CN113690118B - Novel helix slow wave structure with variable pitch and variable inner diameter - Google Patents

Abstract

The invention provides a variable-pitch and variable-inner-diameter helical line slow wave structure, and belongs to the technical field of vacuum electronics. The slow wave structure enables return wave oscillation and higher harmonics to be restrained by specifically changing the inner diameter and the thread pitch of the spiral line, and obtains higher efficiency of the traveling wave tube, the electronic efficiency can reach 16% when the output power of a Q wave band is saturated, and the electronic efficiency can reach 4% when the output power is backed off by 6 dB.

Description

A novel helical slow-wave structure with variable pitch and variable inner diameter

technical field

The invention belongs to the technical field of vacuum electronics, and in particular relates to a novel helical slow wave structure with variable pitch and variable inner diameter.

Background technique

With the rapid development of electronic communication technology, communication systems have higher and higher requirements on the frequency and efficiency of power amplifier devices. Semiconductor devices are currently difficult to meet the urgent needs of future communication systems due to their own heat dissipation, frequency, efficiency, and power limitations. demand, and vacuum electronic devices such as traveling wave tubes have great advantages in this regard. As a final stage power amplifier, traveling wave tube is widely used in electronic equipment such as radar, electronic countermeasures, communication, and precision guidance.

An important criterion for measuring the performance of the traveling wave tube is the efficiency of the traveling wave tube. In the future communication system, since the power amplifier generally works in the linear region rather than the saturation point, it is required that the high-frequency power amplifier should also have high efficiency when the output power is backed by 6dB. The researchers employed a series of different techniques to improve the efficiency of the TWT. For now, there are mainly the following two methods: the first is the speed resynchronization technology; the second is the step-down collector technology. Velocity resynchronization technology refers to reducing the necessary velocity difference between the electron beam and the high-frequency traveling wave field by changing the phase velocity or the electron beam velocity when the beam interaction tends to be stable, so as to re-excite the effective beam wave. A technique of interaction. At present, this technology is mainly realized by three methods: phase speed gradient method, phase speed jump method and voltage jump method. Considering the difficulty of processing, especially in the case of high frequency band, compared with voltage jump, phase speed jump and fades are a more efficient and easy way to resynchronize tempo.

Due to its advantages of high frequency, wide bandwidth and high signal transmission rate, the Q-band helical traveling wave tube will have important application prospects in future communication systems. For the helical slow-wave structure, the traditional method mainly uses pitch jumps and gradients, so that the phase velocity of the high-frequency electromagnetic field produces corresponding jumps and gradients to achieve velocity resynchronization, thereby improving the efficiency of the traveling wave tube. However, the helical slow-wave structure with simple pitch change is difficult to suppress the high-power back-wave oscillation existing in the TWT, and cannot guarantee the stable operation of the TWT; on the other hand, this method still can improve the efficiency of the TWT. It cannot meet the efficiency requirement of the future communication system for the output power backoff of 6dB. For example, patent CN20669744U discloses a slow-wave structure and high-frequency structure of a helical traveling wave tube including multi-gradient sections. The electron efficiency is 10.11%; in 2016, Wang Fan's master's thesis "Research on 8-18GHz high-power helical traveling wave tube" discussed a variable pitch and variable inner diameter helical traveling wave tube, but its The frequency band is relatively low, and the variable inner diameter structure is only used to suppress the back wave oscillation, which is completely different from the method of changing the pitch and changing the inner diameter proposed in this patent.

Therefore, the helical slow-wave structure that can be used to realize the high efficiency of the Q-band traveling wave tube and effectively suppress the back-wave oscillation is a key problem that needs to be solved urgently.

SUMMARY OF THE INVENTION

In view of the technical problems existing in the background art, the purpose of the present invention is to provide a novel helical slow-wave structure with variable pitch and variable inner diameter. By changing the inner diameter and pitch of the helix, the slow-wave structure suppresses the back-wave oscillation and higher harmonics, and obtains a higher efficiency of the traveling wave tube. At the same time, it also has a higher efficiency when the output power is backed by 6dB. .

