Single-balanced radio frequency mixer circuit based on carbon nanotube Schottky diode

Abstract

The invention discloses a single-balanced radio frequency mixer circuit based on a carbon nanotube Schottky diode, and belongs to the technical field of communication. Comprising a radio frequency signal input end, a local oscillator signal input end, an intermediate frequency signal output end, a radio frequency input end band-pass filter, a local oscillator input end band-pass filter, an intermediate frequency output end low-pass filter, a 180-degree mixed junction structure, a first carbon nanotube Schottky diode chip and a second carbon nanotube Schottky diode chip. And a first grounding through hole and a second grounding through hole. The 180-degree mixed junction structure designed based on the microstrip line technology is adopted, in-phase equal power distribution of radio frequency signals and differential equal power distribution of local oscillator signals are achieved, and the problems that in an existing high-frequency mixer circuit, due to large parasitic parameters, signal transmission loss is large, and the working frequency band is limited are solved.

Description

Technical Field

[0001] This application belongs to the field of communication technologies, and particularly relates to a single-balanced radio frequency mixer circuit based on a carbon nanotube Schottky diode. Background Art

[0002] For traditional millimeter-wave mixers based on Schottky diodes, due to the parasitic parameters inherent in the diode material itself, the signal transmission loss is large, the operating frequency band is limited, and it is difficult to improve the integration level. The root cause of this problem lies in the physical properties of the material itself and it is difficult to completely eliminate it through simple technical means.

[0003] Although the millimeter-wave mixer designed with a waveguide cavity structure has excellent performance, its volume is large and the structure is complex, which cannot meet the urgent requirements of modern commercial products for miniaturization and integration. To address this challenge, the industry usually adopts a chip design, such as using the CMOS process. However, for millimeter-wave band mixers designed based on the CMOS process, especially thin-film gallium arsenide circuits, their manufacturing process is relatively complex and cumbersome, the cost remains high, and there are high technical thresholds and uncertainties in the production process.

[0004] Existing single-balanced mixers based on the 180° hybrid junction structure also have obvious limitations in design. These mixers usually lead out the intermediate-frequency output terminal through the series connection of two diodes. This design not only increases the complexity of the circuit but also requires additional technical means such as 0-ohm resistors, air bridges, and gold wire bonding wires to optimize the layout and connection. The introduction of these technical means not only increases the production cost and process complexity but may also have an adverse impact on the overall performance and stability of the mixer.

[0005] In view of the above problems, a new radio frequency mixer circuit needs to be proposed. Summary of the Invention

[0006] To solve the deficiencies of the existing technologies described above, this application provides a single-balanced radio frequency mixer circuit based on a carbon nanotube Schottky diode, which is used to solve the problems of large signal transmission loss and limited operating frequency band caused by large parasitic parameters in existing high-frequency mixer circuits. It includes a radio frequency signal input terminal, a local oscillator signal input terminal, an intermediate-frequency signal output terminal, a radio frequency input band-pass filter, a local oscillator input band-pass filter, an intermediate-frequency output low-pass filter, a 180° hybrid junction structure, a first carbon nanotube Schottky diode chip, a second carbon nanotube Schottky diode chip, a first ground via, and a second ground via; The RF input bandpass filter is located between the RF signal input terminal and the 180° hybrid junction structure; the LO input bandpass filter is located between the LO signal input terminal and the 180° hybrid junction structure; the IF output low-pass filter is located between the IF signal output terminal and the 180° hybrid junction structure; The first carbon nanotube Schottky diode chip is located between the 180° hybrid junction structure and the first ground via hole, and is connected to the 180° hybrid junction structure and the first ground via hole through a first gold wire bonding; The second carbon nanotube Schottky diode chip is located between the 180° hybrid junction structure and the second ground via hole, and is connected to the 180° hybrid junction structure and the second ground via hole through a second gold wire bonding.

[0007] Further, the active layers of the Schottky diode chips of the first carbon nanotube and the second carbon nanotube are semiconductor-type high-density array carbon nanotubes.

