A circuit structure of a high-frequency terahertz receiving front end

Abstract

The present invention discloses a circuit structure of a high-frequency band terahertz receiving front end, wherein the circuit structure of the terahertz receiving front end includes a frequency mixing structure, a frequency multiplication structure and an output end DC / IF pad, wherein the frequency multiplier structure includes a local oscillator input probe, a first low-pass filter, a first transmission line, and a nonlinear Schottky diode pair structure connected in sequence; the frequency mixing structure includes: a radio frequency receiving end, a Schottky diode, a matching circuit, and a second low-pass filter, wherein the radio frequency receiving end receives an external terahertz signal, and the output end DC / IF pad feeds a DC bias; the local oscillator signal frequency multiplied by the single-stage nine-frequency multiplication structure is mixed with the received terahertz signal through the frequency mixing structure through the matching circuit, and finally filtered through a low-pass filter, and then output by the DC / IF pad. The terahertz high-frequency band receiving front end designed by the present invention has a simple structure, high integration, high conversion gain, and low noise and power consumption.

Description

Technical Field

[0001] The present invention relates to the field of terahertz technology, and in particular to a circuit structure of a high-frequency band terahertz receiving front end. Background Art

[0002] Terahertz waves (0.1-10THz) are the transitional region between macroscopic electronics and microscopic optics. They are the only remaining frequency band in the electromagnetic spectrum that has not been fully developed. Due to its location, its research theory lies between mature microwave electronics theory and optical theory, combining the advantages of both and showing many superior properties. Terahertz technology has very important academic and application value in defense and military, biomedicine, astronomy and meteorology, wireless communications and other related fields.

[0003] Due to the penetrability, safety, transient and other characteristics of terahertz waves, it has great advantages in detection technology. High sensitivity, high integration, low noise, and integration of amplitude, phase, and polarization information detection will be the key issues to be studied and broken through. Although terahertz detection technology has been developed in China, most of them are in a relatively low-frequency band, and due to the constraints of incomplete diode models and insufficient driving source power, the power, gain, noise, power consumption and other performances are relatively poor. At present, my country does not have detection technology above 800GHz in the terahertz high frequency band. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the high-frequency band terahertz receiving front end in the prior art has poor integration, low gain and high loss, and lacks an efficient and low-noise high-frequency band terahertz source. The purpose is to provide a circuit structure of a high-frequency band terahertz receiving front end. The present invention designs a low-noise and high-efficiency terahertz high-frequency band receiving front end in the terahertz high frequency band above 800GHz. The signal source is mixed with a local oscillator signal that has been multiplied by nine times the frequency to complete terahertz higher frequency band signal demodulation. The terahertz high-frequency band receiving front end designed by the present invention has a simple structure, high integration, low noise and loss, and high gain.

[0005] The present invention is achieved through the following technical solutions:

[0006] A circuit structure of a high-frequency band terahertz receiving front end, the circuit structure of the receiving front end includes a mixing structure, a frequency doubling structure and an output end, the frequency doubling structure includes a local oscillator input probe, a first low-pass filter and a first transmission line connected in sequence, and also includes a nonlinear Schottky diode pair structure, the nonlinear Schottky diode pair structure adopts a single-stage co-directional parallel structure, and uses nine times the frequency for the input local oscillator signal to obtain a high-frequency band terahertz base wave; the nonlinear Schottky diode pair structure is arranged on both sides of the first transmission line, and a single-stage nine times the frequency is adopted to reduce noise and improve integration; both sides of the nonlinear Schottky diode pair structure (i.e., the Schottky diode pair connected in parallel in the same direction) are connected to ground ports, and components such as impedance and capacitance are not connected, so that the Schottky diode pair performs nonlinear work according to the input signal source to reduce noise;

[0007] The mixing structure includes a radio frequency receiving end, a Schottky diode, a ground port, a matching circuit, and a second low-pass filter, wherein the first low-pass filter is connected to the matching circuit via a first transmission line, the matching circuit is connected to the anode of the Schottky diode, and the cathode of the Schottky diode is connected to the ground port; the radio frequency receiving end is connected to the anode of the Schottky diode, and the radio frequency receiving end is also connected to the second low-pass filter;

[0008] It also includes an output end, which is connected to the second low-pass filter; the local oscillator input probe is externally connected to an input waveguide, the radio frequency receiving end is connected to an external terahertz signal, and the output end is connected to a DC diode bias voltage and an external output waveguide through an IF / DC pad.

