阅读说明：本技术 一种混合b/c类低噪声压控振荡器 (mixed B/C type low-noise voltage-controlled oscillator ) 是由 姚若河 刘爽 王立姣 于 2019-08-05 设计创作，主要内容包括：本发明公开了一种混合B/C类低噪声压控振荡器,包括：自开关电流源电路,在初始工作时,自开关电流源电路中的电流源处于开启的状态,为压控振荡器提供起振电流；尾电流整形压控振荡器电路,该电路的尾电流源电流随着电路振荡增大,其电流被比例镜像到自开关电流源电路,并最终关断起振电流；所述尾电流整形压控振荡电路包括尾电流整形电路,用于提供近似脉冲的尾电流,将谐振电路产生的振荡信号反馈到尾电流源使尾电流波形与输出电压波形同步。本发明将谐振电路产生的振荡信号反馈到尾电流源使尾电流波形与输出电压波形同步,提供近似脉冲的尾电流,使在对噪声电流敏感度低的时刻注入更多电流减小相位噪声。(the invention discloses a mixed B/C low-noise voltage-controlled oscillator, which comprises: the self-switching current source circuit is used for providing oscillation starting current for the voltage-controlled oscillator when a current source in the self-switching current source circuit is in a starting state during initial work; the tail current shaping voltage-controlled oscillator circuit is characterized in that the tail current source current of the circuit increases along with the oscillation of the circuit, the current of the tail current source current is proportionally mirrored to a self-switching current source circuit, and the oscillation starting current is finally turned off; the tail current shaping voltage-controlled oscillation circuit comprises a tail current shaping circuit, wherein the tail current shaping circuit is used for providing tail current similar to pulse, and an oscillation signal generated by the resonance circuit is fed back to a tail current source to enable the tail current waveform to be synchronous with the output voltage waveform. The invention feeds back the oscillation signal generated by the resonant circuit to the tail current source to synchronize the tail current waveform with the output voltage waveform, provides the tail current similar to the pulse, and injects more current at the moment with low sensitivity to the noise current to reduce the phase noise.)

1. A hybrid class B/C low noise voltage controlled oscillator comprising:

the self-switching current source circuit is used for providing oscillation starting current for the voltage-controlled oscillator when a current source in the self-switching current source circuit is in a starting state during initial work;

the tail current shaping voltage-controlled oscillator circuit is characterized in that the tail current source current of the circuit increases along with the oscillation of the circuit, the current of the tail current source current is proportionally mirrored to a self-switching current source circuit, and the oscillation starting current is finally turned off;

the tail current shaping voltage-controlled oscillation circuit includes:

the resonance circuit is an inductance-capacitance type resonance circuit and determines the resonance frequency;

a cross-coupled transistor pair for providing a negative resistance to cancel the impedance created by the resonant cavity;

The tail current shaping circuit is used for providing tail current similar to pulse and feeding back an oscillation signal generated by the resonance circuit to the tail current source to synchronize the waveform of the tail current with the waveform of the output voltage;

The tail current shaping circuit specifically comprises:

the grid electrodes of the M3 and M3 of the third NMOS tube are connected with a self-switching current source circuit, the drain electrode of M3 is connected with the cross-coupling transistor pair, and the source electrode of M3 is connected with the ground;

the grid electrode of a fourth NMOS transistor M4 and M4 is connected with a self-switching current source circuit, the drain electrode of M4 is connected with the cross-coupling transistor pair, and the source electrode of M4 is connected with the ground;

one end of the first resistor R1 and R1 is connected with the grid of M3, and the other end is connected with a bias voltage Vb;

one end of the second resistor R2 and R2 is connected with the grid of M4, and the other end is connected with Vb;

one end of the third capacitor C3, C3 is connected to the output port Vouta, and the other end is connected to the gate of the third NMOS transistor M3;

one end of the fourth capacitor C4, C4 is connected to the output port Voutb, and the other end is connected to the gate of the fourth NMOS transistor M4.

