High-power directional coupler for real-time measurement of transmission energy of high-power circular waveguide

Abstract

The invention relates to a high-power directional coupler for real-time measurement of high-power circular waveguide transmission energy. The design comprises a circular waveguide, two coupling holes and two rectangular waveguides vertically connected with the circular waveguide. High-power microwaves are transmitted in the circular waveguide, the two coupling holes are formed in the wall face of the circular waveguide, and the center-to-center distance is lambda / 4 + n * lambda / 2 (lambda is the transmission wavelength, and n is a non-negative integer). The rectangular waveguide is vertically connected with the circular waveguide through the coupling hole, the short side of the rectangular waveguide is axially parallel to the circular waveguide, and the rectangular waveguide is used for receiving coupling energy and measuring transmission power through the power sensor. By averaging transmission energy at the two coupling holes, interference errors caused by echoes are eliminated, and forward transmission energy is accurately measured. According to the design, the fluctuation problem in single-hole measurement is effectively avoided, and the device has the advantages of wide frequency band, low coupling coefficient, high reliability and high power endurance capability, and is suitable for energy real-time measurement and monitoring of a high-power microwave system.

Description

Technical Field

[0001] The invention belongs to the field of microwave power measurement, and in particular relates to a high-power directional coupler suitable for real-time measurement of circular waveguide transmission energy in a high-power microwave emission, transmission and receiving system. Background Art

[0002] As an important part of modern electronic engineering, high-power microwave technology plays an irreplaceable role in radar, communication, weapon systems, scientific experiments and other fields. In high-power microwave systems, accurate monitoring of microwave power is of great significance for optimizing system operating efficiency and ensuring equipment safety. In microwave power measurement technology, circular waveguide is a commonly used transmission structure in high-power microwave systems, and the transmission mode generally adopts TE 01 mode, which has the advantage of being able to support high-power, low-loss microwave transmission.

[0003] Commonly used microwave power measurement methods include water load method and directional coupler method. As a widely used power measurement method in the early days, the water load method works by absorbing microwave energy and converting it into heat, and then calculating the power value by measuring the temperature rise. Although this method has certain feasibility under low power conditions, it has gradually failed to meet the requirements of real-time and accuracy under high power conditions due to the complexity of the system, long thermal equilibrium time and large measurement errors. The traditional single-hole directional coupler couples energy to the secondary waveguide for measurement by opening a hole on the waveguide wall. However, when used in a high-power circular waveguide, if the load end impedance is not matched or the echo is large, a standing wave field distribution will be formed in the transmitted circular waveguide. The measurement result is closely related to the position of the hole, resulting in large fluctuations in the measured value and a significant increase in error. The multi-hole parallel directional coupler uses multiple holes to offset interference waves, but the spacing between its coupling holes is strictly limited by the wavelength, resulting in a narrow bandwidth, which is not suitable for high-power measurement requirements with a wide bandwidth. In addition, multiple openings increase the coupling strength, making it difficult to meet the low coupling coefficient requirements in high-power measurements. At the same time, the local field enhancement between the coupling holes increases the risk of ignition of the directional coupler. At the same time, the traditional microwave power measurement method generally uses a matching load such as a water load to connect to the output end to simulate the overall working state of the high-power microwave system, ignoring the impact of the subsequent transmission segment on the overall microwave power transmission, resulting in large measurement errors, and unable to measure and detect the actual working state of the microwave system in real time.

[0004] Therefore, developing a directional coupler with high precision, wide bandwidth, low coupling coefficient and the ability to adapt to high-power operating conditions is the key to solving the bottleneck of existing technologies. Summary of the invention

[0005] The purpose of the present invention is to propose a high-power directional coupler for real-time measurement of high-power circular waveguide transmission energy, which can perform real-time high-precision power measurement of high-power microwave systems, reduce the measurement error introduced by the load end echo, and meet the high-precision, wide bandwidth and high reliability requirements of high-power microwave systems for energy measurement.

[0006] In order to achieve the above object, the specific scheme of the present invention is as follows: comprising a circular waveguide, two coupling holes, and two rectangular waveguides:

[0007] The circular waveguide is a high-power circular waveguide used to transmit electromagnetic waves in a high-power microwave system;

[0008] The two coupling holes are opened on the circular waveguide wall, and the center distance between the two coupling holes is equal to λ / 4+n*λ / 2, wherein λ is the transmission wavelength of the electromagnetic wave in the circular waveguide, and n is any non-negative integer.

