Carbon nanotube field effect transistor based voltage controlled oscillator

Abstract

The application relates to a carbon nanotube field effect transistor-based voltage-controlled oscillator, belonging to the technical field of oscillators, which comprises a delay unit group containing n delay units and a varactor unit group containing n varactor units, each delay unit of the delay unit group forms a feedback loop, the output ends of each unit of the delay unit group are connected to a control voltage Vctrl output end through corresponding units of the varactor unit group respectively, and the power supply ends of each unit of the delay unit group are connected to a VDD end; the related 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 make the voltage-controlled oscillator have smaller parasitic delay while not losing the performance of the devices, and overcome the wiring parasitic redundancy problem of the traditional voltage-controlled oscillator.

Description

Technical Field

[0001] This invention relates to the field of oscillator technology, and more particularly to a voltage-controlled oscillator based on a carbon nanotube field-effect transistor. Background Technology

[0002] Voltage-controlled oscillators (VCOs) are fundamental components in building wireless communication systems. Typically, the frequency range of a VCO is controlled by converting the control voltage into current. A typical implementation uses a current source as a voltage-to-current converter. This method enables voltage-to-current conversion even at very low supply voltages. However, the drawback is that the input voltage range of its delay unit is limited by the threshold voltage of its transistor.

[0003] A voltage-controlled oscillator (VCO) is mainly composed of several cascaded delay units. When the Barkhausen criterion is satisfied, the output signal of a certain unit flips and generates a periodic oscillation signal when it passes through the entire loop and returns to the input of that unit. The important advantages of VCO are its wide tuning range and small area. The parasitic delay caused by the internal circuit connection lines of the VCO is described by the parasitic resistance R and parasitic capacitance C. The smaller the parasitic delay, the lower the power consumption and the better the frequency tuning of the VCO. Due to the limitations of traditional semiconductor manufacturing processes, the connection between the load capacitor and the delay unit of existing CMOS transistors is achieved by the back-end metal interconnect process. This method has long traces and introduces a lot of parasitic delay. To achieve a high-performance VCO, it is necessary to overcome the parasitic limitations caused by the conventional interconnection of load capacitor and delay unit. There are two main ways to reduce the parasitic delay of interconnects: one is to use metal interconnects with lower resistivity and higher electron mobility, and the other is to reduce the volume and size of the interconnects. However, both of these methods start from the back-end process and cannot truly remove the parasitic delay. Summary of the Invention

[0004] The present invention aims to provide a voltage-controlled oscillator based on carbon nanotube field-effect transistors to overcome the shortcomings of the prior art. The technical problem to be solved by the present invention is achieved through the following technical solution.

[0005] This invention provides a voltage-controlled oscillator based on a carbon nanotube field-effect transistor, wherein the voltage-controlled oscillator comprises delay units D1, D2, ... D n The delay unit group consists of variable container units T1, T2, ... T n The variable container unit group is composed of n = 2i + 1, where i is a positive integer greater than zero;

[0006] Wherein, the delay units D1, D2, ... D nThe delay units D1, D2, ... D are active loads composed of carbon nanotube field-effect transistors, each having an input terminal, an output terminal, and a power supply terminal. n The input and output terminals are connected in series to form a ring circuit, and the delay units D1, D2, ... D n The power supply terminal is connected to the VDD terminal;

[0007] The variable container units T1, T2, ... T n-1 One end is connected to the control voltage V ctrl The input terminal is electrically connected, and the other terminal is connected to the delay units D2, ... D. n Electrical connection at the input terminal; Variable capacitor unit T n One end is connected to the control voltage V ctrl The input terminal is electrically connected, and the other terminal is electrically connected to the output terminal of the delay unit D1. The variable capacitor unit T... n-1 The output terminal is used as the output terminal V of the voltage-controlled oscillator. out .

[0008] In the above scheme, the delay units D1, D2, ... D n With the variable container units T1, T2, ... T n Shared metal electrodes.

[0009] In the above scheme, the delay units D1, D2, ... D n Each has a first carbon-based PMOS transistor M1 and a second carbon-based PMOS transistor M2.

[0010] In the above scheme, the variable container units T1, T2, ... T n It is the third carbon-based PMOS transistor, M3.

[0011] In the above scheme, 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 terminal of the delay unit.

[0012] In the above scheme, the drain of the first carbon-based PMOS transistor M1 is grounded.

[0013] In the above scheme, the gate of the second carbon-based PMOS transistor M2 serves as the input terminal of the delay unit.

[0014] In the above scheme, 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.

[0015] In the above scheme, the gate of the third carbon-based PMOS transistor M3 is connected to the control voltage V. ctrlAt the input terminal, the source of the third carbon-based 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 variable capacitor unit.

[0016] In the above scheme, 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 gate of the first carbon-based PMOS transistor M1 share a common metal electrode.

