Voltage-controlled oscillation circuit

Abstract

The present invention provides a voltage-controlled oscillation circuit. The voltage-controlled oscillation circuit comprises an LC resonant cavity and a negative resistance network; the negative resistance network comprises a first transistor, a second transistor, a first feedback unit, and a second feedback unit which are symmetrically arranged; the LC resonant cavity comprises multiple stages of resonant units connected in series; the first resonant access end of the LC resonant cavity is connected to the base electrode or the gate electrode of the first transistor; a second resonant access end is connected to the base electrode or the gate electrode of the second transistor; the first feedback unit is arranged between the collector electrode and the base electrode of the first transistor or between the drain electrode and the gate electrode of the first transistor; the second feedback unit is arranged between the collector electrode and the base electrode of the second transistor or between the drain electrode and the gate electrode of the second transistor; the feedback units are each composed of an active transistor. The present invention solves the problem of being difficult in achieving a frequency adjustment range and low-phase noise performance of a voltage-controlled oscillator, and outputs various frequency division signals while obtaining better phase noise performance.

Description

A voltage-controlled oscillator circuit Technical Field

[0001] The present invention relates to the field of chip design, and in particular to a voltage-controlled oscillator circuit. Background Art

[0002] Low phase noise in voltage-controlled oscillators (VCOs) is essential for many transmitting and receiving systems. The phase noise of the transmit or receive local oscillator (LO) plays a critical role in adjacent channel rejection and transmit signal purity. When receiving frequency modulation (FM) or phase modulation (PM), LO phase noise limits the final signal-to-noise ratio (SNR). Therefore, low phase noise in VCOs is a design goal that the industry has consistently pursued and strived to achieve.

[0003] The performance of a voltage-controlled oscillator (VCO) is limited by the circuit's Q factor. The negative-resistance VCO (Negative Resistance Voltage-Controlled Oscillator) achieves a high Q factor and is currently the most widely used VCO circuit structure. In practical applications, transistors inevitably generate thermal noise, flicker noise, and shot noise during operation, which contributes to phase noise in the VCO circuit. Furthermore, lossy components in the circuit's load, resonant cavity, and bias network can exacerbate phase noise, making low phase noise performance difficult to achieve in a VCO.

[0004] The quality factor of the resonant cavity is the main factor affecting phase noise. The quality factor of the resonant cavity is strongly correlated with the quality factor of the varactor diode. Varactors are generally used in LC resonant cavities to increase the frequency control function, thereby changing the oscillation frequency of the resonant circuit. The frequency adjustment range is determined by the capacitance variation range of the varactor diode. To achieve a specific frequency and tuning range, technicians in this field usually use small-sized varactor diodes. However, small-sized varactors will reduce the quality factor of the resonant cavity, resulting in lower phase noise.

[0005] In order to solve the problems of low phase noise and difficult frequency adjustment range in a negative resistance voltage-controlled oscillator, the present invention proposes a voltage-controlled oscillator circuit.

[0006] Summary of the Invention

[0007] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that will be provided later.

[0008] In order to overcome the above-mentioned defects, the present invention aims to provide a voltage-controlled oscillator circuit capable of providing a variety of optimizable frequency-divided signal outputs and low phase noise.

[0009] According to one aspect of the present invention, a voltage-controlled oscillator circuit is provided, comprising an LC resonant cavity and a negative resistance network. The negative resistance network comprises a symmetrically arranged first transistor, a second transistor, a first feedback unit, and a second feedback unit. The LC resonant cavity comprises multiple series-connected resonant units, each of which comprises a first inductor, a first varactor diode, a second capacitor diode, and a second inductor. The first end of the first inductor is connected to the anode of the first varactor diode, the cathode of the first varactor diode is connected to the cathode of the second varactor diode to form a set of back-to-back varactor units, and the anode of the second varactor diode is connected to the first end of the second inductor. The two ends of the LC resonant cavity serve as the first resonant access end and the second resonant access end of the LC resonant cavity, respectively. The first resonant access end is connected to the base or gate of the first transistor, and the second resonant access end is connected to the base or gate of the second transistor. The first feedback unit is arranged between the collector and base or between the drain and gate of the first transistor, and the second feedback unit is arranged between the collector and base or between the drain and gate of the second transistor. The feedback units are composed of active transistors.