[0009] The working principle is:

[0010] The circuit structure of the terahertz receiving front end of the present invention is realized by combining a frequency doubling structure and a frequency mixing structure. The frequency mixing structure adopts a simple structure optimization design because of the high-frequency characteristics of terahertz. First, a low-frequency waveguide signal is input through a local oscillator input probe and filtered through a first low-pass filter; the filtered signal passes through a nonlinear Schottky diode pair structure to obtain a signal with a nine-fold harmonic component. The nonlinear Schottky diode pair structure is connected to the ground in parallel. This structure reduces the coupling effect and reduces noise; secondly, the signal is filtered through a matching circuit and matches the mixer impedance. The nine-fold terahertz fundamental wave is mixed with the received terahertz signal through a parallel grounded Schottky diode, filtered through a second low-pass filter, and finally a demodulated signal is obtained and output. Specifically:

[0011] By feeding the DC bias into the IF / DC pad at the output end, the bias working voltage is loaded to the Schottky diodes in parallel on both sides through the first transmission line, and the input fundamental signal is coupled to the center through the nonlinear Schottky diode in the bias state to form an output signal with a nine-fold frequency harmonic component; the stray signals outside the nine-fold frequency are filtered again through the matching circuit and the mixer impedance is matched. The high-frequency band output signal of the nine-fold frequency harmonic component is obtained. Similarly, by feeding the DC bias into the IF / DC pad at the output end, the Schottky diode in the mixing structure is in a working bias state, and the terahertz receiving signal and the fundamental signal are mixed by the Schottky diode to form a nonlinear wave, and finally other harmonics are filtered out by the second low-pass filter to output the demodulated spectrum of RF-LO.

[0012] The nonlinear Schottky diode pair structure of the nine-fold frequency multiplication adopts a structure of parallel connection in the same direction, the bias circuit loading is relatively flexible, the structure is simple, the noise coupling is reduced, the loss is low, and the overall processing and assembly requirements are relatively low; the Schottky diode pair of the nonlinear Schottky diode pair structure is grounded on both sides respectively, and is not connected to other related electronic devices to reduce noise interference and delay effects caused by other devices; the Schottky diode bias DC source of the frequency doubling structure and the mixing structure of the present invention is fed in through the output end, the structure is simple, easy to integrate, and noise is reduced.

[0013] The present invention designs a low-noise and high-efficiency terahertz high-frequency band receiving front end above 800GHz. The signal source is mixed with a local oscillator signal that has been nine times the frequency to complete terahertz higher frequency band signal demodulation. The terahertz high-frequency band receiving front end designed by the present invention has a simple structure, high integration, and low noise and loss.

[0014] Preferably, the input signal frequency of the local oscillator input probe is 94 GHz.

[0015] Preferably, the nonlinear Schottky diode pair structure includes a first Schottky diode and a second Schottky diode, one side of the first transmission line is connected to the anode of the first Schottky diode, the other side of the first transmission line is connected to the anode of the second Schottky diode, and the cathode of the first Schottky diode and the cathode of the second Schottky diode are both connected to the ground port.

[0016] Preferably, the first Schottky diode and the second Schottky diode are both Schottky diodes with high frequency characteristics.

[0017] Preferably, the first Schottky diode and the second Schottky diode in the nonlinear Schottky diode pair structure are directly grounded.

[0018] Preferably, the diameters of the first Schottky diode and the second Schottky diode are both as small as 1 μm, thereby improving the frequency characteristics.

[0019] Preferably, the first low-pass filter, the second low-pass filter and the matching circuit are all in the form of high-low impedance lines.

[0020] Preferably, the circuit structure of the receiving front end is manufactured by GaAs compound semiconductor technology, and uses a GaAs substrate with a higher dielectric constant and better performance.

[0021] Preferably, the DC diode bias voltage is applied to the output end, that is, fed in through the DC / IF pad, that is, the bias voltage is fed in by the DC / IF pad. This structure can reduce coupling and noise interference.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] 1. Based on the high-frequency characteristics of terahertz, the present invention adopts an optimized design for both the frequency mixing and frequency doubling structure Schottky diodes, so that the bias voltage input terminal is flexible in design and simple in structure; the frequency doubler adopts a single-stage nine-fold frequency form, the Schottky diode pair adopts a co-directional parallel structure, and the frequency mixing structure Schottky diodes are connected in parallel to the ground structure, so that the bias DC end can be directly loaded through the output end, reducing the complexity of the mechanism, lowering noise interference, and lowering losses, which is suitable for the high-frequency band characteristics of terahertz.

