Terahertz mixer and communication device
By integrating RF coplanar waveguide interfaces and anti-parallel diodes into the terahertz mixer, the problems of large size and difficulty in integration of terahertz mixers are solved, achieving high integration and low-loss signal transmission, and improving production efficiency and electrical performance consistency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- THE 13TH RES INST OF CHINA ELECTRONICS TECH GRP CORP
- Filing Date
- 2026-03-19
- Publication Date
- 2026-07-14
AI Technical Summary
Existing terahertz mixers rely on metal waveguides, resulting in large sizes that cannot meet the application requirements for high integration.
The mixer integrates key components such as RF coplanar waveguide interface, anti-parallel diode pair, impedance matching circuit and filter on the same substrate, and generates intermediate frequency signal by mixing the second harmonic of RF and local oscillator signals to achieve the integration of the mixer.
It improves the compactness and reliability of devices, reduces signal transmission loss, simplifies the production process, and enhances the consistency of electrical performance and testing efficiency.
Smart Images
Figure CN122394584A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of mixer technology, and more particularly to a terahertz mixer and communication equipment. Background Technology
[0002] Terahertz waves have shorter wavelengths, wider bandwidths, and better directionality compared to microwaves, and also possess abundant untapped spectrum resources, making them promising for applications in cutting-edge fields such as security imaging and high-speed wireless communication.
[0003] Terahertz mixers are key electronic devices for modulating low-frequency signals to terahertz waves or demodulating useful signals from terahertz waves, playing a crucial role in terahertz application systems. Current terahertz harmonic mixers typically employ discrete Schottky diodes flip-chip soldered onto a passive circuit board, which is then mounted in a waveguide to form a hybrid integrated mixer.
[0004] However, current terahertz mixers typically rely on metal waveguides as the transmission structure. Although they can achieve high-frequency mixing, the large size of metal waveguides makes them difficult to integrate with other components, thus failing to meet the requirements of highly integrated applications. Summary of the Invention
[0005] This invention provides a terahertz mixer and communication device to solve the problem that current terahertz mixers are too large to be integrated.
[0006] In a first aspect, embodiments of the present invention provide a terahertz mixer, including a substrate, and a radio frequency coplanar waveguide interface, a radio frequency impedance matching circuit, a parallel short-circuit stub, a radio frequency filter, a pair of anti-parallel diodes, a local oscillator first impedance matching circuit, a local oscillator filter, a DC blocking capacitor, a local oscillator second impedance matching circuit, and a local oscillator coplanar waveguide interface disposed on the substrate and connected in sequence. The output terminal of the local oscillator filter and the input terminal of the DC blocking capacitor are connected to one end of the intermediate frequency filter, and the other end of the intermediate frequency filter is connected to the intermediate frequency coplanar waveguide interface. The RF coplanar waveguide interface, the RF end impedance matching circuit, the parallel short-circuit stub, and the RF end filter are used to transmit the RF signal to one end of the anti-parallel diode pair; the local oscillator end coplanar waveguide interface, the local oscillator end second impedance matching circuit, the DC blocking capacitor, the local oscillator end filter, and the local oscillator end first impedance matching circuit are used to transmit the local oscillator signal to the other end of the anti-parallel diode pair; the anti-parallel diode pair is used to perform second harmonic mixing on the received RF signal and local oscillator signal to generate an intermediate frequency (IF) signal; the IF end filter and the IF coplanar waveguide interface are used to transmit the IF signal.
[0007] In one possible implementation, the RF impedance matching circuit, the local oscillator first impedance matching circuit, and the local oscillator second impedance matching circuit are all composed of microstrip lines.
[0008] In one possible implementation, the anti-parallel diode pair includes a first diode and a second diode; The anode of the first diode is connected to the cathode of the second diode, and the cathode of the first diode is connected to the anode of the second diode; the anode of the first diode serves as the input terminal of the anti-parallel diode pair, and the cathode of the first diode serves as the output terminal of the anti-parallel diode pair.
[0009] In one possible implementation, the RF filter, the IF filter, and the local oscillator filter are all composed of microstrip lines.
[0010] In one possible implementation, the DC blocking capacitor is a metal-dielectric capacitor or a coupling capacitor.
