Class-C voltage-controlled oscillator with negative-pressure substrate bias and use method of class-C voltage-controlled oscillator

Abstract

The invention relates to a class-C voltage-controlled oscillator with negative-pressure substrate bias and a use method thereof. Aiming at the problem that a traditional C-type voltage-controlled oscillator is difficult to start, the C-type voltage-controlled oscillator provided by the scheme adopts different circuits to simultaneously control the grid voltage and the substrate voltage of the cross-coupled pair transistors, so that the transistors are effectively prevented from entering a linear region, and the C-type voltage-controlled oscillator is quickly started and stably works in a C-type oscillation mode. The circuit structure of the scheme comprises an NMOS (N-channel Metal Oxide Semiconductor) cross coupling circuit, a PMOS (P-channel Metal Oxide Semiconductor) cross coupling circuit, an LC resonant cavity circuit, an amplitude detection circuit, a Schmidt signal processing circuit and a negative voltage charge pump circuit. Wherein the Schmidt signal processing circuit and the negative voltage charge pump circuit rapidly process an initial oscillation signal and provide negative voltage required by the system, and a substrate of the NMOS cross coupling tube is biased. According to the scheme, the design structure is simple, the tuning range is wide, and a new thought is provided for research and design of quick start of the C-type voltage-controlled oscillator.

Description

Technical Field

[0001] The present invention relates to the field of circuit design, and in particular to a class C voltage-controlled oscillator with negative voltage substrate bias and a use method thereof. Background Art

[0002] The working principle of the traditional Class B voltage-controlled oscillator is that the DC voltage in the power supply is directly transmitted to the gate of the cross-coupled MOS pair after power-on, so the gate bias voltage is relatively high. At certain working moments, the MOS tube may enter the deep linear region. According to the linear time-varying phase noise model proposed by Hajimiri, that is, the model that introduces the impulse sensitivity function (ISF), the MOS tube entering the deep linear region will significantly deteriorate the phase noise, thereby affecting the overall performance of the oscillator.

[0003] In order to solve the problems of Class B voltage-controlled oscillators, Class C voltage-controlled oscillators came into being. Class C voltage-controlled oscillators add DC blocking capacitors and resistors to the drain of the cross-coupled tube to reduce the transistor gate voltage and effectively prevent the MOS tube from entering the linear region. This design can provide better phase noise performance at the same power consumption, and theoretically the phase noise can be improved by 2.2-3.9dB. At the same time, the Class C voltage-controlled oscillator adjusts the conduction angle of the current to shape the current waveform into a high and narrow pulse, thereby improving the current utilization efficiency, thereby achieving 36% power saving at the same phase noise (PN) performance.

[0004] However, the practical application of Class C voltage-controlled oscillators faces a severe challenge, namely, difficulty in starting. Since the Class C voltage-controlled oscillator circuit has different requirements for the state of the cross-coupled tubes at different times, the low bias voltage may cause the transconductance value of the cross-coupled pair to be too small at the beginning, which in turn causes startup failure and inability to oscillate. This defect seriously limits the application scope of Class C voltage-controlled oscillators.

[0005] At present, there are some technical solutions that attempt to solve the startup problem of Class C voltage-controlled oscillators. For example, one technical solution is to use a voltage converter to adaptively adjust the gate bias voltage of the input transistor pair to achieve stable startup and improve phase noise. However, this solution only controls the gate of the MOS tube pair, the control means are relatively single, and the use of voltage converters and comparators inevitably reduces the conversion speed and increases the complexity of the circuit structure. In addition, the presence of the tail current source also contributes to most of the phase noise, deteriorates the phase noise performance, and reduces the output swing of the voltage-controlled oscillator.

[0006] In order to solve the above problems, a class C voltage controlled oscillator with negative voltage substrate bias and a method of using the same are proposed. Summary of the invention

[0007] The object of the present invention is to provide a class C voltage controlled oscillator with negative voltage substrate bias and a method of using the same to solve the problems in the prior art.