[0024] 2. The present invention designs a terahertz technology receiving front-end circuit structure with high gain, low noise and low loss in the terahertz high frequency band through the integrated frequency doubling and mixing structure circuit optimization design; the circuit structure of the receiving front end includes a mixing structure, a frequency doubling structure and an output end. The frequency doubling structure adopts a single-stage nine-fold frequency form, based on the same-direction parallel structure of Schottky diodes, and is directly connected to the ground on both sides to reduce noise; the Schottky diode of the mixing structure adopts a parallel connection structure, is directly connected to the ground, and is connected to the frequency doubling structure through a matching circuit. The DC bias is loaded on the output end. Due to the presence of a low-pass filter, the high-frequency AC signal will not interfere with the DC voltage.

[0025] 3. The circuit structure of the terahertz high-frequency band receiving front end of the present invention has high gain, low noise, low loss, simple structure, easy integration and assembly, and is suitable for high-frequency bands above ~800 GHz. The simulation results verify the high gain and low noise characteristics of the terahertz receiving front end of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0027] Figure 1 This is a circuit structure diagram of a high-frequency terahertz receiving front end of the present invention.

[0028] Figure 2 This is a circuit structure design diagram of a high-frequency terahertz receiving front end of the present invention.

[0029] Figure 3 This is a simulation result diagram of the present invention.

[0030] Marks and corresponding parts names in the attached drawings:

[0031] 1-local oscillator input probe, 2-first low-pass filter, 3-first transmission line, 4-nonlinear Schottky diode pair structure, 40-first Schottky diode, 41-second Schottky diode, 5-RF receiving end, 6-Schottky diode, 7-matching circuit, 8-second low-pass filter. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0033] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other instances, well-known structures, circuits, materials, or methods are not specifically described in order to avoid obscuring the present invention.

[0034] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0036] Example

[0037] like Figures 1 to 3 As shown, the present invention provides a circuit structure of a high-frequency band terahertz receiving front end, the circuit structure of the receiving front end includes a mixing structure, a frequency doubling structure and an output end, the frequency doubling structure includes a local oscillator input probe 1, a first low-pass filter 2 and a first transmission line 3 connected in sequence, and also includes a nonlinear Schottky diode pair structure 4, the nonlinear Schottky diode pair structure 4 adopts a single-stage co-directional parallel structure, and uses nine times the frequency for the input signal to obtain a high-frequency band terahertz base wave; the nonlinear Schottky diode pair structure 4 is arranged on both sides of the first transmission line 3, and in order to reduce noise and improve integration, a single-stage nine times the frequency is adopted; both sides of the nonlinear Schottky diode pair structure 4 (i.e., the Schottky diode pair connected in parallel in the same direction) are connected to ground ports, and components such as impedance and capacitance are not connected, so that the Schottky diode pair works nonlinearly according to the input signal source, thereby reducing noise;

[0038] The mixing structure includes a radio frequency receiving end 5, a Schottky diode 6, a ground port, a matching circuit 7, and a second low-pass filter 8. The first low-pass filter 2 is connected to the matching circuit 7 through a first transmission line 3. The matching circuit 7 is connected to the positive electrode of the Schottky diode 6, and the negative electrode of the Schottky diode 6 is connected to the ground port; the radio frequency receiving end 5 is connected to the positive electrode of the Schottky diode 6, and the radio frequency receiving end 5 is also connected to the second low-pass filter 8;

[0039] The device also includes an output terminal, which is connected to the second low-pass filter 8; the local oscillator input probe 1 is externally connected to an input waveguide, the radio frequency receiving terminal 5 is connected to an external terahertz signal, and the output terminal is connected to a DC diode bias voltage and an external output waveguide through an IF / DC pad. The DC / IF pad of the output terminal is fed with a DC bias and outputs a signal.

[0040] As a further preferred solution, the input signal frequency of the local oscillator input probe 1 is 94 GHz.

[0041] As a further preferred scheme, the nonlinear Schottky diode pair structure 4 includes a first Schottky diode 40 and a second Schottky diode 41, one side of the first transmission line 3 is connected to the positive electrode of the first Schottky diode 40, and the other side of the first transmission line 3 is connected to the positive electrode of the second Schottky diode 41, and the negative electrode of the first Schottky diode 40 and the negative electrode of the second Schottky diode 41 are both connected to the ground port.

[0042] As a further preferred solution, the first Schottky diode 40 and the second Schottky diode 41 are both Schottky diodes with high frequency characteristics.