[0011] In one possible implementation, the parallel short-circuit stub is a ground wire connected in parallel to the radio frequency signal transmission line.
[0012] In one possible implementation, both the RF coplanar waveguide interface and the local oscillator coplanar waveguide interface are GSG pads of a grounded coplanar waveguide structure.
[0013] In one possible implementation, the intermediate frequency coplanar waveguide interface is a GSG pad.
[0014] In one possible implementation, the substrate is a gallium arsenide substrate.
[0015] In a second aspect, the present invention also provides a communication device, wherein the communication device includes the terahertz mixer described in any one of the first aspects.
[0016] The terahertz mixer provided in this invention integrates key components on the same substrate using a radio frequency (RF) coplanar waveguide interface, a local oscillator (LO) coplanar waveguide interface, and an intermediate frequency (IF) coplanar waveguide interface. This integration improves the compactness and reliability of the device while reducing signal transmission loss. By integrating an RF impedance matching circuit, a parallel short-circuit stub, and an RF filter on the substrate, the input RF signal can be transmitted to one end of the anti-parallel diode pair via the RF coplanar waveguide interface. By integrating a second LO impedance matching circuit, a DC blocking capacitor, a LO filter, and a first LO impedance matching circuit, the LO signal input from the LO coplanar waveguide interface can be transmitted to the other end of the anti-parallel diode pair. After both the RF signal and the LO signal reach the anti-parallel diode pair, the anti-parallel diode pair performs second harmonic mixing on the received RF and LO signals to output the IF signal. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of a terahertz mixer provided in one embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a terahertz mixer provided in another embodiment of the present invention; Figure 3 This is provided by the embodiments of the present invention. Figure 2 Schematic diagram of single-sideband conversion loss of a terahertz mixer; Figure 4 This is provided by the embodiments of the present invention. Figure 2 Schematic diagram of the RF port voltage standing wave ratio of a terahertz mixer; Figure 5 This is provided by the embodiments of the present invention. Figure 2 Schematic diagram of the VSWR of the intermediate frequency port voltage of a terahertz mixer; Figure 6 This is provided by the embodiments of the present invention. Figure 2 A schematic diagram of the standing wave ratio at the local oscillator port of a terahertz mixer. Detailed Implementation
[0018] The present application will be described more clearly below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the function of the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all fall within the protection scope of the present application.
[0019] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.
[0020] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.
[0021] In the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0022] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.
[0023] Furthermore, the term "multiple" mentioned in the embodiments of this application should be interpreted as two or more.
[0024] First, the terms used in the embodiments of this application will be explained: A mixer is a circuit whose output signal frequency is equal to the sum, difference, or other combination of the frequencies of the two input signals. Mixers typically consist of nonlinear components and frequency selection circuits, and are generally used to generate intermediate frequency (IF) signals.
[0025] Coplanar waveguide: It is a center signal line with two parallel ground planes on both sides, and both of them are fabricated on the same surface of a dielectric substrate.
[0026] Metal waveguide: A hollow metal tube used to transmit high-frequency electromagnetic waves.
[0027] Impedance matching circuits are crucial circuit networks in RF, microwave, and high-speed circuit design. They are used to ensure impedance matching between the signal source and the load, thereby enabling efficient energy transfer and minimizing signal reflection.
[0028] Filters: Their core function is to allow specific frequency components of a signal to pass through while significantly attenuating or suppressing other frequency components, thereby achieving signal purification, separation, and optimization.
[0029] DC blocking capacitor: In mixer circuits, it mainly serves to isolate DC components and transmit AC signals, ensuring the accuracy of signal processing.
[0030] GSG pads are ground-signal-ground pads, typically consisting of three pads in a group, with the signal pad (S) located between the two ground pads (G). The ground pads provide shielding for the signal pads, reducing signal leakage and external interference, preventing signal interference to the substrate, and improving the integrity and accuracy of signal transmission. The characteristic impedance of the GSG pad structure matches the characteristic impedance of the RF signal path, contributing to efficient signal transmission and reducing signal reflection.