[0008] To achieve the above object, the present invention provides the following technical solution: a class C voltage-controlled oscillator with negative substrate bias, comprising: An NMOS cross-coupling circuit and a PMOS cross-coupling circuit are used to generate an oscillation signal; An LC resonant cavity circuit, connected to the NMOS cross-coupling circuit and the PMOS cross-coupling circuit, for determining an oscillation frequency; An amplitude detection circuit, used for detecting the output signal amplitude of the Class C voltage-controlled oscillator; A Schmidt signal processing circuit, connected to the amplitude detection circuit, for quickly processing the detected signal amplitude and generating a control signal; a negative voltage charge pump circuit, connected to the Schmidt signal processing circuit, and configured to generate a negative voltage according to the control signal; A 4-bit switched capacitor array circuit for adjusting the tuning range of the class C voltage controlled oscillator; Among them, the negative voltage generated by the negative voltage charge pump circuit is connected to the substrate of the cross-coupled pair of transistors of the NMOS cross-coupling circuit and / or the PMOS cross-coupling circuit to control the threshold voltage of the cross-coupled pair of transistors to prevent them from entering the linear region. At the same time, combined with the method of controlling the gate voltage of the cross-coupled pair of transistors, the working performance of the Class C voltage-controlled oscillator is jointly improved.

[0009] Optionally, also include: The control process includes using the idea of ​​current competition to control the gate voltage of the voltage-controlled oscillator NMOS tube pair and controlling the substrate bias voltage of the cross-coupled transistor.

[0010] Optionally, the idea of ​​current competition is used to control the gate voltage of the voltage-controlled oscillator NMOS tube pair as follows: When the oscillation starts, the gate voltage is increased to make the voltage-controlled oscillator reach the Class B oscillation state; then the gate voltage of the NMOS tube pair is reduced to switch to the Class C oscillation state.

[0011] Optionally, the substrate bias voltage for controlling the cross-coupled transistor is specifically: The output of the voltage-controlled oscillator is detected by the amplitude detection circuit. When the signal of the Class B voltage-controlled oscillator oscillation is detected, the Schmidt signal processing circuit quickly processes the signal detected by the amplitude detection circuit, and sends the processed signal to the negative voltage charge pump circuit to generate a negative voltage, and finally connects this negative voltage to the substrate of the tube.

[0012] Optionally, the 4-bit switched capacitor array circuit selects the capacitor branch connected in parallel to the resonant circuit through an internally generated control signal to adjust the tuning range of the class C voltage-controlled oscillator.

[0013] Optionally, the class C voltage-controlled oscillator removes the tail current source, thereby increasing the output swing of the voltage-controlled oscillator.

[0014] An electronic device, characterized by the Class C voltage-controlled oscillator as described above.

[0015] A method for using a class C voltage-controlled oscillator, comprising: Start the Class C voltage controlled oscillator; The gate voltage of the NMOS tube pair is controlled by using the idea of ​​current competition, so that the voltage-controlled oscillator reaches the class B oscillation state and then changes to the class C oscillation state; The negative voltage charge pump circuit is controlled to generate negative voltage through the amplitude detection circuit and the Schmidt signal processing circuit, and the negative voltage is connected to the substrate of the cross-coupled pair of tubes; The 4-bit switched capacitor array circuit is adjusted as needed to change the tuning range of the class C voltage controlled oscillator.

[0016] Beneficial effects: The present invention proposes a design concept for a Class C voltage-controlled oscillator that simultaneously controls the gate voltage and substrate voltage of a cross-coupled pair of transistors. This innovative design quickly and effectively prevents the cross-coupled pair of transistors in the voltage-controlled oscillator from entering the linear region, and then can quickly change the working state after the Class B oscillation to become a Class C voltage-controlled oscillator, significantly improving the working performance of the voltage-controlled oscillator. Compared with the traditional Class C voltage-controlled oscillator, the new Class C voltage-controlled oscillator provided by the present invention has the following significant advantages while achieving the optimal phase noise performance: 1. Large output swing: By removing the tail current source transistor, the present invention increases the output swing of the voltage-controlled oscillator and further improves its phase noise performance.

