A low phase noise quadrature voltage-controlled oscillator

Abstract

This invention discloses a low-phase-noise quadrature voltage-controlled oscillator (VCO), relating to the field of quadrature VCO technology, and is used to solve the technical problem that existing quadrature VCOs are unable to simultaneously achieve quadrature signal output and low phase noise at high frequencies. The low-phase-noise quadrature VCO of this invention includes a first VCO and a second VCO; the first VCO has a first coupling circuit, and the second VCO has a second coupling circuit; the first coupling circuit and / or the second coupling circuit have at least one pair of inductors, and the first and second coupling circuits form a transformer; the first VCO is used to generate a first oscillation signal, and the second VCO is used to generate a second oscillation signal; the transformer maintains a 90° phase difference between the first and second oscillation signals, and outputs the signals.

Description

Technical Field

[0001] This invention relates to the field of quadrature voltage-controlled oscillators (VCOs), and more specifically, to a low-phase-noise quadrature voltage-controlled oscillator. Background Technology

[0002] As a core component of a frequency source system, the quadrature voltage-controlled oscillator is essentially an integrated circuit that generates two high-frequency oscillation signals with orthogonal phases through voltage control. It plays a key role in fields such as wireless communication, radar systems, and software-defined radio. Its core function is to generate orthogonal local oscillator signals with high stability and tunability. The dual-output phase-quadrature characteristics can simplify signal processing procedures such as mixing and modulation, and support multi-channel synchronous operation.

[0003] Traditional quadrature voltage-controlled oscillators (VCOs) employ active coupling technology to increase injection strength and improve the accuracy of quadrature phase. However, changes in the transconductance and parasitic capacitance of the coupling transistors often degrade phase noise and reduce the frequency tuning range. Existing superharmonic coupled quadrature VCOs require additional inductors and transformers, which increases the occupied area and costs. At the same time, in high-frequency scenarios, tuning compression and phase noise problems caused by parasitic parameters make them unable to meet the requirements of modern wireless communication systems for high frequency, low noise, and wide tuning range. They cannot simultaneously achieve quadrature signal output and low phase noise at high frequencies. Summary of the Invention

[0004] The purpose of this invention is to provide a low-phase-noise quadrature voltage-controlled oscillator (VCO) to solve the technical problem that existing VCOs cannot simultaneously achieve quadrature signal output and low phase noise at high frequencies, and to reduce costs. In view of this, this invention is achieved through the following solution.

[0005] This invention provides a low-phase-noise quadrature voltage-controlled oscillator, comprising:

[0006] The first voltage-controlled oscillator has a first coupling circuit;

[0007] The second voltage-controlled oscillator has a second coupling circuit;

[0008] The first coupling circuit and / or the second coupling circuit have at least one pair of inductors, and the first coupling circuit and the second coupling circuit form a transformer;

[0009] The first voltage-controlled oscillator is used to generate a first oscillation signal, and the second voltage-controlled oscillator is used to generate a second oscillation signal; the transformer is used to maintain a 90° phase difference between the first oscillation signal and the second oscillation signal, and then outputs them.

[0010] Compared with existing technologies, the low-phase-noise quadrature voltage-controlled oscillator of the present invention achieves quadrature phase output by setting up a first voltage-controlled oscillator and a second voltage-controlled oscillator, and forming a transformer with the first coupling circuit of the first voltage-controlled oscillator and the second coupling circuit of the second voltage-controlled oscillator. The first oscillation signal and the second oscillation signal generated by the first voltage-controlled oscillator and the second voltage-controlled oscillator are maintained at a 90° phase difference through the transformer before being output. In the above technical solution, even-order harmonics can be introduced by the transformer formed by the first coupling circuit and the second coupling circuit to achieve broadband waveform shaping and reduce phase noise. Compared with the existing quadrature voltage-controlled oscillator structure, there is no need to use additional coupling circuits to generate quadrature signals, avoiding the introduction of parasitics and reducing the area. Through the above technical solution of the present invention, the technical problem that existing quadrature voltage-controlled oscillators are unable to simultaneously achieve quadrature signal output and low phase noise at high frequencies is solved, and the cost can be reduced at the same time due to the reduction in area.

[0011] Furthermore, in the low phase noise quadrature voltage-controlled oscillator of the present invention, the first coupling circuit includes a first capacitor, a ninth inductor, and a tenth inductor;

[0012] The first end of the ninth inductor is connected to the first end of the tenth inductor, and the connection is connected to the power supply terminal; the second end of the ninth inductor is connected to the first end of the first capacitor, and the second end of the first capacitor is connected to the second end of the tenth inductor.