[0043] As a further preferred solution, the first Schottky diode 40 and the second Schottky diode 41 in the nonlinear Schottky diode pair structure 4 are directly grounded.

[0044] As a further preferred solution, the diameters of the first Schottky diode 40 and the second Schottky diode 41 are both as small as 1 μm, thereby improving the frequency characteristics.

[0045] As a further preferred solution, the first low-pass filter 2, the second low-pass filter 8, and the matching circuit 7 are all in the form of high-low impedance lines.

[0046] As a further preferred solution, the circuit structure of the receiving front end is manufactured by GaAs compound semiconductor technology, and uses a GaAs substrate with a higher dielectric constant and better performance.

[0047] As a further preferred solution, the DC diode bias voltage is applied to the output end, that is, applied through the DC / IF pad, that is, the bias voltage is fed in by the DC / IF pad. This structure can reduce coupling and noise interference.

[0048] The working principle is:

[0049] The circuit structure of the terahertz receiving front end of the present invention is realized by combining a frequency doubling structure and a frequency mixing structure. The frequency mixing structure adopts a simple structure optimization design because of the high-frequency characteristics of terahertz. First, a low-frequency waveguide signal is input through a local oscillator input probe 1, and filtered through a first low-pass filter 2; the filtered signal passes through a nonlinear Schottky diode pair structure 4, and the nonlinear Schottky diode pair structure 4 is in the form of parallel connection to the ground. This structure reduces the coupling effect, reduces noise, and obtains a high-frequency signal; secondly, the high-frequency signal passes through a matching circuit 7 to mix the nine-fold terahertz fundamental wave with the received terahertz signal through a parallel grounded Schottky diode, and is filtered through a second low-pass filter 8, and finally a demodulated signal is obtained and output. Specifically:

[0050] By feeding the DC bias into the IF / DC pad at the output end, the bias working voltage is loaded to the Schottky diodes in parallel on both sides through the first transmission line 3, and the input fundamental wave signal is coupled to the center through the nonlinear Schottky diode in the bias state to form an output signal with nine times the frequency harmonic component; and filtering and impedance matching are performed again through the matching circuit 7. An output signal with high-frequency harmonic components is obtained. Similarly, by feeding the DC bias into the IF / DC pad at the output end, the Schottky diode in the mixing structure is in a working bias state, and the terahertz receiving signal and the fundamental wave signal are mixed through the Schottky diode to form a nonlinear wave, and finally other harmonics are filtered out through the second low-pass filter 8 to output the demodulated spectrum of RF-LO.

[0051] The nonlinear Schottky diode pair structure 4 of the nine-fold frequency multiplication adopts a structure of parallel connection in the same direction, the bias circuit loading is relatively flexible, the structure is simple, the noise coupling is reduced, and the overall processing and assembly requirements are relatively low; the Schottky diode pair of the nonlinear Schottky diode pair structure 4 is grounded on both sides respectively, and is not connected to other related electronic devices to reduce noise interference and delay effects caused by other devices; the Schottky diode bias DC source of the frequency doubling structure and the mixing structure of the present invention is fed in through the output end, the structure is simple, easy to integrate, and noise is reduced.

[0052] The present invention designs a low-noise and high-efficiency terahertz high-frequency band receiving front end above 800GHz. The signal source is mixed with a local oscillator signal that has been nine times the frequency to complete terahertz higher frequency band signal demodulation. The terahertz high-frequency band receiving front end designed by the present invention has a simple structure, high integration, and low noise and loss.

[0053] When implementing: the circuit structure diagram is as follows Figure 1 As shown, in order to increase the design efficiency and reduce the processing difficulty, and because a GaAs substrate with a higher dielectric constant is used, the disadvantage of the large size of the high and low impedance lines can be compensated to a certain extent, so the first low-pass filter 2, the second low-pass filter 8 and the matching circuit 7 in the design of the present invention (the traditional high and low impedance line form is adopted, and the low-pass filter can prevent the high-order harmonics generated by the subsequent diode frequency doubling from leaking to the input end in addition to filtering.)

[0054] The working process is as follows: the input waveguide inputs the LO fundamental wave through the local oscillator input probe 1, and the fundamental wave is filtered through the first low-pass filter 2 to remove the stray frequency signal and form a signal with a relatively single frequency. The center is coupled through the biased Schottky diodes connected in parallel in the same direction to form a nonlinear wave with nine times the frequency harmonic component. Through the matching circuit 7, other stray frequency signals are filtered out and the impedance is matched with the mixing structure. In the mixing structure, the RF receiving end 5 receives the high-frequency terahertz spectrum carrying the signal, and mixes the LO fundamental wave signal input from the matching circuit 7 through the nonlinear device Schottky diode 6 to obtain a nonlinear spectrum with RF-LO harmonic components, and then through the second low-pass filter 8, the demodulated signal of the RF-LO harmonic component is obtained and output from the output end and the DC / IF pad.

