A terahertz second harmonic mixer and integrated circuit

Abstract

The application discloses a terahertz second harmonic mixer and an integrated circuit, and relates to the technical field of terahertz, and the terahertz second harmonic mixer comprises: a reverse-parallel diode pair and an intermediate frequency output circuit; the reverse-parallel diode pair is composed of two reverse-parallel Schottky diodes based on HEMT process compatibility; the reverse-parallel diode pair is connected with the intermediate frequency output circuit; wherein the transmission medium for connecting the reverse-parallel diode pair with the intermediate frequency output circuit is a coplanar waveguide; the reverse-parallel diode pair is used for frequency mixing received radio frequency signals and local oscillator signals and generating mixed frequency signals, and the intermediate frequency output circuit is used for filtering the mixed frequency signals and outputting. The application can solve the problems of high power consumption of the mixer in the prior art and high difficulty of monolithic integration of the mixer and the HEMT semiconductor device.

Description

Technical Field

[0001] This invention relates to the field of terahertz technology, and in particular to a terahertz second harmonic mixer and integrated circuit. Background Technology

[0002] Terahertz (THz) waves refer to electromagnetic waves with frequencies ranging from 0.1 to 10 THz (1 THz = 10¹² Hz) and wavelengths ranging from 3 mm to 0.03 mm. Due to a long-term lag behind the development of millimeter-wave and optical technologies, terahertz waves are the only remaining unexplored and unutilized segment of the electromagnetic spectrum, leading to the so-called "terahertz gap." Terahertz waves, with their high frequency, wide bandwidth, low photon energy, strong penetrability, selective absorption, and atmospheric attenuation characteristics, can be applied in communication technology and astronomy. With the advancement of science and technology, low-frequency electromagnetic spectrum resources are becoming increasingly scarce, leading to the exploration of applications in the terahertz band. Terahertz transmitters and receivers have become key technologies urgently needing breakthroughs in communication systems within this band.

[0003] Terahertz transceiver systems are core components in terahertz system applications, mainly including mixers, frequency multipliers, filters, power amplifiers, and low-noise amplifiers. Mixers using traditional Schottky diodes, due to their waveguide-fed nature, are difficult to integrate monolithically with HEMT amplifiers, leading to increased process losses in the transceiver system. Summary of the Invention

[0004] The purpose of this invention is to provide a terahertz second harmonic mixer and integrated circuit to reduce the power consumption of the mixer and the difficulty of monolithic integration of the mixer with HEMT semiconductor devices.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a terahertz second harmonic mixer, comprising at least: a pair of anti-parallel diodes and an intermediate frequency output circuit; the pair of anti-parallel diodes is composed of two Schottky diodes based on HEMT technology in anti-parallel connection;

[0007] The anti-parallel diode pair is connected to the intermediate frequency output circuit; wherein, the transmission medium connecting the anti-parallel diode pair and the intermediate frequency output circuit is a coplanar waveguide;

[0008] The reverse parallel diode is used to mix the received radio frequency signal and local oscillator signal to generate a mixed frequency signal. The intermediate frequency output circuit is used to filter the mixed frequency signal to obtain an intermediate frequency signal and output the intermediate frequency signal.

[0009] Optionally, the HEMT-compatible Schottky diode includes:

[0010] Indium phosphide substrate;

[0011] A gate, a drain, and a source are formed on the indium phosphide substrate; wherein the source and the drain are connected together to form a cathode; and the gate is an anode.

[0012] Optionally, the terahertz second harmonic mixer also includes: an RF probe unit and an RF matching circuit;

[0013] Both the RF matching circuit and the IF output circuit are connected to the RF probe unit; the RF matching circuit is connected to the first terminal of the anti-parallel diode pair.

[0014] The RF matching circuit, the IF output circuit, and the RF probe unit are all located on the first side of the anti-parallel diode pair.

[0015] Optionally, the terahertz second harmonic mixer also includes: a local oscillator matching circuit and a local oscillator probe unit;

[0016] The local oscillator matching circuit is connected to the local oscillator probe unit; the local oscillator matching circuit is connected to the second terminal of the anti-parallel diode pair;

[0017] The local oscillator matching circuit and the local oscillator probe unit are both located on the second side of the reverse parallel diode pair; the second side is the opposite side of the first side.

