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

Abstract

The application 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 arranged on the wall surface of the circular waveguide, and the 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, and the short side of the rectangular waveguide is parallel to the axial direction of the circular waveguide, which is used for receiving coupled energy and measuring transmission power through a power sensor. By averaging the transmission energy at the two coupling holes, the interference error caused by the echo is eliminated, and the forward transmission energy is accurately measured. The design effectively avoids the fluctuation problem in single-hole measurement, has the advantages of wide frequency band, low coupling coefficient, high reliability and high power resistance, and is suitable for real-time measurement and monitoring of high-power microwave system energy.

Description

Technical Field

[0001] This invention belongs to the field of microwave power measurement, specifically relating to a high-power directional coupler suitable for real-time measurement of the energy transmitted through a circular waveguide in a high-power microwave transmitting, receiving system. Background Technology

[0002] High-power microwave technology, as a crucial component of modern electronic engineering, plays an irreplaceable role in fields such as radar, communications, weapon systems, and scientific experiments. In high-power microwave systems, accurate monitoring of microwave power is of paramount importance for optimizing system operating efficiency and ensuring equipment safety. In microwave power measurement technology, circular waveguides are a commonly used transmission structure in high-power microwave systems, and the transmission mode typically employs TE (Transmission Transmission). 01 This mode has the advantage of supporting high-power, low-loss microwave transmission.

[0003] Commonly used microwave power measurement methods include the water-load method and the directional coupler method. The water-load method, a widely used early power measurement technique, works by absorbing microwave energy and converting it into heat, then calculating the power value by measuring the temperature rise. While feasible at low power levels, this method has become increasingly inadequate for real-time and accuracy requirements at high power levels due to system complexity, long thermal equilibrium times, and significant measurement errors. Traditional single-aperture directional couplers couple energy to a secondary waveguide through openings in the waveguide wall. However, in high-power circular waveguides, impedance mismatch at the load end or large echoes can lead to standing wave fields in the transmitted circular waveguide. Measurement results are closely related to the opening position, resulting in large fluctuations and significantly increased errors. Multi-aperture parallel directional couplers use multiple openings to cancel interference waves, but the spacing between these openings is strictly limited by wavelength, resulting in narrow bandwidth and unsuitability for broadband high-power measurements. Furthermore, multiple openings increase coupling strength, making it difficult to meet the low coupling coefficient requirements of high-power measurements. Simultaneously, local field enhancement between coupling holes increases the risk of arcing in the directional coupler. Additionally, traditional microwave power measurement methods typically connect matching loads such as water loads to the output end to simulate the overall operating state of a high-power microwave system, neglecting the impact of subsequent transmission sections on the overall microwave power transmission. This results in significant measurement errors and makes it impossible to measure and detect the actual operating 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 overcoming the current technological bottlenecks. Summary of the Invention

[0005] The purpose of this invention is to propose a directional coupler for real-time measurement of energy transmitted through high-power circular waveguides. This directional coupler enables real-time, high-precision power measurement of high-power microwave systems, reduces measurement errors introduced by load-end echoes, and meets the high-precision, wide-bandwidth, and high-reliability requirements of high-power microwave systems for energy measurement.

[0006] To achieve the above objectives, the specific solution of the present invention is as follows: it includes a circular waveguide, two coupling apertures, 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 formed on the wall of the circular waveguide, and the center distance between the two coupling holes is equal to 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;

[0009] The two rectangular waveguides are perpendicularly connected to the circular waveguide, and the connection is located at the two coupling holes to receive the energy transmitted through coupling. The short side of the rectangular waveguide is parallel to the transmission direction of the circular waveguide.

[0010] Through the two coupling apertures, energy is directionally coupled from the circular waveguide to the two rectangular waveguides, and the mode also changes from TE in the circular waveguide. 01 The mode changes to the dominant mode TE of the rectangular waveguide. 10 The method involves measuring the coupling power in two rectangular waveguides separately and, in conjunction with the coupling coefficient, averaging the power at the two points using the spatial distribution characteristics of traveling and standing waves in a circular waveguide, thereby obtaining the energy transmitted in the forward direction in the circular waveguide.

