A Q-band broadband 45W space traveling wave tube NPR performance design method for communication satellites

Abstract

The present invention provides a method for designing the NPR performance of a Q-band broadband 45W space traveling wave tube for a communication satellite. By selecting appropriate voltage and current, a high-frequency parameter with high efficiency tending to flatten high-frequency dispersion is selected in high-frequency parameter selection. In the design of the beam-wave interaction structure, a positive jump pitch combination is adopted in the input section to fully modulate the electron beam so as to improve the stability of the whole tube. The output section spiral line innovatively adopts a "double excitation" pitch combination structure. With the gradual enhancement of the electron beam clustering effect, differential modulation at different frequencies is performed through this pitch combination structure, so as to effectively improve the in-band power flatness and the NPR index. The pitch is increased after the energy exchange section at the end of the output spiral line, so as to effectively reduce the electron beam defocusing and improve the flow rate of the whole tube on the one hand; on the other hand, the matching with the energy transmission system is improved, the output standing wave is reduced, and the NPR index can also be further improved.

Description

Technical Field

[0001] The invention relates to the field of communication satellite Q-band broadband 45W space traveling wave tubes, and in particular to a communication satellite Q-band broadband 45W space traveling wave tube NPR performance design method. Background Art

[0002] Space traveling wave tubes are widely used in communication satellite systems due to their high power, high efficiency, ultra-wideband, high reliability, long life and radiation resistance. As the final amplifier of satellite communication, space traveling wave tubes play an important role in signal amplification and transmission. In satellite communication, in order to reduce the power consumption of satellite payloads, a multi-carrier working mode is used to increase the data transmission capacity of the system under limited available frequency bandwidth. It is necessary to realize multi-channel communication through a single space traveling wave tube amplifier, that is, the working bandwidth of the traveling wave tube is divided into multiple channels, and multiple signals can be transmitted simultaneously. Due to the influence of nonlinear distortion in the traveling wave tube, the concurrence of multiple signals during the communication process will cause mutual interference between multiple signals, affecting the accuracy of satellite communication and data transmission. In order to ensure the quality of communication, the space traveling wave tube is required to have good linearity. In order to reduce the mutual crosstalk between signals and reduce the bit error rate of the system, the traditional method adopts the working point power back-off method to reduce the influence of nonlinear distortion. On the one hand, reducing the signal power affects the communication distance, and on the other hand, it also reduces the working efficiency of the traveling wave tube, causing losses to communication satellites with extremely tight energy. Therefore, traditional linearity indicators such as AM-AM characteristics and AM-PM characteristics are not sufficient to accurately measure the linearity of the TWT in multi-carrier operation mode, and more advanced linearity indicators need to be specified. Noise power ratio (NPR) is particularly suitable for analyzing the linear characteristics of TWT amplifiers driven by multi-carrier signals. This criterion can take into account all types of interference, including noise, intermodulation, inter-channel interference and external channel interference.

[0003] Noise power ratio is an important indicator proposed by users for space traveling wave tube amplifiers and space traveling wave tubes for communication satellites in recent years. It is used to test the amplitude linearity of transponders working under wide bandwidth and multi-channel conditions. The amplitude linearity of traditional amplifiers is characterized by third-order intermodulation indicators, while NPR is a measurement method that is closer to the real signal. It uses broadband modulation or noise signals with notches as excitation signals to measure intermodulation and noise floor at the RF output end, and has been accepted and used by more and more users. Broadband signal generation with notches Use a vector signal generator equipped with options to generate multi-carrier continuous wave (MCCW) signals for simulating broadband signals. Reduce a set of CW single-tone signals to generate notched signals with steep edges and a maximum switching ratio of 50 dB. Users can use the control menu to adjust the position and width of the signal notch. Use a signal and spectrum analyzer equipped with options to easily measure the depth of the notch position of the signal after passing through the DUT.