[0018] Optionally, the terahertz second harmonic mixer also includes: a diode grounding unit;

[0019] Both the local oscillator matching circuit and the local oscillator probe unit are connected to the first terminal of the diode grounding unit; the second terminal of the diode grounding unit is grounded.

[0020] Optionally, the intermediate frequency output circuit includes an intermediate frequency probe unit and an intermediate frequency filter circuit;

[0021] The first end of the intermediate frequency filter circuit is connected to the radio frequency probe unit, and the second end of the intermediate frequency filter circuit is connected to the intermediate frequency probe unit. The intermediate frequency probe unit is used to output the intermediate frequency signal.

[0022] Optionally, the intermediate frequency filter circuit employs a fan-shaped filter microstrip.

[0023] Optionally, the coplanar waveguide includes:

[0024] Indium phosphide substrate;

[0025] The first matching microstrip is located in the middle of the indium phosphide substrate;

[0026] Grounding microstrips located on both sides of the indium phosphide substrate.

[0027] Optionally, the RF probe unit includes a first interface and a first plate capacitor; the local oscillator probe unit includes a second interface and a second plate capacitor.

[0028] The radio frequency matching circuit is composed of a second matching microstrip; the local oscillator matching circuit is composed of a third matching microstrip; the second matching microstrip includes multiple sub-microstrips with different widths.

[0029] Compared with existing technologies, the terahertz second harmonic mixer provided by this invention adopts a space-fed method and designs a novel anti-parallel Schottky diode pair based on HEMT-compatible technology. This successfully realizes a second harmonic mixer that can be monolithically integrated with an HEMT low-noise amplifier. While ensuring low mixer loss, it effectively realizes the monolithic integration of the mixer and amplifier in the terahertz transceiver system, reducing process errors.

[0030] In a second aspect, the present invention also provides an integrated circuit, comprising at least: the terahertz second harmonic mixer and the HEMT low-noise amplifier as described in any of the preceding claims; wherein the terahertz second harmonic mixer and the HEMT low-noise amplifier are integrated on the same monolithic chip;

[0031] The terahertz second harmonic mixer is connected to the HEMT low-noise amplifier.

[0032] Compared with the prior art, the integrated circuit provided by the present invention can integrate the terahertz second harmonic mixer and HEMT low noise amplifier described in any of the above claims onto the same monolithic chip. While ensuring that the mixer loss is not high, it effectively realizes the monolithic integration of the mixer and amplifier in the terahertz transceiver system and reduces process errors. Attached Figure Description

[0033] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0034] Figure 1 A schematic block diagram of a terahertz second harmonic mixer provided for one embodiment of the present invention;

[0035] Figure 2 A top view of a design chip for a terahertz second harmonic mixer provided for one embodiment of the present invention;

[0036] Figure 3 A schematic diagram of a coplanar waveguide provided in one embodiment of the present invention;

[0037] Figure 4 This refers to a mixer that is individually packaged, as is common in the prior art.

[0038] Figure 5 This is a block diagram of a separately packaged mixer in the prior art;

[0039] Figure 6 A top view of a reverse parallel diode pair provided in one embodiment of the present invention;

[0040] Figure 7 A comparison diagram of gate change states of a HEMT-compatible Schottky diode provided for an embodiment of the present invention;

[0041] Figure 8 A simulation diagram of a terahertz second harmonic mixer provided for one embodiment of the present invention;

[0042] Figure 9 This is a schematic diagram of the manufacturing process of mixers and amplifiers in existing terahertz transceiver systems.

[0043] Figure 10 This is a schematic diagram of the manufacturing process of a mixer and amplifier integrated circuit in a terahertz transceiver system provided as an embodiment of the present invention.