For achieving the above object, technical scheme of the present invention is as follows:

A helical slow wave structure with variable pitch and variable inner diameter, comprising a helix, an attenuator, a clamping rod and a tube shell; wherein the helix is fixed by three evenly distributed clamping rods, and the other end of the clamping rod is fixed to the tube shell superior;

The spiral line includes an input section, an output section and a cut-off area; the cut-off area is located between the input section and the output section for cutting off the feedback path;

The attenuator includes a centralized attenuator and a distributed attenuator; wherein, the centralized attenuator is arranged on both sides of the cut-off area for absorbing reflected waves and returning waves, and the distributed attenuator is arranged in the input section, and its function is to absorb reflected waves and return waves;

The pitch of the input segment is fixed, the inner diameter is gradually changing, and the inner diameter S ₁ at the starting end and the diameter S ₂ in the cut-off area satisfy the relationship S ₁ =1.0769S ₂ , and the electronic injection is at the end of the input segment after the speed modulation and density modulation of the input segment. To achieve electronic clustering and establish growth waves;

The inner diameter of the output section changes gradually, the pitch jumps, and the output section is divided into a phase speed increase section, a negative jump section, a positive jump section and a phase speed reduction section in turn, and the pitch of each section corresponds to P ₁ , P ₂ , P ₃ and P ₄ , the axial lengths are L ₂ , L ₃ , L ₄ and L ₅ respectively, the phase velocity increasing segment is used to compensate the electron phase, and the clustered electrons at the end of the input segment are further clustered, and the phase velocity decreases The segment transfers the energy of the electron injection to the electromagnetic field as much as possible to complete the energy output; among them, P ₂ =0.974P ₁ , P ₃ =1.026P ₁ , P ₄ =0.962P ₁ , L ₂ =0.22L, L ₃ =0.08L , L ₄ =0.2L, L ₅ =0.087L;

The inner diameter of the input section and the output end helix are the same in the cut-off area and at both ends, and the pitches of the input section and the phase velocity increasing section are the same, both of which are P ₁ .

Further, the axial length L ₁ of the input section should satisfy the relation: L ₁ =0.4L-0.413L, where L is the overall length of the slow-wave structure, which is 80-100 mm.

Further, the length _of the pitch P1 is preferably 0.3-0.5 mm.

Further, the axial length of the cutting area is 1-2 mm.

Further, one or more distributed attenuators are set so that the gain of the electronic injector after passing through the input section does not exceed 26dB.

Further, the attenuation amounts of the distributed attenuator and the centralized attenuator are different.

The mechanism of the invention is as follows: the input section uses its radius change to change the phase velocity of the high-frequency field, and the electron injection achieves electron clustering at the end of the input section after the speed modulation and density modulation of this section to establish a growing wave; the output section is in the The inner diameter of the helix is a gradient segment, and the pitch is jumped to compensate for the electron phase and further cluster the clustered electrons at the end of the input segment, and at the same time, the energy of the electron injection is given to the electromagnetic field as much as possible to complete the energy output. . Considering that the electron injection radius will gradually increase at the back end of the slow-wave structure when the TWT is working, and the filling ratio of the electron injection needs to be kept within a certain range to obtain the best injection-wave interaction effect, so the inner diameter of the slow-wave structure is Synchronized with the increase of the electron beam radius in some regions, it is beneficial for the high-frequency field to obtain more energy from the electron beam, thereby improving the efficiency.

To sum up, due to the adoption of the above-mentioned technical solutions, the beneficial effects of the present invention are:

1. The phase velocity increasing section of the output section of the present invention is set to a structure with a negative pitch jump followed by a positive jump. This structure effectively suppresses high-order harmonic components, makes the clustering effect better, and greatly improves the traveling wave. Electronic efficiency of the tube.

2. The present invention adopts a helical slow-wave structure with variable pitch and variable inner diameter, and the change of phase velocity generated by the variable phase speed increases the start-up length of the back-wave oscillation, thereby effectively suppressing the back-wave oscillation in the traveling wave tube and ensuring that the traveling wave tube is in Stable operation at high gain. At the same time, the inner diameter of the slow-wave structure in the output section also increases correspondingly in the region where the electron injection radius gradually increases, so that the filling ratio is kept within a range with a better injection-wave interaction effect, which is beneficial to obtain a better injection-wave interaction effect. Thus, the electronic efficiency of the traveling wave tube is improved.

3. The spiral slow-wave structure proposed by the present invention is suitable for the Q-band, that is, the frequency is 36-40 GHz, the electronic efficiency can reach 16% when the output power is saturated, and the electronic efficiency can reach 4% when the output power is backed by 6dB.

Description of drawings

1 is a view of a single-period helical slow-wave structure of an embodiment;

Among them, (a) is the left view, (b) is the main view, and (c) is the 3D model of the partial structure.

FIG. 2 is a schematic diagram of the helix in the slow-wave structure of the present invention.

