Terahertz broadband frequency multiplier structure based on gap waveguide

Abstract

The invention discloses a terahertz broadband frequency multiplier structure based on a gap waveguide, and belongs to the technical field of terahertz frequency multiplication. A microwave signal is fed in from the input end of the broadband frequency multiplier and is input into the nonlinear diode through the low-pass filter, the microwave signal excites the nonlinear diode to generate harmonic waves, and the terahertz signal is selectively output through the high-pass filter and is transmitted to the output port. The terahertz broadband frequency multiplier based on the gap waveguide designed by the invention is wider in working bandwidth and easy to dissipate heat, can effectively avoid the problem that power continuity between spliced frequency bands needs to be considered in frequency band splicing in a terahertz broadband system, and can effectively reduce the complexity of a high-frequency terahertz frequency multiplication link.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz frequency doubling, and in particular relates to a terahertz broadband frequency multiplier structure based on a gap waveguide. Background Art

[0002] Terahertz source is the primary problem that needs to be solved in the development of terahertz science and technology. It is the core key component of terahertz system. Its development plays a vital role in promoting the research and development of a series of major instruments such as vector network analyzers, spectrum analyzers, signal sources, security inspection instruments, and promoting the practical application of terahertz systems. Terahertz frequency doubling technology is an important technical approach to realize terahertz source, and it is also a hot research topic of terahertz source in the world. Its theoretical basis is based on the nonlinear effect of nonlinear devices. The working principle is to generate each harmonic of the input signal through nonlinear devices, and use filtering and other circuits to extract the required frequency components and suppress other harmonics and fundamental components. The use of frequency doubling to generate terahertz waves has the advantages of compact structure, large temperature dynamic range, high efficiency and high stability, and occupies a major position in the current research of terahertz sources. At present, the research and development of terahertz frequency doubling technology usually adopts a waveguide-microstrip line hybrid transmission mechanism. The input signal is fed into the waveguide port and transitioned to the microstrip transmission line through probe coupling. The signal selective input is achieved by using a filter based on microstrip transmission line. After the microstrip filtering structure, it enters the nonlinear device diode through a microstrip-based impedance matching network to generate high-order harmonics, and then harmonic selection is achieved through a filter based on microstrip transmission line. Finally, it is coupled to the standard rectangular waveguide through the probe to achieve the output of terahertz signals.

[0003] The main problem of the prior art is that it uses a waveguide-microstrip hybrid transmission mechanism. Due to factors such as the single-mode working conditions of the rectangular waveguide and the probe transition bandwidth, the working frequency bandwidth of the single-module frequency multiplier is limited to the single-mode working frequency range of the rectangular waveguide, and the working bandwidth is difficult to further improve. The present invention aims at the bandwidth limitation faced by the development of single-module terahertz frequency multipliers. It changes the transmission architecture in the terahertz frequency multiplier through gap waveguide technology, breaks the conventional design idea of ​​the frequency multiplier, and uses the inherent broadband properties of the new architecture transmission system to solve the problem of multi-band splicing of bandwidth expansion of existing frequency multiplier devices. It develops an ultra-wideband device with a single-module frequency multiplier signal output working frequency covering two or even multiple waveguide bands. Summary of the invention

[0004] In view of the above technical problems existing in the prior art, the present invention proposes a terahertz broadband frequency multiplier structure based on gap waveguide, which overcomes the shortcomings of the prior art and has good effects.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A terahertz broadband frequency multiplier structure based on a gap waveguide, comprising a low-pass filter, a nonlinear diode and a high-pass filter;

[0007] A low-pass filter is configured to implement low-frequency signal input and high-frequency signal cutoff;

[0008] a nonlinear diode configured to generate harmonics;

[0009] A high-pass filter is configured to pass high-frequency signals and cut off low-frequency signals;

[0010] The microwave signal is fed into the input end of the frequency multiplier structure and input into the nonlinear diode through a low-pass filter. The microwave signal excites the nonlinear diode to generate harmonics and selectively outputs the third harmonic terahertz signal through a high-pass filter and transmits it to the output port of the frequency multiplier structure.