[0044] Figure reference numerals: 10-Reverse parallel diode pair; 20-IF output circuit; 21-IF probe unit; 22-IF filter circuit; 30-RF probe unit; 31-Dielectric; 32-Electric field; 33-Ground plane metal; 34-Transmission line; 35-Ground metal; 36-Metal via; 40-RF matching circuit; 50-Local oscillator matching circuit; 60-Local oscillator probe unit; 70-Diode grounding unit; 80-First coplanar waveguide; 81-Second coplanar waveguide; 82-Third coplanar waveguide; 83-Fourth coplanar waveguide; 90-First air bridge; 91-Second air bridge Air bridge; 92-Third air bridge; 93-Fourth air bridge; 94-Fifth air bridge; 101-Indium phosphide substrate; 102-Anode mesa of HEMT-compatible Schottky diode 1; 103-Cathode mesa of HEMT-compatible Schottky diode 2; 104-Cathode mesa of HEMT-compatible Schottky diode 1; 105-Anode mesa of HEMT-compatible Schottky diode 2; 106-Anode metal finger of HEMT-compatible Schottky diode 1; 107-Anode metal finger of HEMT-compatible Schottky diode 2. Detailed Implementation

[0045] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0046] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0047] In this invention, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between the associated objects, indicating that three relationships can exist.

[0048] A mixer is used to combine two signals to produce a new frequency component. A mixer receives two input signals, typically a local oscillator signal and a radio frequency (RF) signal. These two signals are multiplied internally within the mixer to produce the new frequency component.

[0049] like Figure 1 and Figure 2 As shown, this embodiment of the invention provides a terahertz second harmonic mixer, which includes at least: an anti-parallel diode pair 10 and an intermediate frequency output circuit 20; the anti-parallel diode pair 10 is composed of two HEMT-compatible Schottky diodes connected in anti-parallel.

[0050] The reverse parallel diode pair 10 is connected to the intermediate frequency output circuit 20; wherein, the transmission medium connecting the reverse parallel diode pair 10 and the intermediate frequency output circuit 20 is a coplanar waveguide;

[0051] The reverse parallel diode is used to mix the received RF signal and local oscillator signal to generate a mixed frequency signal. The intermediate frequency output circuit is used to filter the mixed frequency signal to obtain the intermediate frequency signal and output the intermediate frequency signal.

[0052] Specifically, a Schottky diode based on HEMT process compatibility includes: an indium phosphide (InP) substrate; a gate, a drain, and a source formed on the indium phosphide substrate; wherein the source and drain are connected together to form a cathode; and the gate is an anode.

[0053] In other words, a Schottky diode based on HEMT technology is implemented by shorting the source and drain of an InP-based HEMT transistor as the cathode and using the gate of the InP-based HEMT transistor as the anode.

[0054] In essence, HEMT stands for High Electron Mobility Transistor. It is a heterojunction field-effect transistor. HEMT achieves high-speed and high-frequency performance by combining an interface between two conductor materials with different band gaps, utilizing the high mobility of channel carriers. HEMT-compatible processes refer to processes that allow HEMT devices to coexist with other semiconductor devices on the same wafer during manufacturing. The goal of this process is to achieve the integration of multiple devices without sacrificing performance, thereby improving the overall performance and reliability of the system.

[0055] In existing technologies, two main reasons prevent the fabrication of traditional Schottky diodes and HEMT devices from being realized on the same wafer. First, the substrates used in traditional mixers are typically made of materials such as gallium arsenide and quartz, which are different from the indium phosphide substrates used in HEMT devices. Second, the manufacturing processes for traditional Schottky diodes and HEMT devices are completely different, making them incompatible.

[0056] As can be seen from the above, in this embodiment of the invention, the Schottky diode based on HEMT-compatible technology connects the source and drain of its transistor together to form a cathode. That is, the Schottky diode structure is achieved by shorting the source and drain of an InP-based HEMT device, thereby realizing the process integration of the mixer and the HEMT amplifier circuit, achieving monolithic integration of the diode and transistor under the same process. The forward voltage drop of the Schottky diode based on HEMT-compatible technology reduces power loss and improves efficiency. Furthermore, its fast switching speed makes it suitable for high-frequency applications, and its short reverse recovery time reduces energy loss during switching. In summary, the Schottky diode based on HEMT-compatible technology has the advantages of low power consumption and monolithic integration with other HEMT-based semiconductor devices.