[0031] Terahertz mixers are key electronic devices for modulating low-frequency signals to terahertz waves or demodulating useful signals from terahertz waves, playing a crucial role in terahertz application systems. Compared to the microwave band, terahertz frequency sources with sufficient output power and phase noise performance are more difficult to implement. The local oscillator input frequency of a harmonic mixer only needs to be one-Nth of that of a fundamental frequency mixer (N is 2, 4, 6, ...), effectively reducing the difficulty of implementing the local oscillator frequency source.
[0032] Currently, terahertz harmonic mixers employ discrete Schottky diodes flip-chip soldered onto a passive circuit board, which are then mounted within a waveguide to form a hybrid integrated mixer. This type of mixer, due to its metal waveguide structure, is large, heavy, and has low integration density. Furthermore, the suspended microstrip line design results in a large aspect ratio, making it prone to breakage and hindering fabrication and assembly. Assembly process errors in the terahertz band significantly impact the device's electrical performance; hybrid integration demands high assembly precision, leading to complex and inefficient assembly processes, and assembly errors result in low consistency in device electrical performance. Moreover, hybrid integrated mixers can only undergo frequency conversion loss and other electrical characteristic tests via a waveguide interface after assembly, making automated batch testing impossible and resulting in low testing efficiency. In summary, hybrid integrated terahertz harmonic mixers face technical challenges such as large size, difficulty in integration, and challenges in mass production.
[0033] To meet the development needs of miniaturization, high integration, and industrialization of terahertz application systems, there is an urgent need for a miniaturized, highly integrated terahertz mixer.
[0034] Figure 1 This is a schematic diagram of a terahertz mixer provided in an embodiment of the present invention. (Refer to...) Figure 1The terahertz mixer includes: a substrate 200, and a radio frequency coplanar waveguide interface 20, a radio frequency impedance matching circuit 30, a parallel short-circuit stub 40, a radio frequency filter 50, a pair of reverse parallel diodes 60, a local oscillator first impedance matching circuit 70, a local oscillator filter 80, a DC blocking capacitor 90, a local oscillator second impedance matching circuit 100, and a local oscillator coplanar waveguide interface 110, wherein the output terminal of the local oscillator filter 80 and the input terminal of the DC blocking capacitor 90 are connected to one end of the intermediate frequency filter 120, and the other end of the intermediate frequency filter 120 is connected to the intermediate frequency coplanar waveguide interface 130.
[0035] The radio frequency (RF) coplanar waveguide interface 20, RF-end impedance matching circuit 30, parallel short-circuit stub 40, and RF-end filter 50 are used to transmit the RF signal to one end of the anti-parallel diode pair 60. The local oscillator (LO) coplanar waveguide interface 110, LO second impedance matching circuit 100, DC blocking capacitor 90, LO filter 80, and LO first impedance matching circuit 70 are used to transmit the local oscillator (LO) signal to the other end of the anti-parallel diode pair 60. The anti-parallel diode pair 60 is used to perform second harmonic mixing of the received RF signal and LO signal to generate an intermediate frequency (IF) signal. The IF filter 120 and IF coplanar waveguide interface 130 are used to transmit the IF signal.
[0036] Second harmonic mixing refers to mixing two input signals to generate an output signal with a frequency that is the second harmonic (i.e., twice the frequency) of one of the input signals. This output signal is then mixed with the local oscillator signal to obtain the desired intermediate frequency signal.
[0037] When both a radio frequency (RF) signal and a local oscillator (LO) signal are input to the mixer simultaneously, nonlinear effects generate various frequency combinations, including harmonic components of the input signal. Frequency conversion can be achieved by selectively amplifying the second harmonic mixing component using a pair of anti-parallel diodes.
[0038] The terahertz mixer provided in this invention integrates key components on the same substrate using a radio frequency (RF) coplanar waveguide interface, a local oscillator (LO) coplanar waveguide interface, and an intermediate frequency (IF) coplanar waveguide interface. This integration improves the compactness and reliability of the device while reducing signal transmission loss. By integrating an RF impedance matching circuit, a parallel short-circuit stub, and an RF filter on the substrate, the input RF signal can be transmitted through the RF coplanar waveguide interface to one end of the anti-parallel diode pair. By integrating a second LO impedance matching circuit, a DC blocking capacitor, a LO filter, and a first LO impedance matching circuit, the LO signal input from the LO coplanar waveguide interface can be transmitted to the other end of the anti-parallel diode pair. The anti-parallel diode pair then performs second harmonic mixing on the received RF signal and the LO signal to output the IF signal.