[0011] Preferably, the input port of the frequency multiplier structure adopts a standard rectangular waveguide port form, and adopts a standard rectangular waveguide-ridge waveguide-gap ridge waveguide form to realize the working mode TE 10 The transition to the quasi-TEM mode is completed, completing the broadband impedance transition conversion from the standard rectangular waveguide port to the gap waveguide port. Absorbers are set on both sides of the middle ridge of the ridge waveguide to suppress the resonant mode.

[0012] Preferably, the low-pass filter adopts a high-low impedance step filter based on a gap waveguide.

[0013] Preferably, the high-low impedance step filter based on the gap waveguide can adopt other filtering structures based on the gap waveguide including the bandgap filtering structure.

[0014] Preferably, the high-pass filter adopts a ridge waveguide structure, and high-pass filtering is achieved by utilizing the low-frequency cutoff characteristics of the ridge waveguide structure.

[0015] Preferably, the absorber is a rectangular cubic absorber.

[0016] Preferably, the transition conversion between the standard rectangular waveguide and the gap waveguide is achieved by combining a narrow side height gradient matching transition based on a standard rectangular waveguide and a gradient transition based on a ridge waveguide.

[0017] Preferably, in the gradual transition structure design of the ridge waveguide at the input end of the frequency multiplier structure, a double-layer structure is adopted.

[0018] Beneficial technical effects brought by the present invention:

[0019] The gap waveguide-based terahertz broadband frequency multiplier designed in the present invention has a wider operating bandwidth and is easy to dissipate heat. In the terahertz broadband system, it can effectively avoid the problem of frequency band splicing that requires consideration of power continuity between spliced ​​frequency bands, and at the same time can effectively reduce the complexity of the high-frequency terahertz frequency multiplication link. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the overall design scheme of the terahertz broadband frequency multiplier structure based on gap waveguide;

[0021] Figure 2 Schematic diagram of high and low impedance filtering structure based on gap waveguide;

[0022] Figure 3 This is a simulation result diagram of high and low impedance filtering structure based on gap waveguide;

[0023] Figure 4 Schematic diagram of the ridge waveguide high-pass filter structure;

[0024] Figure 5 This is the simulation result diagram of the ridge waveguide high-pass filter structure. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0026] The overall solution adopted by the gap waveguide-based terahertz broadband frequency doubling device structure designed by the present invention is as follows: Figure 1 As shown, the microwave signal (36.7 GHz to 73.3 GHz) is fed into the input end of the broadband frequency multiplier. It is input into the nonlinear diode device through the low-pass filter structure. The microwave signal excites the diode to generate harmonics and passes through the high-pass filter to selectively output the third harmonic 0.11 THz to 0.22 THz terahertz signal and transmit it to the output port, as follows:

[0027] The input port takes into account the device connection method in the actual system and the subsequent test requirements. The input port adopts the standard rectangular waveguide port form and adopts the standard waveguide-ridge waveguide-gap ridge waveguide form to realize TE 10 The transition to the quasi-TEM mode completes the broadband impedance transition conversion from the standard waveguide port to the gap waveguide port. In this structural design, in order to avoid the emergence of the resonant mode, absorbers are added on both sides of the middle ridge of the ridge waveguide to suppress the resonant mode.

[0028] The input filter structure design uses a high-low impedance step filter based on a gap waveguide, such as Figure 2 As shown, it has good transmission characteristics in the range of 36.6GHz to 73.3GHz, such as Figure 3 As shown, the reflection coefficient S 11are all less than -17dB, and in the range of 0.11THz to 0.22THz, the reflection coefficient S 11 They are all greater than -0.5dB, indicating that the signal in the frequency range of 0.11THz to 0.22THz will be truncated and cannot be effectively transmitted.

[0029] Combining the electric field distribution characteristics and physical structure characteristics of the gap waveguide, the present invention adopts a 3rd balanced frequency doubling structure to effectively suppress even harmonics and improve output power. The overall circuit adopts an unbiased design to simplify the overall circuit. Diode matching is achieved by changing the ridge width in the ridge gap waveguide.

