High frequency system structure suitable for 0.5THz backward wave tube

Abstract

The present invention provides a high-frequency system structure suitable for a 0.5THz backward wave tube, comprising: a box-shaped output window, a rectangular grating slow-wave structure, a first linear transition waveguide, a first gradient waveguide, a second linear transition waveguide, a second gradient waveguide, a wedge-shaped gradient attenuator, a third standard waveguide WR‑1.5, and a first electron injection channel and a second electron injection channel; wherein the apertured rectangular grating waveguide is obtained by opening a rectangular hole in the center of the upper surface of the grating of each single rectangular grating. The present invention can load a circular electron beam by adding a rectangular aperture in the high-frequency system structure, and compared with a typical single rectangular grating slow-wave structure, the slow-wave structure has a higher coupling impedance and dispersion curve.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic technology, and in particular to a high-frequency system structure suitable for a 0.5THz backward wave tube. Background Art

[0002] The application of terahertz waves in security inspection, communication, imaging technology, etc. requires terahertz radiation sources above the watt level. Up to now, only vacuum electronic devices and plasma electronics can generate high-power terahertz waves. Higher power, lower cost, smaller size, and easier to carry vacuum electronic devices are the future development direction of high-power terahertz radiation sources. In order to achieve these goals, it is necessary to improve the injection wave interaction of vacuum electronic devices, reduce the reflection of high-frequency signals, and design a suitable output structure. Among terahertz electric vacuum devices, the backward wave oscillator (BWO) is one of the ideal devices for generating terahertz waves. It has high efficiency, low cost, relatively small size, and light weight, and can generate high-power terahertz radiation.

[0003] Most of the existing backward wave oscillators use folded waveguides or rectangular gratings as their slow-wave structures. For terahertz stop-band oscillators based on folded waveguides, the processing of the folded waveguide slow-wave structure becomes very difficult in the terahertz band, and the processing accuracy is difficult to guarantee. In addition, the frequency tuning range of the folded waveguide backward wave tube is also very narrow. For a 0.13THz folded waveguide backward wave oscillator, its electrical adjustment bandwidth is only 1GHz.

[0004] Rectangular grating slow-wave structure Rectangular grating backward wave tubes such as cosine-shaped rectangular grating slow-wave structure, ridge-loaded open rectangular grating, stepped groove staggered double-grating slow-wave structure, etc. These structures are relatively complex and difficult to process in the terahertz band, and generally use strip electron beams, which make focusing more complicated in practice. Summary of the invention

[0005] The present invention provides a high-frequency system structure suitable for a 0.5THz backward wave tube, which is used to solve the defects of the backward wave tube in the prior art that the backward wave tube is not suitable for processing and has a narrow point adjustment bandwidth, facilitates the processing of the backward wave tube, and improves the injection wave interaction and output of the backward wave tube.

[0006] The present invention provides a high-frequency system structure suitable for a 0.5THz backward wave tube, comprising: a box-shaped output window, a rectangular grating slow-wave structure, a first linear transition waveguide, a first gradual waveguide, a second linear transition waveguide, a second gradual waveguide, a wedge-shaped gradual attenuator, a third standard waveguide WR-1.5, and a first electron injection channel and a second electron injection channel;

[0007] One end of the box-shaped output window is connected to one end of the first gradual change waveguide, the other end of the first gradual change waveguide is connected to one end of the first linear transition waveguide, the other end of the first linear transition waveguide is connected to one end of the rectangular grating slow-wave structure, the other end of the rectangular grating slow-wave structure is connected to one end of the second linear transition waveguide, the other end of the second linear transition waveguide is connected to one end of the second gradual change waveguide, the other end of the second gradual change waveguide is connected to one end of the third standard waveguide WR-1.5, and the other end of the second standard waveguide WR-1.5 is nested in the wedge-shaped gradual attenuator;

[0008] The first electron injection channel is connected to the first gradual change waveguide, and is interlinked with the first gradual change waveguide, the first linear transition waveguide, and the rectangular grating slow-wave structure; the second electron injection channel is connected to the second gradual change waveguide, and is interlinked with the second linear transition waveguide and the rectangular slow-wave structure;

[0009] The rectangular grating slow-wave structure is an open-hole rectangular grating waveguide, and the open-hole rectangular grating waveguide is obtained by opening a rectangular hole in the center of the upper surface of the grating of each single rectangular grating.