[0013] Furthermore, in the low phase noise quadrature voltage-controlled oscillator of the present invention, the second coupling circuit includes a second capacitor, an eleventh inductor, and a twelfth inductor;

[0014] The first end of the twelfth inductor is connected to the first end of the eleventh inductor, and the connection is connected to the power supply terminal; the second end of the twelfth inductor is connected to the first end of the second capacitor, and the second end of the second capacitor is connected to the second end of the eleventh inductor.

[0015] Furthermore, in the low phase noise quadrature voltage-controlled oscillator of the present invention, the tenth inductor and the eleventh inductor are coupled to a transformer.

[0016] Furthermore, in the low phase noise quadrature voltage-controlled oscillator of the present invention, the first voltage-controlled oscillator further includes a first inductor, a second inductor, a third inductor, a fourth inductor, a first NMOS transistor, and a second NMOS transistor;

[0017] The gate of the first NMOS transistor is connected to the second terminal of the fourth inductor, the drain of the first NMOS transistor is connected to the first terminal of the first inductor, and the source of the first NMOS transistor is grounded; the gate of the second NMOS transistor is connected to the first terminal of the third inductor, the drain of the second NMOS transistor is connected to the second terminal of the second inductor, and the source of the second NMOS transistor is grounded; the second terminal of the first inductor is connected to the first terminal of the second inductor, and this connection also serves as the second terminal of the first capacitor and the second terminal of the tenth inductor; the second terminal of the third inductor is connected to the first terminal of the fourth inductor, and this connection also serves as the first bias voltage terminal; the first inductor is coupled to the third inductor transformer, and the second inductor is coupled to the fourth inductor transformer.

[0018] Furthermore, in the low phase noise quadrature voltage-controlled oscillator of the present invention, the second voltage-controlled oscillator further includes a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a third NMOS transistor, and a fourth NMOS transistor;

[0019] The gate of the third NMOS transistor is connected to the second terminal of the eighth inductor, the drain of the third NMOS transistor is connected to the first terminal of the fifth inductor, and the source of the third NMOS transistor is grounded; the gate of the fourth NMOS transistor is connected to the first terminal of the seventh inductor, the drain of the fourth NMOS transistor is connected to the second terminal of the sixth inductor, and the source of the fourth NMOS transistor is grounded; the second terminal of the fifth inductor is connected to the first terminal of the sixth inductor, and this connection also serves as the second terminal of the second capacitor and the second terminal of the eleventh inductor; the second terminal of the seventh inductor is connected to the first terminal of the eighth inductor, and this connection also serves as the second bias voltage terminal; the fifth inductor is transformer-coupled with the seventh inductor, and the sixth inductor is transformer-coupled with the eighth inductor. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic diagram of the low phase noise quadrature voltage-controlled oscillator of the present invention;

[0022] Figure 2 This is a schematic diagram of the transient simulation at the output end in Simulation 1 of the present invention;

[0023] Figure 3 This is a schematic diagram of phase noise simulation in Simulation 2 of the present invention.

[0024] Figure label:

[0025] Figure 1 In the diagram: L1, first inductor; L2, second inductor; L3, third inductor; L4, fourth inductor; L5, fifth inductor; L6, sixth inductor; L7, seventh inductor; L8, eighth inductor; L9, ninth inductor; L10, tenth inductor; L11, eleventh inductor; L12, twelfth inductor; M1, first NMOS transistor; M2, second NMOS transistor; M3, third NMOS transistor; M4, fourth NMOS transistor; VB1, first bias voltage; VB2, second bias voltage; C1, first capacitor; C2, second capacitor. Detailed Implementation

[0026] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0029] Traditional quadrature voltage-controlled oscillators (VCOs) employ active coupling technology to increase injection strength and improve the accuracy of quadrature phase. However, changes in the transconductance and parasitic capacitance of the coupling transistors often degrade phase noise and reduce the frequency tuning range. Existing superharmonic coupled quadrature VCOs require additional inductors and transformers, which increases the occupied area and costs. At the same time, in high-frequency scenarios, tuning compression and phase noise problems caused by parasitic parameters make them unable to meet the requirements of modern wireless communication systems for high frequency, low noise, and wide tuning range. They cannot simultaneously achieve quadrature signal output and low phase noise at high frequencies.

