stub is inserted. In the variable LC series resonator shown in the figure, an open end stub 53 connected by a wire bond 52 is added to the anode side of the variable capacitance diode 50. In addition, a phase line 51 such as a transmission line is added to the cathode side of the variable capacitance diode 50. The phase line 51 corresponds to a line pattern corresponding to an inductor in the diagram shown in FIG. 1-1, and an inductance for constituting the variable LC series resonator 24 in the diagram shown in FIG. That is, it corresponds to the line 41.

  FIG. 12 is a Smith chart showing a change in impedance of the variable LC series resonator shown in FIG. In FIG. 12, point D corresponds to point D on the Smith chart of FIG. 7, and is in a region where the tuning sensitivity at the desired frequency is reduced. On the other hand, in the variable LC series resonator in which the tip open stub 53 is inserted, the tip open stub 53 has a capacitance component (cancellation capacity) for canceling an additional inductance component such as the wire bond 52. The impedance Z1 seen from the point E moves to the capacitive side region as shown by the point E in FIG. On the other hand, the phase line 51 has an inductance component, and the impedance Z2 viewed from the point F in FIG. 11 can be moved to a region near the short-circuit point indicated by the point F in FIG. Tuning sensitivity can be increased as a resonator.

  That is, the open end stub 53 is inserted as a capacitor connected in series with the additional inductance for the purpose of canceling the additional inductance component. A detailed procedure for determining the canceling capacity of the tip open stub 53 will be described later.

FIG. 13 is a diagram showing an equivalent circuit of the variable LC series resonator composed of the variable capacitance diode shown in FIG. 8, and FIG. 14 is a diagram showing an equivalent circuit at the design frequency in the same variable LC series resonator. It is. As shown in FIG. 13, the equivalent circuit of the variable capacitance diode can be expressed as a series circuit of an equivalent circuit of the intrinsic portion of the variable capacitance diode and an inductance L _t for the lead. The equivalent circuit of the variable capacitance diode intrinsic part can be expressed as a series-parallel resonant circuit in which a parasitic capacitance C _P is connected in parallel to a series connection circuit of a parasitic inductance L _P , a series resistance R _S , and a barrier capacitance C _j. . Equivalent circuit of a variable LC series resonator, and inductance L _d of the phase line in the equivalent circuit of the variable capacitance diode, the addition of the wire inductance L _W and a circuit cancels capacitance C _S of the open stub is connected in series Can be expressed as

Next, the cancellation capacitance C _S of the open-end stub for canceling the additional inductance L _{W of the} wire and the inductance L _{t of the} lead is calculated.

First, the impedance viewed variable capacitance diode side inductance side of the variable LC series resonator and Z _K, the impedance of the variable capacitance diode intrinsic part Z _a, the impedance of the non-variable capacitance diodes intrinsic part if Z _b, The impedance Z _{K when the} variable capacitance diode is viewed from the inductance side of the variable LC series resonator can be expressed by the following equation.

Z _K = Z _a + Z _b (1)

Also, it puts the inductance is added to the variable capacitance diode intrinsic part and L _{the add,} L _{the add} is expressed by the following equation.

L _add = L _W + L _t (2)

In order to cancel the additional inductance shown in Expression (2), the imaginary part of the impedance of the LC series resonance circuit composed of L _{add in} Expression (2) and the cancel capacitance C _{S of the} open-ended stub becomes zero. Such a capacitance value may be selected.

On the other hand, the impedance Z _b other than the variable capacitance diode intrinsic unit shown in formula (1) can be expressed by the following equation.

_{Z b = j (ωL add -1} / ωC) ····· (3)
However, ω = 2πf ₀ and f ₀ is a design frequency.