[0004] High-throughput communication satellites have put forward clear requirements for the NPR performance of Q-band broadband 45W space traveling waves. After theoretical analysis, it is necessary to optimize and improve the dispersion of the traveling wave tube slow-wave circuit and the injection wave interaction structure of the slow-wave circuit to achieve the improvement of the product NPR index under the premise of ensuring high efficiency. The existing high-throughput communication satellites have the problems of low NPR index of data capacity and transmission distortion. Therefore, a communication satellite Q-band broadband 45W space traveling wave tube NPR performance design method is proposed. Summary of the invention

[0005] The purpose of the present invention is to: in view of the problems raised by the existing background technology, in order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions: a communication satellite Q-band broadband 45W space traveling wave tube NPR performance design method, comprising step one, selecting voltage and current, selecting high-frequency parameters with high efficiency that tend to flatten high-frequency dispersion in high-frequency parameter selection; step two, in the design of the beam-wave interaction structure, a positive jump pitch combination is adopted in the input section to fully modulate the electron beam, and the output section spiral line innovatively adopts a "double excitation" pitch combination structure; step three, differential modulation at different frequencies is performed through this pitch combination structure; step four, the pitch is increased after the energy exchange section at the end of the output spiral line.

[0006] As a preferred technical solution of the present invention, it also includes a slow-wave circuit design method, which includes using a positive jump pitch combination in the input modulation section to make the electron beam well modulated, and the input length is as long as possible, and the output spiral line clustering section innovatively uses a "double excitation" pitch combination structure, and as the electron beam clustering gradually increases, the electron beams at different frequency points are differentially modulated.

[0007] As a preferred technical solution of the present invention, the slow-wave circuit design method also includes: outputting a spiral line synchronization segment, performing two negative jumps, reducing the line wave phase speed, maintaining the synchronization relationship between injection waves, improving electronic efficiency, and reducing nonlinear distortion, and increasing the pitch at the end of the output spiral line energy exchange segment.

[0008] As a preferred technical solution of the present invention, it also includes a slow-wave circuit, wherein the synchronization voltage of the slow-wave circuit is selected to be 8700V and the total current is 36mA.

[0009] As a preferred technical solution of the present invention, the pitch of the slow-wave circuit input modulation segment mainly includes p1 and p2, where p1=0.31mm, p2=0.322mm, wherein the corresponding length of p1 is 18mm, the length of the gradient segment from p1 to p2 is 8mm, and the corresponding length of the uniform pitch segment of p2 is 21.8mm.

[0010] As a preferred technical solution of the present invention, the pitches of the slow-wave circuit output cluster segments mainly include p3, p4, and p5, among which p3=0.327mm, p4=0.337mm, and p5=0.318mm, wherein the corresponding length of p3 is 20mm, the length of the gradient segment from p3 to p4 is 4.6mm, the corresponding length of the uniform pitch segment of p4 is 4.6mm, the length of the gradient segment from p4 to p5 is 6mm, and the corresponding length of the uniform pitch segment of p5 is 2mm.

[0011] As a preferred technical solution of the present invention, the slow-wave circuit output synchronization segment pitches mainly include p6 and p7, wherein p6=0.31mm, p7=0.273mm, and the lengths of the two gradient segments are 5.4mm and 3.8mm respectively.

[0012] As a preferred technical solution of the present invention, the pitch of the slow-wave circuit output energy exchange section is mainly p7, with a length of 1.2 mm, and the output end has a large pitch of p8=0.342 mm and a length of 0.8 mm.

[0013] As a preferred technical solution of the present invention, it also includes a high-frequency structure. The high-frequency structure optimizes and flattens the dispersion, and the injection wave interaction structure optimizes and improves the in-band power flatness. The design obtains a Q band with a bandwidth of 4GHz and an output power greater than 45W. The electronic efficiency fluctuation value is reduced from 2.29% to 0.31%, and the NPR values ​​of the three high, medium and low frequency points are all better than 15dBc.