[0010] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5THz backward wave tube, wherein the rectangular slow-wave structure includes: a first partial periodic structure, a drift section and a second partial periodic structure, and the drift section is located between the first partial periodic structure and the second partial periodic structure.

[0011] Furthermore, the high-frequency system structure suitable for a 0.5THz backward wave tube provided by the present invention, wherein the hole width and hole depth of the rectangular hole in the hole-perforated rectangular grating waveguide have a size relationship of 2:1, the hole-perforated rectangular grating width w satisfies 0.7λ0<w<λ0, wherein λ0 is the wavelength corresponding to the center frequency, the rectangular grating slow-wave structure waveguide height b satisfies 0.5w<b<0.8w, and the grating period p of the hole-perforated rectangular grating satisfies:

[0012]

[0013] Where f0 is the center frequency of the backward wave tube, and V0 is the speed of the loaded electron beam.

[0014] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the lengths of the first partial periodic structure and the second partial periodic structure are both 90 rectangular gate periods, and the length of the drift section is 2.5 rectangular gate periods.

[0015] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5THz backward wave tube, wherein the box-shaped output window comprises: a first standard waveguide WR-1.5, a second standard waveguide WR-1.5, a first circular waveguide, a second circular waveguide and a circular dielectric window;

[0016] Among them, one end of the first standard waveguide WR-1.5 is connected to one end of the first circular waveguide, the other end of the first circular waveguide is connected to one side of the circular dielectric window, the other side of the circular dielectric window is connected to one end of the second circular waveguide, and the other end of the second circular waveguide is connected to the second standard waveguide WR-1.5.

[0017] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward waveguide, wherein the first gradient waveguide and the second gradient waveguide are asymmetric gradient waveguides.

[0018] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the circular dielectric window is made of sapphire.

[0019] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the first gradient waveguide and the first linear transition waveguide are connected by a circular arc, and the second gradient waveguide and the second linear transition waveguide are connected by a circular arc.

[0020] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the material of the wedge-shaped tapered attenuator is beryllium oxide.

[0021] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the rectangular grating slow-wave structure, the first linear transition waveguide, the first gradual waveguide, the second linear transition waveguide, the second gradual waveguide, the first circular waveguide, the second circular waveguide, the first standard waveguide WR-1.5 and the second standard waveguide WR-1.5, the third standard waveguide WR-1.5, the first electron injection channel and the second electron injection channel are made of oxygen-free copper.

[0022] The high-frequency system structure suitable for a 0.5THz backward wave tube provided by the present invention comprises: a box-shaped output window, a rectangular grating slow-wave structure, a first linear transition waveguide, a first gradual waveguide, a second linear transition waveguide, a second gradual waveguide, a wedge-shaped gradual attenuator, a third standard waveguide WR-1.5, a first electron injection channel, a second electron injection channel and the like; and one end of the box-shaped output window is connected to one end of the first gradual waveguide, the other end of the first gradual waveguide is connected to one end of the first linear transition waveguide, the other end of the first linear transition waveguide is connected to one end of the rectangular grating slow-wave structure, the other end of the rectangular grating slow-wave structure is connected to one end of the second linear transition waveguide, and the second linear transition waveguide is connected to one end of the rectangular grating slow-wave structure. The other end of the second tapered waveguide is connected to one end of the second tapered waveguide, the other end of the second tapered waveguide is connected to one end of the third standard waveguide WR-1.5, and the other end of the second standard waveguide WR-1.5 is nested in the wedge-shaped tapered attenuator; the first electron injection channel is connected to the first tapered waveguide, and is interlinked with the first tapered waveguide, the first linear transition waveguide and the rectangular grating slow-wave structure, the second electron injection channel is connected to the second tapered waveguide, and is interlinked with the second linear transition waveguide and the rectangular slow-wave structure; the rectangular grating slow-wave structure is an open-hole rectangular grating waveguide, and the open-hole rectangular grating waveguide is obtained by opening a rectangular hole in the center of the upper surface of the grating of each single rectangular grating. The present invention forms a structure of a high-frequency system that can be used for a terahertz backward wave tube through the above-mentioned connection method, and because the open-hole rectangular grating slow-wave structure is adopted, it can be used to load a circular electron beam, and can form a modified coupling impedance and dispersion curve to improve the beam-wave interaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 It is a typical schematic diagram of a single rectangular grating slow wave structure in the prior art;

