CN115549591A - Voltage Controlled Oscillator Based on Carbon Nanotube Field Effect Transistor - Google Patents

Abstract

The invention relates to a voltage-controlled oscillator based on a carbon nanotube field-effect transistor, which belongs to the technical field of oscillators. The voltage-controlled oscillator includes: a delay unit group including n delay units and a varactor including n varactor units The unit group, each delay unit of the delay unit group forms a feedback loop, the output terminals of each unit of the delay unit group are respectively connected to the control voltage Vctrl output terminal through each unit of the corresponding varactor unit group, and the power supply of each unit of the delay unit group Terminals are respectively connected to the VDD terminal; relevant devices in each unit of the delay unit group share metal electrodes with each unit of the corresponding varactor unit group. The application can increase the frequency modulation range of the voltage-controlled oscillator, overcome the frequency modulation problem caused by the limited control voltage range of the traditional voltage-controlled oscillator, and at the same time, enable the voltage-controlled oscillator to have a smaller parasitic delay without loss The performance of the device overcomes the parasitic redundancy problem of the traditional voltage-controlled oscillator.

Description

Voltage Controlled Oscillator Based on Carbon Nanotube Field Effect Transistor

technical field

The invention relates to the technical field of oscillators, in particular to a voltage-controlled oscillator based on carbon nanotube field effect transistors.

Background technique

A voltage-controlled oscillator is a basic element in building a wireless communication system. Usually, the regulation of the frequency range of a voltage-controlled oscillator is achieved by converting the control voltage into a current. A typical implementation is to use a current source as the transition from voltage to current. converter, this approach enables voltage-to-current conversion even at very low supply voltages, but has the disadvantage that the input voltage range of its delay unit is limited by the threshold voltage of its transistors.

The voltage-controlled oscillator is mainly composed of several delay units cascaded. When the Barkhausen criterion is satisfied, when the output signal of a certain unit passes through the entire loop and returns to the input of the unit, the signal is reversed to generate a periodic oscillation signal. The important advantages of the oscillator are wide tuning range and small area. The parasitic delay caused by the circuit connection lines inside the voltage controlled oscillator is described by the parasitic resistance R and the parasitic capacitance C. The smaller the parasitic delay, the smaller the voltage controlled oscillator. The lower the power consumption, the better the frequency tuning. Due to the limitations of the traditional semiconductor process, the connection between the load capacitance of the existing CMOS transistor and the delay unit is realized by the subsequent metal interconnection process. To realize a high-performance voltage-controlled oscillator, it is necessary to break through the parasitic limitation brought by the interconnection of the conventional load capacitor and the delay unit. There are two main ways to reduce the interconnection parasitic delay: 1. One is to use metal interconnection lines with lower resistivity and higher electron mobility, and the second is to reduce the volume and size of interconnection lines. However, these two methods start from the back-end process and cannot truly achieve parasitic delay. removal of .

Contents of the invention

The present invention intends to provide a voltage-controlled oscillator based on carbon nanotube field effect transistors to solve the deficiencies in the prior art. The technical problems to be solved by the present invention are achieved through the following technical solutions.

The present invention provides a voltage-controlled oscillator based on a carbon nanotube field-effect transistor. The voltage-controlled oscillator is composed of a delay unit group consisting of delay units D ₁ , D ₂ ,...D _n and a varactor unit T ₁ , T ₂ ,... T _n varactor unit group, n=2i+1, i is a positive integer greater than zero;

Wherein, the delay units D ₁ , D ₂ , ... D _n are active loads composed of carbon nanotube field effect transistors, respectively having an input terminal, an output terminal and a power supply terminal, and the delay unit D ₁ , D ₂ ,...D _n input terminals and output terminals are connected in series to form a ring circuit, and the power supply terminals of the delay units D ₁ , D ₂ ,...D _n are connected to the VDD terminal;

One end of the variable capacitor units T ₁ , T ₂ , ... T _n-1 is electrically connected to the input end of the control voltage V _ctrl , and the other end is electrically connected to the input end of the delay unit D ₂ , ... D _n ; One end of the capacitor unit T _n is electrically connected to the input end of the control voltage V _ctrl , and the other end is electrically connected to the output end of the delay unit D1, and the output end of the variable capacitor unit T _{n-1 is} used as the output end V of the voltage-controlled oscillator. _out .