[0030] Please see Figure 1To address the aforementioned technical problems, this invention provides a low-phase-noise quadrature voltage-controlled oscillator, comprising a first voltage-controlled oscillator and a second voltage-controlled oscillator; wherein:

[0031] The first voltage-controlled oscillator has a first coupling circuit, and the second voltage-controlled oscillator has a second coupling circuit; the first coupling circuit and / or the second coupling circuit have at least one pair of inductors, and the first coupling circuit and the second coupling circuit form a transformer; the first voltage-controlled oscillator is used to generate a first oscillation signal, and the second voltage-controlled oscillator is used to generate a second oscillation signal; the transformer is used to maintain a 90° phase difference between the first oscillation signal and the second oscillation signal, and outputs the signal.

[0032] In the low-phase-noise quadrature voltage-controlled oscillator of the present invention, by setting a first voltage-controlled oscillator and a second voltage-controlled oscillator, and forming a transformer with the first coupling circuit of the first voltage-controlled oscillator and the second coupling circuit of the second voltage-controlled oscillator, the first oscillation signal and the second oscillation signal generated by the first voltage-controlled oscillator and the second voltage-controlled oscillator are output after maintaining a 90° phase difference between the first oscillation signal and the second oscillation signal through the transformer, thereby achieving quadrature phase output. In the above technical solution, even-order harmonics can be introduced by the transformer formed by the first coupling circuit and the second coupling circuit to achieve broadband waveform shaping and reduce phase noise. Compared with the existing quadrature voltage-controlled oscillator structure, there is no need to use additional coupling circuits to achieve quadrature signal generation, avoiding the introduction of parasitics and reducing the area. Through the above technical solution of the present invention, the technical problem that existing quadrature voltage-controlled oscillators are difficult to achieve quadrature signal output and low phase noise at high frequencies is solved, and the cost can be reduced at the same time due to the reduction in area.

[0033] In one possible implementation, the low-phase-noise quadrature voltage-controlled oscillator of the present invention includes a first coupling circuit comprising a first capacitor C1, a ninth inductor L9, and a tenth inductor L10. The first end of the ninth inductor L9 is connected to the first end of the tenth inductor L10, and the connection point is connected to the power supply terminal. The second end of the ninth inductor L9 is connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is connected to the second end of the tenth inductor L10. With this technical solution, the combination of the first capacitor C1 and the ninth inductor L9 forms a high-frequency filtering network, which can control harmonic content and optimize waveform quality. Simultaneously, the design of connecting the center tap of the ninth inductor L9 and the tenth inductor L10 to the power supply terminal forms a common-mode rejection path, effectively suppressing the influence of power supply noise on the oscillation signal. Furthermore, compared to traditional designs requiring additional coupling circuits, the transformer structure used in this technical solution saves chip area.

[0034] In one possible implementation, the low-phase-noise quadrature voltage-controlled oscillator of the present invention includes a second coupling circuit comprising a second capacitor C2, an eleventh inductor L11, and a twelfth inductor L12. The first end of the twelfth inductor L12 is connected to the first end of the eleventh inductor L11, and the connection point is connected to the power supply terminal. The second end of the twelfth inductor L12 is connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 is connected to the second end of the eleventh inductor L11. With this technical solution, the combination of the second capacitor C2 and the twelfth inductor L12 forms a high-frequency filtering network, which can control harmonic content and optimize waveform quality. Simultaneously, the design of connecting the center tap of the twelfth inductor L12 and the eleventh inductor L11 to the power supply terminal forms a common-mode rejection path, effectively suppressing the influence of power supply noise on the oscillation signal. Furthermore, compared to traditional designs requiring additional coupling circuits, the transformer structure used in this technical solution saves chip area.

[0035] In one possible implementation, the low-phase-noise quadrature voltage-controlled oscillator of the present invention features transformer coupling between the tenth inductor L10 and the eleventh inductor L11, with a coupling coefficient of K. Using this technology, the transformer transfers energy through magnetic induction. When the first voltage-controlled oscillator generates an oscillation signal, energy is transferred to the second voltage-controlled oscillator via transformer coupling, and vice versa. This bidirectional coupling ensures a stable quadrature phase relationship. The even-order harmonics introduced by the transformer coupling effectively lock the phase difference between the two oscillators, maintaining it precisely at 90°. Because it is unaffected by changes in transistor transconductance, this locking mechanism is more stable than traditional active coupling techniques. The transformer coupling can shape the oscillation waveform, suppressing odd harmonics while enhancing even harmonics, thereby reducing phase noise.

