A frequency multiplication backward wave oscillator and harmonic amplification method

Abstract

The application discloses a frequency multiplication backward wave oscillator and a harmonic amplification method. The frequency multiplication backward wave oscillator comprises a first slow wave structure and a second slow wave structure. The first slow wave structure comprises a first electron beam channel and a first grating extending along the first electron beam channel. The second slow wave structure comprises a second electron beam channel and a second grating and a third grating extending along the second electron beam channel. The working frequency of the third grating is N times of the working frequencies of the first grating and the second grating, wherein N is a positive integer. A connecting waveguide is connected between the first electron beam channel and the second electron beam channel. A first output port is arranged on the second electron beam channel. The application can significantly reduce the starting current density, improve the output power and shorten the starting time by using one slow wave structure to generate electromagnetic waves for one electron beam and then delivering the electromagnetic waves to another slow wave structure to modulate another electron beam.

Description

Technical Field

[0001] This invention relates to the field of vacuum electronic devices, specifically to a frequency doubling backward wave oscillator and a harmonic amplification method. Background Technology

[0002] As an important high-power radiation source device, the backward-wave tube has a compact structure, a wide frequency tuning range, and its output is unaffected by the load, producing a stable frequency output signal. It can generate high-power, wide-bandwidth, and high-efficiency electromagnetic radiation in the millimeter-wave and even terahertz bands. Therefore, the backward-wave tube is often used as a radiation source to generate microwaves, millimeter waves, and THz.

[0003] Currently, the output power of terahertz backward wave tubes (TWBs) is at the milliwatt level, and there is a need to develop towards higher output power. Existing technologies for improving the output power of TWBs can be broadly categorized into three types: First, synthesizing the signals generated by multiple identical TWBs. However, this method requires stringent consistency in the frequency and phase of each signal, making it difficult to implement. Furthermore, each TWB requires an independent electron-optical system, and directly synthesizing the TWB signals inevitably leads to excessively large and heavy overall device size. Second, optimizing the design of existing terahertz TWBs, including their electron gun, focusing system, and electron collector, while improving the fabrication precision, ultimately aims to increase output power and improve performance. However, this method only increases the output power of the TWB by improving related components and fabrication precision, resulting in limited power enhancement. Third, exploring new slow-wave structures to improve the high-frequency characteristics of the TWB and thus enhance its performance. This method can directly improve the properties of slow-wave structures and has research potential. However, the design of slow-wave structures is difficult to fabricate due to their small size, resulting in high production costs. Summary of the Invention

[0004] One objective of this invention is to provide a frequency-doubling backward wave oscillator, which has two slow-wave structures. The electromagnetic wave generated by the oscillation of the electron beam in one slow-wave structure modulates the electron beam in the other slow-wave structure, which can effectively reduce the starting current density, extract high-frequency electromagnetic waves more quickly, improve the fundamental frequency output power, quickly obtain frequency-doubling output, and significantly improve output performance.

[0005] This invention is achieved through the following technical solution:

[0006] A frequency-doubling backward wave oscillator includes a first slow-wave structure and a second slow-wave structure. The first slow-wave structure includes a first electron beam channel and a first grating extending along the first electron beam channel. The second slow-wave structure includes a second electron beam channel and a second grating and a third grating extending along the second electron beam channel. The operating frequency of the third grating is N times the operating frequencies of the first grating and the second grating, where N is a positive integer. A connecting waveguide connects the first electron beam channel and the second electron beam channel. A first output port is provided on the second electron beam channel.

[0007] In this technical solution, the frequency doubling backward wave oscillator includes a first and a second slow wave structure. The first and second slow wave structures can be two parallel slow wave structures or two stacked slow wave structures. Preferably, the first slow wave structure is the lower slow wave structure and the second slow wave structure is the upper slow wave structure.

