Ultrahigh-frequency terahertz wave band signal transmitting system

Abstract

The invention belongs to the field of terahertz detection, and relates to an ultrahigh-frequency terahertz wave band signal transmitting system, which comprises a high-power source, a secondary frequency multiplier, a third frequency multiplier and a first amplifier, and is characterized in that when 500GHz circuit cascade connection is carried out, the high-power source is realized through 36 times of frequency multiplication of * 2 * 3 * 2 * 3; when 1THz circuits are cascaded, a high-power source is realized through 72 times of frequency multiplication of * 2 * 3 * 2 * 2 * 3; wherein 2 is a secondary frequency multiplier, and 3 is a tertiary frequency multiplier; two or three groups of secondary frequency multipliers are arranged according to different output frequencies and are realized through a solid-state semiconductor device based on a solid-state frequency multiplication circuit cascading mode, the secondary frequency multipliers and the tertiary frequency multiplier are selected to amplify a high-power source signal for multiple times so as to meet the required terahertz wave requirement of 500GHz or 1THz, and through the parallel arrangement of the secondary frequency multipliers, the output frequency of the high-power source signal is improved. Noise and performance loss are reduced, the structure is relatively compact, and the antenna can work in a room temperature environment.

Description

Technical Field

[0001] The present application belongs to the field of terahertz detection, and in particular to an ultra-high frequency terahertz band signal transmission system. Background Art

[0002] Terahertz waves can penetrate a variety of dielectric materials and non-polar materials, achieving high-resolution imaging of the interior of opaque objects. At the same time, terahertz photons have low energy and will not cause damage to the sample being measured or the human body.

[0003] The basic principle of terahertz imaging is as follows Figure 1 As shown, it includes a terahertz source, a terahertz transmitting antenna, a target, a terahertz receiving antenna, a detector, a signal processing and a display. The terahertz source outputs terahertz waves through the terahertz transmitting antenna to illuminate the target, and the terahertz waves reflected or transmitted by the target are converged and collected by the terahertz receiving antenna and enter the detector. After signal processing, the image of the target is finally displayed on the display. When performing terahertz imaging on a metal surface, since terahertz waves cannot penetrate, only reflective imaging can be selected.

[0004] When testing cracks on metal surfaces, tests have shown that when the frequency exceeds 430GHz, the location of a 20μm defect can be determined from the imaging results, but due to the low spatial resolution, the boundary of the defect is not clear; as the frequency increases, the boundary of the defect gradually becomes clearer. However, when the frequency exceeds 1.5THz, the emission source signal is sharply weakened, the signal-to-noise ratio deteriorates, and the location of the defect cannot be effectively identified.

[0005] Since the input power and output voltage of the TDS detector are proportional, by reading the original data, the reflectivity of the defect can be approximately calculated to be 78%; when the operating frequency is selected as 500GHz, the focal spot area is about 0.1mm 2 , for a 0.02mm×1mm defect, the proportion is 1 / 5. Compared with a complete target, a target with a defect can reflect about 95.6% of the energy. Therefore, a reasonable design of the radiation resolution of the detector can detect the defect location; similarly, when the operating frequency is 1THz, a target with a defect can reflect about 85.3% of the energy.

[0006] Therefore, the current options for accurate and convenient metal surface defect detection are 500GHz or 1THz terahertz sources. However, for non-destructive detection of submillimeter-level defects, high system resolution is required and the technical difficulty is relatively high. The existing technology has not been able to achieve 500GHz defect detection, and it is impossible to achieve effective metal surface defect detection.

[0007] Therefore, how to effectively perform terahertz detection of defects on metal surfaces is a problem that needs to be solved. Summary of the invention

[0008] The purpose of the present application is to provide an ultra-high frequency terahertz band signal transmission system to solve the problem that it is difficult to achieve ultra-high frequency terahertz band signal transmission in the prior art, that is, it is impossible to effectively detect defects on the metal surface.