[0014] As a preferred technical solution of the present invention, the NPR index of the slow-wave circuit after optimization meets the technical requirement of ≥15.0dB.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] In the scheme of the present invention:

[0017] 1. The power flatness within the frequency band is improved by adopting the "double excitation" pitch combination structure. At the same time, the pitch is increased after the resynchronization section at the end of the output helix line. On the one hand, the electron beam defocusing is effectively reduced and the flow rate of the whole tube is improved; on the other hand, the matching with the energy transmission system is improved, the output standing wave is reduced, and the NPR index can be further improved, solving the problem of low NPR index that affects the data capacity and transmission distortion of high-throughput communication satellites;

[0018] 2. By selecting appropriate voltage and current, high-frequency parameters with high efficiency that tend to flatten high-frequency dispersion are selected in high-frequency parameter selection. In the design of the beam-wave interaction structure, a positive jump pitch combination is used in the input section to fully modulate the electron beam to improve the stability of the entire tube. The output section spiral line innovatively adopts a "double excitation" pitch combination structure. As the electron beam clustering effect gradually increases, differential modulation at different frequencies is performed through this pitch combination structure, which effectively improves the in-band power flatness and the NPR index. The pitch is increased after the energy exchange section at the end of the output spiral line. On the one hand, it effectively reduces the electron beam defocusing and improves the flow rate of the entire tube; on the other hand, it improves the matching with the energy transmission system, reduces the output standing wave, and can further improve the NPR index. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a slow-wave circuit design method provided by the present invention;

[0020] Figure 2 This is a pitch distribution diagram of the slow-wave circuit provided by the present invention. DETAILED DESCRIPTION

[0021] To make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiment is a specific implementation of the present invention and is not limited to all embodiments.

[0022] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents some embodiments of the present invention. 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.

[0023] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features and technical solutions therein can be combined with each other. It should be noted that similar numbers and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0024] Example: See Figure 1-2A method for designing the NPR performance of a Q-band broadband 45W space traveling wave tube for a communication satellite comprises the following steps: first, selecting a suitable voltage and current, and selecting a high-frequency parameter with high efficiency that tends to flatten the high-frequency dispersion in the high-frequency parameter selection; second, in the design of the beam-wave interaction structure, a positive jump pitch combination is adopted in the input section to make the electron beam fully modulated to improve the stability of the whole tube; the output section spiral line innovatively adopts a "double excitation" pitch combination structure, and as the electron beam clustering effect gradually increases; third, differential modulation is performed at different frequencies through this pitch combination structure, so as to effectively improve the in-band power flatness and the NPR index; fourth, the pitch is increased after the energy exchange section at the end of the output spiral line, which, on the one hand, effectively reduces the electron beam defocusing and improves the flow rate of the whole tube; on the other hand, it improves the matching with the energy transmission system, reduces the output standing wave, and can also further improve the NPR index.

[0025] See also Figure 1 , and also includes a slow-wave circuit design method. The slow-wave circuit design method includes using a positive jump pitch combination in the input modulation section to make the electron beam well modulated, and the input length is as long as possible to improve the working stability of the whole tube. The output spiral line clustering section innovatively adopts a "double excitation" pitch combination structure. As the electron beam clustering gradually increases, the electron beams at different frequency points are differentially modulated to further reduce the power fluctuation within the band and improve the NPR index.

[0026] See also Figure 1 , Figure 2 The slow-wave circuit design method also includes: in the synchronous section of the output spiral line, two negative jumps are performed to reduce the phase velocity of the line wave, maintain the synchronization relationship between the injection waves, improve the electronic efficiency, and reduce the nonlinear distortion. The pitch is increased at the end of the energy exchange section of the output spiral line. On the one hand, it effectively reduces the defocusing of the electron injection and improves the flow rate of the whole tube; on the other hand, it improves the matching with the energy transmission system, reduces the output cold injection wave, and can also further improve the NPR index.