[0008] In this technical solution, the first slow-wave structure includes a first electron beam channel, which is connected to an electron beam generating unit integrated into the oscillator or externally, to input a first electron beam into the first electron beam channel. The first slow-wave structure also includes a first grating extending along the first electron beam channel. The first grating can be a planar grating, a symmetrical grating, or an interlaced grating; preferably, it is a planar grating. When the first electron beam propagates along the first electron beam channel passes through the periodic structure of the first grating, it excites a first electromagnetic wave. Through the frequency selection characteristics of the slow-wave circuit, the electron beam interacts with the first electromagnetic wave of a specific frequency, causing velocity and density modulation of the first electron beam, leading to clustering. Ultimately, the first electron beam exchanges energy with the first electromagnetic wave.

[0009] In this technical solution, the second slow-wave structure includes a second electron beam channel. Similarly, the second electron beam channel is connected to an electron beam generating unit that is integrated into the oscillator or externally, so as to input a second electron beam into the second electron beam channel. The second slow-wave structure also includes a second grating and a third grating extending along the second electron beam channel. The third grating serves as a frequency doubling region, and its operating frequency is set to N times that of the first grating and the second grating.

[0010] A connecting waveguide between the second slow-wave structure and the first slow-wave structure connects the first and second electron beam channels, allowing the first electromagnetic wave generated in the first electron beam channel to be transmitted to the second electron beam channel via the connecting waveguide. In this technical solution, the area of ​​the connecting waveguide on the electron beam transmission cross-section should be smaller than the area of ​​the electron beam transmission cross-section, so that the second electron beam in the second electron beam channel, after modulation, can continue to move towards the third grating through the cross-section where the connecting port of the connecting waveguide is located, and under the action of the third grating, it is frequency-multiplied and output, extracting electromagnetic waves of several times the frequency, and outputting them through the second output port.

[0011] In this technical solution, the operating frequencies of the first and second gratings are lower than those of the frequency-doubled third grating. The low-frequency first electron beam is more likely to oscillate when passing through the first grating and is also more likely to interact with the generated first electromagnetic wave. Subsequently, the first electromagnetic wave is transmitted to the second grating with the same operating frequency as the first grating via a connecting waveguide. After coupling with the second grating, the second electron beam is quickly modulated to generate the second electromagnetic wave, which not only effectively improves the modulation effect of the second electron beam but also significantly increases the output power of the second electromagnetic wave. Subsequently, the modulated second electron beam can quickly extract the frequency-doubled power when passing through the third grating, thereby effectively reducing the oscillation current density of the third grating and greatly improving the efficiency of the generated third electromagnetic wave.

[0012] In some embodiments, two output ports can be opened on the second electron beam channel: one for outputting the second electromagnetic wave at the base frequency and part of the first electromagnetic wave, and the other for outputting the third electromagnetic wave at a frequency multiple.

[0013] In this technical solution, a slow-wave structure is used to oscillate an electron beam to generate electromagnetic waves, and then the electromagnetic waves are transmitted to another slow-wave structure to modulate another electron beam. This can significantly improve the output efficiency and shorten the oscillation time, providing a new approach for the development of terahertz vacuum electronic devices.

[0014] In a preferred embodiment of the present invention, the length of the first grating is greater than the length of the second grating along the extension direction of the electron beam channel. The first and second gratings operate at the same frequency so that the electromagnetic wave generated by the first grating can rapidly modulate the second electron beam passing through the second grating after interacting with the first electron beam. In this technical solution, the length of the first grating needs to be long enough to allow sufficient space for the first electron beam to oscillate as it passes through, while the second grating is mainly used for the rapid modulation of the second electron beam by the first electromagnetic wave. Therefore, the space of the second grating can be small enough to provide sufficient space for connecting the waveguide and the third grating.

[0015] In some preferred embodiments, the length of the first grating is 2 to 10 times the length of the second grating. Preferably, the length of the first grating is 2 to 5 times the length of the second grating.