[0008] Further, the substrates of the Schottky diode chips of the first carbon nanotube and the second carbon nanotube are quartz substrates with a thickness of 500 microns.

[0009] Further, the Schottky diode chips of the first carbon nanotube and the second carbon nanotube are the same chips, and the electrodes connected to the 180° hybrid junction structure are different.

[0010] Further, the cathode of the Schottky diode chip of the first carbon nanotube is connected to the 180° hybrid junction structure, and the anode of the Schottky diode chip of the second carbon nanotube is connected to the 180° hybrid junction structure.

[0011] Further, the anode of the Schottky diode chip of the first carbon nanotube is connected to the 180° hybrid junction structure, and the cathode of the Schottky diode chip of the second carbon nanotube is connected to the 180° hybrid junction structure.

[0012] Further, the Schottky diode chips of the first carbon nanotube and the second carbon nanotube operate at zero bias voltage.

[0013] Further, the characteristic impedance of the 180° hybrid junction structure within the operating frequency band is 70.711 ohms.

[0014] Further, the RF input bandpass filter and the LO input bandpass filter are parallel-coupled microstrip line bandpass filters.

[0015] Further, the parallel-coupled microstrip line band-pass filter is formed by two unshielded parallel microstrip transmission lines each equal to a quarter of the radio frequency signal wavelength, which are placed closely adjacent to each other.

[0016] Further, the intermediate frequency output low-pass filter is a high-low impedance microstrip line low-pass filter.

[0017] Further, the intermediate frequency output low-pass filter is successively composed of a high-impedance microstrip line and a low-impedance microstrip line. The characteristic impedance of the high-impedance microstrip line is 120 ohms, and the characteristic impedance of the low-impedance microstrip line is 30 ohms.

[0018] The single-balanced mixer circuit with a carbon nanotube Schottky diode design having a high cut-off frequency proposed in this application achieves low conversion loss at a frequency of 30 GHz. The 180° hybrid junction structure designed based on microstrip line technology is used to achieve equal-power distribution of the radio frequency signal in-phase and differential equal-power distribution of the local oscillator signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the existing technical solutions, the following will briefly introduce the drawings required for use in the description of the embodiments or the existing technical solutions. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 Schematic diagram of the single-balanced radio frequency mixer circuit based on carbon nanotube Schottky diodes of the present application; Figure 2 Physical photo of the single-balanced radio frequency mixer based on carbon nanotube Schottky diodes of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] To make the objectives, technical solutions, and advantages of the present application clearer, the following will clearly and completely describe the technical solutions of the present application in conjunction with specific embodiments and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0022] This application presents a circuit including a mixer PCB (printed circuit board), two carbon nanotube Schottky diode chip dies with a size of 1000 square microns, and multiple gold wire bonding wires. The above mixer circuit board is implemented on a Rogers 5880 substrate with a thickness of 5 mil using microstrip line technology. Among them, the 180° hybrid junction structure, RF input band-pass filter circuit, local oscillator input band-pass filter circuit, and intermediate frequency output low-pass filter circuit all use microstrip line technology, and the metal thickness of the microstrip line circuit is 35 microns.

[0023] The present invention uses a 5-mil-thick Rogers 5880 as the substrate, and its low dielectric constant and reasonable substrate thickness significantly reduce parasitic capacitance and signal loss, especially in the frequency band above 30 GHz. Using microstrip line technology on the PCB to achieve efficient signal transmission reduces the parasitic parameters caused by wire length and structure in traditional circuits. By adjusting the design of the PCB layout, the impedance matching of the circuit is optimized, reducing signal reflection and transmission loss. The compact design of the PCB makes the layout of each part in the circuit more reasonable, reducing the parasitic capacitance in the signal transmission path.