[0039] In some embodiments, the RF impedance matching circuit 30, the local oscillator first impedance matching circuit 70, and the local oscillator second impedance matching circuit 100 are all composed of microstrip lines.
[0040] In this embodiment, the RF impedance matching circuit 30 employs a microstrip line matching circuit to match the 50Ω impedance to the optimal RF impedance point of the mixer, reducing the frequency conversion loss of the mixer. The local oscillator first impedance matching circuit 70 employs a microstrip line matching circuit to tune the anti-parallel diode pair 60 at the local oscillator end for both RF and local oscillator frequency load impedances, further reducing frequency conversion loss. The local oscillator second impedance matching circuit 100 employs a microstrip line matching circuit to match the 50Ω impedance to the optimal local oscillator impedance point of the mixer, improving mixing performance.
[0041] For example, the RF impedance matching circuit 30, the local oscillator first impedance matching circuit 70, and the local oscillator second impedance matching circuit 100 can be composed of a single-section microstrip line matching, a quarter-wavelength impedance transformer, a stub line matching, a tapered transmission line matching, or a multi-section microstrip line matching network.
[0042] Single-segment microstrip line matching is suitable for narrowband matching scenarios, achieving complex impedance matching through a microstrip line of a specific length and characteristic impedance. For example, a quarter-wavelength microstrip line can be used as a matching stub in a microstrip patch antenna to connect the antenna end to a standard 50-ohm microstrip line. Quarter-wavelength impedance transformers insert a microstrip line between the source and the load to achieve impedance transformation for purely resistive loads, commonly used in single-band power amplifier or filter designs. Stub line matching introduces reactive components to offset load reactance by connecting open / short-circuit stubs in parallel or series with the main microstrip line; these include single and double stubs, and are often used in tuning circuits in microwave integrated circuits. Tapered transmission line matching achieves continuous change in characteristic impedance by gradually altering the microstrip line width or dielectric thickness; types include exponential tapered, linear tapered, and Klopp-Fenstein tapered, suitable for ultra-wideband applications such as millimeter-wave communication and high-speed digital signal transmission. Multi-segment microstrip line matching networks consist of multiple microstrip line segments connected in series, extending bandwidth through step-by-step impedance transformation. For example, multi-section λ / 4 converters can achieve octave band matching and are often used in broadband amplifier or antenna array feed networks.
[0043] In this embodiment, by setting an impedance matching circuit at the radio frequency end, weak signals can enter the mixer completely and without noise, maximizing signal power transmission, ensuring signal linearity and low noise, and suppressing harmonics and spurious signals. Setting an impedance matching circuit at the local oscillator end allows for the most efficient control of the mixer's switching operation with minimal local oscillator power, driving nonlinear devices into their optimal operating range, optimizing conversion losses, and providing a DC bias path.
[0044] In some embodiments, the anti-parallel diode pair 60 includes a first diode and a second diode. The anode of the first diode is connected to the cathode of the second diode, and the cathode of the first diode is connected to the anode of the second diode. The anode of the first diode serves as the input terminal of the anti-parallel diode pair, and the cathode of the first diode serves as the output terminal of the anti-parallel diode pair.
[0045] In this embodiment, the anti-parallel diode pair 60 is implemented using on-chip high cutoff frequency gallium arsenide Schottky diode technology. By optimizing the structure of the anti-parallel diode pair, parasitic parameters are reduced, and second harmonic mixing with low conversion loss in the terahertz band is achieved.
[0046] In the fabrication of terahertz mixers, gallium arsenide Schottky diodes and circuitry can be integrated in a single process, significantly simplifying the manufacturing process and improving production efficiency. Furthermore, this diode structure offers superior performance in terahertz mixers, reducing signal loss and distortion during mixing. Regarding circuit connections, the first and second diodes are connected in a specific manner to form a reverse-parallel diode pair 60. This connection method ensures more stable current transmission in the circuit, and the input and output terminals facilitate circuit integration and overall layout, contributing to the miniaturization and integration of the entire terahertz mixer.
[0047] In some embodiments, the RF filter 50, the IF filter 120, and the local oscillator filter 80 are all composed of microstrip lines.