[0027] See also Figure 1-Figure 2, also includes a slow-wave circuit, the synchronization voltage of the slow-wave circuit is selected to be 8700V, the total current is 36mA, the input modulation segment pitch of the slow-wave circuit mainly includes p1 and p2, wherein p1=0.31mm, p2=0.322mm, wherein the corresponding length of p1 is 18mm, the length of the gradient segment from p1 to p2 is 8mm, and the corresponding length of the uniform pitch segment of p2 is 21.8mm, the output cluster segment pitch of the slow-wave circuit mainly includes p3, p4, and p5, wherein p3=0.327mm, p4=0.337mm, and p5=0.318mm, wherein the corresponding length of p3 is 20mm, the length of the gradient segment from p3 to p4 is 4.6mm, the corresponding length of the uniform pitch segment of p4 is 4.6mm, the length of the gradient segment from p4 to p5 is 6mm, and the corresponding length of the uniform pitch segment of p5 is 2mm, the pitch of the output synchronization segment of the slow-wave circuit mainly includes p6 and p7, among which p6=0.31mm, p7=0.273mm, and the lengths of the two gradient segments are 5.4mm and 3.8mm respectively. The pitch of the output energy exchange segment of the slow-wave circuit is mainly p7, with a length of 1.2mm, and the large pitch at the output end is p8=0.342mm, with a length of 0.8mm. It also includes a high-frequency structure, and the high-frequency structure is optimized to flatten the dispersion, and the injection wave interaction structure is optimized to improve the power flatness within the band. The design obtains a Q band with a bandwidth of 4GHz and an output power greater than 45W. The electronic efficiency fluctuation value is reduced from 2.29% to 0.31%, and the NPR values ​​of the three frequency points of high, medium and low are all better than 15dBc. The NPR index of the optimized slow-wave circuit meets the technical requirement of ≥15.0dB.

[0028] Working principle: During the use of the present invention, step one, select appropriate voltage and current, and select high-frequency parameters with high efficiency that tend to flatten high-frequency dispersion in high-frequency parameter selection; step two, in the design of the beam-wave interaction structure, a positive jump pitch combination is used in the input section to fully modulate the electron beam to improve the stability of the entire tube; the output section spiral line innovatively adopts a "double excitation" pitch combination structure, as the electron beam clustering effect gradually increases; step three, differential modulation at different frequencies is performed through this pitch combination structure, which effectively improves the in-band power flatness and improves the NPR index; step four, the pitch is increased after the energy exchange section at the end of the output spiral line, which effectively reduces the electron beam defocusing and improves the circulation of the entire tube. rate; on the other hand, it improves the matching with the energy transmission system, reduces the output standing wave, and can further improve the NPR index. The slow-wave circuit design method includes using a positive jump pitch combination in the input modulation section to make the electronic beam well modulated, and the input length is as long as possible to improve the working stability of the whole tube. The output spiral line clustering section innovatively adopts a "double excitation" pitch combination structure. As the electronic beam clustering gradually increases, the electronic beams at different frequency points are differentially modulated, so that the power fluctuation within the band is further reduced, and the NPR index is improved. The slow-wave circuit design method also includes: the output spiral line synchronization section, two negative jumps, while reducing the line wave phase speed to maintain the synchronization relationship between the beam waves to improve the electronic While increasing efficiency, it reduces nonlinear distortion. The pitch at the end of the energy exchange section of the output spiral line is increased. On the one hand, it effectively reduces electron injection defocusing and improves the flow rate of the whole tube; on the other hand, it improves the matching with the energy transmission system, reduces the output cold injection wave, and can further improve the NPR index. The synchronous voltage of the slow-wave circuit is selected as 8700V and the total current is 36mA. The pitch of the input modulation section of the slow-wave circuit mainly includes p1 and p2, among which p1=0.31mm, p2=0.322mm, among which the corresponding length of p1 is 18mm, the length of the gradient section from p1 to p2 is 8mm, and the corresponding length of the uniform pitch section of p2 is 21.8mm. The pitch of the output clustering section of the slow-wave circuit mainly includes p3, p4, and p5. Among them, p3=0.327mm, p4=0.337mm, p5=0.318mm, wherein the corresponding length of p3 is 20mm, the length of the gradient section from p3 to p4 is 4.6mm, the corresponding length of the uniform pitch section of p4 is 4.6mm, the length of the gradient section from p4 to p5 is 6mm, and the corresponding length of the uniform pitch section of p5 is 2mm. The pitch of the output synchronization section of the slow wave circuit mainly includes p6 and p7, wherein p6=0.31mm, p7=0.273mm, and the lengths of the two gradient sections are 5.4mm and 3.8mm respectively. The pitch of the output energy exchange section of the slow wave circuit is mainly p7, with a length of 1.2mm, and the output end large pitch p8=0.342mm, with a length of 0.8mm, and also includes a high-frequency structure, the high-frequency structure optimizes and flattens the dispersion, the injection wave interaction structure optimizes and improves the in-band power flatness, the design obtains the Q band, the bandwidth is 4GHz, the output power is greater than 45W, the electronic efficiency fluctuation value is reduced from 2.29% to 0.31%, and the NPR values ​​of the three frequency points of high, medium and low are all better than 15dBc. The NPR index of the slow-wave circuit after optimization meets the technical requirement of ≥15.0dB. .