[0036] In one possible implementation, the low phase noise quadrature voltage-controlled oscillator of the present invention further includes a first inductor L1, a second inductor L2, a third inductor L3, a fourth inductor L4, a first NMOS transistor M1, and a second NMOS transistor M2; the gate terminal of the first NMOS transistor M1 is connected to the second terminal of the fourth inductor L4, the drain terminal of the first NMOS transistor M1 is connected to the first terminal of the first inductor L1, and the source terminal of the first NMOS transistor M1 is grounded; the gate terminal of the second NMOS transistor M2 is connected to the third inductor L3. The first terminal of the first inductor L1 is connected to the first terminal of the second inductor L2, and the drain terminal of the second NMOS transistor M2 is connected to the second terminal of the second inductor L2. The source terminal of the second NMOS transistor M2 is grounded. The second terminal of the first inductor L1 is connected to the first terminal of the second inductor L2, and this connection also serves as the second terminal of the first capacitor C1 and the second terminal of the tenth inductor L10. The second terminal of the third inductor L3 is connected to the first terminal of the fourth inductor L4, and this connection also serves as the terminal of the first bias voltage VB1. The first inductor L1 and the third inductor L3 are transformer-coupled, and the second inductor L2 and the fourth inductor L4 are transformer-coupled. With this technical solution, the cross-coupling configuration of the first NMOS transistor M1 and the second NMOS transistor M2 provides negative resistance, compensating for the energy loss of the LC resonant circuit (composed of an inductor L and a capacitor C forming a frequency selection network). The transformer coupling of the first inductor L1 and the third inductor L3, and the second inductor L2 and the fourth inductor L4 enhances the signal injection efficiency and improves the oscillation stability. At the same time, the DC bias provided by the independent bias voltage terminal avoids the interference of the bias circuit to the high-frequency signal.

[0037] In one possible implementation, the low phase noise quadrature voltage-controlled oscillator of the present invention further includes a fifth inductor L5, a sixth inductor L6, a seventh inductor L7, an eighth inductor L8, a third NMOS transistor M3, and a fourth NMOS transistor M4; the gate terminal of the third NMOS transistor M3 is connected to the second terminal of the eighth inductor L8, the drain terminal of the third NMOS transistor M3 is connected to the first terminal of the fifth inductor L5, and the source terminal of the third NMOS transistor M3 is grounded; the gate terminal of the fourth NMOS transistor M4 is connected to the seventh inductor L5. The first terminal of L7 is connected, the drain terminal of the fourth NMOS transistor M4 is connected to the second terminal of the sixth inductor L6, and the source terminal of the fourth NMOS transistor M4 is grounded; the second terminal of the fifth inductor L5 is connected to the first terminal of the sixth inductor L6, and this connection also serves as the second terminal of the second capacitor C2 and the second terminal of the eleventh inductor L11; the second terminal of the seventh inductor L7 is connected to the first terminal of the eighth inductor L8, and this connection also serves as the second bias voltage VB2 terminal; the fifth inductor L5 is transformer-coupled with the seventh inductor, and the sixth inductor is transformer-coupled with the eighth inductor L8. With this technical solution, the cross-coupling configuration of the third NMOS transistor M3 and the fourth NMOS transistor M4 provides negative resistance, compensating for the energy loss of the LC resonant circuit (composed of an inductor L and a capacitor C forming a frequency selection network); the transformer coupling of the fifth inductor L5 with the seventh inductor L7, and the sixth inductor L6 with the eighth inductor L8 enhances signal injection efficiency and improves oscillation stability, while providing DC bias through independent bias voltage terminals avoids interference from the bias circuit to high-frequency signals.

[0038] Furthermore, simulation experiments were conducted on the aforementioned low phase noise quadrature voltage-controlled oscillator of the present invention. Specifically, the simulation experimental components of the present invention were constructed using SMIC 55nm RF CMOS technology on a Red Hat system based on the Cadence IC617 simulation experimental platform. The simulation process of the present invention used the Spectre RF simulation tool to simulate the circuit of the present invention, with a given power supply voltage VDD of 1.2V, an operating temperature of 27℃, and first bias voltages VB1 and VB2 both of 0.5V.

[0039] Simulation 1: Under the above operating conditions, using the Spectre RF simulation tool, a corresponding output port was added to the drain terminal of each transistor to perform transient simulation of the low phase noise quadrature voltage-controlled oscillator of this invention. The results are as follows: Figure 2 As shown, Figure 2 This is the transient simulation diagram of the output terminal in Simulation 1, where the horizontal axis represents the transient time in nanoseconds (ns), and the vertical axis represents the voltage of the oscillation signal in volts (V). Figure 2It can be seen that the two signals output by the low phase noise quadrature voltage-controlled oscillator of the present invention are 90 degrees out of phase.