3 is a waveform diagram and a spectrogram of the embodiment when working at 39 GHz;

Among them, (a) is a waveform diagram, and (b) is a spectrogram.

4 is a schematic diagram of the output power and a schematic diagram of the electronic efficiency of the helical traveling wave tube with variable pitch and variable inner diameter in the embodiment;

Among them, (a) is the output power and electron efficiency at saturation, (b) is the output power and electron efficiency when the output power is backed by 6dB.

FIG. 5 is a schematic diagram of the gain of the helical traveling wave tube with variable pitch and variable inner diameter in the embodiment.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

A helical slow-wave structure with variable pitch and variable inner diameter, including a helix, an attenuator, a clamping rod and a tube shell; its structural view is shown in Figure 1, wherein the helix is fixed by three evenly distributed clamping rods, The other end of the clamping rod is fixed on the tube shell, as shown in (a) in Figure 1;

The spiral line includes an input section, an output section and a cut-off area, and its schematic diagram is shown in Figure 2;

The input segment is used for the velocity modulation and density modulation of electrons, and its inner diameter is a gradual structure to suppress the back-wave oscillation. After the velocity modulation and density modulation of the input segment, the electron injection realizes electron clustering at the end of the input segment and establishes a growing wave. ;

The output section includes a phase velocity increase section, a negative transition section, a positive transition section and a phase velocity reduction section; wherein, the phase velocity increase section compensates the electron phase, and continues to cluster the clustered electrons entering the output section, The phase velocity reduction section transfers the energy of the electron injection to the electromagnetic field as much as possible to complete the energy output;

The cut-off area is located between the input section and the output section, and its function is to cut off the feedback path and suppress the reflection oscillation.

The attenuator includes a centralized attenuator and a distributed attenuator; wherein, the centralized attenuator is arranged on both sides of the cut-off area to absorb reflected waves and returning waves, and the distributed attenuator is arranged in the input section, and its function is also to absorb reflections Wave and return wave; the attenuator is formed by spraying carbon on the clamping rod, and its thickness and range determine the amount of attenuation.

Each part of the present invention will be described in detail below.

In the present invention, the input section corresponds to the AB ₁ section in FIG. 2 , and this section performs electron velocity modulation and density modulation to realize electron clustering and establish a growing wave. The inner diameter of the whole section is gradually changed from S ₁ to S ₂ to suppress the back-wave oscillation. The inner diameter S ₁ and the diameter S ₂ in the cut-off area satisfy the following relationship: S ₁ =1.0769S ₂ . The pitch of the AB ₁ section is P ₁ . In order to make the electron injection in the AB ₁ section get a good electron clustering effect and suppress the return wave oscillation, the axial length L ₁ of the input section satisfies the following relationship: L ₁ =0.4L-0.45 L, after simulation optimization, the value of this embodiment is L ₁ =0.4108L;

In the present invention, the output section corresponds to the B ₂ F section, including the phase velocity increasing section, corresponding to the B ₂ E section and the phase velocity decreasing section, corresponding to the EF section, wherein the phase velocity increasing section is provided with a pitch negative jump followed by a positive jump. structure, namely B ₂ C, CD, DE segments, its function is to suppress high-order harmonic components and improve electron efficiency; among them, the pitch and distribution of changes in the phase velocity increase segment determine the degree of coupling between electron injection and space charge wave, B ₂ The corresponding pitches of C, CD and DE sections are: P ₁ , P ₂ , P ₃ , and the axial lengths are: L ₂ , L ₃ , L ₄ , which satisfy the following relationship: P ₂ =0.974P ₁ , P ₃ =1.026P ₁ , L ₂ =0.22L, L ₃ =0.08L, L ₄ =0.2L;

The phase velocity reduction section in the output section corresponds to the EF section, the pitch is P ₄ , and the axial length is L ₅ , which satisfies the following relationship: P ₄ =0.962P ₁ , L ₅ =0.087L;

The cut-off area is located between the input section and the output section, and is 1 mm in size. The function is to cut off the feedback path and suppress the self-excited oscillation, including reflection oscillation and return oscillation.

The inner diameter of the helix at the input section and the output end is the same in the cut-off area and at both ends. The pitch of the input section and the phase velocity increasing section are the same, both are P ₁ , where L is 80-100mm, and P ₁ is 0.3- 0.5mm.