[0016] In another preferred embodiment of the present invention, a first Bragg reflector is disposed on the first electron beam channel, and the first Bragg reflector is located between the entrance of the first electron beam channel and the first grating. The first Bragg reflector disposed in the first electron beam channel is used to cut off and reflect the reflected wave signal generated by the first grating, that is, the first electromagnetic wave, so that the first electromagnetic wave signal is mainly output to the second electron beam channel through the connecting waveguide. This effectively avoids the modulation of the first electron beam in the drift tube region by the first electromagnetic wave, thereby increasing the output power of the first grating and making the output spectrum purer.

[0017] Furthermore, the second electron beam channel is equipped with a second Bragg reflector, a third Bragg reflector, and a second output port. The second output port, the second grating, and the connecting waveguide are located between the second and third Bragg reflectors. In this technical solution, the second and third Bragg reflectors on the second electron beam channel are used to cut off and reflect the second electromagnetic wave generated by the second grating, so that the second electromagnetic wave is mainly output through the second output port, further improving the output power of the second electromagnetic wave. In addition, the second and third Bragg reflectors enable dual-frequency output of the second and third electromagnetic waves.

[0018] Furthermore, a fourth Bragg reflector is disposed on the second electron beam channel, located between the second grating and the third grating. The fourth Bragg reflector is used to cut off and reflect the third electromagnetic wave generated on the third grating, so that the third electromagnetic wave is mainly output through the first output port, thereby reducing the oscillation current density of the third electromagnetic wave, reducing the oscillation time, and improving the output performance.

[0019] Furthermore, the first and second electron beam channels are connected to an electron beam emitting surface, which is used to emit electron beams at the same speed into the first and second electron beam channels. In this technical solution, both the first and second electron beam channels are connected to an electron beam emitting surface, which emits the first and second electron beams into the first and second electron beam channels respectively. The two electron beams work simultaneously with the same speed and voltage, ultimately achieving dual-frequency output of the oscillator.

[0020] Furthermore, the electron beam is a strip-shaped electron beam.

[0021] In some preferred embodiments, N is 2 to 5, that is, the operating frequency of the third grating is 2 to 5 times the operating frequency of the first and second gratings. More preferably, N is 2 or 3.

[0022] Furthermore, the operating frequency of the first grating is 50–200 GHz.

[0023] Furthermore, the first grating, the second grating, and the third grating are individually selected from planar gratings, symmetrical gratings, or interlaced gratings.

[0024] Another object of the present invention is to provide a harmonic amplification method based on any of the aforementioned frequency doubling backwave oscillators. Specifically, the harmonic amplification method includes the following steps:

[0025] The first electron beam enters the first electron beam channel, and the second electron beam enters the second electron beam channel;

[0026] The first electron beam is excited by the first grating to generate a first electromagnetic wave. After the first electromagnetic wave interacts with the first electron beam, it is transmitted to the second electron beam channel through the connecting waveguide.

[0027] The first electromagnetic wave entering the second electron beam channel is coupled with the second grating to modulate the second electron beam. The resulting second electromagnetic wave is output through the second output port. Then, the second electron beam is modulated by the third grating to generate a frequency-doubled third electromagnetic wave, which is output through the first output port.

[0028] In this technical solution, the first electromagnetic wave generated by the oscillation of the first electron beam is used to modulate the second electron beam. The second and third electromagnetic waves generated by the modulated second electron beam when passing through the second and third gratings start oscillating rapidly at a lower current density, thereby improving the output performance.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. This invention uses a slow-wave structure to oscillate an electron beam to generate electromagnetic waves, and then transmits the electromagnetic waves to another slow-wave structure to modulate another electron beam. This can significantly improve the output power and shorten the oscillation time, providing a new approach for the development of terahertz vacuum electronic devices.