[0017] 2. Wide tuning range: By adopting a 4-bit switched capacitor array circuit, the present invention can adjust the oscillation frequency more flexibly, thereby obtaining a wider tuning range.

[0018] 3. Simple circuit structure: The circuit design of the present invention is relatively simple, reducing potential problems and power consumption caused by complex circuit structures.

[0019] 4. Fast detection and conversion speed: By using the Schmidt signal processing circuit, the present invention can quickly process the detected signal and quickly switch the working state, thereby improving the response speed of the overall circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the control flow of an embodiment of the present invention; Figure 2 1 is a schematic diagram of the overall framework of a Class C voltage-controlled oscillator according to an embodiment of the present invention; Figure 3 It is a schematic diagram of a 4-bit switched capacitor array circuit, an amplitude detection circuit, a Schmidt signal processing circuit and a negative voltage charge pump circuit according to an embodiment of the present invention; Figure 4 is a schematic diagram of an oscillation curve and gate voltage variation according to an embodiment of the present invention; Figure 5 Schematic diagram of a negative pressure curve generated by a charge pump according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following describes the preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0022] Embodiment:

[0023] The present invention relates to the field of integrated circuit design, and specifically proposes a C-type voltage-controlled oscillator circuit, electronic device and method with negative voltage substrate bias and fast response. In view of the problems of startup difficulty, phase noise degradation and output swing limitation existing in the existing C-type voltage-controlled oscillator, the present invention proposes an innovative design scheme, which realizes fast startup, stable operation and performance optimization of the voltage-controlled oscillator by simultaneously controlling the gate voltage and substrate voltage of the cross-coupled tube. The following is a detailed description of the technical scheme of the present invention.

[0024] In view of the shortcomings of the prior art, the present invention proposes a design scheme for a Class C voltage-controlled oscillator that simultaneously controls the gate voltage and substrate voltage of a cross-coupled pair of transistors. The scheme has the following features: Simultaneous control of gate and substrate voltage: The present invention effectively avoids the tube from entering the linear region by simultaneously controlling the gate voltage and substrate voltage of the cross-coupled tube, achieving rapid startup and stable operation in the Class C mode. This innovative design significantly improves the working performance of the voltage-controlled oscillator.

[0025] Removing the tail current source: The present invention removes the tail current source transistor, increases the output swing of the voltage-controlled oscillator, and further improves the phase noise performance.

[0026] Wide tuning range: By adopting a 4-bit switched capacitor array circuit, the present invention can adjust the oscillation frequency more flexibly and obtain a wider tuning range.

[0027] Fast detection and conversion: By using the Schmidt signal processing circuit and the negative voltage charge pump circuit, the present invention realizes fast detection and conversion, and improves the response speed of the overall circuit.

[0028] The following is a detailed description of the technical solution of the present invention: Circuit Structure The circuit structure of the present invention is mainly composed of an NMOS cross-coupling circuit, a PMOS cross-coupling circuit, an LC resonant cavity circuit, an amplitude detection circuit, a Schmidt signal processing circuit, a negative voltage charge pump circuit and a 4-bit switch capacitor array circuit.

[0029] (1) NMOS cross-coupling circuit and PMOS cross-coupling circuit: The NMOS cross-coupling circuit and the PMOS cross-coupling circuit together form a positive feedback loop for generating an oscillation signal. The use of a complementary CMOS cross-coupling pair can increase the negative resistance, saving half of the current to make the voltage-controlled oscillator oscillate. In the present invention, only the NMOS pair works in the C-type mode. Because the current flowing through the NMOS pair and the PMOS pair when they are turned on is the same, when only the NMOS pair is biased in the C-type mode, the current flowing through the PMOS pair is also approximately the same.