[0009] The two rectangular waveguides are vertically connected to the circular waveguide, and the connection positions are located at two coupling holes for receiving energy transmitted by coupling, and the short sides of the rectangular waveguides are parallel to the transmission direction of the circular waveguide;

[0010] Through the two coupling holes, energy is directionally coupled from the circular waveguide to the two rectangular waveguides, and the mode is also coupled from the TE in the circular waveguide to the two rectangular waveguides. 01 The mode becomes the main TE mode of the rectangular waveguide 10 Mode, the energy transmitted in the forward direction in the circular waveguide is calculated by measuring the coupling coefficient and the transmission power in the rectangular waveguide.

[0011] The spacing between the two coupling holes can be changed by adjusting the value of the parameter n to meet the requirements of different transmission wavelengths and avoid sparking in the high-power transmission system; the diameter of the coupling hole is less than half of the transmission wavelength to ensure that the field distribution in the circular waveguide is basically unaffected, thereby not interfering with the normal operation of the high-power microwave system; the number of the coupling holes is two, which are located on the wall of the circular waveguide at a distance of λ / 4+n*λ / 2 to offset the interference caused by the echo at the load end and improve the stability of the measurement;

[0012] The width of the rectangular waveguide matches the transmission frequency in the circular waveguide to improve coupling efficiency and reduce reflection; the short side direction of the rectangular waveguide is along the transmission direction of the circular waveguide, so that the TE transmitted in the circular waveguide along the tangential direction of the circular waveguide at the coupling hole 01 Mode point field, and the main mode TE along the short side of the rectangular waveguide 10The mode electric field can be coupled as much as possible, which is conducive to the generation and establishment of the main mode in the rectangular waveguide; a power sensor is arranged in the rectangular waveguide for real-time measurement of the energy transmitted through the rectangular waveguide; the power sensor is associated with the coupling coefficient of the circular waveguide and the rectangular waveguide through a calibration procedure, thereby improving the accuracy of power measurement, and the theoretical measurement error is within 3dB; the rectangular waveguide is a standard waveguide corresponding to the frequency band of the transmitted electromagnetic wave frequency, and the length is adjusted according to the transmission wavelength to avoid mode interference of the coupled energy during the transmission process.

[0013] A low-loss coupling structure is adopted at the connection between the circular waveguide and the rectangular waveguide to ensure that the power loss during directional energy coupling is minimized; the connection method supports wide-band coupling to meet the energy measurement requirements in different wavelength ranges; the circular waveguide and the rectangular waveguide are made of metals with high heat resistance and high conductivity, and a water cooling system can be selected according to actual conditions to withstand long-term operation of high-power microwaves; the inner wall surface of the rectangular waveguide is provided with an anti-reflection coating to further reduce energy loss and improve measurement accuracy.

[0014] By measuring the transmission energy at the two coupling holes and using the properties of the traveling standing wave to average the energy at the two points, the forward transmission energy of the high-power microwave system can be obtained. In the case of incomplete matching at the load end, the echo interference can be eliminated, and the measurement error is smaller than that of the traditional single-hole qualitative coupler. The working bandwidth of the directional coupler is larger than that of the traditional multi-hole parallel directional coupler, and the transmission energy measurement can be realized in a larger frequency range. Real-time data acquisition and processing are realized during the measurement process, providing online monitoring capabilities for the high-power microwave system.

[0015] The design method of the high-power directional coupler mainly includes the following steps:

[0016] Step 1: According to the working requirements of the high-power microwave system, determine the size, material, operating frequency range and power level of the circular waveguide and rectangular waveguide, and calculate the transmission wavelength of the electromagnetic wave in the circular waveguide;

[0017] Step 2: Determine the diameter and position of the coupling hole according to the transmission wavelength, power and coupling coefficient requirements. The diameter of the coupling hole is less than half of the transmission wavelength. The spacing between the two coupling holes is λ / 4+n*λ / 2, where λ is the transmission wavelength of the electromagnetic wave in the circular waveguide, and n is any non-negative integer.

