A frequency doubler circuit based on carbon nanotube schottky diodes

Abstract

The utility model discloses a kind of frequency multiplier circuit based on carbon nanotube schottky diode, comprising: carbon nanotube schottky diode device, input end's based on fundamental wave 1 / 4 wavelength ground transmission line, output end's based on second harmonic 1 / 4 wavelength open-circuit transmission line, input impedance matching network and output impedance matching network.Carbon nanotube schottky diode is located between the 1 / 4 wavelength ground transmission line of input end and the 1 / 4 wavelength open-circuit line of output end;Input impedance matching network is located before the 1 / 4 wavelength ground transmission line of input end;Output impedance matching network is located after the 1 / 4 wavelength open-circuit line of output end.The utility model is verified by the process of carbon nanotube device frequency multiplication circuit, realizes the echo loss under better fundamental wave and frequency multiplication frequency and lower frequency multiplication conversion loss, greatly improves the frequency multiplication efficiency of schottky diode device.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor technology, specifically to a frequency multiplier circuit based on a carbon nanotube Schottky diode. Background Technology

[0002] In millimeter-wave and terahertz systems, traditional silicon-based or group III-V Schottky diode frequency multipliers are limited by high parasitic capacitance and low cutoff frequency, resulting in significant high-frequency harmonic losses, low efficiency, and difficulty in operating stably at high frequencies.

[0003] Semiconductor-type carbon nanotubes, with their quasi-one-dimensional structure leading to ultra-low intrinsic capacitance, ultra-high carrier mobility, and excellent thermal conductivity, offer a breakthrough solution for high-frequency frequency multipliers. However, existing designs fail to fully integrate the nonlinear characteristics of carbon nanotube devices with the impedance matching mechanism of RF circuits, resulting in insufficient fundamental suppression, limited harmonic extraction efficiency, and poor three-dimensional integration compatibility, thus restricting their application potential in the millimeter-wave / terahertz frequency bands. Therefore, there is an urgent need for a high-efficiency frequency multiplier design method based on carbon nanotube Schottky diodes, which optimizes the quarter-wavelength transmission line structure to achieve wide bandwidth, high conversion efficiency, and high-frequency signal generation. Utility Model Content

[0004] The purpose of this invention is to design and develop a high-frequency doubler circuit with low frequency doubling loss suitable for carbon-based micro / nano fabrication technology based on a monolithic microwave integrated circuit with a high-performance carbon nanotube Schottky diode. This invention simultaneously realizes a high-performance carbon-based Schottky RF diode and a corresponding small-sized RF passive circuit with a fundamental suppression and harmonic extraction structure on silicon-based, quartz, or other substrates, thereby expanding the application potential of carbon-based integrated circuits in the field of high-frequency RF front-ends.

[0005] To achieve the above objectives, the present invention proposes the following technical solution.

[0006] A frequency multiplier circuit based on a carbon nanotube Schottky diode includes: a carbon nanotube Schottky diode device, a grounded transmission line based on the fundamental wave 1 / 4 wavelength at the input end, an open-circuit transmission line based on the second harmonic 1 / 4 wavelength at the output end, an input impedance matching network, and an output impedance matching network. The carbon nanotube Schottky diode device is located between the fundamental 1 / 4 wavelength ground transmission line at the input end and the second harmonic 1 / 4 wavelength open-circuit transmission line at the output end; the input impedance matching network is located before the fundamental 1 / 4 wavelength ground transmission line at the input end; and the output impedance matching network is located after the second harmonic 1 / 4 wavelength open-circuit transmission line at the output end.

[0007] Furthermore, the channel layer of the carbon nanotube Schottky diode is a semiconductor carbon nanotube, which includes randomly arranged network carbon nanotubes or oriented array carbon nanotubes.

[0008] Furthermore, the carbon nanotube Schottky diode is composed of individual carbon nanotube Schottky diodes connected in series. The cathode of the carbon nanotube Schottky diode is connected to the input terminal via a fundamental 1 / 4 wavelength ground transmission line and the input impedance matching network. The anode of the carbon nanotube is connected to the output terminal via a second harmonic 1 / 4 wavelength open-circuit transmission line and the output impedance matching network. The carbon nanotube Schottky diode operates at zero bias voltage.