[0025] Figure 2 It is a structural schematic diagram of a high-frequency system structure applicable to a 0.5THz backward wave tube provided by the present invention;

[0026] Figure 3 This is a schematic diagram of an open-hole rectangular slow-wave structure provided by the present invention;

[0027] Figure 4 It is a schematic diagram of the specific structure of the slow-wave structure provided by the present invention;

[0028] Figure 5 This is a relationship diagram of the influence of the aperture size of the apertured rectangular grating slow-wave structure provided by the present invention on the dispersion characteristics;

[0029] Figure 6 It is a comparison diagram of the dispersion curve of the apertured rectangular grating slow-wave structure provided by the present invention and the dispersion curve of a typical single rectangular grating;

[0030] Figure 7 It is a comparison diagram of the coupling impedance of the apertured rectangular grid slow-wave structure provided by the present invention and the coupling impedance of a typical single rectangular grid;

[0031] Figure 8 It is the S parameter diagram of the high frequency system provided by the present invention;

[0032] Fig. 9 Output comparison diagram of the high frequency system provided by the present invention with and without a drift section added;

[0033] Fig.10 is the power spectrum output by the high frequency system provided by the present invention;

[0034] Fig.11 It is a diagram of the electronic tuning range of the high frequency system provided by the present invention;

[0035] Fig.12 It is a high frequency system output characteristic diagram provided by the present invention;

[0036] Reference numerals:

[0037] 1: The first part of the periodic structure 2: The second part of the periodic structure 3: Drift section; structure;

[0038] 4: first linear transition wave 5: second linear transition wave 6: first gradual waveguide; guide; guide;

[0039] 7: Second gradient waveguide; 8: First standard waveguide 9: Second standard waveguide

[0040] WR-1.5; WR-1.5;

[0041] 10: third standard waveguide 11: circular dielectric window; 12: first circular waveguide;

[0042] WR-1.5;

[0043] 13: second circular waveguide; 14: wedge-shaped tapered attenuator; 15: first electron beam channel;

[0044] 16: The second electron beam channel; 17: Rectangular grating slow-wave structure; 18: Box-shaped output window. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0046] Combine the following Figure 1-Figure 3 As shown, a high-frequency system structure suitable for a 0.5 THz backward wave tube provided in an embodiment of the present invention is described, including: a box-shaped output window 18, a rectangular grating slow-wave structure 17, a first linear transition waveguide 4, a first gradual waveguide 6, a second linear transition waveguide 5, a second gradual waveguide 7, a wedge-shaped gradual attenuator 14, a third standard waveguide WR-1.510, and a first electron injection channel 15 and a second electron injection channel 16;

[0047] One end of the box-shaped output window 18 is connected to one end of the first gradual change waveguide 6, the other end of the first gradual change waveguide 6 is connected to one end of the first linear transition waveguide 4, the other end of the first linear transition waveguide 4 is connected to one end of the rectangular grating slow-wave structure 17, the other end of the rectangular grating slow-wave structure 17 is connected to one end of the second linear transition waveguide 5, the other end of the second linear transition waveguide 5 is connected to one end of the second gradual change waveguide 7, the other end of the second gradual change waveguide 7 is connected to one end of the third standard waveguide WR-1.510, and the other end of the second standard waveguide WR-1.59 is nested in the wedge-shaped gradual attenuator 14;

[0048] The first electron injection channel 15 is connected to the first gradual change waveguide 6, and is interlinked with the first gradual change waveguide 6, the first linear transition waveguide 4 and the rectangular grating slow-wave structure 17; the second electron injection channel 16 is connected to the second gradual change waveguide 7, and is interlinked with the second linear transition waveguide 5 and the rectangular slow-wave structure;

[0049] The rectangular grating slow-wave structure 17 is an open-hole rectangular grating waveguide, which is obtained by opening a rectangular hole in the center of the upper surface of each single rectangular grating.