2. a hybrid class B/C low noise voltage controlled oscillator according to claim 1 wherein Vb is lower than the threshold voltages of M3 and M4;

The self-switching current source circuit includes:

The dynamic switch circuit is used for shaping the current of a tail current source in the voltage-controlled oscillator circuit through the mirror image tail current to obtain dynamic bias voltage;

the oscillation starting current source circuit is used for determining the switch of the oscillation starting current source according to the dynamic bias voltage;

the dynamic switching circuit specifically includes:

The grid electrode of the M5 of the fifth PMOS tube M5 is connected with the drain electrode thereof, the drain electrode of the M5 is connected with the oscillation starting current source circuit, and the source electrode of the M5 is connected with the power supply voltage;

a gate of the M7 of the seventh NMOS transistor M7 is connected with a gate of the M4, a drain of the M7 is connected with the oscillation starting current source circuit, and a source of the M7 is connected with the ground;

The grid electrode of the M8 of the eighth NMOS tube M8 is connected with the grid electrode of the M3, the drain electrode of the M8 is connected with the oscillation starting current source circuit, and the source electrode of the M8 is connected with the ground;

one end of each of the fifth capacitors C5 and C5 is connected with the drains of M7 and M8, and the other end is grounded.

3. the hybrid class B/C low noise voltage-controlled oscillator according to claim 2, wherein the oscillation starting current source circuit specifically comprises:

the gates of the M6 and M7 of the sixth NMOS transistor M6 are connected to the drains of M8, the drain of M6 is connected to the cross-coupled transistor pair, and the source of M6 is connected to ground.

4. a hybrid class B/C low noise voltage controlled oscillator according to claim 3, wherein: the current magnitude of M5 is compared with that of M7 and M8, and dynamic voltage is provided by charging and discharging C5 so as to control the switch of M6.

5. a hybrid class B/C low noise voltage controlled oscillator according to claim 1, wherein the resonant circuit specifically comprises:

one end of the first capacitor C1, C1 is connected to the tuning voltage Vtune, and the other end is connected to the first output port Vouta;

one end of the second capacitor C2, C2 is connected to the tuning voltage Vtune, and the other end is connected to the second output port Voutb;

one end of the first inductor L1 and L1 is connected with a power supply voltage, and the other end is connected with C1;

one end of the second inductor L2 and L2 is connected with the power supply voltage, and the other end is connected with C2.

6. The mixed class-B/C low-noise voltage-controlled oscillator of claim 5, wherein the C1 and C2 are variable capacitors, and when the input tuning voltage Vtune changes, the C1 and C2 change accordingly, so as to change the oscillation frequency; vouta and Voutb are respectively connected with two ends of the resonant circuit and are output of the oscillator.

7. a hybrid class B/C low noise voltage controlled oscillator according to claim 5, wherein said cross-coupled transistor pair comprises in particular:

the grid electrode of the first NMOS transistor M1, the grid electrode of the M1 is connected with the second output port Voutb, the drain electrode of the M1 is connected with the first output port Vouta, and the source electrode of the M1 is connected with the source electrode of the M2;

the gates of the second NMOS transistor M2 and M2 are connected to the first output port Vouta, the drain of M2 is connected to the second output port Voutb, and the source of M2 is connected to the source of M1.

8. a hybrid class B/C low noise voltage controlled oscillator according to claim 1, comprising:

the self-switching current source circuit is used for providing oscillation starting current for the voltage-controlled oscillator when a current source in the self-switching current source circuit is in a starting state during initial work;

the tail current shaping voltage-controlled oscillator circuit is characterized in that the tail current source current of the circuit increases along with the oscillation of the circuit, the current of the tail current source current is proportionally mirrored to a self-switching current source circuit, and the oscillation starting current is finally turned off;

the tail current shaping voltage controlled oscillator circuit comprises:

The resonance circuit is an inductance-capacitance type resonance circuit and determines the resonance frequency;

a cross-coupled transistor pair for providing a negative resistance to cancel the impedance created by the resonant cavity;

the tail current shaping circuit is used for providing tail current similar to pulse and feeding back an oscillation signal generated by the resonance circuit to the tail current source to synchronize the waveform of the tail current with the waveform of the output voltage;

the resonant circuit specifically includes:

one end of the first capacitor C1, C1 is connected to the tuning voltage Vtune, and the other end is connected to the first output port Vouta;

one end of the second capacitor C2, C2 is connected to the tuning voltage Vtune, and the other end is connected to the second output port Voutb;

one end of the first inductor L1 and L1 is connected with a power supply voltage, and the other end is connected with C1;

one end of the second inductor L2 and L2 is connected with a power supply voltage, and the other end is connected with C2;

the C1 and C2 are variable capacitors, and when the input tuning voltage Vtune changes, C1 and C2 change accordingly, so that the oscillation frequency is changed; vouta and Voutb are respectively connected with two ends of the resonance circuit and are output of the oscillator;

the cross-coupled transistor specifically includes:

The grid electrode of the first NMOS transistor M1, the grid electrode of the M1 is connected with Voutb, the drain electrode of the M1 is connected with Vouta, and the source electrode of the M1 is connected with the source electrode of the second NMOS transistor M2;

The grid electrode of the M2 of the second NMOS transistor M2 is connected with Vouta, the drain electrode of the M2 is connected with Voutb, and the source electrode of the M2 is connected with the source electrode of the M1;

The tail current shaping circuit specifically comprises:

the grid electrode of the M3 of the third NMOS transistor M3 is connected with the grid electrode of the eighth NMOS transistor M8, the drain electrode of the M3 is connected with the source electrode of the M1, and the source electrode of the M3 is connected with the ground;

the grid electrode of the M4 of the fourth NMOS transistor M4 is connected with the grid electrode of the seventh NMOS transistor M7, the drain electrode of M4 is connected with the source electrode of M2, and the source electrode of M4 is connected with the ground;

One end of a first resistor R1 and R1 is connected with the grid of M3, and the other end is connected with a bias voltage Vb;

one end of the second resistor R2 and R2 is connected with the grid of M4, and the other end is connected with Vb;

one end of the third capacitor C3, C3 is connected with Vouta, and the other end is connected with the grid of M3;

one end of the fourth capacitor C4, C4 is connected with Voutb, and the other end is connected with the grid of M4;

the bias voltage Vb is lower than the threshold voltages of M3 and M4;

the self-switching current source circuit includes:

the dynamic switching circuit is used for shaping the current of a tail current source in the voltage-controlled oscillator through the mirror image tail current to obtain a dynamic bias voltage;

the oscillation starting current source circuit is used for determining the switch of the oscillation starting current source according to the dynamic bias voltage;

The dynamic switching circuit specifically includes:

the grid electrode of the M5 of the fifth PMOS tube M5 is connected with the drain electrode of M5, the drain electrode of M5 is connected with the grid electrode of the sixth NMOS tube M6, and the source electrode of M5 is connected with power supply voltage;

a seventh NMOS transistor M7, wherein the gate of the M7 is connected with the gate of the M4, the drain of the M7 is connected with the gate of the M6, and the source of the M7 is connected with the ground;

The gate of the M8 of the eighth NMOS transistor M8 is connected with the gate of M3, the drain of M8 is connected with the gate of M6, and the source of M8 is connected with the ground;

one end of a fifth capacitor C5, C5 is connected with the drains of M7 and M8, and the other end is grounded;

the oscillation starting current source circuit is composed of a sixth NMOS transistor M6, the drains of gates M7 and M8 of M6 are connected, the drain of M6 is connected with the sources of M1 and M2, and the source of M6 is connected with the ground;

the current magnitude of M5 is compared with that of M7 and M8, and dynamic voltage is provided by charging and discharging C5 so as to control the switch of M6.