[0009] The technical solution of the present application is: an ultra-high frequency terahertz band signal transmission system, comprising a high power source, a secondary frequency multiplier, a tertiary frequency multiplier and a first amplifier; when a 500GHz circuit is cascaded, the high power source is multiplied by ×2×3×2×3 for a total of 36 times; when a 1THz circuit is cascaded, the high power source is multiplied by ×2×3×2×2×3 for a total of 72 times; wherein 2 is a secondary frequency multiplier, 3 is a tertiary frequency multiplier, the output end of the high power source is connected to the first amplifier, and the first amplifier The output end is connected to the secondary frequency multiplier, and the secondary frequency multiplier at the last end is connected to the tertiary frequency multiplier. The secondary frequency multipliers are set in two or three groups according to different output frequencies. When the circuit cascade is performed at 500GHz, two groups of secondary frequency multipliers are set; when the circuit cascade is performed at 1THz, three groups of secondary frequency multipliers are set; when the circuit cascade is performed at 1THz, two groups of secondary frequency multipliers are set in parallel and connected in series with the last group of secondary frequency multipliers; when the circuit cascade is performed at 500GHz, two groups of secondary frequency multipliers are set in parallel.

[0010] Preferably, the high-power source includes a signal source, a first filter, a second amplifier and a power synthesis module. The input signal of the signal source is a microwave signal, and the input signal is amplified 6 times and then enters the first filter for filtering; the output end of the first filter is connected to the second amplifier, and the output end of the second amplifier is connected to the power synthesis module, and the power synthesis module performs power amplification on the input signal of the signal source again.

[0011] Preferably, the power synthesis module comprises a primary power divider, a secondary power divider, a third amplifier, a primary power synthesizer and a secondary power synthesizer; the output end of the second amplifier is connected to the primary power divider, there are two groups of secondary power dividers and both are connected to the output end of the primary power divider, the two groups of secondary power dividers are arranged in parallel, the input signal is split into two identical parts after passing through the primary power divider and are respectively input into the two groups of secondary power dividers; there are four groups of third amplifiers and are arranged at the output end of the secondary power divider, the four groups of third amplifiers are arranged in groups of two, every two groups of third amplifiers are connected to the output end of one group of secondary power dividers, and the two groups of third amplifiers connected to the same secondary power divider are arranged in parallel, the secondary power divider splits the power into two identical parts again after receiving the input signal and inputs them into the two connected groups of third amplifiers; There are two groups of first-level power synthesizers, which are respectively connected to the output ends of four groups of third amplifiers connected in parallel. The two groups of first-level power synthesizers are also arranged in parallel. The second-level power synthesizer is connected to the output ends of the two groups of first-level power synthesizers.

[0012] Preferably, the third frequency multiplier comprises a first input probe, a first output probe, a first diode chip, a second filter and a first output conversion structure; the output end of the first input probe is connected to the first output conversion structure, the output end of the first diode chip is connected to the first output probe, and the output end of the second filter is connected to the first diode chip; there are two first diode chips and the two first diode chips are installed in parallel on a circuit located in a waveguide structure, and the first output conversion structure adopts a suspended microstrip-waveguide transition structure, which contains a suspended microstrip circuit and a rectangular waveguide; one end of the first diode chip is connected to the microstrip circuit, and the other end is connected to the cavity to form an RF / DC ground; the baseband signal is coupled into the suspended microstrip circuit through the first input probe, and high-order harmonics are generated at the first diode chip, and then the first output probe couples the required third harmonic to the rectangular waveguide output.

[0013] Preferably, the secondary frequency multiplier includes a second input probe, a second output probe, a second diode chip, a DC filter and a second output conversion structure, the output end of the second input probe is connected to the second output conversion structure, the output end of the second diode chip is connected to the second output probe, and the output end of the DC filter is connected to the second diode chip; there are two second diode chips and the two second diode chips are installed in reverse series on a circuit with a rectangular waveguide; an external bias circuit is provided to be connected to the DC filter through a gold wire, and the second output conversion structure adopts a suspended microstrip-waveguide transition structure, which contains a suspended microstrip circuit and a rectangular waveguide; the signal in the input rectangular waveguide is fed into the second diode chip, and the correspondingly generated secondary harmonics will be output from the standard rectangular waveguide at the other end along the suspended microstrip circuit after matching and coupling circuits.

[0014] Preferably, the first input probe, the first output probe, the second input probe and the second output probe are all E-plane probes; and the microstrip circuit is a quartz circuit.

[0015] Preferably, the diodes in the secondary frequency multiplier and the tertiary frequency multiplier are both Schottky diodes; the dielectric substrate of the Schottky diode is a GaAs layer with a thickness of 30 µm; the anode pad in the Schottky diode is connected to the cathode through an air bridge finger to form an ohmic contact.