[0057] The specific structure of the terahertz second harmonic mixer is as follows: Figure 1 and Figure 2As shown, the terahertz second harmonic mixer also includes: an RF probe unit 30 and an RF matching circuit 40; the RF matching circuit 40 and the intermediate frequency output circuit 20 are both connected to the RF probe unit 30; the RF matching circuit 40 is connected to the first terminal of the anti-parallel diode pair 10; the RF matching circuit 40, the intermediate frequency output circuit 20, and the RF probe unit 30 are all located on the first side of the anti-parallel diode pair 10. The RF matching circuit 40 is used to optimize the transmission of RF signals and reduce reflection and mismatch losses.

[0058] The intermediate frequency output circuit 20 includes an intermediate frequency probe unit 21 and an intermediate frequency filter circuit 22. The first end of the intermediate frequency filter circuit 22 is connected to the radio frequency probe unit 30, and the second end of the intermediate frequency filter circuit 22 is connected to the intermediate frequency probe unit 21. The intermediate frequency probe unit 21 is used to output the filtered mixed frequency signal, which is also the intermediate frequency signal.

[0059] The terahertz second harmonic mixer also includes: a local oscillator matching circuit 50, a local oscillator probe unit 60, and a diode grounding unit 70;

[0060] The local oscillator matching circuit 50 is connected to the local oscillator probe unit 60; the local oscillator matching circuit 50 is connected to the second terminal of the reverse parallel diode pair 10; both the local oscillator matching circuit 50 and the local oscillator probe unit 60 are located on the second side of the reverse parallel diode pair 10; the second side is the opposite side of the first side.

[0061] Both the local oscillator matching circuit 50 and the local oscillator probe unit 60 are connected to the first terminal of the diode grounding unit 70; the second terminal of the diode grounding unit 70 is grounded. The diode grounding unit 70 is also located on the second side. The diode grounding unit achieves grounding of the reverse parallel diode pair by connecting to the grounding microstrip through a corresponding plate capacitor.

[0062] Regarding coplanar waveguides, for example Figure 3 As shown, a coplanar waveguide isolates two parallel conductors from a dielectric 31, which lies in the same plane, while an electric field 32 passes through the dielectric. In the coplanar waveguide structure, the bottom of the dielectric 31 is a ground plane metal 33, the middle part of the top of the dielectric 31 is a transmission line 34, and the metals on both sides of the transmission line 34 are ground metals 35. A vertical metal via 36 ensures consistent grounding of the top ground metal 35 and the bottom ground plane metal 33. Compared to suspended microstrip lines, coplanar waveguides have a simpler structure, wider bandwidth, lower loss at high frequencies, and are easier to integrate with other microwave components.

[0063] In an optional embodiment, the coplanar waveguide includes: an indium phosphide substrate; a first matching microstrip located in the middle of the indium phosphide substrate; and ground microstrips located on both sides of the indium phosphide substrate. The first matching microstrip and the ground microstrip are made of gold.

[0064] Indium phosphide substrates have high electron migration speeds, making them ideal materials for fabricating ultra-high-speed and ultra-high-frequency components. HEMT-compatible processes using indium phosphide substrates can achieve monolithic integration of mixers and HEMT low-noise amplifiers.

[0065] Regarding the specific connection of the coplanar waveguides to the various circuits of the terahertz second harmonic mixer, combined with... Figure 1 and Figure 2 As can be understood, the transmission medium between each pair of the RF probe unit 30, the RF matching circuit 40, and the intermediate frequency output circuit 20 is the first coplanar waveguide 80, that is, the RF probe unit 30 and the RF matching circuit 40 are connected to the intermediate frequency output circuit 20 through the first coplanar waveguide 80; the transmission medium between the RF matching circuit 40 and the anti-parallel diode pair 10 is the second coplanar waveguide, that is, the RF matching circuit 40 is connected to the first end of the anti-parallel diode pair 10 through the second coplanar waveguide 81.