[0050] Furthermore, the first gradual change waveguide 6, the second gradual change waveguide 7, the third gradual change waveguide, the first linear transition waveguide 4, the second linear transition waveguide 5, the first electron beam channel 15, and the rectangular slow wave structure in this embodiment are connected to form a closed structure with a hollow interior, and this closed structure is the body of the backward wave tube. The backward wave refers to a slow electromagnetic wave whose phase velocity is opposite to the group velocity. The device that uses the backward wave to interact with the electron beam to form a high-frequency self-excited oscillation is the backward wave tube.

[0051] The condition for a device to achieve self-excited oscillation is that there must be feedback between the output and input ends of the device. A small part of the output energy is fed back to the input end as an input signal through the feedback loop, thereby maintaining the oscillation. The backward wave tube does not have an external feedback loop. It uses the feedback inside the device to achieve self-excited oscillation. In the traditional traveling wave tube, in addition to the slow wave line, which can be a transmission route for electromagnetic waves, the electron beam itself is also a transmission line. This is because the electron beam after being affected by the high-frequency field will form a velocity modulation and turn into a density modulation. This density modulation is manifested as an uneven distribution of space charge. Due to this uneven distribution, a space charge force appears, which results in a wave process of the electron beam, which becomes a space charge wave. It can be proved that the phase velocity of the space charge wave is close to the velocity of the electron beam, and its group velocity is equal to the electron beam velocity. Moreover, the phase velocity and the group velocity are always in the same direction, that is, it is always positive dispersion.

[0052] In this way, since the propagation direction of the space charge wave energy (group velocity) in the electron beam can only be the direction of the electron beam's movement, when a feedback loop is needed to achieve self-excited oscillation, it is only required that the energy of the electromagnetic wave on the slow wave line must propagate in the opposite direction of the electron beam's movement. But on the other hand, in order to achieve effective interaction between the electron beam and the high-frequency traveling wave field, so that the electron beam can transfer energy to the high-frequency field to amplify it, the traveling wave tube theory shows that the electron beam and the traveling wave field should be synchronized in phase velocity. It can be seen that the realization of self-excited oscillation puts forward the following requirements for the high-frequency traveling wave propagating on the slow wave line: in order to synchronize with the electron beam to exchange energy, its phase velocity should be the same as the direction of the electron beam's movement; and in order to form a feedback circuit to generate energy feedback to achieve self-excitation, its energy propagation direction, that is, the group velocity direction, must be opposite to the direction of the electron beam's movement. This requirement means that the slow wave line must have negative dispersion characteristics, that is, the slow wave transmitted on it must be a backward wave, and such a traveling wave tube oscillator is called a backward wave tube.

[0053] At the same time, the box-shaped output window 18 in the embodiment of the present invention can vacuum seal the interior of the backward wave tube and can feed electromagnetic energy well. Up to now, only vacuum electronic devices and plasma electronics can generate high-power terahertz waves, so the vacuum environment of the backward wave tube is very important. The wedge-shaped tapered attenuator 14 is used, and the tip of the wedge extends forward to absorb the electromagnetic waves reflected back from the tip of the waveguide.

[0054] In this embodiment, a rectangular hole is opened on the upper surface of each single rectangular grating of the rectangular slow-wave grating to obtain an open-aperture rectangular grating structure. Compared with the traditional slow-wave grating structure without apertures, such as the cosine-shaped rectangular grating slow-wave structure, the ridge-loaded open rectangular grating, the step-groove staggered double-grating slow-wave structure, etc., there are two advantages. The first is easy processing, and the second is that compared with the defect that the slow-wave grating without apertures can only use a strip electron beam, the open-aperture rectangular grating structure in this embodiment can load a circular electron beam. Since the circular electron beam is easier to focus than the strip electron beam, the open-aperture rectangular grating structure has a higher coupling impedance and dispersion curve.

[0055] In addition, the apertured rectangular grating slow-wave structure 17 of the present embodiment has a simple geometric structure and is easy to process. In the terahertz band, UV-LIGA (ultraviolet lithography) and micro-milling technology can be used to achieve high precision.