[0016] The ultra-high frequency terahertz band signal transmission system of the present application is realized by solid-state semiconductor devices and based on the cascade of solid-state frequency multiplication circuits. Secondary frequency multipliers and tertiary frequency multipliers are selected to amplify the high-power source signal multiple times to meet the terahertz wave requirements of the required frequency. The parallel setting of secondary frequency multipliers is used to reduce noise and performance loss. The structure is relatively compact and can work in room temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0018] Figure 1 This is the schematic diagram of the 1THz terahertz source solution for this application; Figure 2 This is the schematic diagram of the 85GHz high power source solution for this application; Figure 3 This is the schematic diagram of the unbalanced third frequency multiplier for this application; Figure 4 This is a simplified structural diagram of the balanced secondary frequency multiplier of this application; Figure 5 This is the schematic diagram of the balanced secondary frequency multiplier for this application.

[0019] 1. High power source; 2. Second frequency multiplier; 3. Third frequency multiplier; 4. First amplifier; 5. Signal source; 6. First filter; 7. Second amplifier; 8. Primary power divider; 9. Second power divider; 10. Third amplifier; 11. Primary power combiner; 12. Second power combiner; 13. First input probe; 14. First output probe; 15. First diode chip; 16. Second filter; 17. First output conversion structure; 18. Second input probe; 19. Second output probe; 20. Second diode chip; 21. DC filter; 22. Second output conversion structure. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] An ultra-high frequency terahertz band signal transmission system can realize 500GHz or 1THz terahertz wave signal transmission.

[0022] There are two existing ways to realize terahertz sources, one is an optical method and the other is an electronic method. The optical method is to emit terahertz waves by generating continuous waves through optical frequency mixing quantum cascade lasers or generating pulses through optical rectification of femtosecond laser pulses; the electronic method is to emit terahertz waves through vacuum electronic devices such as traveling wave tubes and echo tubes or solid-state semiconductor devices such as transistors and diodes. Taking into account factors such as complexity, power, development cost, and research foundation, the terahertz source of this application is realized by an electronic method, specifically by solid-state semiconductor devices and based on the cascade of solid-state frequency multiplication circuits. Its structure is relatively compact and can work at room temperature.

[0023] like Figure 1 , the system for solid-state frequency multiplication circuit cascade includes a high power source 1, a secondary frequency multiplier 2, a tertiary frequency multiplier 3 and a first amplifier 4. The high power source 1 uses a high power solid-state source of about 85GHz. Specifically, when the circuit cascade is performed at 500GHz, 83GHz is used, which contains a 6-fold power amplifier. The first-stage double frequency multiplication and the first-stage triple frequency multiplication increase the frequency to 500GHz, that is, the 13.88GHz signal is multiplied by ×2×3×2×3 for a total of 36 times. When the circuit cascade is performed at 1THz, 85GHz is used, which contains a 6-fold power amplifier. The second-stage double frequency multiplication and the first-stage triple frequency multiplication increase the frequency to 1THz. The final 1THz terahertz source scheme is to multiply the 14.16GHz signal by ×2×3×2×2×3 for a total of 72 times. Among them, 2 is the secondary frequency multiplier 2, and 3 is the tertiary frequency multiplier 3.

[0024] For an N-fold frequency multiplier designed based on resistive devices, according to the Page-Pantell inequality, the theoretical conversion efficiency is η = P N / P 1 ≤ 1 / N 2 That is, for the second and third frequency multipliers, the maximum frequency multiplication efficiency that can be achieved in theory is 25% and 11% respectively; for the N-th frequency multiplier designed based on capacitive devices, according to the Manley-Rowe relationship, the maximum conversion efficiency can reach 100% in theory.

[0025] However, due to the losses caused by the series resistance in the device and the peripheral matching filter circuit, the frequency doubling efficiency will be far lower than the maximum theoretical value. In order to ensure sufficient signal-to-noise ratio of the entire system and considering the difficulty of circuit development, the output power indicators of 500GHz and 1THz terahertz sources are 0dBm and -10dBm respectively. With reference to previous research experience, the frequency doubling efficiency is estimated. The indicators of each level of the terahertz source are calculated as shown in Table 1.

[0026] Table 1 Technical parameters of various components of terahertz source Freq(GHz) Frequency Output power (mW) efficiency Remark 83 6 250 ---- With power amplifier 16 2 35 15% 500 3 1 3% Freq(GHz) Frequency Output power (mW) efficiency Remark 85 6 350 ---- With power amplifier 170 2 50 15% Power synthesis 340 2 5 10% 1000 3 0.1 2% like Figure 2 , wherein the high power source 1 includes a signal source 5, a first filter 6, a second amplifier 7 and a power synthesis module. The input signal of the signal source 5 is a microwave signal. After being amplified 6 times, the input signal enters the first filter 6 for filtering to remove clutter; the output end of the first filter 6 is connected to the second amplifier 7 for power amplification.