[0029] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the above specific implementation methods. Therefore, any modification or equivalent replacement of the present invention; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the invention are included in the scope of the claims of the present invention.

Claims

1. A communication satellite Q-band broadband 45W space traveling wave tube NPR performance design method, characterized in that: The following steps are involved: Step 1: Select voltage and current, and select high-frequency parameters that tend to flatten high-frequency dispersion in high-frequency parameter selection; Step 2: In the design of the beam-wave interaction structure, a positive jump pitch combination is used in the input section to fully modulate the electron beam, and the output section spiral line innovatively adopts a "double excitation" pitch combination structure; Step 3: Differential modulation at different frequencies is performed through this pitch combination structure; Step 4: Increase the pitch after the energy exchange section at the end of the output spiral line; The invention also includes a slow wave circuit design method, wherein the slow wave circuit design method includes adopting a positive jump pitch combination in the input modulation section to make the electron beam well modulated, and the input length is as long as possible, and adopting a "double excitation" pitch combination structure in the output spiral line clustering section, and differentially modulating the electron beams at different frequency points as the electron beam clustering gradually increases; In the synchronous section of the output spiral line, two negative jumps are performed to reduce the phase speed of the line wave, maintain the synchronization relationship between the injection waves, improve the electronic efficiency, and reduce the nonlinear distortion. At the end of the energy exchange section of the output spiral line, the pitch is increased; The synchronous voltage of the slow wave circuit is selected as 8700V and the total current is 36mA; The pitch of the input modulation section of the slow wave circuit mainly includes p1 and p2, wherein p1=0.31mm, p2=0.322mm, wherein the corresponding length of p1 is 18mm, the length of the gradual change section from p1 to p2 is 8mm, and the corresponding length of the uniform pitch section of p2 is 21.8mm; The pitches of the slow wave circuit output clustering segments are mainly p3, p4, and p5, wherein p3=0.327mm, p4=0.337mm, and p5=0.318mm, wherein the corresponding length of p3 is 20mm, the length of the gradual transition segment from p3 to p4 is 4.6mm, the corresponding length of the uniform pitch segment of p4 is 4.6mm, the length of the gradual transition segment from p4 to p5 is 6mm, and the corresponding length of the uniform pitch segment of p5 is 2mm; The slow wave circuit output synchronization segment pitches are mainly p6 and p7, where p6=0.31mm, p7=0.273mm, and the lengths of the two gradient segments are 5.4mm and 3.8mm respectively; The pitch of the output energy exchange section of the slow wave circuit is mainly p7, with a length of 1.2 mm, and the large pitch of the output end is p8=0.342 mm, with a length of 0.8 mm.

2. A communication satellite Q-band broadband 45W space traveling wave tube NPR performance design method according to claim 1, characterized in that: It also includes a high-frequency structure, which optimizes and flattens the dispersion, and optimizes the wave injection interaction structure to improve the flatness of the power within the band. The design obtains a Q band with a bandwidth of 4 GHz and an output power greater than 45 W. The electronic efficiency fluctuation value is reduced from 2.29% to 0.31%, and the NPR values ​​at the three frequency points of high, medium and low are all better than 15 dBc.

3. A communication satellite Q-band broadband 45W space traveling wave tube NPR performance design method according to claim 2, characterized in that: The NPR index of the slow-wave circuit after optimization meets the technical requirement of ≥15.0dB.

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