[0066] Combination Figure 1 and Figure 2 As can be understood, the transmission medium between the local oscillator matching circuit 50 and the anti-parallel diode pair 10 is the third coplanar waveguide 82, meaning the local oscillator matching circuit 50 is connected to the second terminal of the anti-parallel diode pair 10 through the third coplanar waveguide 82. The transmission medium between each pair of the local oscillator matching circuit 50, the local oscillator probe unit 60, and the diode grounding unit 70 is the fourth coplanar waveguide 83, meaning the local oscillator matching circuit 50 and the local oscillator probe unit 60 are connected to the diode grounding unit 70 through the fourth coplanar waveguide 83. The second terminal of the intermediate frequency filter circuit 22 is connected to the intermediate frequency probe unit 21 through the fifth coplanar waveguide.

[0067] As can be seen from the above, all circuits in the terahertz second harmonic mixer use coplanar waveguides as the transmission medium for signal transmission.

[0068] Terahertz second harmonic mixers may also include an air bridge. The air bridge is made of metal. For example, the air bridge in a mixer is made of gold. The base portions of the air bridge are located on the upper and lower grounded metals, and the bridge surface portions are mounted on the base portions on both sides.

[0069] like Figure 2 As shown, the first air bridge 90 is located at the connection between the plate capacitor of the RF probe unit 30 and the first coplanar waveguide 80; the second air bridge 91 is located at the connection between the intermediate frequency output circuit 20 and the first coplanar waveguide 80; the third air bridge 92 is located at the connection between the RF matching circuit 40 and the first coplanar waveguide 80; the fourth air bridge 93 is located at the connection between the diode grounding unit 70 and the fourth coplanar waveguide 83; and the fifth air bridge 94 is located at the connection between the plate capacitor of the local oscillator probe unit 60 and the fourth coplanar waveguide 83. Using air bridges can reduce parasitic capacitance, improve isolation, and reduce power consumption.

[0070] The advantages of the terahertz second harmonic mixer provided in the embodiments of the present invention are analyzed as follows:

[0071] (1) The anti-parallel diode pair in the prior art mixer uses two traditional Schottky diodes, while the anti-parallel diode pair in the terahertz second harmonic mixer provided in this embodiment of the invention uses Schottky diodes based on HEMT compatible technology.

[0072] As mentioned in the background section, HEMTs are the optimal choice for low-noise amplifiers due to their high-frequency and low-noise characteristics. Therefore, existing terahertz transceiver systems mainly include components such as mixers, frequency multipliers, filters, power amplifiers, and HEMT low-noise amplifiers. The traditional connection method involves designing and packaging these component modules separately. Therefore, existing Schottky diode mixers are packaged separately as individual modules within the terahertz transceiver system. Figure 4 The mixer consists of two separately packaged Schottky diodes.

[0073] According to the traditional principle of packaging each module separately, the packaging errors are multiplied, and the external connections between the packaged modules will also generate process losses, thus affecting the performance of the entire terahertz transceiver system.

[0074] The terahertz second harmonic mixer in this embodiment of the invention uses a Schottky diode based on HEMT-compatible technology. Therefore, it can be integrated with the HEMT low-noise amplifier on the same chip. That is, the mixer circuit and the amplifier circuit can be cascaded and manufactured on the same substrate. Then, only one packaging is required, which reduces the packaging error and process error when the mixer module and the amplifier module are packaged separately and then connected.

[0075] (2) In the prior art, the traditional Schottky diode mixer uses waveguide feeding, that is, the signal first propagates in the waveguide in the form of TE10 mode and then, after being converted by the probe, the signal propagates in the form of quasi-TEM mode on the suspended microstrip line.

[0076] The terahertz second harmonic mixer provided in this embodiment of the invention uses a coplanar waveguide for spatial feeding to achieve the transmission of terahertz wave signals.

[0077] Therefore, combining (1) and (2), it can be seen that the terahertz second harmonic mixer provided in this embodiment of the invention uses both a coplanar waveguide and a Schottky diode based on HEMT compatible technology, which is more conducive to the monolithic integration of the terahertz second harmonic mixer with other HEMT microwave components (such as HEMT low noise amplifiers).