[0027] The output end of the second amplifier 7 is connected to the power synthesis module, and the power synthesis module performs power amplification on the input signal of the signal source 5 again. However, considering that more noise will be generated after multiple amplifications of the input signal and the series resistance in each device and the peripheral matching filter circuit will produce very large losses, the signal-to-noise ratio is low and the frequency doubling efficiency will be far lower than the theoretical value. Therefore, the present application adopts power synthesis to power amplify the input signal.

[0028] The power synthesis module specifically includes a primary power divider 8, a secondary power divider 9, a third amplifier 10, a primary power synthesizer 11 and a secondary power synthesizer 12. The output end of the second amplifier 7 is connected to the primary power divider 8, and there are two groups of secondary power dividers 9, both of which are connected to the output end of the primary power divider 8. The two groups of secondary power dividers 9 are arranged in parallel, and the input signal is split into two equal parts after passing through the primary power divider 8 and respectively input into the two groups of secondary power dividers 9.

[0029] There are four groups of third amplifiers 10 and they are arranged at the output end of the secondary power divider 9. The four groups of third amplifiers 10 are arranged in pairs. Every two groups of third amplifiers 10 are connected to the output end of one group of secondary power divider 9, and the two groups of third amplifiers 10 connected to the same secondary power divider 9 are arranged in parallel. After receiving the input signal, the secondary power divider 9 splits the power into two identical parts again and inputs them into the two connected groups of third amplifiers 10, completing the secondary power decomposition. There are two groups of first-level power synthesizers 11, which are respectively connected to the output ends of four groups of third amplifiers 10 connected in parallel. The two groups of first-level power synthesizers 11 are also arranged in parallel to achieve first-level power synthesis. The second-level power synthesizer 12 is connected to the output ends of the two groups of first-level power synthesizers 11 to achieve second-level power synthesis.

[0030] At this point, while achieving high-power terahertz signal output, the stability and quality of the signal are guaranteed and noise and loss are reduced.

[0031] The output end of the high power source 1 is connected to the first amplifier 4, the output end of the first amplifier 4 is connected to the secondary frequency multiplier 2, the secondary frequency multiplier 2 at the rear end is connected to the tertiary frequency multiplier 3, and the terahertz wave output by the high power source 1 is power amplified. The secondary frequency multiplier 2 is set in two or three groups according to the output frequency. When a 500 GHz circuit cascade is performed, two groups of secondary frequency multipliers 2 are set; when a 500 GHz circuit cascade is performed, two groups of secondary frequency multipliers 2 are set; when a 1 THz circuit cascade is performed, three groups of secondary frequency multipliers 2 are set.

[0032] When a 1THz circuit is cascaded, two groups of secondary frequency multipliers 2 are arranged in parallel and connected in series with the last group of secondary frequency multipliers 2; when a 500GHz circuit is cascaded, two groups of secondary frequency multipliers 2 are arranged in parallel; the parallel arrangement is used to achieve power decomposition, reduce noise, and improve signal transmission quality.

[0033] Then the secondary frequency multiplier 2 is connected to the tertiary frequency multiplier 3 to achieve frequency multiplication of corresponding ratios.

[0034] like Figure 3 Preferably, the third frequency multiplier 3 adopts an unbalanced circuit structure, and the third frequency multiplier 3 includes a first input probe 13, a first output probe 14, a first diode chip 15, a second filter 16 and a first output conversion structure 17. The output end of the first input probe 13 is connected to the first output conversion structure 17, the output end of the first diode chip 15 is connected to the first output probe 14, and the output end of the second filter 16 is connected to the first diode chip 15. There are two first diode chips 15, and the two first diode chips 15 are installed in parallel on the circuit located in the waveguide structure. The first output conversion structure 17 adopts a suspended microstrip-waveguide transition structure, which contains a suspended microstrip circuit and a rectangular waveguide. One end of the first diode chip 15 is connected to the microstrip circuit, and the other end is connected to the cavity to form an RF / DC ground. The baseband signal is coupled into the suspended microstrip circuit through the first input probe 13, and high-order harmonics are generated at the first diode chip 15, and then the first output probe 14 couples the required third harmonic to the rectangular waveguide output.