[0010] In one embodiment, the LC resonant cavity is a symmetrical structure.

[0011] In one embodiment, a plurality of symmetrical coupling structures are provided in the LC resonant cavity.

[0012] In one embodiment, the multi-stage series resonant unit is a two-stage resonant unit, and both ends of the LC resonant cavity respectively constitute extraction points of the half-order fundamental frequency signal.

[0013] In one embodiment, the multi-stage series resonant unit is a three-stage resonant unit, and any set of symmetrical points of the LC resonant cavity constitute extraction points of the half-order fundamental frequency signal, and the symmetrical points do not include the tuning end of the varactor diode.

[0014] In one embodiment, the voltage-controlled oscillation circuit further includes a frequency dividing unit, which extracts a half fundamental frequency signal to generate a quarter fundamental frequency signal.

[0015] Preferably, the first inductor and the second inductor provided between the two groups of variable capacitance units in any two stages of resonance units connected in series are the same inductor.

[0016] Preferably, the multiple resonant units share a tuning power supply.

[0017] In one embodiment, the first feedback unit includes a first active transistor, the emitter collector or source of the first active transistor is grounded through a resistor, the base or gate is connected to the base or gate of the first transistor through an inductor, the collector or drain is connected to the power supply terminal, the collector of the first active transistor is connected to the base or the drain is connected to the gate, and the second feedback unit includes a second active transistor, the emitter collector or source of the second active transistor is grounded through a resistor, the base or gate is connected to the base or gate of the second transistor through an inductor, the collector or drain is connected to the power supply terminal, and the collector of the second active transistor is connected to the base or the drain is connected to the gate.

[0018] In one embodiment, the voltage-controlled oscillation circuit further includes a first capacitor and a second capacitor, wherein the first capacitor is arranged between the base or gate of the first transistor and the first resonant access end of the LC resonant cavity, and the second capacitor is arranged between the base or gate of the second transistor and the second resonant access end of the LC resonant cavity.

[0019] In one embodiment, the negative resistance network further includes a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor, the third capacitor is arranged between the base and the emitter or between the gate and the source of the first transistor, the fourth capacitor is arranged between the base and the emitter or between the gate and the source of the second transistor, and the fifth capacitor and the sixth capacitor are connected in series between the source or emitter of the first transistor and the source or emitter of the second transistor.

[0020] In one embodiment, the negative resistance network further includes a third inductor, a fourth inductor, a first resistor, and a second resistor. The emitter or source of the first transistor is grounded through the third inductor and the first resistor connected in series, and the emitter or source of the second transistor is grounded through the fourth inductor and the second resistor connected in series.

[0021] The voltage-controlled oscillator circuit provided by the present invention sets an LC resonant cavity of a multi-stage series resonant unit at the base of two symmetrical transistors, utilizes the transmission response of the LC resonant cavity to filter the noise spectrum, optimizes the noise performance of the baseband signal, and improves the phase noise performance of the voltage-controlled oscillator circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above features and advantages of the present invention will be better understood after reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings.

[0023] FIG1 is a circuit diagram of a negative resistance voltage controlled oscillator according to the prior art;

[0024] FIG2 is a circuit diagram of a voltage-controlled oscillator circuit in an embodiment according to one aspect of the present invention;

[0025] FIG3 is a schematic diagram of a circuit structure of an LC resonant cavity in an embodiment according to one aspect of the present invention;

[0026] FIG4 is a schematic diagram of the circuit structure of an LC resonant cavity in another embodiment according to one aspect of the present invention;

[0027] FIG5 is a schematic diagram of a circuit structure of an LC resonant cavity in another embodiment according to one aspect of the present invention;

[0028] FIG6 is a schematic diagram of the circuit structure of an LC resonant cavity in another embodiment according to one aspect of the present invention;

[0029] FIG7 is a schematic diagram of a circuit structure of an LC resonant cavity in another embodiment according to one aspect of the present invention;