[0031] 2. The present invention sets the lengths of the first grating and the second grating, which have the same operating frequency, to be 2 to 10 times the length of the first grating. This allows the first grating to have enough space to allow the first electron beam to oscillate, while the second grating has enough space to allow the electromagnetic wave to quickly modulate the second electron beam. At the same time, it provides enough space for connecting the waveguide and the third grating so that the overall structure of the frequency doubling backwave oscillator is compact.

[0032] 3. This invention utilizes at least one Bragg reflector to cut off and reflect electromagnetic waves, causing the generated electromagnetic waves to move mainly along specific directions, thereby further improving the output power of the electromagnetic waves and making the output spectrum purer.

[0033] 4. This invention employs two electron beams with the same frequency, speed, and voltage to work and be adjusted simultaneously, ultimately achieving dual-frequency output. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 This is a schematic diagram of the frequency doubling backward wave oscillator in a specific embodiment of the present invention;

[0036] Figure 2The output power results of a single 110GHz flat comb slow wave structure backwave tube are shown in Figure (a), and the output power results of the second electromagnetic wave output through the second output port in a specific embodiment of the present invention are shown in Figure (b) and the spectrum diagram (c).

[0037] Figure 3 In a specific embodiment of the present invention, the current density is 50 A / cm². 2 A comparison of the output power of the third electromagnetic wave output through the first output port and the output power of a single 220GHz planar comb slow-wave structure backwave tube structure, a structure lacking the first grating structure, and a structure lacking the second grating structure (a), with a current density of 40A / cm². 2 Output power comparison chart (b) and spectrum chart (c);

[0038] Figure 4 This is a flowchart of the harmonic amplification method in a specific embodiment of the present invention.

[0039] The attached diagram shows the markings and corresponding component names:

[0040] 1-First grating, 2-Second grating, 3-Third grating, 4-Connecting waveguide, 5-First output port, 6-Second output port, 7-First electron beam channel, 8-Second electron beam channel, 9-Electron beam emitting surface, 10-First Bragg reflector, 11-Second Bragg reflector, 12-Third Bragg reflector, 13-Fourth Bragg reflector. Detailed Implementation

[0041] 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. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0042] In the description of this invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0043] Example 1:

[0044] like Figure 1The frequency doubling backward wave oscillator shown includes a first slow wave structure and a second slow wave structure. The first slow wave structure includes a first electron beam channel 7 and a first grating 1 extending along the first electron beam channel 7. The second slow wave structure includes a second electron beam channel 8 and a second grating 2 and a third grating 3 extending along the second electron beam channel 8. The operating frequency of the third grating 3 is N times the operating frequency of the first grating 1 and the second grating 2, where N is a positive integer. A connecting waveguide 4 connects the first electron beam channel 7 and the second electron beam channel 8. A first output port 5 is provided on the second electron beam channel 8.

[0045] During operation, first and second electron beams with the same speed are input into the first and second electron beam channels, respectively. When the first electron beam passes through the first grating, it excites a first electromagnetic wave of a specific frequency, such as 110 GHz. The first electron beam interacts with the first electromagnetic wave, transferring energy to it. The first electromagnetic wave is then output to the second electron beam channel via a connecting waveguide, where it couples with the second grating to modulate the second electron beam and generate a second electromagnetic wave. The second electromagnetic wave and a portion of the first electromagnetic wave can be output through the second output port. Subsequently, the second electron beam is frequency multiplied by the third grating to generate a third electromagnetic wave with a frequency of 220 GHz, which is then output through the first output port.

[0046] In one or more embodiments, such as Figure 1 As shown, the first electron beam channel 7 and the second electron beam channel 8 are connected by an electron beam emitting surface 9, which is used to emit electron beams at the same speed into the first electron beam channel 7 and the second electron beam channel 8.

[0047] In some embodiments, the electron beam is a strip electron beam.

[0048] In some embodiments, N is 2 to 5, preferably 2 or 3.

[0049] In some embodiments, the first grating 1 operates at a frequency of 50–200 GHz.