[0009] Furthermore, the input terminal based on a fundamental 1 / 4 wavelength grounded transmission line and the output terminal based on a second harmonic 1 / 4 wavelength open-circuit transmission line are resonant units based on transmission line structures.

[0010] Furthermore, the transmission line structure includes, but is not limited to, microstrip lines, striplines, or coplanar waveguide structures.

[0011] Furthermore, the transmission line structure includes, but is not limited to, a 1 / 4 wavelength grounding structure implemented by segments of the same node.

[0012] Furthermore, the input impedance matching network and the output impedance matching network are impedance matching networks based on transmission line structures, including but not limited to microstrip lines, striplines, or coplanar waveguide structures.

[0013] Furthermore, the materials of the fundamental 1 / 4 wavelength grounded transmission line constituting the input end, the second harmonic 1 / 4 wavelength open-circuit transmission line constituting the output end, the input impedance matching network, and the output impedance matching network are selected from any one or more of gold, copper, or aluminum.

[0014] Furthermore, the circuit also includes a silicon-based substrate or a quartz substrate for carrying the carbon nanotube Schottky diode device, the input terminal's fundamental 1 / 4 wavelength ground transmission line, the output terminal's second harmonic 1 / 4 wavelength open-circuit transmission line, the input impedance matching network, and the output impedance matching network.

[0015] Furthermore, the thickness of the silicon-based or quartz substrate is less than 500 micrometers, and a back gold structure is provided on the back side of the silicon-based or quartz substrate.

[0016] The advantages and technical effects of this utility model are as follows: This invention relates to a frequency doubler circuit based on a carbon nanotube Schottky diode. It utilizes a high-performance carbon nanotube Schottky diode as the core device to provide nonlinear characteristics, realizing a low-loss, high-frequency frequency doubler on a carbon-based monolithic microwave integrated circuit. The input impedance of the 1 / 4 wavelength short-circuited transmission line is open, preventing the fundamental frequency from being short-circuited to ground and ensuring the fundamental signal is injected into the diode. The same transmission line behaves as a half-wavelength short-circuited transmission line for the second harmonic, with a short-circuited input impedance, effectively blocking the loss of the second harmonic at the input port. The 1 / 4 wavelength open line at the output end is short-circuited at the fundamental frequency. The circuit effectively blocks the fundamental frequency and presents an open circuit for the second harmonic, ensuring efficient transmission of the second harmonic. Compared with frequency multiplier circuits using traditional silicon-based Schottky diode devices, the frequency multiplier circuit based on high-performance carbon nanotube Schottky diodes provided in this invention is suitable for monolithic microwave integrated circuit technology based on carbon-based micro / nano fabrication. It proposes an effective implementation of impedance matching between the RF passive circuit and the carbon-based nonlinear device, based on a 1 / 4 wavelength grounded transmission line for the fundamental frequency and a 1 / 4 wavelength open-circuit transmission line for the second harmonic, along with an impedance matching network. This supports on-chip generation of high-frequency signals with low frequency doubling loss. Furthermore, the RF passive circuit supports single-layer metal processing for carbon-based micro / nano fabrication, enabling miniaturized chip design and significantly reducing the overall area of ​​the carbon-based frequency multiplier chip. In addition, this invention takes the fabrication of carbon nanotube Schottky diode devices and frequency multiplier chip circuits on a high-resistivity silicon substrate as an example. Compared with the frequency doubling performance of a single Schottky diode without RF passive circuitry, the carbon nanotube frequency multiplier monolithic microwave integrated circuit can improve the frequency doubling conversion loss by nearly 10 dB. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.

[0018] Figure 1 A schematic diagram of a carbon nanotube frequency doubler circuit provided by this utility model.

[0019] Figure 2 A circuit diagram of a carbon nanotube frequency doubler provided for this utility model.

[0020] Figure 3 A photograph of a carbon nanotube frequency doubler circuit chip provided for this utility model.