[0011] The spacing between the two coupling holes can be varied by adjusting the value of parameter n to adapt to different transmission wavelengths and avoid arcing in high-power transmission systems. The diameter of the coupling hole is less than half the transmission wavelength to ensure that the field distribution within the circular waveguide is largely unaffected, thus not interfering with the normal operation of the high-power microwave system. There are two coupling holes, spaced λ / 4 + n*λ / 2 apart, located on the wall of the circular waveguide to cancel out interference caused by load-end echoes and improve measurement stability.

[0012] The width of the rectangular waveguide is matched to the transmission frequency within the circular waveguide to improve coupling efficiency and reduce reflection; the short side of the rectangular waveguide is along the transmission direction of the circular waveguide, such that the TE frequency propagating along the tangential direction of the circular waveguide at the coupling aperture... 01 Mode point field, and the dominant mode TE along the short side of the rectangular waveguide. 10The mode electric fields can be coupled as much as possible, which is beneficial to the generation and establishment of the dominant mode in the rectangular waveguide. A power sensor is installed in the rectangular waveguide to measure the energy transmitted through it in real time. The power sensor is correlated with the coupling coefficient of the circular waveguide and the rectangular waveguide through a calibration program, thereby improving the accuracy of power measurement. The theoretical measurement error is within 3 dB. The rectangular waveguide is a standard waveguide corresponding to the frequency band of the transmitted electromagnetic wave, and its length is adjusted according to the transmission wavelength to avoid mode interference of coupled energy during transmission.

[0013] The connection between the circular and rectangular waveguides employs a low-loss coupling structure to minimize power loss during directional energy coupling. This connection method supports wideband coupling, meeting energy measurement requirements across different wavelength ranges. Both the circular and rectangular waveguides are made of highly heat-resistant and highly conductive metals, and a water-cooling system can be selected to withstand long-term operation of high-power microwaves. The inner surface of the rectangular waveguide is coated with an anti-reflective layer to further reduce energy loss and improve measurement accuracy.

[0014] By measuring the transmitted energy at two coupling apertures and averaging the energy at the two points using the properties of traveling and standing waves, the forward transmitted energy of the high-power microwave system can be obtained. This eliminates echo interference even under conditions of imperfect load matching, and the measurement error is smaller than that of a traditional single-aperture directional coupler. Furthermore, the directional coupler has a larger operating bandwidth than traditional multi-aperture parallel directional couplers, enabling transmitted energy measurement over a wider frequency range. Real-time data acquisition and processing are achieved during the measurement process, providing online monitoring capabilities for the high-power microwave system.

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

[0016] Step 1: Based on the operating requirements of the high-power microwave system, determine the dimensions, materials, operating frequency range, and power rating of the circular and rectangular waveguides, and calculate the transmission wavelength of electromagnetic waves within the circular waveguide;

[0017] Step 2: Determine the diameter and position of the coupling aperture according to the requirements of transmission wavelength, power and coupling coefficient. The diameter of the coupling aperture is less than half of the transmission wavelength. The distance between the two coupling apertures 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 wideband matching characteristics, and ensure stable transmission of high-power microwaves;

[0019] Step 4: After fabricating the directional coupler, conduct experimental tests to verify the coupling coefficient, frequency band range, power carrying capacity, and measurement accuracy. Perform secondary calibration on the power sensor to ensure that the directional coupler meets the design specifications.

[0020] The beneficial effects of this invention are as follows: it enables real-time measurement of transmitted energy in a high-power microwave system under operating conditions, and allows for monitoring of the actual state of the high-power microwave system; the dual coupling aperture design significantly reduces the sensitivity of measured values ​​to traveling and standing waves, improving measurement stability and accuracy; the small aperture and optimized spacing design effectively reduce arcing under high-power conditions; it achieves wide bandwidth adaptability, meeting the needs of multi-frequency energy measurement; the structural design is simple, easy to process and maintain, and suitable for large-scale industrial production and widespread application. Attached Figure Description

[0021] Figure 1 A schematic diagram of the overall structure of a high-power directional coupler used for real-time measurement of energy transmitted through a high-power circular waveguide.