[0078] For other circuit structures, such as intermediate frequency (IF) filters, a fan-shaped microstrip filter is used. The main advantages of using a fan-shaped microstrip filter structure in IF filter circuits are as follows: 1) Saves circuit area: Compared to traditional linear or rectangular structures, the fan-shaped structure can utilize board space more effectively, especially when multiple filters or circuit components need to be integrated. The fan-shaped microstrip filter structure helps to achieve circuit miniaturization, which is particularly important for portable devices and high-density integrated systems. 2) The fan-shaped microstrip filter structure has a wider bandwidth than traditional rectangular filters. This design improves the filter's bandwidth to a certain extent, making it more suitable for applications requiring a wider frequency range.

[0079] For example, an RF matching circuit consists of a second matching microstrip; the second matching microstrip includes multiple sub-microstrips with different widths.

[0080] For example, the local oscillator matching circuit consists of a third matching microstrip; the third matching microstrip includes multiple sub-microstrips with different widths.

[0081] Because microstrip lines can be designed in various geometries, such as straight lines, bends, and spirals, this provides great flexibility for the design of impedance matching networks. By adjusting the length, width, and substrate thickness of the microstrip lines, different impedance matching requirements can be easily achieved. Therefore, both the RF matching circuit and the local oscillator matching circuit use corresponding matching microstrips, which can reduce the circuit footprint of the mixer.

[0082] For example, the RF probe unit consists of a first interface and a first plate capacitor. It is understood that the RF probe unit and the RF matching circuit are directly connected via a first coplanar waveguide.

[0083] For example, the local oscillator probe unit consists of a second interface and a second plate capacitor.

[0084] For example, the intermediate frequency probe unit consists of a third interface and a third plate capacitor.

[0085] Understandably, the RF matching circuit and the RF probe unit are connected through corresponding matching microstrips, the local oscillator matching circuit and the local oscillator probe unit are connected through corresponding matching microstrips, the RF probe unit and the intermediate frequency filter circuit are connected through corresponding coplanar waveguides, and the RF probe unit and the intermediate frequency probe unit are connected through corresponding coplanar waveguides.

[0086] It should be noted that the above structure in the embodiments of the present invention is specially designed because conventional mixer circuits in the prior art have large area losses, for example... Figure 5As shown, a conventional mixer circuit in the prior art includes: RF DC ground, RF probe transition, RF matching circuit, conventional Schottky diode unit, local oscillator matching circuit, local oscillator low-pass filter, local oscillator probe transition, intermediate frequency low-pass filter, RF input standard waveguide, height reduction waveguide corresponding to the RF input standard waveguide, local oscillator input standard waveguide, and height reduction waveguide corresponding to the local oscillator input standard waveguide. Their connection relationships are as follows: Figure 6 As shown, details will not be elaborated upon here. Figure 6 As can be seen, the RF signal input and local oscillator signal input of a traditional Schottky diode mixer are converted into quasi-TEM mode signals by a probe, and then the signals continue to propagate on the waveguide. The traditional circuit structure is usually long and narrow.

[0087] Unlike existing mixers that incorporate traditional Schottky diodes, the terahertz second harmonic mixer in this invention utilizes a coplanar waveguide, which can... Figure 6 The corresponding intermediate frequency output circuit is obtained by folding. Figure 1 The circuit is positioned in the middle, which reduces the area occupied by the circuit.

[0088] The circuit working principle of the terahertz second harmonic mixer in this embodiment of the invention is explained as follows:

[0089] The first interface of the RF probe unit receives the RF signal and transmits it to the first diode of the reverse parallel Schottky diode pair through the first plate capacitor and the RF matching circuit.

[0090] The second interface in the local oscillator probe receives the local oscillator signal, which is then transmitted to the second diode of the reverse parallel Schottky diode pair via the second plate capacitor and the local oscillator matching circuit.

[0091] Second harmonic mixing is achieved by using reverse parallel diodes. The generated intermediate frequency (IF) signal is output through an IF probe. The IF low-pass filter circuit filters the radio frequency (RF) signal and the local oscillator (LO) signal through a sector filter.