[0030] FIG8 is a schematic diagram of the circuit structure of an LC resonant cavity in another embodiment according to one aspect of the present invention;

[0031] FIG9 is a schematic diagram of a circuit structure of a voltage-controlled oscillator circuit in another embodiment according to one aspect of the present invention;

[0032] FIG. 10 is a schematic diagram illustrating a circuit structure of a voltage-controlled oscillator circuit in another embodiment according to one aspect of the present invention. DETAILED DESCRIPTION

[0033] The following description is provided to enable those skilled in the art to make and use the present invention and to incorporate it into a specific application context. Various modifications and uses in different applications will be readily apparent to those skilled in the art, and the general principles defined herein are applicable to a wide range of embodiments. Thus, the present invention is not limited to the embodiments set forth herein, but should be accorded the broadest scope consistent with the principles and novel features disclosed herein.

[0034] In the following detailed description, many specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the practice of the present invention need not be limited to these specific details. In other words, known structures and devices are shown in block diagram form without detailed display to avoid obscuring the present invention.

[0035] Unless expressly stated otherwise, all features disclosed in this specification (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent, or similar purpose. Therefore, unless expressly stated otherwise, each feature disclosed is only an example of a group of equivalent or similar features.

[0036] Note that where used, the terms left, right, front, back, top, bottom, forward, reverse, clockwise, and counterclockwise are used for convenience only and do not imply any specific fixed direction. Instead, they are used to reflect the relative position and / or orientation of various parts of an object. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected," "connect," and "crossover" should be understood in a broad sense. For example, they may refer to direct connection, indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention.

[0038] Note that, where used, "further," "preferably," "further," and "more preferably" are simply prefaces for describing another embodiment based on the preceding embodiment. The contents of the "further," "preferably," "further," or "more preferably" combined with the preceding embodiment constitute a complete configuration of another embodiment. Multiple "further," "preferably," "more preferably," or "more preferably" clauses appended to the same embodiment can be arbitrarily combined to form yet another embodiment.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Note that the various aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention.

[0040] FIG1 is a circuit diagram of a negative resistance voltage controlled oscillator according to the prior art. As shown in FIG1 , the negative resistance voltage controlled oscillator includes an LC resonant cavity and a negative resistance transistor AT. The LC resonant cavity is composed of an inductor L and a varactor diode C. VAR By tuning the voltage, the varactor diode C VAR The capacitance value can change the oscillation frequency of the output signal. The negative resistance transistor AT offsets the loss caused by the parasitic resistance R in the resonant circuit, thereby maintaining the signal oscillation.

[0041] A voltage-controlled oscillator (VCO) consists of an LC resonant cavity and a negative resistance network. The LC cavity is a circuit that converts a fundamental frequency signal into an AC oscillating signal with varying frequency division ratios. The frequency, amplitude, and waveform of the output signal are determined solely by the circuit's parameters. A conventional LC cavity consists of a resonant inductor and a varactor diode connected in series or parallel. The negative resistance network compensates for the impedance of the LC cavity.

[0042] According to one aspect of the present invention, a voltage-controlled oscillation circuit is provided to solve the problem of difficulty in achieving frequency adjustment range and low phase noise performance, provide lower phase noise, and output multiple frequency signals.

[0043] FIG2 shows a schematic circuit diagram of a voltage-controlled oscillator circuit according to an embodiment of the inventive concept of the present invention. As shown in FIG2 , in this embodiment, the voltage-controlled oscillator circuit includes an LC resonant cavity A and a negative resistance network B. The LC resonant cavity A comprises a plurality of series-connected resonant units A1 to AN, where N is a natural number greater than or equal to 1. Each resonant unit includes two inductors and two varactor diodes. The LC resonant cavity has a symmetrical structure. The negative resistance network B includes two symmetrically arranged transistors.