[0056] The high-frequency system structure suitable for a 0.5THz backward wave tube provided by the present invention comprises: a box-shaped output window 18, a rectangular grating slow-wave structure 17, a first linear transition waveguide 4, a first gradual waveguide 6, a second linear transition waveguide 5, a second gradual waveguide 7, a wedge-shaped gradual attenuator 14, a third standard waveguide WR-1.510, and a first electron injection channel 15 and a second electron injection channel 16 and other structures; and one end of the box-shaped output window 18 is connected to one end of the first gradual waveguide 6, the other end of the first gradual waveguide 6 is connected to one end of the first linear transition waveguide 4, the other end of the first linear transition waveguide 4 is connected to one end of the rectangular grating slow-wave structure 17, the other end of the rectangular grating slow-wave structure 17 is connected to one end of the second linear transition waveguide 5, and the second linear transition waveguide 5 is connected to one end of the second linear transition waveguide 5. The other end of the waveguide 5 is connected to one end of the second gradient waveguide 7, the other end of the second gradient waveguide 7 is connected to one end of the third standard waveguide WR-1.510, and the other end of the second standard waveguide WR-1.59 is nested in the wedge-shaped gradient attenuator 14; the first electron injection channel 15 is connected to the first gradient waveguide 6, and is interlinked with the first gradient waveguide 6, the first linear transition waveguide 4 and the rectangular grating slow-wave structure 17, the second electron injection channel 16 is connected to the second gradient waveguide 7, and is interlinked with the second linear transition waveguide 5 and the rectangular slow-wave structure; the rectangular grating slow-wave structure 17 is an open-hole rectangular grating waveguide, and the open-hole rectangular grating waveguide is obtained by opening a rectangular hole in the center of the upper surface of the grating of each single rectangular grating. The present invention forms a structure of a high-frequency system that can be used for a terahertz backward wave tube through the above-mentioned connection method, and because the open-hole rectangular grating slow-wave structure 17 is adopted, it can be used to load a circular electron beam, and can form a modified coupling impedance and dispersion curve to improve the injection-wave interaction.

[0057] Further, combined with Figure 3 As shown, the high-frequency system structure suitable for a 0.5THz backward wave tube provided by an embodiment of the present invention, wherein the hole width and hole depth of the rectangular hole in the hole-perforated rectangular grating waveguide have a size relationship of 2:1, the hole-perforated rectangular grating width w satisfies 0.7λ0<w<λ0, wherein λ0 is the wavelength corresponding to the center frequency, the rectangular grating slow-wave structure 17 waveguide height b satisfies 0.5w<b<0.8w, and the grating period p of the hole-perforated rectangular grating satisfies:

[0058]

[0059] Where f0 is the center frequency of the backward wave tube, and V0 is the speed of the loaded electron beam.

[0060] Specifically, the hole width and hole depth have a 2:1 size relationship to ensure that the horizontal and vertical distances between the electron beam and the grid are equal, which is conducive to the interaction between the electron beam and the slow wave. The lower cutoff frequency of the rectangular grid slow wave structure is According to the design experience of rectangular grating slow-wave structure, the relationship between the lower cutoff frequency and the center frequency of the fundamental mode is roughly f0=1.1~1.2fc, that is, 0.55λ0<w<0.6λ0. Considering the influence of the opening on the grating width, the grating width is appropriately expanded to 0.7λ0<w<λ0. Through simulation, it is found that the output can remain stable when the rectangular waveguide height b is within 0.5w<b<0.8w. Since the backward wave tube works in the backward wave state, the corresponding phase shift is in. In order to ensure the working state, the intermediate value is taken, that is, under this phase shift, the electron beam is synchronized with the slow wave, and the slow wave phase velocity v p The same as the electron beam velocity V0, the longitudinal propagation constant From the phase shift relation Available

[0061] Moreover, when the rectangular grating period length p is 0.14mm, the slot width d is half of the period length, the waveguide height b is 0.3mm, the slot depth h is 0.11mm, the grating width w is 0.45mm, the opening width u is 0.12mm, the opening height q is 0.06mm, and the electron beam radius is 0.05mm. The dispersion characteristic describes the relationship between the phase velocity and frequency of electromagnetic waves in the slow-wave system, which largely determines the electronic tuning range of the backward wave tube and is an important characteristic of the slow-wave structure. The slow-wave structure was simulated using microwave three-dimensional simulation software, and the influence of the opening size on the dispersion curve was obtained as shown in the figure. Figure 5 As shown in the figure, the straight lines in the figure represent the electron beam lines corresponding to the dispersion curves when the working voltage is 24kV. It can be seen that as the opening width increases, the upper limit frequency increases, the frequency band is widened, and the opening depth has little effect on the dispersion. Figure 1 The dispersion characteristics and coupling impedance of the common single rectangular grating slow-wave structure shown are respectively given by Figure 6and Figure 7 It can be seen that compared with the ordinary single rectangular gate, under the same electron injection voltage, the slow-wave structure has a higher operating frequency and coupling impedance, which means that to achieve the same operating frequency, the electron injection voltage required for the open rectangular gate can be smaller than the ordinary single rectangular gate with the same structure, and has a higher injection-wave interaction.