[0092] The specific signal transmission process is as follows: The radio frequency (RF) signal is input through the RF probe unit, passes through the plate capacitor, and reaches the first coplanar waveguide. After passing through the first coplanar waveguide and being filtered by the RF matching circuit, it passes through the second coplanar waveguide and reaches the diode on one side of the anti-parallel diode pair. The local oscillator (LO) signal is input through the LO probe unit, passes through the plate capacitor, and reaches the fourth coplanar waveguide. After passing through the fourth coplanar waveguide, it passes through the diode grounding unit and the LO matching circuit and is filtered. Then, it passes through the third coplanar waveguide and reaches the diode on the other side of the anti-parallel diode pair. The anti-parallel connection of two diodes with identical parameters should only generate even-order harmonic related components. The odd-order components cancel each other out. After passing through the RF matching microstrip, only the second harmonic is generated. The second harmonic is transmitted through the RF matching circuit to the first coplanar waveguide, then filtered by the intermediate frequency (IF) filter circuit, and finally output from the IF probe unit through the plate capacitor.

[0093] In one alternative implementation, for example Figure 6 This diagram illustrates the structure of a reverse-parallel Schottky diode pair for HEMT-compatible technology. On an indium phosphide substrate 101, the source and drain of the HEMT device are shorted and extended to form the cathode of the HEMT-compatible Schottky diode. The gate of the HEMT device, connected to the cathode, serves as the anode metal finger of the HEMT-compatible Schottky diode 1. Directly connected to the second coplanar waveguide 81 are the anode mesa 102 of the HEMT-compatible Schottky diode 1 and the cathode mesa 103 of the HEMT-compatible Schottky diode 2, with the anode mesa 102 of the HEMT-compatible Schottky diode 1 and the cathode mesa 103 of the HEMT-compatible Schottky diode 2 also connected. The third coplanar waveguide 82 is directly connected to the cathode mesa 104 of HEMT-compatible Schottky diode 1 and the anode mesa 105 of HEMT-compatible Schottky diode 2, and the cathode mesa 104 of HEMT-compatible Schottky diode 1 is connected to the anode mesa 105 of HEMT-compatible Schottky diode 2. The two upper gates form the anode metal fingers 106 of HEMT-compatible Schottky diode 1, and the two lower gates form the anode metal fingers 107 of HEMT-compatible Schottky diode 2.

[0094] Optionally, the doped layer in the HEMT-compatible Schottky diode is a delta-doped layer. The thickness of the delta-doped layer can be referenced from relevant technologies, and this embodiment does not impose specific limitations.

[0095] Optionally, to further modify the gate width and gate length of HEMT-compatible Schottky diodes, i.e., to further reduce the gate width and increase the gate length. For example... Figure 7 As shown, the gate length of the HEMT-compatible Schottky diode on the left is 5µm, and increasing the gate length makes it 10µm as shown on the right. 0.25 is the gate width.

[0096] The terahertz second harmonic mixer in this embodiment was simulated and tested using HFSS and ADS software. The simulation results are as follows: Figure 8 As shown, the frequency conversion loss is less than 26.2dB.

[0097] The present invention also provides an integrated circuit, comprising at least: a terahertz second harmonic mixer and an HEMT power amplifier as described in any of the above embodiments; the terahertz second harmonic mixer and the HEMT low-noise amplifier are integrated on the same monolithic chip; the terahertz second harmonic mixer is connected to the HEMT low-noise amplifier.

[0098] Figure 9 The manufacturing process of mixers and amplifiers in existing terahertz transceiver systems is as follows: First, the mixer (i.e., a mixer using traditional Schottky diodes) circuit design and the amplifier (i.e., a HEMT low-noise amplifier) ​​circuit design are carried out separately; second, the mixer circuit and the amplifier circuit are manufactured separately; third, the mixer circuit and the amplifier circuit are packaged separately; finally, the separately packaged mixer and the separately packaged amplifier are externally connected.

[0099] The manufacturing process of the mixer and amplifier in the aforementioned terahertz transceiver system results in two packaging errors, as well as external connection errors.