[0044] Resonant unit A1 includes an inductor L11, a varactor diode Cv11, a varactor diode Cv12, and an inductor L12. One end of inductor L11 is connected to the anode of varactor diode Cv11, and the cathode of varactor diode Cv11 is connected to the cathode of varactor diode Cv12 to form a set of back-to-back varactor units. The anode of varactor diode Cv12 is connected to inductor L12. Resonant unit AN includes an inductor LN1, a varactor diode CvN1, a varactor diode CvN2, and an inductor LN2. One end of inductor LN1 is connected to the anode of varactor diode CvN1, and the cathode of varactor diode CvN1 is connected to the cathode of varactor diode CvN2 to form a set of back-to-back varactor units. The anode of varactor diode CvN2 is connected to inductor LN2.

[0045] The bases of the two symmetrically arranged transistors in the negative resistance network B are connected to the LC resonant cavity A and output a fundamental frequency signal. The fundamental frequency signal can change the oscillation frequency of the fundamental frequency signal through the LC resonant cavity A.

[0046] Figure 3 shows a circuit diagram of an LC resonant cavity in an embodiment. As shown in Figure 3, in this embodiment, the LC resonant cavity is a resonant unit A1 connected in series with a resonant unit A2. The resonant unit A1 includes an inductor L11, a varactor diode Cv11, a capacitor diode Cv12, and an inductor L12. The inductor L11 is connected to the anode of the varactor diode Cv11, and the cathode of the varactor diode Cv11 is connected to the cathode of the varactor diode Cv12 to form a group of back-to-back varactor units. The anode of the varactor diode Cv12 is connected to one end of the inductor L12, and the cathode of the varactor diode Cv11 and the cathode of the varactor diode Cv12 provide a tunable power supply through a tunable power supply.

[0047] The resonant unit A2 includes an inductor L21, a varactor diode Cv21, a capacitor diode Cv22 and an inductor L22. The inductor L21 is connected to the anode of the varactor diode Cv21, and the cathode of the varactor diode Cv21 is connected to the cathode of the varactor diode Cv22 to form a group of back-to-back varactor units. The cathode of the varactor diode Cv21 and the cathode of the varactor diode Cv22 provide a tunable power supply through a tunable power supply, and the anode of the varactor diode Cv22 is connected to the inductor L22.

[0048] The inductor L12 in the resonance unit A1 is connected to the inductor L21 in the resonance unit A2.

[0049] Specifically, the fundamental frequency signal is input from the inductor L11 in the resonance unit A1 and the inductor L22 in the resonance unit A2. The phase difference between the input end of the inductor L11 and the input end of the inductor L22 is 180 degrees, which respectively constitute the extraction points of the half fundamental frequency signal. The half fundamental frequency signal is output from the other end of the inductor L11 and the other end of the inductor L22, respectively.

[0050] Alternatively, the inductor L12 and the inductor L21 may be set to be the same inductor.

[0051] FIG4 shows a schematic diagram of an LC resonant cavity circuit in another specific embodiment. As shown in FIG4 , the LC resonant cavity comprises a resonant unit A1, a resonant unit A2, and a resonant unit A3 connected in series in sequence. The resonant unit A1 and the resonant unit A2 share the same series inductor L2, and the resonant unit A2 and the resonant unit A3 share the same series inductor L3. The fundamental frequency signal is input from one end of the inductor L1 and the inductor L4. The inductor L1 is connected to the anode of the varactor diode Cv1, the cathode of the varactor diode Cv1 is connected to the cathode of the varactor diode Cv2, the anode of the varactor diode Cv2 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to the anode of the varactor diode Cv3, the cathode of the varactor diode Cv3 is connected to the cathode of the varactor diode Cv4, the anode of the varactor diode Cv4 is connected to one end of the inductor L3, the other end of the inductor L3 is connected to the anode of the varactor diode Cv5, the cathode of the varactor diode Cv5 is connected to the cathode of the sixth varactor diode Cv6, and the anode of the sixth varactor diode Cv6 is connected to the inductor L4.

[0052] The phase difference between the midpoint between the varactor diode Cv2 and the inductor L2 and the midpoint between the inductor L3 and the varactor diode Cv5 is 180 degrees, forming symmetrical points in the LC resonant cavity and outputting half the fundamental frequency signal respectively.