In the above solution, the delay units D ₁ , D ₂ , ... D _n share metal electrodes with the varactor units T ₁ , T ₂ , ... T _n .

In the above solution, the delay units D ₁ , D ₂ , . . . _Dn respectively have a first carbon-based PMOS transistor M1 and a second carbon-based PMOS transistor M2.

In the above solution, the varactor units T ₁ , T ₂ , . . . T _n are the third carbon-based PMOS transistors M3.

In the above solution, the gate of the first carbon-based PMOS transistor M1 is connected to the source of the first carbon-based PMOS transistor M1, and serves as an output terminal of the delay unit.

In the above solution, the drain of the first carbon-based PMOS transistor M1 is grounded.

In the above solution, the gate of the second carbon-based PMOS transistor M2 serves as the input end of the delay unit.

In the above solution, the source of the second carbon-based PMOS transistor M2 is connected to the VDD terminal, and the drain of the second carbon-based PMOS transistor M2 is connected to the source of the first carbon-based PMOS transistor M1.

In the above solution, the gate of the third carbon-based PMOS transistor M3 is connected to the input terminal of the control voltage V _ctrl , and the source of the third carbon-based PMOS transistor M3 is connected to the third carbon-based PMOS transistor M3. The drain of M3 is connected and connected to the output end of the delay unit corresponding to the varactor unit.

In the above solution, the source of the third carbon-based PMOS transistor M3, the drain of the third carbon-based PMOS transistor M3, the source of the first carbon-based PMOS transistor M1, and the first carbon-based PMOS transistor M1 The gate of the base PMOS transistor M1 shares a metal electrode.

Embodiments of the present invention include the following advantages:

The voltage-controlled oscillator based on the carbon nanotube field-effect transistor provided by the embodiment of the present invention connects the two ends of each unit of the varactor unit group in the voltage-controlled oscillator to the output terminal of the control voltage Vctrl and the corresponding voltage-controlled oscillator respectively. The output terminals of each unit of the delay unit group in the device are used to control the transmission. The capacitance value of the time-varying capacitor unit is proportional to the difference between the control voltage and the average output voltage of the corresponding delay unit, so that even at a small supply voltage It can provide a large range of control voltage, thereby increasing the frequency modulation range, and overcoming the frequency modulation problem caused by the limitation of the control voltage range of the traditional voltage-controlled oscillator. Each unit of the varactor unit group shares metal electrodes, and the varactor unit and the delay unit are miniaturized and integrated at the device level, so that the voltage-controlled oscillator has a smaller parasitic delay without losing the performance of the device, which overcomes the traditional The wiring parasitic redundancy problem of the VCO.

Description of drawings

FIG. 1 is a schematic composition diagram of an embodiment of a voltage-controlled oscillator based on a carbon nanotube field effect transistor of the present invention.

Fig. 2 is a circuit diagram of a delay unit of the present invention.

Fig. 3 is a circuit diagram of a varactor unit of the present invention.

Fig. 4 is a circuit connection diagram of the delay unit and the varactor unit of the present invention.

Fig. 5 is a schematic structural diagram of a delay unit and a varactor unit of the present invention.

FIG. 6 is a structural schematic diagram of a metal electrode shared by related devices and a varactor unit in the delay unit of the present invention.