[0048] In this embodiment, the RF end filter 50 employs a microstrip notch filter circuit to achieve total reflection suppression of the local oscillator signal and low-loss transmission of RF and IF signals. The local oscillator end filter 80 employs a low-pass filter microstrip circuit to achieve low-loss transmission of local oscillator and IF signals and total reflection suppression of the RF signal. The IF end filter 120 employs a microstrip notch filter circuit to achieve open-circuit total reflection suppression of the local oscillator signal and low-loss transmission of the IF signal.
[0049] For example, the RF filter 50, the IF filter 120, and the local oscillator filter 80 can be bandpass, lowpass, highpass, or bandstop filters.
[0050] Parallel-coupled microstrip line bandpass filters consist of parallel-arranged microstrip lines and utilize electromagnetic field coupling to achieve bandpass characteristics, making them suitable for microwave integrated circuits. During design, transmission zeros can be optimized using ADS software to improve out-of-band rejection. Edge-coupled microstrip line filters achieve strong coupling through the close arrangement of microstrip lines at their edges, commonly used in compact designs. Multi-zero topologies can be employed to enhance frequency selectivity. Stepped-impedance microstrip line filters utilize impedance steps of microstrip lines of varying widths to generate transmission zeros, helping to improve passband flatness and out-of-band rejection. Cross-coupled microstrip line filters introduce cross-coupling structures to generate additional zeros in the transmission characteristics, improving out-of-band rejection and transition steepness. Stub-loaded microstrip line filters, including open-circuit or short-circuit stubs, are used to achieve low-pass or high-pass characteristics, with frequency response controlled by adjusting the stub length and position.
[0051] For example, the RF filter 50, the IF filter 120, and the local oscillator filter 80 can be fan-shaped filter structures, which have the advantages of compact structure and low loss.
[0052] In this embodiment, by setting filters at the RF end, local oscillator end, and intermediate frequency end respectively, total reflection suppression of the local oscillator signal and low-loss transmission of RF and intermediate frequency signals can be achieved.
[0053] In some embodiments, the DC blocking capacitor 90 is a metal-dielectric capacitor or a coupling capacitor.
[0054] In this embodiment, the DC blocking capacitor 90 is a MIM (metal-dielectric-metal) capacitor or a coupling capacitor to achieve low-loss transmission of the local oscillator signal and isolation of the intermediate frequency signal.
[0055] In this embodiment, by setting DC blocking capacitors at the local oscillator end and the intermediate frequency end, low-loss transmission of the local oscillator signal and isolation of the intermediate frequency signal can be achieved.
[0056] In some embodiments, the parallel short-circuit stub 40 is a ground wire connected in parallel to the radio frequency signal transmission line.
[0057] In this embodiment, the parallel short-circuit stub 40 is a ground stub connected in parallel to the radio frequency signal transmission line. The ground stub behaves as an open circuit at the radio frequency, ensuring low-loss transmission of the radio frequency signal, while providing a current loop to ground for the intermediate frequency signal.
[0058] In some embodiments, the RF coplanar waveguide interface 20 and the local oscillator coplanar waveguide interface 110 are both GSG pads of a grounded coplanar waveguide structure. The IF coplanar waveguide interface 130 is a GSG pad.
[0059] In this embodiment, the RF coplanar waveguide interface 20 uses GSG pads with a grounded coplanar waveguide structure to achieve low-loss transmission of RF signals. The local oscillator coplanar waveguide interface 110 uses GSG pads with a grounded coplanar waveguide structure to achieve low-loss transmission of local oscillator signals. The intermediate frequency coplanar waveguide interface 130 uses ground-signal-ground pads to meet the requirements for on-chip testing and screening.
[0060] For example, the RF coplanar waveguide interface 20 may include a first RF input port ground point, an RF input port signal point, and a second RF input port ground point. The first RF input port ground point, the RF input port signal point, and the second RF input port ground point form a coplanar waveguide. The RF input port signal point is connected to the input terminal of the RF impedance matching circuit. The first RF input port ground point and the second RF input port ground point are grounded through a grounding via.