[0050] In some embodiments, the first grating 1, the second grating 2, and the third grating 3 are individually selected from planar gratings, symmetrical gratings, or staggered gratings.

[0051] In this embodiment, a slow-wave structure is used to oscillate an electron beam to generate electromagnetic waves, and then the electromagnetic waves are transmitted to another slow-wave structure to modulate another electron beam. This can significantly reduce the oscillation current density, increase the output power, and shorten the oscillation time, providing a new approach for the development of terahertz vacuum electronic devices.

[0052] Example 2:

[0053] Based on Embodiment 1, along the extension direction of the electron beam channel, the length of the first grating 1 is greater than the length of the second grating 2.

[0054] In this embodiment, the length of the first grating needs to be long enough so that the first electron beam has enough space to oscillate when it passes through, while the second grating is mainly used for the first electromagnetic wave to rapidly modulate the second electron beam. Therefore, the space of the second grating can be small enough to provide enough space for connecting the waveguide and the third grating.

[0055] In some preferred embodiments, the length of the first grating 1 is 2 to 10 times the length of the second grating 2.

[0056] Example 3:

[0057] Based on the above embodiments, such as Figure 1 As shown, a first Bragg reflector 10 is provided on the first electron beam channel 7, and the first Bragg reflector 10 is located between the entrance of the first electron beam channel 7 and the first grating 1.

[0058] In some preferred embodiments, the second electron beam channel 8 is provided with a second Bragg reflector 11, a third Bragg reflector 12, and a second output port 6. The second output port 6, the second grating 2, and the connecting waveguide 4 are located between the second Bragg reflector 11 and the third Bragg reflector 12. By utilizing the second and third Bragg reflectors, dual-frequency output of the second and third electromagnetic waves is achieved.

[0059] In some preferred embodiments, a fourth Bragg reflector 13 is disposed on the second electron beam channel 8, the fourth Bragg reflector 13 being located between the second grating 2 and the third grating 3.

[0060] In one or more embodiments, the first Bragg reflector may be a cylindrical reflector, a planar rectangular reflector, or a rectangular grating reflector. Preferably, the first Bragg reflector is a rectangular grating Bragg reflector.

[0061] In this embodiment, the Bragg reflector cuts off and reflects electromagnetic waves, causing the generated electromagnetic waves to move mainly in a specific direction, which further improves the output power of the electromagnetic waves and makes the output spectrum purer.

[0062] Example 4:

[0063] like Figure 4 The harmonic amplification method shown here is characterized by employing the frequency doubling backward wave oscillator in any of the aforementioned embodiments. The harmonic amplification method specifically includes the following steps:

[0064] The first electron beam enters the first electron beam channel 7, and the second electron beam enters the second electron beam channel 8;

[0065] The first electron beam is excited by the first grating 1 to generate a first electromagnetic wave. After the first electromagnetic wave interacts with the first electron beam, it is transmitted to the second electron beam channel 7 through the connecting waveguide 4.

[0066] After the first electromagnetic wave entering the second electron beam channel 7 is coupled with the second grating 2, it modulates the second electron beam. The generated second electromagnetic wave is output through the second output port 6. Then, the second electron beam is modulated by the third grating 3 to generate a frequency-doubled third electromagnetic wave, which is output through the first output port 5.

[0067] Example 5:

[0068] To further illustrate the technical effects of this invention, particle simulation calculations were performed on the frequency doubling backward wave oscillator of this application after modeling. Considering losses, the output power and spectrum of the second output port after modulation by the upper fundamental wave structure are shown below. Figure 2 As shown, where Figure 2 (a) Output power results for a single 110GHz planar comb slow-wave structure backwave tube. Figure 2 (b) shows the output power of the first output port in the double-layer cascaded structure of the present invention. By comparison, it can be seen that the present invention achieves greater output power with a faster start-up speed under the same operating parameters.