FIG. 7 is a circuit diagram of a voltage-controlled oscillator based on carbon nanotube field effect transistors in an embodiment of the present invention.

detailed description

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in Figure 1, the present invention provides a voltage-controlled oscillator based on carbon nanotube field-effect transistors, the voltage-controlled oscillator includes: the voltage-controlled oscillator is composed of delay units D ₁ , D ₂ ,... ...D _n composed of delay unit groups and varactor unit groups with varactor units T ₁ , T ₂ ,...T _n , n=2i+1, i is a positive integer greater than zero, that is, n is greater than 1 odd natural number;

Wherein, the delay units D ₁ , D ₂ , ... D _n are active loads composed of carbon nanotube field effect transistors, respectively having an input terminal, an output terminal and a power supply terminal, and the delay unit D ₁ , D ₂ ,...D _n input terminals and output terminals are connected in series to form a ring circuit, and the power supply terminals of the delay units D ₁ , D ₂ ,...D _n are connected to the VDD terminal;

One end of the variable capacitor units T ₁ , T ₂ , ... T _n-1 is electrically connected to the input end of the control voltage V _ctrl , and the other end is electrically connected to the input end of the delay unit D ₂ , ... D _n ; One end of the capacitor unit Tn _is electrically connected to the input end of the control voltage V _ctrl , and the other end is electrically connected to the output end of the delay unit D1, and the output end of the variable capacitor unit Tn _{-1 is} used as the output end V of the voltage-controlled oscillator. _out .

In this embodiment, since the output terminals of the delay units D ₁ , D ₂ , ... D _n are respectively connected to the output terminals of the control voltage Vctrl through the corresponding varactor units T ₁ , T ₂ , ... T _n , it can be adjusted by The capacitance values of the _varactor units T1, T2, ... _Tn provide _a wide range of control voltages.

As shown in FIG. 2, the delay unit includes a first carbon-based PMOS transistor M1 and a second carbon-based PMOS transistor M2, and the gate of the first carbon-based PMOS transistor M1 is connected to the gate of the first carbon-based PMOS transistor M1. The source is connected as the output terminal of the delay unit, the drain of the first carbon-based PMOS transistor M1 is grounded, the gate of the second carbon-based PMOS transistor M2 is used as the input terminal of the delay unit, and the second carbon-based PMOS transistor M2 is used as the input terminal of the delay unit. The source of the base PMOS transistor M2 is connected to the VDD terminal, and the drain of the second carbon-based PMOS transistor M2 is connected to the source of the first carbon-based PMOS transistor M1.

In this embodiment, the first carbon-based PMOS transistor M1 with a negative threshold voltage does not use the traditional gate-to-drain short circuit to form a tube-connected active load, but realizes two-port limit in the form of gate-to-source short circuit. Current source load, can provide stable current, and play the role of over-current protection.

In this embodiment, the connection structure of the first carbon-based PMOS transistor M1 and the second carbon-based PMOS transistor M2 in the delay unit can make the gain of the delay unit insensitive to changes in its input and output voltages, thereby maintaining better linearity of the circuit Spend.

As shown in Figure 3 and Figure 4, the varactor unit uses a third carbon-based PMOS transistor M3, the gate of the third carbon-based PMOS transistor M3 is connected to the input terminal of the control voltage Vctrl, and the third carbon-based PMOS transistor M3 The source of the base PMOS transistor M3 is connected to the drain of the third carbon-based PMOS transistor M3, and is connected to the output terminal of the delay unit corresponding to the varactor unit.

In this embodiment, the two ends of the third carbon-based PMOS transistor M3 are respectively connected to the output end of the control voltage Vctrl and the output end of the delay unit corresponding to the varactor unit to control the third carbon-based PMOS transistor M3 during transmission. The capacitance value is proportional to the difference between the control voltage and the average output voltage of the corresponding delay unit, so that a large range of control voltage can be provided even at a small supply voltage, thereby increasing the frequency modulation range.