[0024] The following combines the attached Figure 1 A single-balanced RF mixer circuit based on carbon nanotube Schottky diodes of the present invention will be specifically described, including an RF signal input terminal 101, a local oscillator signal input terminal 102, an intermediate frequency signal output terminal 103, an RF input band-pass filter 104, a local oscillator input band-pass filter 105, an intermediate frequency output low-pass filter 106, a 180° hybrid junction structure 107, a first carbon nanotube Schottky diode chip 108, a second carbon nanotube Schottky diode chip 109, a first ground via 112, and a second ground via 113. The above intermediate frequency output low-pass filter is a high-low impedance microstrip line low-pass filter. The intermediate frequency output low-pass filter is successively composed of a high-impedance microstrip line and a low-impedance microstrip line. The characteristic impedance of the high-impedance microstrip line is 120 ohms, and the characteristic impedance of the low-impedance microstrip line is 30 ohms.

[0025] Among them, the RF input band-pass filter 104 is located between the RF signal input terminal 101 and the 180° hybrid junction structure 107; the local oscillator input band-pass filter 105 is located between the local oscillator signal input terminal 102 and the 180° hybrid junction structure 107; the intermediate frequency output low-pass filter 106 is located between the intermediate frequency signal output terminal 103 and the 180° hybrid junction structure 107; the RF input band-pass filter, the local oscillator input band-pass filter, and the intermediate frequency low-pass filter are all integrated on the PCB substrate, avoiding additional filter components, simplifying the system structure, and improving the overall efficiency and reliability of the system.

[0026] The first carbon nanotube Schottky diode chip 108 is located between the 180° hybrid junction structure 107 and the first ground via 112, and is connected to the 180° hybrid junction structure 107 and the first ground via 112 by a first gold wire bonding wire 110; the second carbon nanotube Schottky diode chip 109 is located between the 180° hybrid junction structure 107 and the second ground via 113, and is connected to the 180° hybrid junction structure 107 and the second ground via 113 by a second gold wire bonding wire 111. The present invention uses the gold wire bonding technology to connect the carbon-based Schottky diode chip die to the signal transmission line on the PCB, ensuring that the signal transmission path is short and stable, while improving the reliability and flexibility of the connection. Connecting with gold wire bonding wires reduces the parasitic capacitance between contact points, thus greatly improving the high-frequency performance of the circuit. Compared with the traditional silicon-based circuit and coplanar waveguide structure, the present invention avoids the complex electrical jumper design, reduces the parasitic capacitance and parasitic inductance generated during the connection process, and thus improves the high-frequency performance and signal integrity of the circuit.

[0027] The active layers of the Schottky diode chip 108 of the first carbon nanotube and the Schottky diode chip 109 of the second carbon nanotube are semiconductor-type high-density array carbon nanotubes, which fully utilize the characteristics of high carrier mobility, high saturation velocity and low intrinsic capacitance of the high-density and high-purity array carbon nanotubes, and enhance the potential of the carbon-based Schottky diode to work in the terahertz band. The substrate is a 500-micron-thick quartz substrate, and using quartz as the substrate can greatly reduce the parasitic parameters of the carbon nanotube Schottky diode.

[0028] The Schottky diode chip 108 of the first carbon nanotube and the Schottky diode chip 109 of the second carbon nanotube are the same chips, and the electrodes connected to the 180° hybrid junction structure 107 are different. The cathode of the Schottky diode chip 108 of the first carbon nanotube is connected to the 180° hybrid junction structure 107, and the anode of the Schottky diode chip 109 of the second carbon nanotube is connected to the 180° hybrid junction structure 107. In another embodiment, the anode of the Schottky diode chip 108 of the first carbon nanotube is connected to the 180° hybrid junction structure 107, and the cathode of the Schottky diode chip 109 of the second carbon nanotube is connected to the 180° hybrid junction structure 107. The Schottky diode chip 108 of the first carbon nanotube and the Schottky diode chip 109 of the first carbon nanotube operate at zero bias voltage.

[0029] The present invention adopts a structure in which interdigital electrodes are connected in parallel, increasing the channel width, effectively reducing the series resistance of the Schottky diode, improving the cut-off frequency of the carbon nanotube Schottky diode, and ensuring that the carbon-based Schottky diode has a faster response speed and smaller signal distortion when operating at high frequencies (above 30 GHz). As the frequency increases, the wires of the device package cannot be simply regarded as a transmission line without resistance, capacitance, and inductance, but a transmission line with resistance, capacitance, inductance, and even conductance. To reduce the influence of the parasitic parameters of the package.