[0040] Simulation 2: Under the above operating conditions, using the Spectre RF simulation tool, corresponding output ports were added to the two output terminals of each negative resistance unit to perform PSS+PNOISE simulation on the low phase noise quadrature voltage-controlled oscillator of the present invention. The results are as follows: Figure 3 As shown, Figure 3 This is the phase noise simulation graph for Simulation 2, where the horizontal axis represents the offset frequency in Hz, and the vertical axis represents the phase noise of the output signal in dBc / Hz. From... Figure 3 It can be seen that the phase noise of the low phase noise quadrature voltage-controlled oscillator of the present invention is -117.4481dBc / Hz at a frequency offset of 1MHz at a working frequency of 10GHz.

[0041] The simulation results above show that the low phase noise quadrature voltage-controlled oscillator proposed in this invention can achieve quadrature phase output with low power consumption and low voltage, while using the head transformer (i.e., the transformer formed by the first coupling circuit and the second coupling circuit) for injection coupling. It also has the advantages of harmonic shaping and low phase noise.

[0042] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low-phase-noise quadrature voltage-controlled oscillator, characterized in that, include: The first voltage-controlled oscillator has a first coupling circuit; The second voltage-controlled oscillator has a second coupling circuit; The first coupling circuit and / or the second coupling circuit have at least one pair of inductors, and the first coupling circuit and the second coupling circuit form a transformer; The first voltage-controlled oscillator is used to generate a first oscillation signal, and the second voltage-controlled oscillator is used to generate a second oscillation signal; The transformer is used to maintain a 90° phase difference between the first and second oscillation signals, and then outputs the signal. The first coupling circuit includes a first capacitor, a ninth inductor, and a tenth inductor; the first end of the ninth inductor is connected to the first end of the tenth inductor, and the connection is connected to the power supply terminal; the second end of the ninth inductor is connected to the first end of the first capacitor, and the second end of the first capacitor is connected to the second end of the tenth inductor. The second coupling circuit includes a second capacitor, an eleventh inductor, and a twelfth inductor; the first end of the twelfth inductor is connected to the first end of the eleventh inductor, and the connection point is connected to the power supply terminal; the second end of the twelfth inductor is connected to the first end of the second capacitor, and the second end of the second capacitor is connected to the second end of the eleventh inductor. The tenth inductor and the eleventh inductor are coupled to the transformer; The first voltage-controlled oscillator further includes a first inductor, a second inductor, a third inductor, a fourth inductor, a first NMOS transistor, and a second NMOS transistor; the gate of the first NMOS transistor is connected to the second terminal of the fourth inductor, the drain of the first NMOS transistor is connected to the first terminal of the first inductor, and the source of the first NMOS transistor is grounded; the gate of the second NMOS transistor is connected to the first terminal of the third inductor, the drain of the second NMOS transistor is connected to the second terminal of the second inductor, and the source of the second NMOS transistor is grounded; the second terminal of the first inductor is connected to the first terminal of the second inductor, and this connection also serves as the second terminal of the first capacitor and the second terminal of the tenth inductor; the second terminal of the third inductor is connected to the first terminal of the fourth inductor, and this connection also serves as the second bias voltage terminal; the first inductor is coupled to the third inductor transformer, and the second inductor is coupled to the fourth inductor transformer; The second voltage-controlled oscillator further includes a fifth inductor, a sixth inductor, a seventh inductor, an eighth inductor, a third NMOS transistor, and a fourth NMOS transistor; the gate of the third NMOS transistor is connected to the second terminal of the eighth inductor, the drain of the third NMOS transistor is connected to the first terminal of the fifth inductor, and the source of the third NMOS transistor is grounded; the gate of the fourth NMOS transistor is connected to the first terminal of the seventh inductor, the drain of the fourth NMOS transistor is connected to the second terminal of the sixth inductor, and the source of the fourth NMOS transistor is grounded; the second terminal of the fifth inductor is connected to the first terminal of the sixth inductor, and this connection also serves as the second terminal of the second capacitor and the second terminal of the eleventh inductor; the second terminal of the seventh inductor is connected to the first terminal of the eighth inductor, and this connection also serves as the second bias voltage terminal; the fifth inductor is transformer-coupled with the seventh inductor, and the sixth inductor is transformer-coupled with the eighth inductor.

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