[0069] The output power and spectrum diagram of the first output port are shown below. Figure 3 As shown, after frequency doubling and modulation by the third grating, a 220GHz output wave was obtained. Compared to the 220GHz planar comb-shaped backwave tube structure, the lack of the first and second grating structures reduces the starting current density, resulting in milliwatt-level power output. Furthermore, by reducing the current density, the dual-layer cascaded structure of this invention can still start oscillating at a relatively fast speed to achieve watt-level output, while other comparative structures cannot start oscillating and have no output. Meanwhile, as... Figure 3 As shown in (c), the dual-layer slow-wave structure of this application achieves frequency doubling output from 110 GHz to 220 GHz.

[0070] The terms "first," "second," and "third," etc., used in this invention (e.g., first grating, second grating, third grating, first electron beam channel, second electron beam channel, etc.) are merely for clarity of description and are not intended to limit any order or emphasize importance. Furthermore, the term "connection" used in this invention, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0071] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A frequency-multiplied backward wave oscillator characterized by, The device includes a first slow-wave structure and a second slow-wave structure. The first slow-wave structure includes a first electron beam channel (7) and a first grating (1) extending along the first electron beam channel (7). The second slow-wave structure includes a second electron beam channel (8) and a second grating (2) and a third grating (3) extending along the second electron beam channel (8). The operating frequency of the third grating (3) is N times the operating frequency of the first grating (1) and the second grating (2), where N is a positive integer. A connecting waveguide (4) is connected between the first electron beam channel (7) and the second electron beam channel (8). A first output port (5) is provided on the second electron beam channel (8). A first Bragg reflector (10) is provided on the first electron beam channel (7), and the first Bragg reflector (10) is located between the entrance of the first electron beam channel (7) and the first grating (1). A second Bragg reflector (11), a third Bragg reflector (12) and a second output port (6) are provided on the second electron beam channel (8), and the second output port (6), the second grating (2) and the connecting waveguide (4) are located between the second Bragg reflector (11) and the third Bragg reflector (12). A fourth Bragg reflector (13) is provided on the second electron beam channel (8), and the fourth Bragg reflector (13) is located between the second grating (2) and the third grating (3).

2. The frequency doubling backward wave oscillator according to claim 1, characterized in that, Along the extension direction of the electron beam channel, the length of the first grating (1) is greater than the length of the second grating (2).

3. The frequency doubling backward wave oscillator according to claim 2, characterized in that, The length of the first grating (1) is 2 to 10 times the length of the second grating (2).

4. The frequency doubling backward wave oscillator according to claim 1, characterized in that, The first electron beam channel (7) and the second electron beam channel (8) are connected by an electron beam emitting surface (9), which is used to emit electron beams at the same speed to the first electron beam channel (7) and the second electron beam channel (8).

5. A frequency-doubling backward wave oscillator according to claim 1, characterized in that, The value of N is 2 to 5.

6. A frequency-doubling backward wave oscillator according to any one of claims 1 to 5, characterized in that, The first grating (1), the second grating (2), and the third grating (3) are each individually selected from a planar grating, a symmetrical grating, or an interlaced grating.

7. A harmonic amplification method, characterized in that, Using any one of claims 1 to 6, the harmonic amplification method includes the following steps: The first electron beam enters the first electron beam channel (7), and the second electron beam enters the second electron beam channel (8). The first electron beam is excited by the first grating (1) to generate the first electromagnetic wave. After the first electromagnetic wave interacts with the first electron beam, it is transmitted to the second electron beam channel (8) through the connecting waveguide (4). After the first electromagnetic wave entering the second electron beam channel (8) is coupled with the second grating (2), it modulates the second electron beam and generates the second electromagnetic wave, which is output through the second output port (6). Then, the second electron beam is modulated by the third grating (3) to generate a frequency-doubled third electromagnetic wave, which is output through the first output port (5).

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