[0053] It can be understood that any set of symmetrical points with a phase difference of 180 degrees in the LC resonant cavity respectively constitute extraction points of the half fundamental frequency signal, and the symmetrical points do not include the tuning end of the varactor diode.

[0054] Several symmetrical coupling structures may also be provided in the LC resonant cavity to reduce the circuit area and expand the frequency tuning range in the LC resonant cavity.

[0055] Figure 5 shows a circuit diagram of an LC resonant cavity in another embodiment. The difference between this embodiment and the embodiment shown in Figure 4 is that a symmetrical coupling structure is provided in the LC resonant cavity, and the inductor L1 and the inductor L4 are coupled.

[0056] Figure 6 shows a circuit diagram of an LC resonant cavity in another embodiment. This embodiment differs from the embodiment shown in Figure 4 in that two symmetrical coupling structures are provided in the LC resonant cavity: inductor L1 is coupled to inductor L2, and inductor L3 is coupled to inductor L4.

[0057] It can be understood that the coupling structure can be provided in any resonance unit, or between two different resonance units, or the coupling structure can be provided in any resonance unit and between two different resonance units.

[0058] Furthermore, the coupling structure in the LC resonant cavity can be implemented in a variety of ways. A symmetrical coupling structure can be achieved by coupling two symmetrical inductors to each other, or by providing one or more coupled inductor pairs at two symmetrical positions.

[0059] It should be emphasized that the coupling structure in the LC resonant cavity needs to be set up completely symmetrically. One or more coupling structures can be set up as needed, so as to change the resonant frequency of the LC resonant cavity while keeping the tuning capacitance unchanged, broaden the tuning range of the frequency in the LC resonant cavity, and do not affect the symmetry of the output signal of the LC resonant cavity.

[0060] Those skilled in the art will appreciate that coupling structures may be provided in other embodiments of the LC resonant cavity to broaden the frequency tuning range of the LC resonant cavity. For example, inductor L11 and inductor L12 in the LC resonant cavity circuit shown in FIG3 may also be coupled to each other.

[0061] FIG7 shows a schematic diagram of an LC resonant cavity circuit in another specific embodiment. Compared with the embodiment shown in FIG4 , the embodiment shown in FIG7 further includes a frequency dividing unit. Two ends of the frequency dividing unit are connected to the extraction points of the half-fundamental frequency signal to output a quarter-fundamental frequency signal.

[0062] Figure 8 shows a schematic diagram of an LC resonant cavity circuit in another specific embodiment. Compared with the embodiment shown in Figure 7, in the embodiment shown in Figure 8, the LC resonant cavity further includes a choke inductor and a grounding inductor. The cathode of the varactor diode Cv1 and the cathode of the varactor diode Cv2 are connected to the tuning power supply via the choke inductor L5, the cathode of the varactor diode Cv3 and the cathode of the varactor diode Cv4 are connected to the tuning power supply via the choke inductor L6, and the cathode of the varactor diode Cv5 and the cathode of the sixth varactor diode Cv6 are connected to the tuning power supply via the choke inductor L7.

[0063] The inductor L1 and the varactor diode Cv1 are grounded through the grounding inductor L8, the varactor diode Cv2 and the inductor L2 are grounded through the grounding inductor L9, the inductor L3 and the varactor diode Cv5 are grounded through the grounding inductor L10, and the varactor diode Cv6 and the inductor L4 are grounded through the grounding inductor L10.

[0064] The grounding inductor can provide a ground potential for the varactor diode.

[0065] It can be understood that the above-mentioned varactor diodes share the same tuning power supply.

[0066] Optionally, the power supply ends of the multiple varactor diodes may be the same tuning power supply or different tuning power supplies.

[0067] By setting up multiple resonant units in the LC resonant cavity, a larger varactor or a smaller inductor can be selected within the same tuning range, which helps optimize the Q value of the resonant cavity to obtain better phase noise performance. At the same time, the half-fundamental frequency signal of the voltage-controlled oscillation circuit is output through the LC resonant cavity, and the transmission response of the resonant cavity is used to filter the noise spectrum, further optimizing the noise performance of the fundamental frequency signal and the half-fundamental frequency signal.