Technical Field

the invention relates to the field of integrated circuits, in particular to a hybrid B/C type low-noise voltage-controlled oscillator.

background

the voltage-controlled oscillator is a main component of a radio frequency transceiver, the performance of the voltage-controlled oscillator directly affects the accuracy of signal transmission and reception, and the phase noise is a key parameter for determining the performance of the voltage-controlled oscillator. As the operating frequency of the circuit increases and the device size decreases, the noise performance of the corresponding oscillator decreases. In a transceiver system, when phase noise exists in the output signal of the oscillator, the frequency spectrum presents a skirt band shape which is no longer an ideal shock function, and an interference signal is down-converted to a low frequency band along with the signal, so that the interference signal generates interference on a wanted channel signal. Therefore, for a system with strict communication quality requirements, a low-noise voltage-controlled oscillator design is particularly necessary.

Disclosure of Invention

the invention aims to overcome the defects of the prior art and provide a mixed B/C type low-noise voltage-controlled oscillator, which feeds an oscillation signal generated by a resonant circuit back to a tail current source to synchronize the tail current waveform with the output voltage waveform and provide tail current similar to pulse, so that more current is injected at the moment of low sensitivity to noise current to reduce phase noise.

the first purpose of the invention is realized by the following technical scheme:

a hybrid class B/C low noise voltage controlled oscillator comprising:

The self-switching current source circuit is used for providing oscillation starting current for the voltage-controlled oscillator when a current source in the self-switching current source circuit is in a starting state during initial work;

the tail current shaping voltage-controlled oscillator circuit is characterized in that the tail current source current of the circuit increases along with the oscillation of the circuit, the current of the tail current source current is proportionally mirrored to a self-switching current source circuit, and the oscillation starting current is finally turned off;

the tail current shaping voltage-controlled oscillation circuit includes:

the resonance circuit is an inductance-capacitance type resonance circuit and determines the resonance frequency;

A cross-coupled transistor pair for providing a negative resistance to cancel the impedance created by the resonant cavity;

the tail current shaping circuit is used for providing tail current similar to pulse and feeding back an oscillation signal generated by the resonance circuit to the tail current source to synchronize the waveform of the tail current with the waveform of the output voltage; therefore, more current is injected when the sensitivity to phase noise is low, and the conversion of noise to output phase noise is reduced;

the tail current shaping circuit specifically comprises:

the grid electrodes of the M3 and M3 of the third NMOS tube are connected with a self-switching current source circuit, the drain electrode of M3 is connected with the cross-coupling transistor pair, and the source electrode of M3 is connected with the ground;

the grid electrode of a fourth NMOS transistor M4 and M4 is connected with a self-switching current source circuit, the drain electrode of M4 is connected with the cross-coupling transistor pair, and the source electrode of M4 is connected with the ground;

one end of the first resistor R1 and R1 is connected with the grid of M3, and the other end is connected with a bias voltage Vb;

one end of the second resistor R2 and R2 is connected with the grid of M4, and the other end is connected with Vb;

one end of the third capacitor C3, C3 is connected to the output port Vouta, and the other end is connected to the gate of the third NMOS transistor M3;

one end of the fourth capacitor C4, C4 is connected to the output port Voutb, and the other end is connected to the gate of the fourth NMOS transistor M4.

preferably, the bias voltage Vb is lower than the threshold voltages of M3 and M4 to reduce the current conduction angle and thus the duty cycle of the noise modulation function.

the self-switching current source circuit includes:

The dynamic switch circuit is used for shaping the current of a tail current source in the voltage-controlled oscillator circuit through the mirror image tail current to obtain dynamic bias voltage;

the oscillation starting current source circuit is used for determining the switch of the oscillation starting current source according to the dynamic bias voltage;

the dynamic switching circuit specifically includes:

The grid electrode of the M5 of the fifth PMOS tube M5 is connected with the drain electrode thereof, the drain electrode of the M5 is connected with the oscillation starting current source circuit, and the source electrode of the M5 is connected with the power supply voltage;

a gate of the M7 of the seventh NMOS transistor M7 is connected with a gate of the M4, a drain of the M7 is connected with the oscillation starting current source circuit, and a source of the M7 is connected with the ground;