[0100] Figure 10 The manufacturing process of the integrated circuit in the terahertz transceiver system provided for the implementation of this invention is as follows: First, the mixer (i.e., a mixer using two HEMT-compatible Schottky diodes) and amplifier (i.e., a HEMT low-noise amplifier) ​​circuits are designed; then, the mixer and amplifier circuits are manufactured; and finally, the mixer and amplifier integrated circuits are packaged in one go.

[0101] In the integrated circuit of this invention, the mixer and HEMT low-noise amplifier are integrated on the same chip, which is a direct chip-level connection, with small error and low signal transmission loss; each packaging process only generates one packaging process error.

[0102] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0103] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely exemplary descriptions of the invention as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A terahertz second harmonic mixer, characterized in that, At least including: Anti-parallel diode pair and intermediate frequency output circuit; The reverse parallel diode pair consists of two HEMT-compatible Schottky diodes connected in reverse parallel. The anti-parallel diode pair is connected to the intermediate frequency output circuit; wherein, the transmission medium connecting the anti-parallel diode pair and the intermediate frequency output circuit is a coplanar waveguide; The reverse parallel diode is used to mix the received radio frequency signal and local oscillator signal to generate a mixed frequency signal. The intermediate frequency output circuit is used to filter the mixed frequency signal to obtain an intermediate frequency signal and output the intermediate frequency signal.

2. The terahertz second harmonic mixer according to claim 1, characterized in that, The HEMT-compatible Schottky diode includes: Indium phosphide substrate; A gate, a drain, and a source are formed on the indium phosphide substrate; wherein the source and the drain are connected together to form a cathode; and the gate is an anode.

3. The terahertz second harmonic mixer according to claim 1, characterized in that, Also includes: RF probe unit and RF matching circuit; Both the RF matching circuit and the IF output circuit are connected to the RF probe unit; the RF matching circuit is connected to the first terminal of the anti-parallel diode pair. The RF matching circuit, the IF output circuit, and the RF probe unit are all located on the first side of the anti-parallel diode pair.

4. The terahertz second harmonic mixer according to claim 3, characterized in that, Also includes: Local oscillator matching circuit and local oscillator probe unit; The local oscillator matching circuit is connected to the local oscillator probe unit; the local oscillator matching circuit is connected to the second terminal of the anti-parallel diode pair; The local oscillator matching circuit and the local oscillator probe unit are both located on the second side of the reverse parallel diode pair; the second side is the opposite side of the first side.

5. The terahertz second harmonic mixer according to claim 4, characterized in that, Also includes: Diode grounding unit; Both the local oscillator matching circuit and the local oscillator probe unit are connected to the first terminal of the diode grounding unit; the second terminal of the diode grounding unit is grounded.

6. The terahertz second harmonic mixer according to claim 3, characterized in that, The intermediate frequency output circuit includes an intermediate frequency probe unit and an intermediate frequency filter circuit; The first end of the intermediate frequency filter circuit is connected to the radio frequency probe unit, and the second end of the intermediate frequency filter circuit is connected to the intermediate frequency probe unit. The intermediate frequency probe unit is used to output the intermediate frequency signal.

7. The terahertz second harmonic mixer according to claim 6, characterized in that, The intermediate frequency filter circuit uses a fan-shaped filter microstrip.

8. The terahertz second harmonic mixer according to claim 1, characterized in that, The coplanar waveguide includes: Indium phosphide substrate; The first matching microstrip is located in the middle of the indium phosphide substrate; Grounding microstrips located on both sides of the indium phosphide substrate.

9. The terahertz second harmonic mixer according to claim 4, characterized in that, The radio frequency probe unit includes a first interface and a first electrode capacitor; the local oscillator probe unit includes a second interface and a second electrode capacitor. The radio frequency matching circuit is composed of a second matching microstrip; the local oscillator matching circuit is composed of a third matching microstrip; the second matching microstrip includes multiple sub-microstrips with different widths.

10. An integrated circuit, characterized in that, It includes at least: a terahertz second harmonic mixer and an HEMT low-noise amplifier as described in any one of claims 1 to 9; wherein the terahertz second harmonic mixer and the HEMT low-noise amplifier are integrated on the same monolithic chip; The terahertz second harmonic mixer is connected to the HEMT low-noise amplifier.

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