[0062] Further, combined with Figure 4 , describing the high-frequency system structure suitable for a 0.5THz backward wave tube provided by the present invention, wherein the rectangular slow-wave structure comprises: a first partial periodic structure 1, a drift segment 3 and a second partial periodic structure 2, and the drift segment 3 is located between the first partial periodic structure 1 and the second partial periodic structure 2.

[0063] Specifically, in the embodiment of the present invention, the rectangular slow wave structure is composed of three parts, namely the first periodic structure 1, the second periodic structure 2 and the drift section 3, wherein the drift section 3 is located between the first periodic structure 1 and the second periodic structure. The first periodic structure 1 causes the electron beam to be pre-grouped and directly stimulates the return wave oscillation in the second periodic structure 2. The drift section 3 does not perform any processing on the electron beam. However, according to Fig. 9 As shown, the difference in the output electromagnetic energy is very obvious when the drift section 3 is added or not added to the rectangular slow-wave structure. That is, after the drift section 3 is added to the rectangular slow-wave structure, the output electromagnetic energy is higher than the energy value without adding the drift section 3. In this embodiment, there is no restriction on the length of the first partial periodic structure 1 and the second partial periodic structure 2, and the lengths of the two can be equal or unequal.

[0064] Furthermore, in the embodiment of the present invention, a high-frequency system structure suitable for a 0.5THz backward wave tube is provided, wherein the lengths of the first partial periodic structure 1 and the second partial periodic structure 2 are both 90 rectangular grating periods, and when the length of the drift section 3 is 2.5 rectangular grating periods, the output electromagnetic energy is maximum.

[0065] Specifically, when the external axial magnetic field is 0.5T, the electron injection voltage is 24kV, and the injection current is 30mA, the drift segment 3 on both sides of the slow-wave structure is 90 cycles, and the particle interaction simulation is performed using PIC simulation software, and compared with the high-frequency structure output without the drift segment 3. Fig. 9 As shown, it can be seen that the output power of the high-frequency structure with the drift section 3 added is significantly higher than the output frequency of the high-frequency structure without the drift section 3. By performing FFT on the output of this embodiment, the output power spectrum can be obtained as shown in FIG. Fig.10 As shown, we can see that the output spectrum is very pure and the frequency corresponding to the peak power is 501.5 GHz.

[0066] By changing the electron beam voltage, the oscillation frequency of the backward wave tube can be changed. Keeping the cathode current and other structural parameters unchanged, changing the working voltage, and through PIC simulation, the relationship between the electron beam voltage and the working frequency of this embodiment is obtained as follows: Fig.11 As shown in Figure 2, when the operating voltage increases from 22kV to 26kV, the operating frequency also increases from 487GHz to 513GHz, and the corresponding output characteristics are Fig.12 It can be seen that within this frequency range, the output power can reach the watt level, with a wide electronic tuning range. With the increase of voltage, the output power and electronic efficiency first increase and then decrease. The electronic efficiency reaches a maximum value of 0.33% near the operating frequency of 501 GHz.

[0067] Further, refer to Figure 1 , the high-frequency system structure suitable for a 0.5THz backward wave tube provided in an embodiment of the present invention, wherein the first gradient waveguide 6 and the second gradient waveguide 7 are asymmetric gradient waveguides.

[0068] Specifically, the gradient waveguide is asymmetrical at both ends, and the gradient waveguide connected to the coupling attenuator is shorter in height and length than the gradient waveguide connected to the box-shaped output window 18, that is, the length of the second gradient waveguide 7 is shorter than the length of the first gradient waveguide 6, and the distance established by the point farthest from the rectangular grating slow-wave structure 17 on the second gradient waveguide 7 is shorter than the distance established by the point farthest from the rectangular grating slow-wave structure 17 on the second gradient waveguide 7. This asymmetric gradient waveguide connection method can minimize the reflection of electromagnetic waves.