[0068] It should be noted that, in the above embodiment, the multi-stage resonant unit is completely symmetrical, that is, the corresponding device parameters or sizes in the multi-stage resonant unit are the same.

[0069] FIG9 shows a schematic diagram of a voltage-controlled oscillator circuit in another specific embodiment. Compared to the embodiment shown in FIG2 , in the embodiment shown in FIG9 , the LC resonant cavity adopts a three-section frequency-dividing resonant cavity. The negative resistance network includes transistors T1 and T2, capacitors C3 and C4, and capacitors C7 and C8. The bases of transistors T1 and T2 are connected to the LC resonant cavity, and the collectors are connected to the power supply terminal. Capacitor C3 is connected between the base and emitter of transistor T1, and capacitor C4 is connected between the base and emitter of transistor T2. The emitter of transistor T1, capacitor C7, capacitor C8, and the emitter of transistor T2 are connected in sequence, and a fundamental frequency signal is output at the common mode point between capacitors C7 and C8.

[0070] The coupling degree between the LC resonant cavity and the negative resistance network can be adjusted by adjusting the capacitors C1 and C2.

[0071] A feedback bias circuit is connected between the base and collector of the transistor T1. The feedback bias circuit includes a transistor T3. The base of the transistor T1 is connected to the base of the transistor T3 via a twelfth inductor L12. The collector of the transistor T3 is grounded via a resistor R2. The emitter is connected to the collector of the transistor T1 via one end of the resistor R1. The other end of the resistor R1 is grounded via a capacitor C5.

[0072] Symmetrically, a feedback bias circuit is connected between the base and collector of the transistor T2. The feedback bias circuit includes a transistor T4. The base of the transistor T2 is connected to the base of the transistor T4 via a thirteenth inductor L13. The collector of the transistor T4 is grounded via a resistor R4. The emitter is connected to the collector of the transistor T2 via one end of a resistor R3. The other end of the resistor R3 is grounded via a capacitor C6.

[0073] The feedback bias circuit suppresses jitter caused by power supply noise caused by external disturbances through feedback from transistors T3 and T4, thereby optimizing the overall phase noise performance of the circuit.

[0074] At the same time, the frequency-divided signal of the voltage-controlled oscillation circuit is output to the load through the resonant cavity, and the transmission response of the resonant cavity is used to filter the noise spectrum, thereby further optimizing the noise performance of the baseband signal.

[0075] Furthermore, the two transistors symmetrically arranged in the negative resistance network are of the same type, for example, they may be triodes or field effect transistors.

[0076] Figure 10 shows a schematic diagram of a voltage-controlled oscillator circuit in another specific embodiment. Compared with the embodiment shown in Figure 9, in the embodiment shown in Figure 10, the two transistors symmetrically arranged in the negative resistance network are field-effect transistors. The source of the first field-effect transistor M1 is grounded through an inductor L14 and a resistor R5 connected in series, and the source of the second field-effect transistor M2 is grounded through an inductor L15 and a resistor R6 connected in series, and the drains of the first field-effect transistor M1 and the second field-effect transistor M2 share a power supply.

[0077] It should be noted that in the above embodiment, the active transistors in the bilaterally symmetrical feedback bias circuits are of the same type, for example, they may be triodes or field effect transistors.

[0078] The voltage-controlled oscillator circuit provided by this invention places an LC resonant cavity at the bases of two symmetrically arranged transistors. The smaller signal amplitude at the transistor bases limits the signal swing of the varactor diode in the resonant cavity, minimizing the thermal effect and noise introduced by the varactor diode, thereby improving the phase noise performance of the voltage-controlled oscillator circuit. Furthermore, the multi-stage cascaded resonant units optimize the Q value of the resonant cavity, achieving better phase noise performance while outputting a variety of frequency-divided signals.

[0079] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. However, it should be understood that the scope of protection of the present invention is subject to the appended claims and is not limited to the specific structures and components of the above-illustrated embodiments. Those skilled in the art may make various changes and modifications to the various embodiments within the spirit and scope of the present invention, and such changes and modifications are also within the scope of protection of the present invention.