[0018] Step 3: Determine the connection method between the circular waveguide and the rectangular waveguide, adopt a low-loss coupling structure, optimize its broadband matching characteristics, and ensure the stable transmission of high-power microwaves;

[0019] Step 4: After processing the directional coupler, perform experimental testing to verify the coupling coefficient, frequency band range, power carrying capacity and measurement accuracy, and perform secondary calibration on the power sensor to ensure that the directional coupler meets the design specifications;

[0020] The beneficial effects of the present invention are as follows: it can perform real-time measurement of the energy transmitted in the system when the high-power microwave system is in operation, and can monitor the actual state of the high-power microwave system; through the dual-coupling hole design, the sensitivity of the measured value to the influence of traveling standing waves is significantly reduced, and the measurement stability and accuracy are improved; the small aperture and optimized spacing design are adopted to effectively reduce the sparking phenomenon under high-power conditions; the wide bandwidth adaptation capability is achieved, which can meet the energy measurement requirements of multiple frequency bands; the structural design is simple, easy to process and maintain, and suitable for industrial large-scale production and wide application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The overall structure diagram of a high-power directional coupler used for real-time measurement of high-power circular waveguide transmission energy;

[0022] Figure 2 A cross-sectional view of a high-power directional coupler used for real-time measurement of high-power circular waveguide transmission energy;

[0023] Figure 3 A top view of a high-power directional coupler used for real-time measurement of high-power circular waveguide transmission energy; DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the implementation scope of the present invention is not limited thereto.

[0025] 1. Directional coupler design

[0026] Circular waveguide: The circular waveguide is designed as a high-power over-modulated circular waveguide, and the transmission mode in the circular waveguide is TE. 01 The inner diameter of the microwave oven is determined according to the target frequency band and power level. The wall thickness is designed to take into account the thermal effect of high-power microwaves and the mechanical stability requirements. At the same time, a water cooling system can be equipped according to actual conditions to ensure long-term high-power microwave transmission.

[0027] Coupling hole design: The coupling hole adopts an equal diameter circular hole structure with a diameter range of 0.01λ to 0.4λ. The specific coupling hole size and coupling hole thickness can be determined based on the actual measured coupling coefficient requirements, using the formula theoretical calculation and simulation calculation of small hole coupling. The hole spacing is λ / 4+n*λ / 2, where n can be determined based on the frequency of the actual high-power microwave system to ensure that the two rectangular waveguides do not overlap. This layout can effectively avoid field concentration under high-power conditions and achieve directional coupling of energy.

[0028] Rectangular waveguide: The width of the rectangular waveguide matches the electromagnetic wave mode in the circular waveguide, and the standard waveguide size is adopted. The short side of the rectangular waveguide is along the transmission direction of the circular waveguide, ensuring the TE 01 The direction of the mode electric field and the main mode TE in the rectangular waveguide 10 The electric field direction of the modes is the same, ensuring the establishment and propagation of the main mode in the rectangular waveguide. The rectangular waveguide length design is optimized according to the transmission wavelength to avoid multi-mode interference affecting the measurement results.

[0029] 2. Transmission power measurement method

[0030] When the load end of the transmission system is not completely matched or there is an echo at the output port, the wave propagating in the reverse direction is superimposed on the forward transmission wave to be measured, forming a traveling standing wave distributed along the circular waveguide. The coupling energy of the coupling holes at different positions along the transmission direction of the circular waveguide is different. The transmission energy in the rectangular waveguide is measured by two power sensors respectively. The two measured values ​​are averaged by combining the coupling coefficient and the traveling standing wave characteristics, and the reverse wave interference at the output end is filtered out to obtain the microwave power value transmitted in the forward direction in the circular waveguide.

[0031] 3. Simulation verification

[0032] The directional coupler structure is simulated and calculated using electromagnetic simulation software such as CST / HFSS to obtain the theoretical coupling coefficient of the directional coupler. An incompletely matched load is placed at the output end of the directional coupler, and the microwave power calculated along the forward transmission in the circular waveguide is calculated based on the measurement values ​​of the two power sensors in the rectangular waveguide. The calculated value is compared with the actual forward transmission power to verify its measurement accuracy and bandwidth range.

[0033] 3. Actual processing measurement

[0034] The designed qualitative coupler structure is mechanically processed, and multiple groups of experimental tests are carried out on the high-power directional coupler of the present invention to verify its measurement accuracy, bandwidth range and power carrying capacity.

Claims

1. A high-power directional coupler for real-time measurement of high-power circular waveguide transmission energy, characterized in that: The directional coupler includes: a circular waveguide, two coupling holes, and two rectangular waveguides. The circular waveguide is a high-power circular waveguide used to transmit electromagnetic waves in a high-power microwave system; The two coupling holes are opened on the circular waveguide wall, and the center distance between the two coupling holes is equal to λ / 4+n*λ / 2, wherein λ is the transmission wavelength of the electromagnetic wave in the circular waveguide, and n is any non-negative integer. The two rectangular waveguides are standard waveguides, vertically connected to the circular waveguide, and the connection positions are located at two coupling holes for receiving energy transmitted by coupling, and the short sides of the rectangular waveguides are parallel to the transmission direction of the circular waveguide; Through the two coupling holes, energy is directionally coupled from the circular waveguide to the two rectangular waveguides, and the mode is also coupled from the TE in the circular waveguide to the two rectangular waveguides. 01 The mode becomes the main TE mode of the rectangular waveguide 10 Mode, the energy transmitted in the forward direction in the circular waveguide is calculated by measuring the coupling coefficient and the transmission power in the rectangular waveguide.