In this embodiment, the varactor unit is connected to the output end of each delay unit, and the change of its capacitance is realized by adjusting the voltage. When the control voltage is small, the capacitance of the varactor unit is small, and the resulting transmission delay is also small , on the contrary, when the control voltage is large, the capacitance of the varactor unit is large, which leads to an increase in transmission delay. In order to obtain a voltage swing as large as possible, the value range of the control voltage is guaranteed to be within the second carbon-based PMOS in the delay unit When the transistor M2 is turned on, the control voltage is selected to reduce the source-drain voltage of the second carbon-based PMOS transistor M2 to reduce signal loss, and reduce the current of the second carbon-based PMOS transistor M2 to reduce power consumption.

As shown in Figure 5, Figure 5-1 is a schematic diagram of the structure of a carbon-based PMOS transistor, Figure 5-2 is a schematic diagram of the structure of the third carbon-based PMOS transistor M3, and Figure 5-3 is a schematic diagram of the structure of the first carbon-based PMOS transistor M1 in the delay unit , the source of the third carbon-based PMOS transistor M3 shares a metal electrode with the drain of the third carbon-based PMOS transistor M3; the source of the first carbon-based PMOS transistor M1 shares a metal electrode with the gate of the first carbon-based PMOS transistor M1 .

As shown in FIG. 6 , the first carbon-based PMOS transistor M1 in the delay units D ₁ , D ₂ , ... D _n shares a metal electrode with the corresponding varactor units T ₁ , T ₂ , ... T _n , Specifically, the source of the third carbon-based PMOS transistor M3, the drain of the third carbon-based PMOS transistor M3, the source of the first carbon-based PMOS transistor M1, and the first carbon-based PMOS transistor The gates of M1 share a metal electrode.

As shown in Figure 7, an embodiment of the present invention provides a voltage-controlled oscillator comprising 5 delay units and 5 varactor units, wherein the delay unit comprises a first carbon-based PMOS transistor M1 and a second carbon-based PMOS transistor M2, the gate of the first carbon-based PMOS transistor M1 is connected to the source of the first carbon-based PMOS transistor M1, and serves as the output end of the delay unit, and the drain of the first carbon-based PMOS transistor M1 ground, the gate of the second carbon-based PMOS transistor M2 is used as the input end of the delay unit, the source of the second carbon-based PMOS transistor M2 is connected to the VDD terminal, and the drain of the second carbon-based PMOS transistor M2 It is connected to the source of the first carbon-based PMOS transistor M1; the varactor unit uses a third carbon-based PMOS transistor M3, and the gate of the third carbon-based PMOS transistor M3 is connected to the input terminal of the control voltage Vctrl, so The source of the third carbon-based PMOS transistor M3 is connected to the drain of the third carbon-based PMOS transistor M3, and connected to the output end of the delay unit corresponding to the varactor unit; in addition, the input end of the first delay unit The output terminal of the fifth delay unit is connected to the output terminal of the voltage-controlled oscillator, and the input terminals of the second delay unit to the fourth delay unit are respectively connected to the corresponding output terminals of the previous delay unit, 5 delays The power supply terminals of the units are respectively connected to the VDD terminals.

It should be pointed out that the above detailed description is exemplary and intended to provide further explanation for the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, singular forms are intended to include plural forms unless the context clearly dictates otherwise. In addition, it should also be understood that when the terms "comprising" and/or "comprises" are used in this specification, it indicates the presence of features, steps, operations, means, components and/or their combination.

It should be noted that the terms "first" and "second" in the description and claims of the present application and the above drawings are used to distinguish similar objects, but not necessarily used to describe a specific sequence or sequence. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.

Furthermore, the terms "comprising" and "having", as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or device comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include steps or units not explicitly listed or for these processes, methods, products, or Other steps or units inherent to equipment.