The grid electrode of the M8 of the eighth NMOS tube M8 is connected with the grid electrode of the M3, the drain electrode of the M8 is connected with the oscillation starting current source circuit, and the source electrode of the M8 is connected with the ground;

one end of the fifth capacitor C5 and C5 is connected with the drains of M7 and M8, and the other end is grounded; the self-switching current source circuit is adopted to realize the conversion of the working mode, has the characteristic of rapid and stable oscillation, and turns off the oscillation starting current source after stable oscillation, thereby reducing the noise contribution in the self-switching tail current source circuit.

furthermore, the oscillation starting current source circuit specifically includes:

the gates of the M6 and M7 of the sixth NMOS transistor M6 are connected to the drains of M8, the drain of M6 is connected to the cross-coupled transistor pair, and the source of M6 is connected to ground.

furthermore, the current magnitude of M5 is compared with the current of M7 and M8, and dynamic voltage is provided by charging and discharging C5, so that the switch of M6 is controlled.

preferably, the resonant circuit specifically includes:

one end of the first capacitor C1, C1 is connected to the tuning voltage Vtune, and the other end is connected to the first output port Vouta;

one end of the second capacitor C2, C2 is connected to the tuning voltage Vtune, and the other end is connected to the second output port Voutb;

one end of the first inductor L1 and L1 is connected with a power supply voltage, and the other end is connected with C1;

one end of the second inductor L2 and L2 is connected with the power supply voltage, and the other end is connected with C2.

furthermore, the C1 and C2 are variable capacitors, and when the input tuning voltage Vtune is changed, the C1 and C2 are changed, so that the oscillation frequency is changed; vouta and Voutb are respectively connected with two ends of the resonant circuit and are output of the oscillator.

further, the cross-coupled transistor pair specifically includes:

the grid electrode of the first NMOS transistor M1, the grid electrode of the M1 is connected with the second output port Voutb, the drain electrode of the M1 is connected with Vouta, and the source electrode of the M1 is connected with the source electrode of the M2;

The gate of the second NMOS transistor M2, M2 is connected to the first output port Vouta, the drain of M2 is connected to Voutb, and the source of M2 is connected to the source of M1.

preferably, the hybrid class B/C low noise voltage controlled oscillator includes:

the self-switching current source circuit is used for providing oscillation starting current for the voltage-controlled oscillator when a current source in the self-switching current source circuit is in a starting state during initial work;

the tail current shaping voltage-controlled oscillator circuit is characterized in that the tail current source current of the circuit increases along with the oscillation of the circuit, the current of the tail current source current is proportionally mirrored to a self-switching current source circuit, and the oscillation starting current is finally turned off;

the tail current shaping voltage controlled oscillator circuit comprises:

The resonance circuit is an inductance-capacitance type resonance circuit and determines the resonance frequency;

A cross-coupled transistor pair for providing a negative resistance to cancel the impedance created by the resonant cavity;

the tail current shaping circuit is used for providing tail current similar to pulse and feeding back an oscillation signal generated by the resonance circuit to the tail current source to synchronize the waveform of the tail current with the waveform of the output voltage;

the resonant circuit specifically includes:

one end of the first capacitor C1, C1 is connected to the tuning voltage Vtune, and the other end is connected to the first output port Vouta;

one end of the second capacitor C2, C2 is connected to the tuning voltage Vtune, and the other end is connected to the second output port Voutb;

one end of the first inductor L1 and L1 is connected with a power supply voltage, and the other end is connected with C1;

one end of the second inductor L2 and L2 is connected with a power supply voltage, and the other end is connected with C2;

The C1 and C2 are variable capacitors, and when the input tuning voltage Vtune changes, C1 and C2 change accordingly, so that the oscillation frequency is changed; vouta and Voutb are respectively connected with two ends of the resonance circuit and are output of the oscillator;

the cross-coupled transistor specifically includes:

The grid electrode of the first NMOS transistor M1, the grid electrode of the M1 is connected with Voutb, the drain electrode of the M1 is connected with Vouta, and the source electrode of the M1 is connected with the source electrode of the second NMOS transistor M2;

the grid electrode of the M2 of the second NMOS transistor M2 is connected with Vouta, the drain electrode of the M2 is connected with Voutb, and the source electrode of the M2 is connected with the source electrode of the M1;

the tail current shaping circuit specifically comprises:

the grid electrode of the M3 of the third NMOS transistor M3 is connected with the grid electrode of the eighth NMOS transistor M8, the drain electrode of the M3 is connected with the source electrode of the M1, and the source electrode of the M3 is connected with the ground;

the grid electrode of the M4 of the fourth NMOS transistor M4 is connected with the grid electrode of the seventh NMOS transistor M7, the drain electrode of M4 is connected with the source electrode of M2, and the source electrode of M4 is connected with the ground;

One end of a first resistor R1 and R1 is connected with the grid of M3, and the other end is connected with a bias voltage Vb;

one end of the second resistor R2 and R2 is connected with the grid of M4, and the other end is connected with Vb;

One end of the third capacitor C3, C3 is connected with Vouta, and the other end is connected with the grid of M3;

one end of the fourth capacitor C4, C4 is connected with Voutb, and the other end is connected with the grid of M4;

The bias voltage Vb is lower than the threshold voltages of M3 and M4;

the self-switching current source circuit includes:

The dynamic switching circuit is used for shaping the current of a tail current source in the voltage-controlled oscillator through the mirror image tail current to obtain a dynamic bias voltage;

the oscillation starting current source circuit is used for determining the switch of the oscillation starting current source according to the dynamic bias voltage;

The dynamic switching circuit specifically includes:

the grid electrode of the M5 of the fifth PMOS tube M5 is connected with the drain electrode of M5, the drain electrode of M5 is connected with the grid electrode of the sixth NMOS tube M6, and the source electrode of M5 is connected with power supply voltage;

a seventh NMOS transistor M7, wherein the gate of the M7 is connected with the gate of the M4, the drain of the M7 is connected with the gate of the M6, and the source of the M7 is connected with the ground;

the gate of the M8 of the eighth NMOS transistor M8 is connected with the gate of M3, the drain of M8 is connected with the gate of M6, and the source of M8 is connected with the ground;

one end of a fifth capacitor C5, C5 is connected with the drains of M7 and M8, and the other end is grounded;

The oscillation starting current source circuit is composed of a sixth NMOS transistor M6, the drains of gates M7 and M8 of M6 are connected, the drain of M6 is connected with the sources of M1 and M2, and the source of M6 is connected with the ground;

the current magnitude of M5 is compared with that of M7 and M8, and dynamic voltage is provided by charging and discharging C5 so as to control the switch of M6.

compared with the prior art, the invention has the following advantages and effects:

1. the invention feeds back the oscillation signal generated by the resonant circuit to the tail current source to synchronize the tail current waveform with the output voltage waveform, provides the tail current similar to the pulse, and injects more current at the moment with low sensitivity to the noise current to reduce the phase noise.

2. according to the invention, the bias voltage Vb is set to be lower than the threshold voltages of the third NMOS transistor M3 and the fourth NMOS transistor M4, so that the current conduction angle and the duty ratio of a noise modulation function are reduced, and the mean square value of an impact sensitive function is further reduced.

3. the invention adopts the self-switching current source circuit to realize the conversion of the working mode, has the characteristic of rapid and stable oscillation, and turns off the oscillation starting current source after the stable oscillation, thereby reducing the noise contribution in the self-switching current source circuit.

drawings

fig. 1 is a circuit structure diagram of a hybrid B/C class low-noise voltage-controlled oscillator according to the present invention.

FIG. 2 is a diagram showing the variation of the output voltage with time during the start-up of a mixed class B/C low-noise voltage-controlled oscillator according to the present invention.

FIG. 3 is a diagram of the variation of phase noise with frequency offset for a hybrid class B/C low noise voltage controlled oscillator according to the present invention.