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

[0023] Figure 3 A top view of a high-power directional coupler used for real-time measurement of energy transmitted through a high-power circular waveguide; Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this is not to limit the scope of the invention to this.

[0025] 1. Directional Coupler Design

[0026] Circular waveguide: The circular waveguide section is designed as a high-power overmode circular waveguide, and the transmission mode within the circular waveguide is TE. 01 The inner diameter of the structure is determined based on the target frequency band and power level. The wall thickness design takes into account the thermal effects and mechanical stability requirements of high-power microwaves, and a water-cooling system can be equipped to ensure long-term transmission of high-power microwaves, depending on the actual situation.

[0027] Coupling aperture design: The coupling aperture adopts a constant-diameter circular aperture structure, with a diameter ranging from 0.01λ to 0.4λ. The specific size and thickness of the coupling aperture can be determined by theoretical calculations and simulations based on the actual measured coupling coefficient requirements. The aperture spacing is λ / 4 + n*λ / 2, where n can be determined according to 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 energy coupling.

[0028] Rectangular waveguide: The width of the rectangular waveguide matches the electromagnetic wave mode within the circular waveguide, using standard waveguide dimensions. The short side of the rectangular waveguide runs along the transmission direction of the circular waveguide, ensuring the TE signal within the circular waveguide. 01 The electric field direction of the mode is related to the dominant mode TE in the rectangular waveguide. 10 The electric fields of the modes are in the same direction to ensure the establishment and propagation of the dominant mode within the rectangular waveguide. The length of the rectangular waveguide is optimized according to the transmission wavelength to avoid multimode interference affecting the measurement results.

[0029] 2. Transmission Power Measurement Method

[0030] When the load end of the transmission system is not perfectly matched or when there is an echo at the output port, the wave propagating in the opposite direction superimposes with the forward transmission wave to be measured, forming a traveling-standing wave distributed along the circular waveguide. The coupling energy of the coupling aperture varies at different positions along the transmission direction of the circular waveguide. By measuring the transmission energy within the rectangular waveguide using two power sensors, and combining the coupling coefficient and the traveling-standing wave characteristics, the two measurements are averaged to filter out the reverse wave interference at the output end, thus obtaining the microwave power value propagating in the forward direction within the circular waveguide.

[0031] 3. Simulation Verification

[0032] The directional coupler structure was simulated using electromagnetic simulation software such as CST / HFSS to obtain the theoretical coupling coefficient. An imperfectly matched load was placed at the output of the directional coupler. Based on measurements from two power sensors within the rectangular waveguide, the calculated microwave power propagating in the forward direction within the circular waveguide was obtained. This calculated power was compared with the actual forward propagation power to verify the measurement accuracy and bandwidth range.

[0033] 3. Actual machining measurement

[0034] The qualitative coupler structure was machined according to the design, and multiple sets of experimental tests were conducted on the high-power directional coupler of the present invention to verify its measurement accuracy, bandwidth range and power carrying capacity.

Claims

1. A directional coupler for real-time measurement of transmitted energy in high-power circular waveguides, characterized in that, The directional coupler includes: a circular waveguide, two coupling apertures, 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 formed on the wall of the circular waveguide, and the center distance between the two coupling holes is equal to 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; The two rectangular waveguides are standard waveguides and are perpendicularly connected to the circular waveguide. The connection is located at the two coupling holes and is used to receive the energy transmitted through coupling. The short side of the rectangular waveguide is parallel to the transmission direction of the circular waveguide. Through the two coupling apertures, energy is directionally coupled from the circular waveguide to the two rectangular waveguides, and the mode also changes from TE in the circular waveguide. 01 The mode changes to the dominant mode TE of the rectangular waveguide. 10 model; By measuring the coupling power in two rectangular waveguides respectively and combining the coupling coefficient, the power at the two points is averaged using the spatial distribution characteristics of traveling and standing waves in a circular waveguide, thus obtaining the energy transmitted in the forward direction in the circular waveguide.