[0069] The number of transition waveguides in this embodiment is 5, the gradient waveguide connected to the box-shaped output window 18 has a length Ds1 = 1.8 mm and a height H1 = 0.9 mm, and the gradient waveguide connected to the attenuator has a length Ds2 = 1.6 mm and a height H2 = 0.6 mm.

[0070] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the first gradient waveguide 6 is connected to the first linear transition waveguide 4 by a circular arc, and the second gradient waveguide 7 is connected to the second linear transition waveguide 5 by a circular arc.

[0071] Specifically, the gradient waveguide and the transition structure of the connecting box-shaped output window 18 are connected in an arc shape to reduce the reflection caused by the gradient waveguide being too high. Similarly, the second gradient waveguide 7 and the second transition waveguide are connected in an arc shape to reduce the reflection caused by the gradient waveguide being too high.

[0072] Further, the high-frequency system structure applicable to the 0.5THz backward wave tube provided in the embodiment of the present invention, wherein the box-shaped output window 18 comprises: a first standard waveguide WR-1.58, a second standard waveguide WR-1.59, a first circular waveguide 12, a second circular waveguide 13 and a circular dielectric window 11;

[0073] Among them, one end of the first standard waveguide WR-1.58 is connected to one end of the first circular waveguide 12, the other end of the first circular waveguide 12 is connected to one side of the circular dielectric window 11, the other side of the circular dielectric window 11 is connected to one end of the second circular waveguide 13, and the other end of the second circular waveguide 13 is connected to the second standard waveguide WR-1.59. In addition, the inner diameter of the circular waveguide is larger than the diagonal of the rectangular cross section of the standard waveguide WR-1.5, so that the electromagnetic waves passing through the standard waveguide WR-1.5 will not be blocked by the circular waveguide. In the embodiment of the present invention, the two sides of the window are circular waveguides of the same size, and are led out by the standard waveguide WR-1.5. The main structural parameters of the box-shaped output window 18 are as follows: the diameter of each circular waveguide is 0.46mm, the length is 0.47mm, the thickness of the circular dielectric window 11 is 0.1mm, and the diameter is 1.5mm.

[0074] Furthermore, in the high-frequency system structure applicable to a 0.5 THz backward wave tube provided in an embodiment of the present invention, the circular dielectric window 11 is made of sapphire.

[0075] Specifically, the circular dielectric window 11 is made of sapphire, and the high-frequency loss angle of sapphire is 2×10 -4 The dielectric constant is 9.4, it has good tensile strength, and the gas leakage at high temperature is very small. In addition, the sealing thickness of the window material in the embodiment of the present invention can be less than 0.1 mm.

[0076] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the wedge-shaped tapered attenuator 14 is made of beryllium oxide.

[0077] Specifically, Figure 2 As shown, the right side of the slow-wave structure of the embodiment is a terminal matching attenuator, namely a wedge-shaped tapered attenuator 14, which is intended to reduce reflections and eliminate parasitic oscillations. This embodiment uses beryllium oxide as the attenuator material, which has a relative dielectric constant of 6.5 and a loss tangent of 0.5. It has stable performance, strong heat dissipation capability, and high hardness. It is a high-loss, easy-to-process material.

[0078] Furthermore, the present invention provides a high-frequency system structure suitable for a 0.5 THz backward wave tube, wherein the rectangular grating slow-wave structure 17, the first linear transition waveguide 4, the first gradient waveguide 6, the second linear transition waveguide 5, the second gradient waveguide 7, the first circular waveguide 12, the second circular waveguide 13, the first standard waveguide WR-1.58, the second standard waveguide WR-1.59, the third standard waveguide WR-1.510, the first electron injection channel 15, and the second electron injection channel 16 are made of oxygen-free copper.