[0021] Figure 4 A comparison diagram of the output power and frequency doubling loss of a carbon nanotube frequency doubler circuit and a single-tube frequency doubler provided for this utility model. Detailed Implementation

[0022] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. The present utility model will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] This embodiment specifically describes a carbon nanotube frequency doubler monolithic microwave integrated circuit provided by this utility model.

[0024] Figure 1 This is a schematic diagram of the principle of a carbon nanotube frequency doubler circuit provided by this utility model. Figure 2 This is a circuit diagram of a carbon nanotube frequency doubler provided by this utility model. The schematic diagram of the frequency doubler includes an input impedance matching network 101, an input end transmission line based on the fundamental wave 1 / 4 wavelength ground 102, a carbon nanotube radio frequency Schottky diode device 103, an output end transmission line based on the second harmonic 1 / 4 wavelength open circuit 104, and an output impedance matching network 105.

[0025] The carbon nanotube Schottky diode device 103 is located between the input end of the fundamental 1 / 4 wavelength ground transmission line 102 and the output end of the second harmonic 1 / 4 wavelength open-circuit transmission line 104; the input impedance matching network 101 is located before the input end of the fundamental 1 / 4 wavelength ground transmission line 102; and the output impedance matching network 105 is located after the output end of the second harmonic 1 / 4 wavelength open-circuit transmission line 104.

[0026] In one specific embodiment, the channel layer of the carbon nanotube Schottky diode 103 is a semiconductor carbon nanotube. This semiconductor carbon nanotube may include randomly arranged network carbon nanotubes or oriented array carbon nanotubes.

[0027] In another embodiment, the carbon nanotube Schottky diode consists of individual carbon nanotube Schottky diodes connected in series. The connection is as follows: the cathode of the carbon nanotube Schottky diode is connected to the input terminal via a fundamental 1 / 4 wavelength ground transmission line 102 and the input impedance matching network 101; the anode of the carbon nanotube is connected to the output terminal via a second harmonic 1 / 4 wavelength open-circuit transmission line 104 and the output impedance matching network 105. This carbon nanotube Schottky diode can operate at zero bias voltage.

[0028] To achieve fundamental suppression and harmonic extraction, the input-side fundamental-wavelength-grounded transmission line 102 and the output-side second-harmonic-wavelength-open-circuit transmission line 104 are designed as resonant units based on transmission line structures. The transmission line structure can include, but is not limited to, microstrip lines, striplines, or coplanar waveguide structures. In another implementation, the transmission line structure may also include a quarter-wavelength-grounded structure segmented from the same node.

[0029] Similarly, the input impedance matching network 101 and the output impedance matching network 105 are also impedance matching networks based on transmission line structures. Their transmission line structures include, but are not limited to, microstrip lines, striplines, or coplanar waveguide structures.

[0030] The materials used to construct the above-mentioned passive RF circuit (including a 1 / 4 wavelength ground transmission line, a 1 / 4 wavelength open-circuit transmission line, an input impedance matching network, and an output impedance matching network) can be selected from any one or more of gold, copper, or aluminum.

[0031] The circuit of this invention also includes a substrate for supporting the carbon nanotube Schottky diode device 103, an input-side fundamental 1 / 4 wavelength ground-based transmission line 102, an output-side second harmonic 1 / 4 wavelength open-circuit transmission line 104, an input impedance matching network 101, and an output impedance matching network 105. This substrate can be a silicon-based substrate or a quartz substrate. In a preferred embodiment, the thickness of the silicon-based or quartz substrate is less than 500 micrometers. Furthermore, a gold-backed structure is provided on the back side of the silicon-based or quartz substrate.

[0032] The purpose of this invention is to expand the application potential of carbon-based integrated circuits in the high-frequency radio frequency front-end field by simultaneously realizing high-performance carbon-based Schottky radio frequency diodes and corresponding small-sized impedance matching networks with fundamental suppression and harmonic extraction structures on silicon-based, quartz, or other substrates.