Detailed Description

the embodiment provides a hybrid B/C type low-noise voltage-controlled oscillator, and solves the problem that the overall performance of a circuit is affected because the receiving signal of a transceiver is seriously interfered by a large phase noise of the output signal of an oscillator in the prior art.

in order to solve the above problems, the general idea of the present embodiment is as follows:

as shown in fig. 1, a hybrid class B/C low noise voltage controlled oscillator includes:

The self-switching current source circuit is used for providing oscillation starting current for the voltage-controlled oscillator when a current source in the self-switching current source circuit is in a starting state during initial work;

The tail current shaping voltage-controlled oscillator circuit is characterized in that the tail current source current of the circuit increases along with the oscillation of the circuit, the current of the tail current source current is proportionally mirrored to a self-switching current source circuit, and the oscillation starting current is finally turned off;

the self-switching current source circuit provides current required by oscillator oscillation starting to ensure that the oscillator is operated to start oscillation quickly by class B operation, and reduces bias voltage to cut off oscillation starting current after stable oscillation; the tail current shaping voltage-controlled oscillator circuit feeds back an oscillation signal generated by the resonant cavity to the tail current source after the oscillation starting current is switched off, so that the tail current waveform and the output voltage waveform synchronously provide tail current similar to pulse, more current is injected when the noise sensitivity is low, the current conduction angle is less than 180 degrees, the oscillator is similar to a C-type working state at the moment, two working states are realized through feedback adjustment between the tail current shaping voltage-controlled oscillator circuit and the self-switching current source circuit, and the tail current shaping voltage-controlled oscillator circuit has the characteristics of low noise and quick oscillation starting.

the tail current shaping voltage controlled oscillator circuit comprises:

the resonance circuit is an inductance-capacitance type resonance circuit and determines the resonance frequency;

a cross-coupled transistor pair for providing a negative resistance to cancel the impedance created by the resonant cavity;

the tail current shaping circuit is used for providing tail current similar to pulse and feeding back an oscillation signal generated by the resonance circuit to the tail current source to synchronize the waveform of the tail current with the waveform of the output voltage;

the resonant circuit specifically includes:

one end of the first capacitor C1, C1 is connected to the tuning voltage Vtune, and the other end is connected to the first output port Vouta;

one end of the second capacitor C2, C2 is connected to the tuning voltage Vtune, and the other end is connected to the second output port Voutb;

one end of the first inductor L1 and L1 is connected with a power supply voltage, and the other end is connected with C1;

one end of the second inductor L2 and L2 is connected with a power supply voltage, and the other end is connected with C2;

the C1 and C2 are variable capacitors, and when the input tuning voltage Vtune changes, C1 and C2 change accordingly, so that the oscillation frequency is changed; vouta and Voutb are respectively connected with two ends of the resonance circuit and are output of the oscillator;

The cross-coupled transistor specifically includes:

The grid electrode of the first NMOS transistor M1, the grid electrode of the M1 is connected with Voutb, the drain electrode of the M1 is connected with Vouta, and the source electrode of the M1 is connected with the source electrode of the second NMOS transistor M2;

The grid electrode of the M2 of the second NMOS transistor M2 is connected with Vouta, the drain electrode of the M2 is connected with Voutb, and the source electrode of the M2 is connected with the source electrode of the M1;

the tail current shaping circuit specifically comprises:

The grid electrode of the M3 of the third NMOS transistor M3 is connected with the grid electrode of the eighth NMOS transistor M8, the drain electrode of the M3 is connected with the source electrode of the M1, and the source electrode of the M3 is connected with the ground;

the grid electrode of the M4 of the fourth NMOS transistor M4 is connected with the grid electrode of the seventh NMOS transistor M7, the drain electrode of M4 is connected with the source electrode of M2, and the source electrode of M4 is connected with the ground;

One end of a first resistor R1 and R1 is connected with the grid of M3, and the other end is connected with a bias voltage Vb;

one end of the second resistor R2 and R2 is connected with the grid of M4, and the other end is connected with Vb;

one end of the third capacitor C3, C3 is connected with Vouta, and the other end is connected with the grid of M3;

One end of the fourth capacitor C4, C4 is connected with Voutb, and the other end is connected with the grid of M4;