[0030] (2) LC resonant cavity circuit: The LC resonant cavity circuit is used to determine the oscillation frequency. It is connected to an active device with negative resistance characteristics (NMOS, PMOS cross-coupled pair of transistors). Negative resistance injects energy to compensate for the loss of the LC oscillation cavity, thereby achieving oscillation.

[0031] (3) Amplitude detection circuit: The amplitude detection circuit is used to detect the output signal amplitude of the voltage-controlled oscillator. When the voltage-controlled oscillator starts oscillating, the amplitude detection circuit sends the detected signal to the Schmidt signal processing circuit for processing.

[0032] (4) Schmitt signal processing circuit: The Schmitt signal processing circuit has two flip thresholds and has a certain degree of anti-interference. At the same time, compared with the comparator, the Schmitt signal processing circuit has a faster response speed and does not need to increase the circuit to generate the reference voltage, thereby reducing the circuit power consumption. After the Schmitt signal processing circuit processes the input signal, it sends the processed signal to the negative voltage charge pump circuit.

[0033] (5) Negative voltage charge pump circuit: The negative voltage charge pump circuit is used to generate a negative voltage and connect this negative voltage to the substrate of the cross-coupled transistor. By adjusting the substrate voltage, the threshold voltage of the transistor can be changed, thereby further preventing the transistor from entering the linear region and optimizing the phase noise performance.

[0034] (6) 4-bit switched capacitor array circuit: The 4-bit switched capacitor array circuit is used to achieve a wider tuning range. The oscillation frequency can be flexibly adjusted by selecting different capacitor branches through internally generated control signals.

[0035] The working principle of the present invention mainly includes two control schemes: controlling the gate voltage by utilizing the idea of ​​current competition and controlling the substrate voltage by amplitude detection and Schmidt signal processing.

[0036] (1) Using the idea of ​​current competition to control gate voltage When the oscillation starts, the gate voltage is increased to make the voltage-controlled oscillator reach the Class B oscillation state. At this time, M22 is a PMOS tube connected in a diode mode, and the voltage on Vbias is relatively large and connected to the gates of the NMOS tube pair M1 and M2. The gate-source voltage of M1 and M2 will be greater than the threshold voltage to make the circuit start to oscillate. At this time, the circuit works in the Class B state. After the oscillation starts, the average current flowing through M1 and M2 gradually increases. Due to the effect of the current mirror, the current flowing through the NMOS tubes M20 and M21 will also increase, the voltage drop on M22 increases, and the capacitor C8 discharges to the ground, reducing the voltage on Vbias, thereby reducing the gate voltage of M1 and M2. M1 and M2 are more in the saturation and cutoff regions, avoiding entering the linear region. If the cross-coupling pair in the Class C oscillator enters the linear region, the current waveform is no longer a narrow pulse, so the current efficiency will decrease, and the flicker noise contribution will increase, deteriorating the phase noise. The present invention avoids this problem by controlling the gate voltage, so that the voltage-controlled oscillator gradually enters the Class C working state.

[0037] (2) Controlling substrate voltage through amplitude detection and Schmitt signal processing When the signal of the Class B voltage-controlled oscillator oscillation is detected, the subsequent circuit controlling the NMOS tube pair substrate starts to work. The amplitude detection circuit detects the output signal amplitude of the voltage-controlled oscillator and sends the detected signal to the Schmitt signal processing circuit for processing. The Schmitt signal processing circuit quickly processes the input signal and sends the processed signal to the negative voltage charge pump circuit. The negative voltage charge pump circuit generates a negative voltage according to the input signal and connects this negative voltage to the substrate of the NMOS cross-coupled transistor pair. At this time, the threshold voltage of the cross-coupled pair tube increases, effectively preventing the tube from entering the linear region, and more in the saturation and cutoff region, thereby optimizing the phase noise performance. At the same time, this design removes the tail current source transistor, increases the output swing of the voltage-controlled oscillator, and further improves the phase noise performance.