[0033] Figure 2 A photograph of a carbon nanotube frequency doubler circuit chip provided by this utility model. Figure 2 The Input Match network is the input impedance matching network; the upper λ / 4@f0 is the 1 / 4 wavelength ground transmission line at the input end. The lower λ / 4@f0 is the 1 / 4 wavelength open-circuit transmission line at the output end between the carbon nanotube Schottky diode device of the CNT SBD and the output impedance network composed of series transmission lines.

[0034] The active layer of the carbon nanotube Schottky diode device is a semiconductor-type arrayed carbon nanotube.

[0035] The 1 / 4 wavelength ground transmission line at the input terminal is designed based on a coplanar waveguide transmission line, making it compatible with carbon-based micro / nano fabrication processes and suitable for RF passive circuits on high-resistivity silicon substrates that do not require metal ground planes. The metal material constituting the 1 / 4 wavelength ground transmission line at the input terminal includes, but is not limited to, gold, copper, and aluminum. The function of the 1 / 4 wavelength ground transmission line at the input terminal is to effectively transmit the fundamental signal, suppress second harmonic signal leakage from the input port, and provide partial impedance to facilitate the implementation of input impedance matching networks. The advantage of the 1 / 4 wavelength ground transmission line at the input terminal is that it can support carbon-based monolithic microwave integrated circuits using single-layer metal processes that do not require metal ground planes.

[0036] The 1 / 4 wavelength open-circuit transmission line at the output end is designed based on a coplanar waveguide transmission line, making it compatible with carbon-based micro / nano fabrication processes and suitable for RF passive circuits on high-resistivity silicon substrates that do not require metal ground planes. The metal material constituting the 1 / 4 wavelength open-circuit transmission line at the input end includes, but is not limited to, gold, copper, and aluminum. The function of the 1 / 4 wavelength open-circuit transmission line at the input end is to effectively transmit the second harmonic signal, suppress leakage of the fundamental signal from the output port, and provide partial impedance to facilitate the implementation of the output impedance matching network. The advantage of the 1 / 4 wavelength open-circuit transmission line at the output end is that it can support carbon-based monolithic microwave integrated circuits using single-layer metal processes that do not require metal ground planes.

[0037] The input impedance matching network is designed using a coplanar waveguide transmission line without the need for a metal ground plane. Its function is to match the impedance formed by the optimal input port impedance of the carbon nanotube Schottky diode and the 1 / 4 wavelength short-circuited transmission line at the input end, thereby reducing the frequency doubling conversion loss of the frequency doubler circuit. The metal material constituting the input impedance matching network includes, but is not limited to, gold, copper, and aluminum.

[0038] The output impedance matching network is designed using a coplanar waveguide transmission line without the need for a metal ground plane. Its function is to match the impedance formed by the optimal output port impedance of the carbon nanotube Schottky diode and the quarter-wavelength open-circuit transmission line at the output end, thereby reducing the frequency doubling conversion loss of the frequency doubler circuit. The metal material constituting the output impedance matching network includes, but is not limited to, gold, copper, and aluminum.

[0039] The frequency doubler circuit based on carbon nanotube Schottky diodes uses a single-tube series connection for its core carbon nanotube Schottky diode device, which can operate at zero bias voltage.

[0040] The frequency doubler circuit based on carbon nanotube Schottky diodes also includes a high-resistivity silicon substrate. All circuit elements in the frequency doubler circuit are fabricated on this high-resistivity silicon substrate. The advantage of using a high-resistivity silicon substrate as the substrate and for the coplanar waveguide transmission line lies in CMOS compatibility and the availability of mature mainstream industrial integration processes, eliminating the need for substrate thinning and metal ground planes. The 1 / 4 wavelength short-circuit transmission line at the input end, the 1 / 4 wavelength open-circuit transmission line at the output end, the input impedance matching network, and the output impedance matching network were all designed through electromagnetic simulation and verified through fabrication using a carbon-based monolithic microwave integrated circuit. After fabrication, the designed frequency doubler circuit was tested using a millimeter-wave test platform.