2. The high power directional coupler according to claim 1, characterized in that: The distance between the two coupling holes can be changed by adjusting the value of parameter n to meet the requirements of different transmission wavelengths and avoid sparking in high-power transmission systems; The diameter of the coupling hole is less than half of the transmission wavelength to ensure that the field distribution in the circular waveguide is basically not affected, thereby not interfering with the normal operation of the high-power microwave system; the number of the coupling holes is two, which are located on the wall of the circular waveguide at a distance of λ / 4+n*λ / 2 to offset the interference caused by the load end echo and improve the stability of the measurement.

3. The high power directional coupler according to claim 1, characterized in that The width of the rectangular waveguide matches the transmission frequency in the circular waveguide to improve coupling efficiency and reduce reflection; the short side direction of the rectangular waveguide is along the transmission direction of the circular waveguide, so that the TE transmitted in the circular waveguide along the tangential direction of the circular waveguide at the coupling hole 01 Mode point field, and the main mode TE along the short side of the rectangular waveguide 10 The mode electric field can be coupled as much as possible, which is conducive to the generation and establishment of the main mode in the rectangular waveguide; a power sensor is arranged in the rectangular waveguide for real-time measurement of the energy transmitted through the rectangular waveguide; the power sensor is associated with the coupling coefficient of the circular waveguide and the rectangular waveguide through a calibration procedure, thereby improving the accuracy of power measurement, and the theoretical measurement error is within 3dB; the rectangular waveguide is a standard waveguide corresponding to the frequency band of the transmitted electromagnetic wave frequency, and the length is adjusted according to the transmission wavelength to avoid mode interference of the coupled energy during the transmission process.

4. The high power directional coupler according to claim 1, characterized in that: A low-loss coupling structure is adopted at the connection between the circular waveguide and the rectangular waveguide to ensure that the power loss during directional energy coupling is minimized; the connection method supports wide-band coupling to meet the energy measurement requirements in different wavelength ranges; the circular waveguide and the rectangular waveguide are made of metals with high heat resistance and high conductivity, and a water cooling system can be selected according to actual conditions to withstand long-term operation of high-power microwaves; the inner wall surface of the rectangular waveguide is provided with an anti-reflection coating to further reduce energy loss and improve measurement accuracy.

5. The high power directional coupler according to claim 1, characterized in that: By measuring the transmission energy at the two coupling holes and using the properties of the traveling standing wave to average the energy at the two points, the forward transmission energy of the high-power microwave system can be obtained. In the case of incomplete matching at the load end, the echo interference can be eliminated, and the measurement error is smaller than that of the traditional single-hole qualitative coupler. The working bandwidth of the directional coupler is larger than that of the traditional multi-hole parallel directional coupler, and the transmission energy measurement can be realized in a larger frequency range. Real-time data acquisition and processing are realized during the measurement process, providing online monitoring capabilities for the high-power microwave system.

6. The design method of the high power directional coupler according to claim 1 mainly comprises the following steps: Step 1: According to the working requirements of the high-power microwave system, determine the size, material, operating frequency range and power level of the circular waveguide and rectangular waveguide, and calculate the transmission wavelength of the electromagnetic wave in the circular waveguide; Step 2: Determine the diameter and position of the coupling hole according to the transmission wavelength, power and coupling coefficient requirements. The diameter of the coupling hole is less than half of the transmission wavelength. The spacing between the two coupling holes is λ / 4+n*λ / 2, where λ is the transmission wavelength of the electromagnetic wave in the circular waveguide, and n is any non-negative integer. Step 3: Determine the connection method between the circular waveguide and the rectangular waveguide, adopt a low-loss coupling structure, optimize its broadband matching characteristics, and ensure the stable transmission of high-power microwaves; Step 4: After processing the directional coupler, an experimental test is performed to verify the coupling coefficient, frequency band range, power carrying capacity and measurement accuracy, and a power sensor is recalibrated to ensure that the directional coupler meets the design specifications.

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