According to the spiral slow-wave structure with variable pitch and variable inner diameter shown in the embodiment of the present invention, the three-dimensional PIC simulation software is used for simulation optimization. When the injection voltage is 8500V, the injection current is 0.06A, and the periodic focusing magnetic field (peak value ~ 0.4T) Under the conditions, the simulation results are shown in Figure 3-5. 3 is a waveform diagram and a spectrogram of the slow-wave structure of the present invention when it operates at 39 GHz; wherein (a) is a waveform diagram, and (b) is a spectrogram. As shown in (a) in Figure 3, the output waveform is basically stable at 5ns and no longer has large fluctuations. The corresponding spectrogram is shown in (b) in Figure 3, indicating that the spectrum is relatively pure and has no other clutter peaks. Wave oscillations and reflection oscillations are well suppressed. 4 is a schematic diagram of the saturated output power and the schematic diagram of the electronic efficiency of the spiral traveling wave tube with variable pitch and variable inner diameter in the embodiment. As shown in the figure, in the frequency range of 36GHz-40GHz, the saturated output power is greater than 84W, and the corresponding electronic efficiency exceeds 16.47%, when the output power falls back to about 6dB, the output power is above 20W, and the corresponding electronic efficiency is higher than 4%, achieving high efficiency. 5 is a schematic diagram of the gain of the helical traveling wave tube with variable pitch and variable inner diameter in the embodiment, the saturation gain in the working frequency band exceeds 46.69dB, and the gain exceeds 55.5dB when the output backs off by 6dB. In general, the present invention achieves suppression of back-wave oscillation and reflection oscillation, while having higher electronic efficiency and output power.

The above descriptions are only specific embodiments of the present invention, and any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or All steps in a method or process, except mutually exclusive features and/or steps, may be combined in any way.

Claims (6)

1. a helical slow wave structure with variable pitch and variable inner diameter, characterized in that, the helical slow wave structure comprises a helix, an attenuator, a clamping rod and a tube shell; wherein, the helix is composed of three evenly distributed clamps. The holding rod is fixed, and the other end of the clamping rod is fixed on the tube shell; The spiral line includes an input section, an output section and a cut-off area; the cut-off area is located between the input section and the output section for cutting off the feedback path; The attenuator includes a centralized attenuator and a distributed attenuator; wherein, the centralized attenuator is arranged on both sides of the cut-off area for absorbing reflected waves and returning waves, and the distributed attenuator is arranged in the input section, and its function is to absorb reflected waves and return waves; The pitch of the input section is fixed, the inner diameter is gradually changing, and the inner diameter S ₁ at the starting end and the diameter S ₂ in the cut-off area satisfy the relationship S ₁ =1.0769S ₂ , and the electronic injection is at the end of the input section after the speed modulation and density modulation of the input section. To achieve electronic clustering and establish growth waves; The inner diameter of the output section changes gradually, the pitch jumps, and the output section is divided into a phase speed increase section, a negative jump section, a positive jump section and a phase speed reduction section in turn, and the pitch of each section corresponds to P ₁ , P ₂ , P ₃ and P ₄ , the axial lengths are L ₂ , L ₃ , L ₄ and L ₅ respectively, the phase velocity increasing segment is used to compensate the electron phase, and the clustered electrons at the end of the input segment are further clustered, and the phase velocity decreases The segment transfers the energy of the electron injection to the electromagnetic field as much as possible to complete the energy output; among them, P ₂ =0.974P ₁ , P ₃ =1.026P ₁ , P ₄ =0.962P ₁ , L ₂ =0.22L, L ₃ =0.08L , L ₄ =0.2L, L ₅ =0.087L, L is the overall length of the slow-wave structure; The inner diameter of the input section and the output end helix are the same in the cut-off area and at both ends, and the pitches of the input section and the phase velocity increasing section are the same, both P ₁ . 2 . The helical slow-wave structure according to claim 1 , wherein the axial length L ₁ of the input section should satisfy the relation: L ₁ =0.4L-0.413L, wherein L is the slow-wave structure. 3 . The overall length is 80-100mm. 3 . The helical slow wave structure according to claim 1 , wherein the length of the pitch P ₁ is 0.3-0.5 mm. 4 . 4 . The helical slow wave structure according to claim 1 , wherein the axial length of the cut-off region is 1-2 mm. 5 . 5 . The helical slow-wave structure according to claim 1 , wherein one or more distributed attenuators are provided, so that the gain of the electron injector after passing through the input section does not exceed 26 dB. 6 . 6 . The helical slow wave structure according to claim 1 , wherein the distributed attenuator and the concentrated attenuator have different attenuations. 7 .

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