[0041] Figure 3 This diagram shows a test comparison between the frequency doubler circuit of a carbon nanotube Schottky diode provided by this invention and the frequency doubler performance of a single diode without any RF passive circuitry. The input fundamental signal frequency is 27–33 GHz, and the output second harmonic signal frequency is 54–66 GHz. Figure 3 As shown, the carbon nanotube Schottky diode frequency doubler circuit exhibits a minimum frequency doubling loss of -15 dB and an output power of 0 dBm in this frequency band. This represents a nearly 10 dB improvement in frequency doubling loss compared to a single-tube frequency doubler circuit without impedance matching and with a quarter-wavelength open-circuit and short-circuit transmission line. Furthermore, the circuit is only 1.3 mm in size. 2 .

[0042] This invention employs a high-performance carbon nanotube Schottky diode to design a frequency doubler circuit. It achieves a miniaturized design with low conversion loss using a single-layer metal RF passive process that does not require metal grounding. It supports mature integrated processes compatible with mainstream industrial CMOS, demonstrating significant technological advancements and economic benefits.

[0043] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of the present invention. 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 invention pertains.

[0044] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A frequency multiplier circuit based on a carbon nanotube Schottky diode, characterized in that, include: Carbon nanotube Schottky diode device, input-side transmission line based on fundamental 1 / 4 wavelength grounding, output-side transmission line based on second harmonic 1 / 4 wavelength open circuit, input impedance matching network and output impedance matching network; The carbon nanotube Schottky diode device is located between the fundamental 1 / 4 wavelength ground transmission line at the input end and the second harmonic 1 / 4 wavelength open-circuit transmission line at the output end; the input impedance matching network is located before the fundamental 1 / 4 wavelength ground transmission line at the input end; and the output impedance matching network is located after the second harmonic 1 / 4 wavelength open-circuit transmission line at the output end.

2. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 1, characterized in that, The channel layer of the carbon nanotube Schottky diode is a semiconductor carbon nanotube, which includes randomly arranged network carbon nanotubes or oriented array carbon nanotubes.

3. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 1, characterized in that, The carbon nanotube Schottky diode consists of individual carbon nanotube Schottky diodes connected in series. The cathode of the carbon nanotube Schottky diode is connected to the input terminal via a fundamental 1 / 4 wavelength ground transmission line and the input impedance matching network. The anode of the carbon nanotube is connected to the output terminal via a second harmonic 1 / 4 wavelength open-circuit transmission line and the output impedance matching network. The carbon nanotube Schottky diode operates at zero bias voltage.

4. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 1, characterized in that, The input terminal, based on a 1 / 4 wavelength grounded transmission line, and the output terminal, based on a 1 / 4 wavelength open-circuit transmission line of the second harmonic, are resonant units based on transmission line structures.

5. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 4, characterized in that, The transmission line structure includes, but is not limited to, microstrip lines, striplines, or coplanar waveguide structures.

6. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 4, characterized in that, The transmission line structure includes, but is not limited to, a 1 / 4 wavelength grounding structure implemented by segmenting the same node.

7. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 1, characterized in that, The input impedance matching network and the output impedance matching network are impedance matching networks based on transmission line structures, including but not limited to microstrip lines, striplines, or coplanar waveguide structures.

8. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 1, characterized in that, The materials of the input terminal based on a fundamental 1 / 4 wavelength ground transmission line, the output terminal based on a second harmonic 1 / 4 wavelength open-circuit transmission line, the input impedance matching network, and the output impedance matching network are selected from any one or more of gold, copper, or aluminum.

9. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to any one of claims 1 to 8, characterized in that, The circuit also includes a silicon-based substrate or a quartz substrate for carrying the carbon nanotube Schottky diode device, the input terminal based on a fundamental 1 / 4 wavelength ground transmission line, the output terminal based on a second harmonic 1 / 4 wavelength open-circuit transmission line, the input impedance matching network, and the output impedance matching network.

10. The frequency multiplier circuit based on a carbon nanotube Schottky diode according to claim 9, characterized in that, The thickness of the silicon-based or quartz substrate is less than 500 micrometers, and a back gold structure is provided on the back side of the silicon-based or quartz substrate.

Images