Therefore, the canceling capacity C _S of the tip open stub can be expressed as the following expression from the condition that Z _b = 0 in the expression (3).
C _S = 1 / (ω ² L _add ) (4)

Under conditions in which the formula (4) is satisfied, the impedance Z _b excluding the variable capacitance diode intrinsic part in the design frequency is 0, the additional inductance L _{the add} is equivalently canceled, indicated only by a variable capacitance diode intrinsic part The equivalent circuit shown in FIG. Therefore, as shown in the equivalent circuit of the figure, a variable LC series resonator having a variable capacitance diode intrinsic portion close to the barrier capacitance C _j inherent to the element and an inductance L _d of the phase line is configured, and the resonant frequency is set at the design frequency. A variable LC series resonator having the maximum change can be obtained.

Next, a tip open stub for realizing the capacitance value C _S shown in Expression (4) will be described. FIG. 15 is a diagram illustrating an equivalent circuit using a distributed constant line having a tip open stub. The impedance Z due to the open-ended stub is the electrical length βL (β = 2π / λ, β: phase constant, L: physical line) from the open end of the open-ended line having the characteristic impedance Z ₀ shown by the equivalent circuit in FIG. The value is determined by the reactance value defined by (length), and can be expressed as the following equation.

Z = −jZ ₀ / tan (βL) (5)

Here, FIGS. 16-1 and 16-2 show the characteristics of the impedance Z shown in the equation (5). More specifically, FIG. 16-1 is a diagram illustrating a change in impedance with respect to a change in the electrical length of the tip open stub, and FIG. 16-2 is a change in capacitance value (f ₀ = 20 GHz) is a diagram showing a.

  As shown in FIG. 16A, the impedance Z of the open-ended stub has an electric length βL of 0 ° to 180 ° (corresponding to 0 to λ / 2 in terms of line length), and −∞ to + ∞. Further, the capacitance value of the tip open stub takes a value as shown in FIG. 16-2 corresponding to the impedance of FIG.

Accordingly, the length L of the open stub for canceling the additional inductance L _{the add} is a cancel capacitor shown in equation (4) using the C _S, the left side of Z of the formula (5), Z = -j / By setting (ωC _S ), it can be expressed as the following equation.

L = tan ⁻¹ (ωC _S Z ₀ ) / β = (λ / 2π) · tan ⁻¹ (ωC _S Z ₀ ) (6)

When the cancellation capacity of the tip open stub is obtained by the equation (4), the width W of the tip open stub is determined by the dielectric constant, thickness, and characteristic impedance Z ₀ of the MIC substrate. The length L of the open end stub is determined by the dielectric constant, thickness, characteristic impedance Z _0, and design frequency f ₀ of the MIC substrate based on the equation (6).

  Note that a configuration other than that shown in FIG. For example, FIG. 17A is a diagram illustrating a configuration of a variable LC series resonator according to another embodiment different from the embodiment illustrated in FIG. 1-1, and FIG. 2 is a diagram showing an equivalent circuit of the variable LC series resonator shown in FIG. In the configuration shown in FIG. 1-1, an RF choke circuit is configured using a λ / 4 tip open stub and a λ / 4 high-impedance line. Therefore, it may be possible to reduce the area occupied by these λ / 4 lines. In such a case, as shown in FIG. 17A, the MMIC has an MIM capacitor at one end of the λ / 4 high impedance line (on the side connected to the power source and on the opposite side to which the open-end stub is connected). In the MIC, a microchip capacitor or the like may be connected. With such a configuration, as shown in the equivalent circuit of FIG. 17-2, the capacitor component due to the open-ended stub and the capacitor component due to the MIM capacitor are configured in parallel, so that the canceling capacitance acts as the sum of both, The length (occupied area) of the tip open stub can be reduced. In addition, the occupied area can be reduced by using a spiral inductor or the like in the λ / 4 high impedance line.

  As described above, according to the variable LC series resonator of this embodiment, the canceling capacity of the capacitive stub connected to the anode of the variable capacity diode cancels the inductance component such as the transmission line, the wire, or the lead. Therefore, even when the influence of the parasitic inductance component and the additional inductance component increases as the tuning frequency increases, a desired tuning sensitivity can be obtained and the use frequency can be increased. be able to.

  Further, according to the voltage controlled oscillator of this embodiment, as described above, the variable LC series resonator that can cope with an increase in the operating frequency is provided, so that the radar that requires high frequency modulation is provided. It can be applied to devices.