[0035] This circuit structure is equivalent to two diode units connected in parallel in the same direction, so it does not have the ability to suppress even harmonics. Since the harmonics are contained outside the loop, the difficulty of circuit matching design is increased. However, this circuit structure can be used in the design of terahertz band multipliers based on discrete devices. It is a feasible solution for developing high-efficiency and high-output power multipliers in the terahertz band. Under the premise of providing an external bias to the diode unit, the process difficulties of the balanced structure are overcome.

[0036] like Figure 4-Figure 5The secondary frequency multiplier 2 adopts a balanced circuit structure, including a second input probe 18, a second output probe 19, a second diode chip 20, a DC filter 21, and a second output conversion structure 22. The output end of the second input probe 18 is connected to the second output conversion structure 22, the output end of the second diode chip 20 is connected to the second input probe 18, and the output end of the DC filter 21 is connected to the second diode chip 20. There are two second diode chips 20, and the two second diode chips 20 are reversely mounted in series on the circuit with a rectangular waveguide.

[0037] The external bias circuit is connected to the DC filter 21 through a gold wire, so that the DC is introduced to provide a bias voltage for the diode unit. The DC filter 21 can prevent the second harmonic from leaking from the external bias circuit. Preferably, the DC filter 21 adopts an H-type filter 6, which has a more compact structure than the high impedance filter 6.

[0038] The second output conversion structure 22 adopts a suspended microstrip-waveguide transition structure, which contains a suspended microstrip circuit and a rectangular waveguide. The signal (TE10 mode) in the input rectangular waveguide is fed into the second diode chip 20, and the corresponding second harmonic (TEM mode) will be output from the standard rectangular waveguide at the other end along the suspended microstrip circuit after matching and coupling circuits. By utilizing the orthogonality of the mode, the isolation between the input and output can be effectively achieved without the need for an external filter 6, which simplifies the circuit and reduces the loss.

[0039] By utilizing the orthogonality of the modes, the isolation between the input and the output can be effectively achieved without the need for an external filter 6, thereby simplifying the circuit and reducing the loss.

[0040] Preferably, the first input probe 13, the first output probe 14, the second input probe 18 and the second output probe 19 are all E-plane probes to ensure signal stability; and the two microstrip circuits are both quartz circuits with high frequency stability.

[0041] The diodes in the second frequency multiplier 2 and the third frequency multiplier 3 are both Schottky diodes. The dielectric substrate of the Schottky diode is a GaAs layer with a thickness of about 30 µm. The anode pad in the Schottky diode is connected to the cathode through an air bridge finger to form an ohmic contact. The design of the air bridge structure can reduce the parasitic capacitance value, which is an influencing parameter of the high-frequency Schottky diode. The air bridge finger is a metal connection between the anode and the anode pad.

[0042] Finally, it should be noted that: the drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other; Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-high frequency terahertz band signal transmission system, characterized in that: The invention comprises a high power source (1), a secondary frequency multiplier (2), a tertiary frequency multiplier (3) and a first amplifier (4); when a 500 GHz circuit is cascaded, the high power source (1) is frequency-multiplied by ×2×3×2×3 for a total of 36 times; when a 1 THz circuit is cascaded, the high power source (1) is frequency-multiplied by ×2×3×2×2×3 for a total of 72 times; wherein 2 is the secondary frequency multiplier (2), 3 is the tertiary frequency multiplier (3), the output end of the high power source (1) is connected to the first amplifier (4), and the output end of the first amplifier (4) is connected to the secondary frequency multiplier ( 2), the secondary frequency multiplier (2) at the rear end is connected to the tertiary frequency multiplier (3), the secondary frequency multiplier (2) is arranged in two or three groups according to different output frequencies, when a 500 GHz circuit cascade is performed, two groups of secondary frequency multipliers (2) are arranged; when a 1 THz circuit cascade is performed, three groups of secondary frequency multipliers (2) are arranged; when a 1 THz circuit cascade is performed, two groups of secondary frequency multipliers (2) are arranged in parallel and connected in series with the last group of secondary frequency multipliers (2); when a 500 GHz circuit cascade is performed, two groups of secondary frequency multipliers (2) are arranged in parallel.