[0017] The embodiments of the present invention have the following advantages:

[0018] The voltage-controlled oscillator (VCO) based on carbon nanotube field-effect transistors provided in this invention connects the two ends of each unit in the variable capacitor unit group of the VCO to the output terminals of the control voltage Vctrl and the output terminals of the corresponding delay unit group in the VCO, respectively. This controls the capacitance value of the variable capacitor unit to be proportional to the difference between the control voltage and the average output voltage of the corresponding delay unit during transmission. This allows a wide range of control voltages to be provided even under very small supply voltages, thereby increasing the frequency modulation range and overcoming the frequency modulation problem caused by the limited control voltage range of traditional VCOs. At the same time, by making the related devices in each unit of the delay unit group share metal electrodes with each unit of the corresponding variable capacitor unit group, the variable capacitor unit and the delay unit are miniaturized and integrated at the device level, giving the VCO a smaller parasitic delay without sacrificing device performance, thus overcoming the wiring parasitic redundancy problem of traditional VCOs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the composition of an embodiment of a voltage-controlled oscillator based on a carbon nanotube field-effect transistor according to the present invention.

[0020] Figure 2 This is a circuit diagram of the delay unit of the present invention.

[0021] Figure 3 This is a circuit diagram of the variable capacitor unit of the present invention.

[0022] Figure 4 This is a circuit connection diagram of the delay unit and the variable capacitor unit of the present invention.

[0023] Figure 5 This is a schematic diagram of the delay unit and variable container unit of the present invention.

[0024] Figure 6 This is a schematic diagram of the structure in which related devices in the delay unit of the present invention share a metal electrode with the variable capacitor unit.

[0025] Figure 7This is a circuit diagram of a voltage-controlled oscillator based on a carbon nanotube field-effect transistor in one embodiment of the present invention. Detailed Implementation

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] like Figure 1 As shown, the present invention provides a voltage-controlled oscillator based on a carbon nanotube field-effect transistor, the voltage-controlled oscillator comprising: the voltage-controlled oscillator having delay units D1, D2, ... D... n The delay unit group consists of variable container units T1, T2, ... T n The variable container unit group is composed of n = 2i + 1, where i is a positive integer greater than zero, that is, n is an odd natural number greater than 1;

[0028] Wherein, the delay units D1, D2, ... D n The delay units D1, D2, ... D are active loads composed of carbon nanotube field-effect transistors, each having an input terminal, an output terminal, and a power supply terminal. n The input and output terminals are connected in series to form a ring circuit, and the delay units D1, D2, ... D n The power supply terminal is connected to the VDD terminal;

[0029] The variable container units T1, T2, ... T n-1 One end is connected to the control voltage V ctrl The input terminal is electrically connected, and the other terminal is connected to the delay units D2, ... D. n Electrical connection at the input terminal; Variable capacitor unit T n One end is connected to the control voltage V ctrl The input terminal is electrically connected, and the other terminal is electrically connected to the output terminal of the delay unit D1. The variable capacitor unit T... n-1 The output terminal is used as the output terminal V of the voltage-controlled oscillator. out .

[0030] In this embodiment, due to the delay units D1, D2, ... D n The output terminals are respectively connected to the corresponding variable container units T1, T2, ... T n Connected to the output of the control voltage Vctrl, the variable capacitor units T1, T2, ... T can be adjusted. n The capacitance value provides a wide range of control voltages.

[0031] like Figure 2As shown, the delay unit includes 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 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 serves as the input terminal of the delay unit. The source of the second carbon-based PMOS transistor M2 is connected to the VDD terminal. The drain of the second carbon-based PMOS transistor M2 is connected to the source of the first carbon-based PMOS transistor M1.

[0032] In this embodiment, the first carbon-based PMOS transistor M1 with a negative threshold voltage does not form a transistor-connected active load in the traditional gate-drain short-circuit form. Instead, it realizes a two-port current-limiting source load in the form of gate-source short-circuit, which can provide stable current and play an overcurrent protection role.

[0033] 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 makes the gain of the delay unit insensitive to changes in its input and output voltages, thereby maintaining good linearity of the circuit.

[0034] like Figure 3 and Figure 4 As shown, the variable capacitor 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. The source and drain of the third carbon-based PMOS transistor M3 are connected and connected to the output terminal of the corresponding delay unit of the variable capacitor unit.

[0035] In this embodiment, by connecting the two ends of the third carbon-based PMOS transistor M3 to the output terminal of the control voltage Vctrl and the output terminal of the delay unit corresponding to the variable capacitor unit respectively, the capacitance value of the third carbon-based PMOS transistor M3 during transmission is proportional to the difference between the control voltage and the average output voltage of the corresponding delay unit. This allows a wide range of control voltages to be provided even under very small supply voltages, thereby increasing the frequency modulation range.