[0061] For example, the local oscillator coplanar waveguide interface 110 includes a first local oscillator input port grounding point, a local oscillator input port signaling point, and a second local oscillator input port grounding point. The first local oscillator input port grounding point, the local oscillator input port signaling point, and the second local oscillator input port grounding point form a coplanar waveguide. The local oscillator input port signaling point is connected to the output terminal of the local oscillator end second impedance matching circuit 100. The first local oscillator input port grounding point and the second local oscillator input port grounding point are grounded through a grounding via.
[0062] By forming a coplanar waveguide from the grounding point of the first local oscillator input port, the signal point of the local oscillator input port, and the grounding point of the second local oscillator input port, the stability and efficiency of signal transmission can be effectively improved. The coplanar waveguide structure helps reduce interference and loss during signal transmission, ensuring high-quality transmission of the local oscillator signal. The signal point of the local oscillator input port is connected to the output of the second impedance matching circuit 100 at the local oscillator end. This connection method allows the local oscillator signal to be accurately transmitted to the second impedance matching circuit 100 at the local oscillator end, providing a stable local oscillator signal source for subsequent signal processing.
[0063] The grounding points of the first and second local oscillator input ports are connected to ground via grounding vias. A well-designed grounding system effectively suppresses electromagnetic interference and improves the circuit's anti-interference capability. Grounding provides a stable reference potential for the signal, preventing fluctuations caused by external interference, thus ensuring the normal operation of the entire circuit system and improving the reliability and stability of the equipment.
[0064] For example, the intermediate frequency (IF) port includes a first IF output port ground point, an IF output port signal point, and a second IF output port ground point. The first IF output port ground point, the IF output port signal point, and the second IF output port ground point form a coplanar waveguide. The IF output port signal point is connected to the output terminal of the IF-end filter 120. The first IF output port ground point and the second IF output port ground point are grounded through a grounding via.
[0065] By forming a coplanar waveguide from the grounding point of the first intermediate frequency (IF) output port, the signal grounding point of the IF output port, and the grounding point of the second IF output port, the IF signal can be effectively transmitted, reducing signal loss and interference during transmission. The coplanar waveguide structure has good electromagnetic characteristics, which is beneficial for improving signal transmission quality. Connecting the signal grounding point of the IF output port to the output of the IF filter 120 allows for signal filtering, removing unwanted high-frequency components and resulting in a purer output IF signal. Furthermore, the grounding points of the first and second IF output ports are connected via grounding vias, providing excellent grounding performance, further enhancing circuit stability, reducing the impact of electromagnetic interference on signal transmission, and thus improving the overall system performance and reliability.
[0066] The coplanar waveguide in this embodiment helps optimize the transmission characteristics of radio frequency signals. The coplanar waveguide structure reduces signal loss and interference during transmission, improving the stability and efficiency of radio frequency signal transmission. Furthermore, by employing a GSG interface, performance indicators such as device frequency conversion loss can be directly tested and screened on-chip, improving circuit testability and testing efficiency, which is beneficial for mass production of devices.
[0067] In some embodiments, the substrate 200 is a gallium arsenide substrate.
[0068] In this embodiment, the substrate 200 uses gallium arsenide of appropriate thickness. This avoids the generation of surface wave modes within the operating frequency range, reducing transmission losses in the terahertz band microstrip line, while also ensuring the substrate's stress resistance and circuit reliability. Furthermore, the gallium arsenide microstrip circuit design, compared to the suspended microstrip circuits used in traditional terahertz mixers, results in a shorter transmission signal wavelength, which is more conducive to reducing circuit size and achieving system miniaturization. Additionally, the use of a thicker gallium arsenide substrate and a reasonable chip aspect ratio enhances the circuit's stress resistance during production and use, improving circuit reliability.
[0069] In this embodiment, a submillimeter-wave (above 300GHz) second harmonic mixer with low conversion loss was realized using mature gallium arsenide monolithic integrated circuit technology. Compared with existing hybrid integrated mixer technologies for this band, components such as Schottky diodes, metal-dielectric-metal capacitors, microstrip lines, and grounding vias are integrated on a single gallium arsenide substrate, which improves integration density, reduces assembly difficulty, and enhances the consistency of electrical performance.