[0038] In summary, the present invention proposes a class C voltage-controlled oscillator signal generating circuit, electronic device and method with negative voltage substrate bias and fast response. The invention solves the startup difficulty problem of the class C voltage-controlled oscillator in the prior art through innovative design. At the same time, the invention also has the advantages of wide tuning range, simple circuit structure, and fast detection and conversion. It provides new ideas and solutions for the research and design of fast startup of class C voltage-controlled oscillators.

[0039] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0040] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A class C voltage-controlled oscillator with negative substrate bias, characterized in that: include: An NMOS cross-coupling circuit and a PMOS cross-coupling circuit are used to generate an oscillation signal; An LC resonant cavity circuit, connected to the NMOS cross-coupling circuit and the PMOS cross-coupling circuit, for determining an oscillation frequency; An amplitude detection circuit, used for detecting the output signal amplitude of the Class C voltage-controlled oscillator; A Schmidt signal processing circuit, connected to the amplitude detection circuit, for quickly processing the detected signal amplitude and generating a control signal; a negative voltage charge pump circuit, connected to the Schmidt signal processing circuit, and configured to generate a negative voltage according to the control signal; A 4-bit switched capacitor array circuit for adjusting the tuning range of the class C voltage controlled oscillator; Among them, the negative voltage generated by the negative voltage charge pump circuit is connected to the substrate of the cross-coupled pair of transistors of the NMOS cross-coupling circuit and / or the PMOS cross-coupling circuit to control the threshold voltage of the cross-coupled pair of transistors to prevent them from entering the linear region. At the same time, combined with the method of controlling the gate voltage of the cross-coupled pair of transistors, the working performance of the Class C voltage-controlled oscillator is jointly improved.

2. The class C voltage controlled oscillator according to claim 1, characterized in that: Also includes: The control process includes using the idea of ​​current competition to control the gate voltage of the voltage-controlled oscillator NMOS tube pair and controlling the substrate bias voltage of the cross-coupled transistor.

3. The class C voltage controlled oscillator according to claim 2, characterized in that: The method of controlling the gate voltage of the voltage-controlled oscillator NMOS tube pair by using the idea of ​​current competition is specifically as follows: When the oscillation starts, the gate voltage is increased to make the voltage-controlled oscillator reach the Class B oscillation state; then the gate voltage of the NMOS tube pair is reduced to switch to the Class C oscillation state.

4. The class C voltage controlled oscillator according to claim 2, characterized in that: The substrate bias voltage of the cross-coupled transistor is specifically: The output of the voltage-controlled oscillator is detected by an amplitude detector. When the signal of the Class B voltage-controlled oscillator oscillation is detected, the Schmidt signal processing circuit quickly processes the signal detected by the amplitude detector, and sends the processed signal to the charge pump circuit to generate a negative voltage, and finally connects this negative voltage to the substrate of the tube.

5. The class C voltage controlled oscillator according to claim 1, characterized in that: The 4-bit switched capacitor array circuit selects the capacitor branch connected in parallel to the resonant circuit through an internally generated control signal to adjust the tuning range of the class C voltage-controlled oscillator.

6. The class C voltage controlled oscillator according to claim 1, characterized in that: The class C voltage-controlled oscillator removes the tail current source, thereby increasing the output swing of the voltage-controlled oscillator.

7. An electronic device, characterized in that: It comprises the class C voltage controlled oscillator as claimed in any one of claims 1 to 6.

8. A method for using a class C voltage-controlled oscillator with negative substrate bias, characterized in that: include: Start the Class C voltage controlled oscillator; The gate voltage of the NMOS tube pair is controlled by using the idea of ​​current competition, so that the voltage-controlled oscillator reaches the class B oscillation state and then changes to the class C oscillation state; The negative voltage charge pump circuit is controlled to generate negative voltage through the amplitude detection circuit and the Schmidt signal processing circuit, and the negative voltage is connected to the substrate of the cross-coupled pair of tubes; The 4-bit switched capacitor array circuit is adjusted as needed to change the tuning range of the class C voltage controlled oscillator.

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