[0030] The characteristic impedance of the 180° hybrid junction structure 107 within the operating frequency band is 70.711 ohms. By finely tuning the characteristic impedance value of the 180° hybrid junction structure, the conversion loss of the carbon-based single-balanced mixer circuit can be further optimized. The RF input bandpass filter 104 and the local oscillator input bandpass filter 105 are parallel-coupled microstrip line bandpass filters. The parallel-coupled microstrip line bandpass filter is composed of two unshielded parallel microstrip transmission lines equal to a quarter of the RF signal wavelength placed closely together. Due to the interaction of the electromagnetic fields between the two transmission lines, there will be power coupling between the two transmission lines. The parallel-coupled microstrip line bandpass filter is a commonly used distributed parameter bandpass filter. The low-pass filter at the intermediate frequency output end is designed based on the high-low impedance line low-pass filter design theory, with simple design, capable of achieving extremely low impedance, and broadening the frequency band range of the low-pass filter. The function of the low-pass filter is to transmit the intermediate frequency output signal and prevent the RF input signal and the local oscillator input signal from being transmitted out from the intermediate frequency output end.

[0031] The present invention adopts the microstrip line design process. The transmission of RF signals can be completed by isolating a single-layer conductive metal strip from the ground plane through a dielectric material, without the need for any surface-mounted components such as surface-mounted resistors, surface-mounted capacitors, surface-mounted inductors, etc., nor the need for the stacking process of multi-layer PCBs, which will directly reduce the manufacturing difficulty, circuit area, and the influence of parasitic effects. The characteristic impedance of the 180-degree hybrid junction in the form of a microstrip line in the present invention is designed to be 70.711 ohms at a frequency of 30 GHz, meeting the technical requirements of the amplitude and phase of the 180-degree hybrid junction. The characteristic impedance of the bandpass filter and the low-pass filter using the microstrip line technology in the present invention is designed to be the standard 50 ohms at a frequency of 30 GHz, facilitating the transmission of RF signals in this mixer and reducing the reflection loss of the RF signals. The operating frequency of the low-pass filter is designed from DC to 5 GHz, and the operating frequency of the bandpass filter is designed from 25 GHz to 35 GHz. The RF input port, the local oscillator input port, and the intermediate frequency output port of the mixer are all designed using microstrip line technology to have a characteristic impedance of the standard 50 ohms at a frequency of 30 GHz.

[0032] In addition, the present invention uses a carbon nanotube Schottky diode bare chip with a high cut-off frequency to implement a carbon nanotube-based millimeter-wave mixer with a frequency greater than 30 GHz on a Rogers 5880 PCB circuit board, which has a low mixer energy conversion loss and good port isolation. At the same time, the present invention uses the gold wire bonding technology to complete the connection between the carbon nanotube Schottky diode bare chip and the Rogers 5880 PCB circuit board using the immersion gold process, ensuring the reliability of the circuit connection and being suitable for long-term operation in complex communication environments.

[0033] Those of ordinary skill in the art should understand that the discussion of any embodiment above is only exemplary and is not intended to imply that the scope of the present application (including the claims) is limited to these examples; under the idea of the present application, the technical features between the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of one or more embodiments of the present application as described above, and they are not provided in detail for the sake of brevity.

[0034] In addition, for the sake of simplicity of description and discussion, and in order not to make one or more embodiments of the present application difficult to understand, the well-known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the accompanying drawings. In addition, the device may be shown in block diagram form to avoid making one or more embodiments of the present application difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which one or more embodiments of the present application are to be implemented (i.e., these details should be fully within the understanding of those skilled in the art). In the case where specific details (such as circuits) are set forth to describe the exemplary embodiments of the present application, it will be apparent to those skilled in the art that one or more embodiments of the present application can be implemented without these specific details or with variations of these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0035] Although the present application has been described in connection with specific embodiments of the present application, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art based on the foregoing description. For example, other memory architectures (such as dynamic RAM (DRAM)) can be used with the embodiments discussed.