[0070] To verify the performance of the terahertz mixer provided by this invention, this invention provides a structure for a 340GHz monolithic integrated second harmonic mixer, such as... Figure 2 As shown, specifically: The substrate 200 uses gallium arsenide with a thickness of 50 μm.
[0071] The radio frequency coplanar waveguide interface 20 includes a grounding point 21, a signal point 22, a grounding point 23, a grounding via 24, a grounding via 25, and a coplanar waveguide signal line 26. The insertion loss of the radio frequency interface is reduced through reasonable size design.
[0072] The RF impedance matching circuit 30 is composed of three high and low impedance microstrip lines 31 to expand the matching bandwidth and reduce frequency conversion loss.
[0073] The parallel short-circuit stub line 40 includes a metal microstrip line 42 and a grounding via 41, realizing low-loss transmission of radio frequency signals and a current loop for intermediate frequency signals.
[0074] The RF end filter 50 includes a microstrip line 51 and a fan-shaped line 52. The fan-shaped line 52 realizes the resonant short circuit of the local oscillator signal, so that the local oscillator signal from the local oscillator end is totally reflected, while ensuring low-loss transmission of RF and intermediate frequency signals.
[0075] The reverse parallel diode pair 60 uses gallium arsenide Schottky diode technology and an optimized device structure to achieve low parasitic parameters and high cutoff frequency.
[0076] The first impedance matching circuit 70 at the local oscillator terminal uses three high- and low-impedance microstrip lines for broadband matching.
[0077] The local oscillator end filter 80 adopts a step impedance low-pass filter to achieve low-loss transmission of local oscillator and intermediate frequency signals and total reflection suppression of radio frequency signals.
[0078] The DC blocking capacitor 90 uses a MIM metal-dielectric-metal capacitor to achieve local oscillator pass and intermediate frequency block.
[0079] The second impedance matching circuit 100 at the local oscillator terminal uses two matching microstrip lines.
[0080] The local oscillator coplanar waveguide interface 110 includes a grounding pressure point 111, a signal pressure point 112, a grounding pressure point 113, a grounding through hole 114, and a grounding through hole 115. The insertion loss of the local oscillator interface is reduced through reasonable size design.
[0081] The intermediate frequency filter 120 includes a quarter-wavelength microstrip line 121, a fan-shaped line 122, and a microstrip line 123. The fan-shaped line 122 is short-circuited at the local oscillator frequency and converted into an open circuit by the microstrip line 121, realizing open-circuit total reflection of the local oscillator signal while ensuring the transmission of the intermediate frequency signal.
[0082] The intermediate frequency coplanar waveguide interface 130 includes a grounding pressure point 131, a signal pressure point 132, a grounding pressure point 133, a grounding via 134, and a grounding via 135, which meet the on-chip testing requirements of the device.
[0083] The final dimensions of the entire mixer are 1.6mm*0.7mm*0.05mm.
[0084] use Figure 2 The terahertz mixer in the image, with a local oscillator input of 170 GHz and a power of 4 mW, performs well in the 330~355 GHz range, such as Figure 3 As shown, the single-sideband conversion loss is approximately 9dB; Figure 4 As shown, the VSWR of the RF port voltage is less than 3; Figure 5 As shown, the VSWR at the intermediate frequency port is less than 1.6. Furthermore, when the input power is 4mW, as... Figure 6As shown, the local oscillator port VSWR is less than 2.2 in the 160~180GHz range. This invention realizes a miniaturized, highly integrated, low-conversion-loss second harmonic mixer suitable for mass production in the 330~355GHz range.
[0085] This application embodiment utilizes mature gallium arsenide monolithic integrated circuit technology to realize a submillimeter-wave low-conversion-loss second harmonic mixer. Compared with existing hybrid integrated mixer technologies in this band, components such as Schottky diodes, metal-dielectric-metal capacitors, microstrip lines, and grounding vias are integrated onto a single gallium arsenide substrate, improving integration density, reducing assembly difficulty, and enhancing the consistency of electrical performance. The use of a thicker gallium arsenide substrate and a reasonable chip aspect ratio enhances the circuit's stress resistance during production and use, improving circuit reliability. Furthermore, the input and output ports employ coplanar waveguide interfaces, allowing for direct on-chip testing and screening of performance indicators such as conversion loss, improving circuit testability and testing efficiency, and facilitating mass production of the device.