[0079] Specifically, the metal structures involved in this embodiment are made of oxygen-free copper. A model of this embodiment is established in a microwave three-dimensional simulation software. Considering the influence of the roughness of the inner surface of the waveguide on the transmission, the boundary condition is set as lossy metal with a conductivity of 1.9×107S / m. The high-frequency system structure of this embodiment is simulated to obtain the transmission characteristics as shown in FIG. Figure 8 As shown, within 490-513 GHz, the S11 of the high-frequency structure is around -20 dB, and the S21 is greater than -4 dB.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-frequency system structure suitable for a 0.5THz backward wave tube, characterized in that: include: A box-shaped output window, a rectangular grating slow-wave structure, a first linear transition waveguide, a first gradual waveguide, a second linear transition waveguide, a second gradual waveguide, a wedge-shaped gradual attenuator, a third standard waveguide WR-1.5, and a first electron injection channel and a second electron injection channel; One end of the box-shaped output window is connected to one end of the first gradual change waveguide, the other end of the first gradual change waveguide is connected to one end of the first linear transition waveguide, the other end of the first linear transition waveguide is connected to one end of the rectangular grating slow-wave structure, the other end of the rectangular grating slow-wave structure is connected to one end of the second linear transition waveguide, the other end of the second linear transition waveguide is connected to one end of the second gradual change waveguide, the other end of the second gradual change waveguide is connected to one end of the third standard waveguide WR-1.5, and the other end of the third standard waveguide WR-1.5 is nested in the wedge-shaped gradual attenuator; The first electron injection channel is connected to the first gradual change waveguide, and is interlinked with the first gradual change waveguide, the first linear transition waveguide, and the rectangular grating slow-wave structure; the second electron injection channel is connected to the second gradual change waveguide, and is interlinked with the second linear transition waveguide and the rectangular grating slow-wave structure; The rectangular grating slow-wave structure is an open-hole rectangular grating waveguide, and the open-hole rectangular grating waveguide is obtained by opening a rectangular hole in the center of the upper surface of each single rectangular grating; The rectangular grating slow-wave structure comprises: a first partial periodic structure, a drift section and a second partial periodic structure, wherein the drift section is located between the first partial periodic structure and the second partial periodic structure; The hole width and hole depth of the rectangular hole in the hole-perforated rectangular grating waveguide have a size relationship of 2:1, and the grating width w of the hole-perforated rectangular grating waveguide satisfies ,in is the wavelength corresponding to the center frequency, and the waveguide height b of the rectangular grating slow-wave structure satisfies , the rectangular grating period p of the apertured rectangular grating waveguide satisfies: ； Where f0 is the center frequency of the backward wave tube, and V0 is the speed of the loaded electron beam.

2. The high-frequency system structure suitable for a 0.5THz backward wave tube according to claim 1, characterized in that: The lengths of the first partial periodic structure and the second partial periodic structure are both 90 rectangular gate periods, and the length of the drift segment is 2.5 rectangular gate periods.

3. The high-frequency system structure suitable for a 0.5THz backward wave tube according to claim 1, characterized in that: The box-shaped output window comprises: a first standard waveguide WR-1.5, a second standard waveguide WR-1.5, a first circular waveguide, a second circular waveguide and a circular dielectric window; Among them, one end of the first standard waveguide WR-1.5 is connected to one end of the first circular waveguide, the other end of the first circular waveguide is connected to one side of the circular dielectric window, the other side of the circular dielectric window is connected to one end of the second circular waveguide, and the other end of the second circular waveguide is connected to the second standard waveguide WR-1.

5.

4. The high-frequency system structure suitable for a 0.5THz backward wave tube according to claim 1, characterized in that: The first tapered waveguide and the second tapered waveguide are asymmetric tapered waveguides.

5. The high-frequency system structure suitable for a 0.5 THz backward wave tube according to claim 3, characterized in that: The circular dielectric window is made of sapphire.

6. The high-frequency system structure suitable for a 0.5 THz backward wave tube according to claim 1, characterized in that: The first gradually changing waveguide and the first linear transition waveguide are connected by a circular arc, and the second gradually changing waveguide and the second linear transition waveguide are connected by a circular arc.

7. The high-frequency system structure suitable for a 0.5 THz backward wave tube according to claim 1, characterized in that: The material of the wedge-shaped tapered attenuator is beryllium oxide.

8. The high-frequency system structure suitable for a 0.5 THz backward wave tube according to claim 3, characterized in that: The rectangular grating slow-wave structure, the first linear transition waveguide, the first gradual waveguide, the second linear transition waveguide, the second gradual waveguide, the first circular waveguide, the second circular waveguide, the first standard waveguide WR-1.5, the second standard waveguide WR-1.5, the third standard waveguide WR-1.5, the first electron injection channel and the second electron injection channel are made of oxygen-free copper.

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