Vb is lower than the threshold voltages of M3 and M4;

the self-switching current source circuit includes:

the dynamic switching circuit is used for shaping the current of a tail current source in the voltage-controlled oscillator through the mirror image tail current to obtain a dynamic bias voltage;

the oscillation starting current source circuit is used for determining the switch of the oscillation starting current source according to the dynamic bias voltage;

the dynamic switching circuit specifically includes:

the grid electrode of the M5 of the fifth PMOS tube M5 is connected with the drain electrode of M5, the drain electrode of M5 is connected with the grid electrode of the sixth NMOS tube M6, and the source electrode of M5 is connected with power supply voltage;

a seventh NMOS transistor M7, wherein the gate of the M7 is connected with the gate of the M4, the drain of the M7 is connected with the gate of the M6, and the source of the M7 is connected with the ground;

the gate of the M8 of the eighth NMOS transistor M8 is connected with the gate of M3, the drain of M8 is connected with the gate of M6, and the source of M8 is connected with the ground;

one end of a fifth capacitor C5, C5 is connected with the drains of M7 and M8, and the other end is grounded;

the oscillation starting current source circuit is composed of a sixth NMOS transistor M6, the drains of gates M7 and M8 of M6 are connected, the drain of M6 is connected with the sources of M1 and M2, and the source of M6 is connected with the ground;

the current magnitude of the M5 is compared with the current of the M7 and the M8, and a dynamic voltage is provided by charging and discharging the fifth capacitor C5 so as to control the switch of the M6.

principle and performance analysis of the present embodiment:

The noise model of Hajimiri proposes the concept of the impulse sensitivity function f (ω 0t), a larger f (ω 0t) means that the same noise current produces more phase noise. Thus, when the oscillator output is close to the zero crossing point (i.e., the moment when the value of f (ω 0t) is maximum), the current injected into the resonant cavity is reduced, and the phase noise is reduced; and the phase noise is positively correlated with the mean square value of the impact sensitive function, and the reduction of the current conduction angle is beneficial to reducing the mean square value of the impact sensitive function.

in conjunction with the above theory, the present embodiment introduces a tail current shaping circuit, which feeds back the output oscillation signal to the gates of M3 and M4 through C3 and C4 to achieve synchronization of the tail current and the voltage waveform, and provides an approximately pulsed tail current with a current conduction angle:

wherein Vth is the threshold voltage of M3 and M4, and Vm is the oscillation swing. According to the formula (1), reducing the gate bias voltage of the third and fourth NMOS transistors M3, M4 to be less than the threshold voltage can reduce the current conduction angle.

However, reducing the gate bias voltage of M3 and M4 has a certain effect on the oscillation starting process, and in order to solve this problem, the present embodiment designs a self-switching current source circuit.

m7, M8 mirror the currents of M3, M4 respectively, and the sum of the currents of M7, M8 is compared with the current of M5, and the difference in current between them is converted by C5 into a change in the gate voltage of M6. When Vb is lower than the threshold voltage of the transistor, the grid voltage of M6 is higher, and M6 provides starting current for the oscillator, similar to a B-type oscillator. As the circuit starts oscillation, C3 and C4 feed back output oscillation signals to the gates of M3, M4, M7 and M8, the sum of currents of M7 and M8 increases, the gate voltage of M6 is reduced to be below the threshold voltage along with the discharge of C5, and the oscillation starting current is turned off. At this time, M3, M4 provide a current maintaining circuit stable oscillation, and the current conduction angle is less than 180 °, similar to a class C oscillator.

the embodiment is realized by using a TSMC 180nm process, the oscillation frequency is 2GHz, the voltage source is 1.8V, and the bias current is 5 mA. Fig. 2 shows the output voltage of the oscillation starting process of the embodiment, and it can be seen that the output waveform can be stabilized at about 80 ns. FIG. 3 shows the phase noise results for the example, with-59.5 dB at 1KHz and-132.7 dB at 1 MHz. The embodiments show that the present invention achieves fast stable oscillation and good noise performance.

The embodiments described above are more specific and detailed, but should not be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the claims.