Claims

1. A voltage-controlled oscillator circuit, characterized in that: The invention comprises an LC resonant cavity and a negative resistance network, wherein the negative resistance network comprises a symmetrically arranged first transistor, a second transistor, a first feedback unit and a second feedback unit, wherein the LC resonant cavity comprises a plurality of series-connected resonant units, wherein each resonant unit comprises a first inductor, a first varactor diode, a second varactor diode and a second inductor, wherein a first end of the first inductor is connected to an anode of the first varactor diode, a cathode of the first varactor diode is connected to a cathode of the second varactor diode to form a group of back-to-back varactor units, an anode of the second varactor diode is connected to a first end of the second inductor, two ends of the LC resonant cavity are respectively used as a first resonant access end and a second resonant access end of the LC resonant cavity, the first resonant access end is connected to a base or a gate of the first transistor, and the second resonant access end is connected to a base or a gate of the second transistor, the first feedback unit is arranged between a collector and a base or between a drain and a gate of the first transistor, the second feedback unit is arranged between a collector and a base or between a drain and a gate of the second transistor, and the feedback unit is composed of an active transistor.

2. The voltage-controlled oscillator circuit according to claim 1, wherein: The LC resonant cavity is a symmetrical structure.

3. The voltage-controlled oscillator circuit according to claim 2, wherein: A plurality of symmetrical coupling structures are arranged in the LC resonant cavity.

4. The voltage-controlled oscillator circuit according to claim 1, wherein: The multi-stage series resonance unit is a two-stage resonance unit, and the two ends of the LC resonance cavity respectively constitute extraction points of the half-order fundamental frequency signal.

5. The voltage-controlled oscillator circuit according to claim 1, wherein: The multi-stage series resonance unit is a three-stage resonance unit, and any group of symmetric points of the LC resonance cavity respectively constitute extraction points of the half-order fundamental frequency signal, and the symmetric points do not include the tuning end of the varactor diode.

6. The voltage-controlled oscillator circuit according to claim 4 or 5, characterized in that: The system also includes a frequency dividing unit, which extracts the half baseband signal to generate a quarter baseband signal.

7. The voltage-controlled oscillator circuit according to any one of claims 1 to 6, characterized in that: The first inductor and the second inductor between the two groups of variable capacitance units in any two stages of resonance units connected in series are the same inductor.

8. The voltage-controlled oscillator circuit according to any one of claims 1 to 6, characterized in that: Multiple resonant units share a tuned power supply.

9. The voltage-controlled oscillator circuit according to claim 1, wherein: The first feedback unit includes a first active transistor, the emitter or source of the first active transistor is grounded through a resistor, the base or gate is connected to the base or gate of the first transistor through an inductor, the collector or drain is connected to the power supply terminal, and the collector of the first active transistor is connected to the base or the drain is connected to the gate; The second feedback unit includes a second active transistor, the emitter or source of the second active transistor is grounded through a resistor, the base or gate is connected to the base or gate of the second transistor through an inductor, the collector or drain is connected to the power supply end, and the collector of the second active transistor is connected to the base or the drain is connected to the gate.

10. The voltage-controlled oscillator circuit according to claim 1, wherein: It also includes a first capacitor and a second capacitor, wherein the first capacitor is arranged between the base or gate of the first transistor and the first resonant access end of the LC resonant cavity, and the second capacitor is arranged between the base or gate of the second transistor and the second resonant access end of the LC resonant cavity.

11. The voltage-controlled oscillator circuit according to claim 1, wherein: The negative resistance network also includes a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor. The third capacitor is arranged between the base and the emitter or between the gate and the source of the first transistor, the fourth capacitor is arranged between the base and the emitter or between the gate and the source of the second transistor, and the fifth capacitor and the sixth capacitor are connected in series between the source or emitter of the first transistor and the source or emitter of the second transistor.

12. The voltage-controlled oscillator circuit according to claim 1, wherein: The negative resistance network also includes a third inductor, a fourth inductor, a first resistor and a second resistor. The emitter or source of the first transistor is grounded through the third inductor and the first resistor connected in series, and the emitter or source of the second transistor is grounded through the fourth inductor and the second resistor connected in series.

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