[0036] One or more embodiments of the present application are intended to cover all such alternatives, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application shall be included within the protection scope of the present application.

Claims

1. A single-balanced radio frequency mixer circuit based on a carbon nanotube Schottky diode, characterized in that, It includes a radio frequency signal input terminal (101), a local oscillator signal input terminal (102), an intermediate frequency signal output terminal (103), a radio frequency input band-pass filter (104), a local oscillator input band-pass filter (105), an intermediate frequency output low-pass filter (106), a 180° hybrid junction structure (107), a first carbon nanotube Schottky diode chip (108), a second carbon nanotube Schottky diode chip (109), a first ground via (112) and a second ground via (113); The radio frequency input band-pass filter (104) is located between the radio frequency signal input terminal (101) and the 180° hybrid junction structure (107); the local oscillator input band-pass filter (105) is located between the local oscillator signal input terminal (102) and the 180° hybrid junction structure (107); the intermediate frequency output low-pass filter (106) is located between the intermediate frequency signal output terminal (103) and the 180° hybrid junction structure (107); The first carbon nanotube Schottky diode chip (108) is located between the 180° hybrid junction structure (107) and the first ground via (112), and is connected to the 180° hybrid junction structure (107) and the first ground via (112) through a first gold wire bonding (110); The second carbon nanotube Schottky diode chip (109) is located between the 180° hybrid junction structure (107) and the second ground via (113), and is connected to the 180° hybrid junction structure (107) and the second ground via (113) through a second gold wire bonding (111).

2. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode as claimed in claim 1, wherein The active layers of the first carbon nanotube Schottky diode chip (108) and the second carbon nanotube Schottky diode chip (109) are semiconductor-type high-density array carbon nanotubes.

3. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode according to claim 1, wherein The substrates of the first carbon nanotube Schottky diode chip (108) and the second carbon nanotube Schottky diode chip (109) are quartz substrates with a thickness of 500 microns.

4. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode according to claim 1, characterized in that, The first carbon nanotube Schottky diode chip (108) and the second carbon nanotube Schottky diode chip (109) are the same chips, and the electrodes connected to the 180° hybrid junction structure (107) are different.

5. The single-balanced radio frequency mixer circuit based on carbon nanotube Schottky diodes according to claim 4, wherein the cathode of the first carbon nanotube Schottky diode chip (108) is connected to the 180° hybrid junction structure (107), and the anode of the second carbon nanotube Schottky diode chip (109) is connected to the 180° hybrid junction structure (107); or, the anode of the first carbon nanotube Schottky diode chip (108) is connected to the 180° hybrid junction structure (107), and the cathode of the second carbon nanotube Schottky diode chip (109) is connected to the 180° hybrid junction structure (107).

6. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode as claimed in claim 1, wherein the Schottky diode chip (108) of the first carbon nanotube and the Schottky diode chip (109) of the second carbon nanotube operate at zero bias voltage.

7. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode as claimed in claim 1, wherein the characteristic impedance of the 180° hybrid junction structure (107) within the operating frequency band is 70.711 ohms.

8. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode as claimed in claim 1, wherein the RF input bandpass filter (104) and the local oscillator input bandpass filter (105) are parallel-coupled microstrip line bandpass filters; The parallel-coupled microstrip line bandpass filter is formed by two unshielded parallel microstrip transmission lines each equal to a quarter of the RF signal wavelength placed closely adjacent to each other.

9. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode as claimed in claim 1, wherein the intermediate frequency output low-pass filter (106) is a high-low impedance microstrip line low-pass filter.

10. The single-balanced RF mixer circuit based on a carbon nanotube Schottky diode as claimed in claim 9, wherein the intermediate frequency output low-pass filter (106) is successively formed by a high-impedance microstrip line and a low-impedance microstrip line, the characteristic impedance of the high-impedance microstrip line being 120 ohms and the characteristic impedance of the low-impedance microstrip line being 30 ohms.

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