[0030] The output port filter design realizes high-pass filtering by using the low-frequency cutoff characteristics of the ridge waveguide, such as Figure 4 As shown in the figure, in the low frequency range of 36.6 GHz to 73.3 GHz, the reflection coefficient is large, and most of the signal energy is reflected. In the range of 0.11 THz to 0.22 THz, the reflection coefficient is relatively small. 11 All are less than -18dB, transmission coefficient S 21 All are greater than -0.6dB, such as Figure 5 As shown, it shows that most of the signal energy is effectively transmitted.

[0031] The present invention proposes a terahertz frequency multiplier architecture design scheme based on gap waveguide, which has the advantages of wide operating frequency band, easy heat dissipation, low loss and easy processing.

[0032] The present invention is based on the structure design of the terahertz frequency multiplier of the gap waveguide. In the embodiment, a high-low-resistance low-pass anti-filter structure is adopted, but it is not limited to this structure, and includes other filtering structures based on the gap waveguide such as a bandgap filtering structure.

[0033] The present invention adopts a ridge waveguide structure as a high-pass filter structure in a terahertz frequency multiplier to achieve the effect of inputting high-frequency signals and cutting off low-frequency signals.

[0034] In order to facilitate testing and connection with standard waveguide devices, the transition between the gap waveguide and the standard rectangular waveguide is achieved by combining the gradient matching transition based on the narrow side height of the rectangular waveguide and the gradient transition based on the ridge waveguide. Furthermore, in the design of the gradient transition structure of the ridge waveguide at the input end, a double-layer structure is adopted to reduce the difficulty of processing.

[0035] In order to suppress the generation of parasitic modes, the present invention adds a rectangular cubic absorber to avoid the occurrence of resonance peaks in the working frequency band.

[0036] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A terahertz broadband frequency multiplier structure based on gap waveguide, characterized in that: Includes low-pass filters, nonlinear diodes, and high-pass filters; A low-pass filter is configured to implement low-frequency signal input and high-frequency signal cutoff; a nonlinear diode configured to generate harmonics; A high-pass filter is configured to pass high-frequency signals and cut off low-frequency signals; The microwave signal is fed into the input end of the frequency multiplier structure and input into the nonlinear diode through a low-pass filter. The microwave signal excites the nonlinear diode to generate harmonics and selectively outputs the third harmonic terahertz signal through a high-pass filter and transmits it to the output port of the frequency multiplier structure.

2. The terahertz broadband frequency multiplier structure based on gap waveguide according to claim 1, characterized in that: The input port of the frequency doubler structure adopts the standard rectangular waveguide port form, and adopts the standard rectangular waveguide-ridge waveguide-gap ridge waveguide form to realize the working mode TE 10 The transition to the quasi-TEM mode is completed to complete the broadband impedance transition conversion from the standard rectangular waveguide port to the gap waveguide port. Absorbers are set on both sides of the middle ridge of the ridge waveguide.

3. The gap waveguide-based terahertz broadband frequency multiplier structure according to claim 1, characterized in that: The low-pass filter uses a high-low impedance step filter based on a gap waveguide.

4. The gap waveguide-based terahertz broadband frequency multiplier structure according to claim 3, characterized in that: The gap waveguide-based high and low impedance step filter uses other gap waveguide-based filtering structures including bandgap filtering structures.

5. The gap waveguide-based terahertz broadband frequency multiplier structure according to claim 1, characterized in that: The high-pass filter adopts a ridge waveguide structure and realizes high-pass filtering through the low-frequency cutoff characteristics of the ridge waveguide structure.

6. The gap waveguide-based terahertz broadband frequency multiplier structure according to claim 2, characterized in that: The absorber is a rectangular cubic absorber.

7. The gap waveguide-based terahertz broadband frequency multiplier structure according to claim 2, characterized in that: The transition conversion between the standard rectangular waveguide and the gap waveguide is achieved by combining the narrow side height gradient matching transition based on the standard rectangular waveguide and the gradient transition based on the ridge waveguide.

8. The gap waveguide-based terahertz broadband frequency multiplier structure according to claim 2, characterized in that: In the design of the gradual transition structure of the ridge waveguide at the input end of the frequency multiplier structure, a double-layer structure is adopted.

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