[0086] In this embodiment, the radio frequency (RF) signal passes through an RF GSG interface, an RF impedance matching circuit, a parallel short-circuit stub, and an RF filter to one end of a reverse parallel diode pair. The local oscillator (LO) signal passes through a LO GSG interface, a LO impedance matching circuit, an isolation capacitor, and a LO filter to the other end of the reverse parallel diode pair. The two signals are mixed using the reverse parallel diode pair to achieve second harmonic mixing. The resulting intermediate frequency (IF) signal is then output to the IF GSG interface via an IF filter. This invention enables a low-conversion-loss, submillimeter-wave monolithically integrated second harmonic mixer with advantages of miniaturization, high integration, and suitability for mass production.
[0087] Furthermore, by employing a series connection of a parallel short-circuit stub, an RF end filter, and a reverse parallel diode pair, the parallel short-circuit stub and the RF end filter provide a virtual ground for the reverse parallel diode pair, thereby eliminating the parasitic resistance and inductance of the physical ground and further increasing the frequency of the terahertz mixer.
[0088] Secondly, the present invention also provides a communication device, which includes any of the above-mentioned terahertz mixers.
[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A terahertz mixer, characterized in that, The device includes a substrate, and a radio frequency coplanar waveguide interface, a radio frequency impedance matching circuit, a parallel short-circuit stub, a radio frequency filter, a pair of reverse parallel diodes, a local oscillator first impedance matching circuit, a local oscillator filter, a DC blocking capacitor, a local oscillator second impedance matching circuit, and a local oscillator coplanar waveguide interface disposed on the substrate and connected in sequence. The output terminal of the local oscillator filter and the input terminal of the DC blocking capacitor are connected to one end of the intermediate frequency filter, and the other end of the intermediate frequency filter is connected to the intermediate frequency coplanar waveguide interface. The radio frequency coplanar waveguide interface, the radio frequency end impedance matching circuit, the parallel short-circuit stub, and the radio frequency end filter are used to transmit the radio frequency signal to one end of the anti-parallel diode pair; the local oscillator end coplanar waveguide interface, the local oscillator end second impedance matching circuit, the DC blocking capacitor, the local oscillator end filter, and the local oscillator end first impedance matching circuit are used to transmit the local oscillator signal to the other end of the anti-parallel diode pair; The reverse parallel diode pair is used to perform second harmonic mixing of the received radio frequency signal and local oscillator signal to generate an intermediate frequency signal; the intermediate frequency end filter and the intermediate frequency coplanar waveguide interface are used to transmit the intermediate frequency signal.
2. The terahertz mixer as described in claim 1, characterized in that, The RF impedance matching circuit, the first impedance matching circuit at the local oscillator end, and the second impedance matching circuit at the local oscillator end are all composed of microstrip lines.
3. The terahertz mixer as described in claim 1, characterized in that, The reverse parallel diode pair includes a first diode and a second diode; The anode of the first diode is connected to the cathode of the second diode, and the cathode of the first diode is connected to the anode of the second diode; the anode of the first diode serves as the input terminal of the anti-parallel diode pair, and the cathode of the first diode serves as the output terminal of the anti-parallel diode pair.
4. The terahertz mixer as described in claim 1, characterized in that, The RF filter, the IF filter, and the local oscillator filter are all composed of microstrip lines.
5. The terahertz mixer as described in claim 1, characterized in that, The DC blocking capacitor is a metal dielectric capacitor or a coupling capacitor.
6. The terahertz mixer as described in claim 1, characterized in that, The parallel short-circuit stub is a grounding wire connected in parallel to the radio frequency signal transmission line.
7. The terahertz mixer as described in claim 1, characterized in that, Both the radio frequency coplanar waveguide interface and the local oscillator coplanar waveguide interface are GSG pads with a grounded coplanar waveguide structure.
8. The terahertz mixer as described in claim 7, characterized in that, The intermediate frequency coplanar waveguide interface is a GSG pad.
9. The terahertz mixer according to any one of claims 1-8, characterized in that, The substrate is a gallium arsenide substrate.
10. A communication device, characterized in that, The communication device includes the terahertz mixer as described in any one of claims 1-9.