2. The directional coupler according to claim 1, characterized in that, The spacing between the two coupling holes can be varied by adjusting the value of parameter n to adapt to the requirements of different transmission wavelengths and avoid arcing in high-power transmission systems. The diameter of the coupling aperture is less than half of the transmission wavelength, so as not to interfere with the normal operation of the high-power microwave system; there are two coupling apertures, separated by λ / 4+n*λ / 2, located on the wall of the circular waveguide to cancel the interference caused by the load end echo and improve the stability of the measurement.

3. The directional coupler according to claim 1, characterized in that... The width of the rectangular waveguide is matched to the transmission frequency within the circular waveguide to improve coupling efficiency and reduce reflection; the short side of the rectangular waveguide is along the transmission direction of the circular waveguide, such that the TE frequency propagating along the tangential direction of the circular waveguide at the coupling aperture... 01 Mode point field, and the dominant mode TE along the short side of the rectangular waveguide. 10 The mode electric fields can be fully coupled, which is beneficial for the generation and establishment of the dominant mode in the rectangular waveguide. A power sensor is installed in the rectangular waveguide to measure the energy transmitted through it in real time. The power sensor is correlated with the coupling coefficient of the circular waveguide and the rectangular waveguide through a calibration program, thereby improving the accuracy of power measurement. The theoretical measurement error is within 3 dB. The rectangular waveguide is a standard waveguide corresponding to the frequency band of the transmitted electromagnetic wave, and its length is adjusted according to the transmission wavelength to avoid mode interference of coupled energy during transmission.

4. The directional coupler according to claim 1, characterized in that, The connection between the circular and rectangular waveguides employs a low-loss coupling structure to minimize power loss during directional energy coupling. The perpendicular connection between the circular and rectangular waveguides supports wideband coupling, meeting energy measurement requirements across different wavelength ranges. Both the circular and rectangular waveguides are made of highly heat-resistant and highly conductive metals, and a water-cooling system can be selected to withstand long-term operation of high-power microwaves. The inner surface of the rectangular waveguide is coated with an anti-reflection layer to further reduce energy loss and improve measurement accuracy.

5. The directional coupler according to claim 1, characterized in that, By measuring the transmitted energy at two coupling apertures and averaging the energy at the two points using the properties of traveling and standing waves, the forward transmitted energy of the high-power microwave system can be obtained. This eliminates echo interference even under conditions of imperfect load matching, and the measurement error is smaller than that of a traditional single-aperture directional coupler. Furthermore, the directional coupler has a larger operating bandwidth than traditional multi-aperture parallel directional couplers, enabling transmitted energy measurement over a wider frequency range. Real-time data acquisition and processing are achieved during the measurement process, providing online monitoring capabilities for the high-power microwave system.

6. The design method of the directional coupler according to claim 1 mainly includes the following steps: Step 1: Based on the operating requirements of the high-power microwave system, determine the dimensions, materials, operating frequency range, and power rating of the circular and rectangular waveguides, and calculate the transmission wavelength of electromagnetic waves within the circular waveguide; Step 2: Determine the diameter and position of the coupling aperture according to the requirements of transmission wavelength, power and coupling coefficient. The diameter of the coupling aperture is less than half of the transmission wavelength. The distance between the two coupling apertures 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 wideband matching characteristics, and ensure stable transmission of high-power microwaves; Step 4: After fabricating the directional coupler, conduct experimental tests to verify the coupling coefficient, frequency band range, power carrying capacity, and measurement accuracy. Perform secondary calibration on the power sensor to ensure that the directional coupler meets the design specifications.

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