  As described above, the voltage controlled oscillator and the variable LC series resonator according to the present invention are useful for a radar apparatus that requires high frequency modulation.

It is a top view which shows the structure of the variable LC series resonator with which the voltage controlled oscillator of this invention was equipped. It is XX sectional drawing of the variable LC series resonator shown to FIGS. 1-1. It is a figure which shows the equivalent circuit of the variable LC series resonator shown to FIGS. 1-1. It is a figure which shows the impedance change of the variable LC series resonator shown in FIG. It is a block diagram which shows the structural example of the voltage control oscillator by which the variable LC series resonator shown to FIGS. 1-1 is mounted. It is sectional drawing which shows the structure of the conventional variable LC series resonator. It is a figure which shows the equivalent circuit of the conventional variable LC series resonator shown in FIG. It is a figure which shows the impedance change of the conventional variable LC series resonator shown in FIG. It is an external pattern diagram of a flip-chip type variable capacitance diode. It is a figure which shows the equivalent circuit of the variable capacitance diode shown in FIG. It is a figure which shows the impedance change of the variable capacitance diode shown in FIG. It is a figure which shows the equivalent circuit of the variable LC series resonator in which the front-end | tip open stub was inserted. It is a figure which shows the impedance change of the variable LC series resonator in which the front-end | tip open stub shown in FIG. 11 was inserted. It is a figure which shows the equivalent circuit by the side of the anode in the variable LC series resonator comprised with the variable capacitance diode shown in FIG. It is a figure which shows the equivalent circuit by the side of the anode in the design frequency in the variable LC series resonator comprised by the variable capacitance diode shown in FIG. It is a figure which shows the equivalent circuit by the distributed constant track | line of a front-end | tip open stub. It is a figure which shows the change of the impedance with respect to the change of the electrical length of a front-end | tip open stub. Is a diagram illustrating a change in capacitance value with respect to the electrical length of the change of the open-end stubs (f ₀ = 20GHz). It is a figure which shows the structure of the variable LC series resonator concerning other embodiment different from Embodiment 1 shown to FIGS. 1-1. It is a figure which shows the equivalent circuit of the variable LC series resonator shown to FIGS.

Explanation of symbols

11, 50, 100 Variable capacitance diode 12, 101 Anode 13, 102 Cathode 14, 52 Wire bond 15, 53 Tip open stub 15 Capacitive stub 16a, 16b λ / 4 high impedance line 17a, 17b λ / 4 tip open stub 18a , 18b Resistors 19, 105 Inductors 20 Tuning circuit unit 21 Oscillator circuit unit 22 Sub-resonator 23 Main resonator 24 Variable LC series resonator 25, 25a, 25b Reference voltage application circuit 33 90 ° inverter 41 Line 51 Phase line 61 Reflective stub 62 Reflection phase circuit 63 Gate phase circuit 64 Source inductor 65 Semiconductor element 104 Through hole

Claims (3)

In a variable LC series resonator composed of a variable capacitance element and an inductor,
A capacitive stub that becomes capacitive near the resonant frequency;
A reference voltage application circuit that is open near the resonance frequency and that provides a barrier potential of the variable capacitance element;
With
A variable LC series resonator, wherein one end of the capacitive stub is connected to a terminal opposite to a terminal to which an inductor of the variable capacitance element is connected. The reference voltage application circuit includes a λ / 4 high impedance line connected to the variable LC series resonator,
λ / 4 tip open stub,
A resistance element;
With
The other end of the λ / 4 high impedance line is connected to the λ / 4 tip open stub in parallel, and connected to a control power source for variably controlling the capacitance value of the variable capacitance element via the resistance element. The variable LC series resonator according to claim 1, wherein: A variable LC series resonator according to claim 1 or 2,
A voltage-controlled oscillator comprising a tuning circuit having a frequency variable function in which a tuning frequency is determined based on a resonance frequency of the variable LC series resonator, and changing a predetermined output signal frequency within a predetermined range.

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