For the convenience of description, spatially relative terms may be used here, such as "on ...", "over ...", "on the surface of ...", "above", etc., to describe the The spatial positional relationship between one device or feature shown and other devices or features. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, devices described as "above" or "above" other devices or configurations would then be oriented "beneath" or "above" the other devices or configurations. under other devices or configurations”. Thus, the exemplary term "above" can encompass both an orientation of "above" and "beneath". The device may be oriented in different ways, rotated 90 degrees or at other orientations, and the spatially relative descriptions used herein interpreted accordingly.

In the above detailed description, reference was made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrated embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A voltage-controlled oscillator based on carbon nanotube field-effect transistors, characterized in that, the voltage-controlled oscillator is composed of delay unit D ₁ , D ₂ , ... D _n delay unit group and a varactor Units T ₁ , T ₂ ,...T _n are composed of varactor unit groups, n=2i+1, i is a positive integer greater than zero, where, The delay units D ₁ , D ₂ , ... D _n are active loads composed of carbon nanotube field effect transistors, respectively having an input terminal, an output terminal and a power supply terminal, and the delay units D ₁ , D ₂ , ... _Dn input terminals and output terminals are connected in series to form a ring circuit, and the power supply terminals of the delay units D ₁ , D ₂ , ... D _n are connected to the VDD terminal; One end of the variable capacitor units T ₁ , T ₂ , ... T _n-1 is electrically connected to the input end of the control voltage V _ctrl , and the other end is electrically connected to the input end of the delay unit D ₂ , ... D _n ; One end of the capacitor unit Tn _is electrically connected to the input end of the control voltage V _ctrl , and the other end is electrically connected to the output end of the delay unit D1, and the output end of the variable capacitor unit Tn _{-1 is} used as the output end V of the voltage-controlled oscillator. _out . 2. The voltage-controlled oscillator based on carbon nanotube field effect transistors according to claim 1, characterized in that, said delay unit D ₁ , D ₂ , ... _Dn and said varactor unit T ₁ , T ₂ ,... T _n common metal electrodes. 3. the voltage-controlled oscillator based on carbon nanotube field effect transistor according to claim 2, is characterized in that, described delay unit D ₁ , D ₂ , ... _Dn has the first carbon-based PMOS tube M1 and The second carbon-based PMOS tube M2. 4 . The voltage-controlled oscillator based on carbon nanotube field effect transistors according to claim 3 , wherein the varactor units T ₁ , T ₂ , . . . T _n are third carbon-based PMOS transistors M3. 5. The voltage-controlled oscillator based on carbon nanotube field effect transistor according to claim 3, characterized in that, the grid of the first carbon-based PMOS transistor M1 is connected to the source of the first carbon-based PMOS transistor M1 Pole connection, and as the output of the delay unit. 6 . The voltage-controlled oscillator based on carbon nanotube field effect transistor according to claim 5 , wherein the drain of the first carbon-based PMOS transistor M1 is grounded. 7. The voltage-controlled oscillator based on a carbon nanotube field effect transistor according to claim 3, wherein the gate of the second carbon-based PMOS transistor M2 is used as an input end of the delay unit. 8. The voltage-controlled oscillator based on carbon nanotube field effect transistors according to claim 7, the source of the second carbon-based PMOS transistor M2 is connected to the VDD end, and the drain of the second carbon-based PMOS transistor M2 is It is connected with the source of the first carbon-based PMOS transistor M1. 9. The voltage-controlled oscillator based on carbon nanotube field effect transistors according to claim 4, wherein the gate of the third carbon-based PMOS transistor M3 is connected to the control voltage V _ctrl input end, so The source of the third carbon-based PMOS transistor M3 is connected to the drain of the third carbon-based PMOS transistor M3, and connected to the output terminal of the delay unit corresponding to the varactor unit. 10. The voltage-controlled oscillator based on carbon nanotube field effect transistor according to claim 4, characterized in that, the source of the third carbon-based PMOS transistor M3, the drain of the third carbon-based PMOS transistor M3 electrode, the source of the first carbon-based PMOS transistor M1 and the gate of the first carbon-based PMOS transistor M1 share a metal electrode.

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