[0036] In this embodiment, the variable capacitor unit is connected to the output terminal of each delay unit. The change in its capacitance is achieved by adjusting the voltage. When the control voltage is small, the capacitance of the variable capacitor unit is small, and the transmission delay is also small. Conversely, when the control voltage is large, the capacitance of the variable capacitor unit is large, which leads to an increase in transmission delay. In order to obtain the largest possible voltage swing, the control voltage value is selected within the range of ensuring that the second carbon-based PMOS transistor M2 in the delay unit is turned on. This reduces the source-drain voltage of the second carbon-based PMOS transistor M2 to reduce signal loss and reduces the current of the second carbon-based PMOS transistor M2, thereby reducing power consumption.

[0037] like Figure 5 As shown, Figure 5-1 This is a schematic diagram of a carbon-based PMOS transistor. Figure 5-2 This is a schematic diagram of the third carbon-based PMOS transistor, M3. Figure 5-3 The diagram shows the structure of the first carbon-based PMOS transistor M1 in the delay unit. The source and drain of the third carbon-based PMOS transistor M3 share a common metal electrode; the source and gate of the first carbon-based PMOS transistor M1 share a common metal electrode.

[0038] like Figure 6 As shown, the delay units D1, D2, ... D n The first carbon-based PMOS transistor M1 and the corresponding variable capacitor units T1, T2, ... T n Specifically, the source, drain, source, and gate of the third carbon-based PMOS transistor M3, the third carbon-based PMOS transistor M3, and the first carbon-based PMOS transistor M1 share a common metal electrode.

[0039] like Figure 7 As shown, one embodiment of the present invention provides a voltage-controlled oscillator comprising five delay units and five variable capacitor units. Each delay unit includes 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 its source and serves as the output 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 serves as the input of the delay unit. The source of the second carbon-based PMOS transistor M2 is connected to VDD. The drain of the second carbon-based PMOS transistor M2 is connected to the first carbon-based PMOS transistor M2. The source of transistor M1 is connected; the variable capacitor unit uses a third carbon-based PMOS transistor M3, the gate of which is connected to the input of the control voltage Vctrl, the source of which is connected to the drain of which is connected to the output of the corresponding delay unit of the variable capacitor unit; in addition, the input of the first delay unit and the output of the fifth delay unit are connected to the output of the voltage-controlled oscillator, the inputs of the second to fourth delay units are respectively connected to the output of their respective preceding delay units, and the power supply terminals of the five delay units are respectively connected to the VDD terminal.

[0040] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, 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 pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0043] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0044] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0045] In the detailed description above, reference has been made to the accompanying drawings, which form part of this document. In the drawings, similar symbols typically identify similar parts unless the context otherwise indicates otherwise. The illustrated embodiments described in the detailed specification, drawings, and claims are not intended to be limiting. Other embodiments may be used and other changes may be made without departing from the spirit or scope of the subject matter presented herein.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A voltage-controlled oscillator based on a carbon nanotube field-effect transistor, characterized in that, The voltage-controlled oscillator consists of delay units D1, D2, ... D1. n The delay unit group consists of variable container units T1, T2, ... T n The variable container units are composed of n = 2i + 1, where i is a positive integer greater than zero. The delay units D1, D2, ... D n The delay units D1, D2, ... D are active loads composed of carbon nanotube field-effect transistors, each having an input terminal, an output terminal, and a power supply terminal. n The input and output terminals are connected in series to form a ring circuit, and the delay units D1, D2, ... D n The power supply terminal is connected to the VDD terminal; the delay units D1, D2, ... D n It has a first carbon-based PMOS transistor M1 and a second carbon-based PMOS transistor M2 respectively; 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 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 serves as the input terminal 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 is connected to the source of the first carbon-based PMOS transistor M1; The variable capacitor units T1, T2, ... Tn are the third carbon-based PMOS transistors M3; the variable capacitor units T1, T2, ... Tn are the third carbon-based PMOS transistors M3. n-1 One end is connected to the control voltage V ctrl The input terminal is electrically connected, and the other terminal is connected to the delay units D2, ... D. n Electrical connection at the input terminals; transformer units T1, T2, ... T n-1 The gate of the third carbon-based PMOS transistor M3 is related to the control voltage V. ctrl Input terminal electrical connection, transformer unit T n The gate of the third carbon-based PMOS transistor M3 in the delay unit D1 is connected to the gate of the second carbon-based PMOS transistor M2. The variable capacitor unit T... n The source of the third carbon-based PMOS transistor M3 serves as the output terminal V of the voltage-controlled oscillator. out ; The source, drain, source, and gate of the third carbon-based PMOS transistor M3, the third carbon-based PMOS transistor M3, and the first carbon-based PMOS transistor M1 share a common metal electrode; the gate of the third carbon-based PMOS transistor M3 is connected to the control voltage V. ctrl At the input terminal, the source of the third carbon-based PMOS transistor M3 is connected to the drain of the third carbon-based PMOS transistor M3, and is connected to the input terminal of the delay unit corresponding to the variable capacitor unit.

2. The voltage-controlled oscillator based on carbon nanotube field-effect transistors according to claim 1, characterized in that, The delay units D1, D2,... D n share the varactor unit T1, T2,... T n a common metal electrode.

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