2. The ultra-high frequency terahertz band signal transmission system according to claim 1, characterized in that: The high power source (1) comprises a signal source (5), a first filter (6), a second amplifier (7) and a power synthesis module. The input signal of the signal source (5) is a microwave signal. After being amplified by 6 times, the input signal enters the first filter (6) for filtering. The output end of the first filter (6) is connected to the second amplifier (7), and the output end of the second amplifier (7) is connected to the power synthesis module. The power synthesis module performs a second power amplification on the input signal of the signal source (5).

3. The ultra-high frequency terahertz band signal transmission system according to claim 2, characterized in that: The power synthesis module comprises a primary power divider (8), a secondary power divider (9), a third amplifier (10), a primary power synthesizer (11) and a secondary power synthesizer (12); the output end of the second amplifier (7) is connected to the primary power divider (8); there are two groups of secondary power dividers (9) and both are connected to the output end of the primary power divider (8); the two groups of secondary power dividers (9) are arranged in parallel; after the input signal passes through the primary power divider (8), the power is split into two equal parts and respectively input to the two groups of secondary power dividers (9). The third amplifiers (10) are arranged in four groups at the output end of the secondary power divider (9), the four groups of the third amplifiers (10) are arranged in pairs, and each two groups of the third amplifiers (10) are connected to the output end of one group of the secondary power divider (9), and the two groups of the third amplifiers (10) connected to the same secondary power divider (9) are arranged in parallel, and the secondary power divider (9) splits the power into two identical parts again after receiving the input signal and inputs the power into the two connected groups of the third amplifiers (10); There are two groups of the first-level power synthesizers (11) which are respectively connected to the output ends of four groups of third amplifiers (10) which are connected in parallel. The two groups of the first-level power synthesizers (11) are also arranged in parallel. The second-level power synthesizer (12) is connected to the output ends of the two groups of the first-level power synthesizers (11).

4. The ultra-high frequency terahertz band signal transmission system according to claim 1, characterized in that: The third frequency multiplier (3) comprises a first input probe (13), a first output probe (14), a first diode chip (15), a second filter (16) and a first output conversion structure (17); the output end of the first input probe (13) is connected to the first output conversion structure (17), the output end of the first diode chip (15) is connected to the first output probe (14), and the output end of the second filter (16) is connected to the first diode chip (15); there are two first diode chips (15) and the two first diode chips (15) are installed in parallel on a circuit located in a waveguide structure; the first output conversion structure (17) adopts a suspended microstrip-waveguide transition structure, which contains a suspended microstrip circuit and a rectangular waveguide; a pad at one end of the first diode chip (15) is connected to the microstrip circuit, and the other end is connected to the cavity to form a radio frequency / direct current ground; the baseband signal is coupled into the suspended microstrip circuit through the first input probe (13), and a high-order harmonic is generated at the first diode chip (15), and then the first output probe (14) couples the required third harmonic to the rectangular waveguide output.

5. The ultra-high frequency terahertz band signal transmission system according to claim 4, characterized in that: The secondary frequency multiplier (2) comprises a second input probe (18), a second output probe (19), a second diode chip (20), a direct current filter (21) and a second output conversion structure (22); the output end of the second input probe (18) is connected to the second output conversion structure (22), the output end of the second diode chip (20) is connected to the second output probe (19), and the output end of the direct current filter (21) is connected to the second diode chip (20); there are two second diode chips (20) and the two second diode chips (20) are reversely connected in series and mounted on a circuit having a rectangular waveguide; an external bias circuit is provided and connected to the direct current filter (21) through a gold wire; the second output conversion structure (22) adopts a suspended microstrip-waveguide transition structure, containing a suspended microstrip circuit and a rectangular waveguide; the signal in the input rectangular waveguide is fed into the second diode chip (20), and the correspondingly generated secondary harmonics are output from the standard rectangular waveguide at the other end along the suspended microstrip circuit after matching and coupling circuits.

6. The ultra-high frequency terahertz band signal transmission system according to claim 5, characterized in that: The first input probe (13), the first output probe (14), the second input probe (18) and the second output probe (19) are all E-plane probes; and the microstrip circuit is a quartz circuit.

7. The ultra-high frequency terahertz band signal transmission system according to claim 5, characterized in that: The diodes in the secondary frequency multiplier (2) and the tertiary frequency multiplier (3) are both Schottky diodes; the dielectric substrate of the Schottky diode is a GaAs layer with a thickness of 30 µm; the anode pad in the Schottky diode is connected to the cathode through an air bridge finger to form an ohmic contact.

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