[0055] The present invention designs a low-noise and high-efficiency terahertz high-frequency band circuit receiving front end, which is based on a nine-fold frequency structure of a single-stage Schottky diode in parallel in the same direction and a mixing structure connected to the ground in parallel. The bias voltages of the Schottky diodes in the frequency-doubling structure and the mixing structure are fed from the output end of the DC / IF pad. The terahertz high-frequency band receiving front end circuit has a simple structure and high integration, and can be used in higher frequency bands.

[0056] According to the circuit simulation, the results are as follows Figure 3 As shown in Table 1, Figure 3 (a) is the conversion gain; (b) is the noise temperature table; the simulation results are: in the range of 830GHz-870GHz, the conversion gain is 25dB-40dB; the noise temperature is 5700K-5800K, and the minimum value is 5700K at 830GHz.

[0057] Table 1 Simulation test results

[0058] Intrinsic input power 94GHz (dBm) 30 RF input power 850GHz (dBm) -30 Conversion gain(dB) 25-40 Temperature noise (T) 5700-5800

[0059] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A circuit structure of a high-frequency terahertz receiving front end, characterized in that: The circuit structure of the receiving front end comprises a frequency mixing structure, a frequency multiplication structure and an output end, wherein the frequency multiplication structure comprises a local oscillator input probe (1), a first low-pass filter (2) and a first transmission line (3) connected in sequence, and further comprises a nonlinear Schottky diode pair structure (4), wherein the nonlinear Schottky diode pair structure (4) adopts a single-stage co-directional parallel structure, wherein the nonlinear Schottky diode pair structure (4) is arranged on both sides of the first transmission line (3), and both sides of the nonlinear Schottky diode pair structure (4) are connected to ground ports; The mixing structure comprises a radio frequency receiving end (5), a Schottky diode (6), a ground port, a matching circuit (7), and a second low-pass filter (8); the first low-pass filter (2) is connected to the matching circuit (7) via a first transmission line (3); the matching circuit (7) is connected to the positive electrode of the Schottky diode (6); and the negative electrode of the Schottky diode (6) is connected to the ground port; the radio frequency receiving end (5) is connected to the positive electrode of the Schottky diode (6); the radio frequency receiving end (5) is also connected to the second low-pass filter (8); and the second low-pass filter (8) is connected to the output end; The local oscillator input probe (1) is externally connected to an input waveguide, the radio frequency receiving end (5) is connected to an external terahertz signal, and the output end is connected to a DC diode bias voltage and an external output waveguide via an IF / DC pad; The nonlinear Schottky diode pair structure (4) comprises a first Schottky diode (40) and a second Schottky diode (41), one side of the first transmission line (3) is connected to the positive electrode of the first Schottky diode (40), the other side of the first transmission line (3) is connected to the positive electrode of the second Schottky diode (41), and the negative electrode of the first Schottky diode (40) and the negative electrode of the second Schottky diode (41) are both connected to a ground port; The circuit structures of the receiving front end are all made by GaAs compound semiconductor technology.

2. The circuit structure of a high-frequency band terahertz receiving front end according to claim 1, characterized in that: The input signal frequency of the local oscillator input probe (1) is 94 GHz.

3. The circuit structure of a high-frequency band terahertz receiving front end according to claim 1, characterized in that: The first Schottky diode (40) and the second Schottky diode (41) are both Schottky diodes with high frequency characteristics.

4. The circuit structure of a high-frequency band terahertz receiving front end according to claim 1, characterized in that: The first Schottky diode (40) and the second Schottky diode (41) in the nonlinear Schottky diode pair structure (4) are both directly grounded.

5. The circuit structure of a high-frequency band terahertz receiving front end according to claim 1, characterized in that: The diameters of the first Schottky diode (40) and the second Schottky diode (41) are both 1 μm.

6. The circuit structure of a high-frequency band terahertz receiving front end according to claim 1, characterized in that: The first low-pass filter (2), the second low-pass filter (8) and the matching circuit (7) are all in the form of high-low impedance lines.

7. The circuit structure of a high-frequency band terahertz receiving front end according to claim 1, characterized in that: The DC diode bias voltage is applied to the output terminal, ie fed in through the DC / IF pad.

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