Six-dimensional test platform for measuring the wavefront shape of W-band microwave signals

Abstract

The present invention relates to a six-dimensional test platform for measuring the wavefront shape of a W band microwave signal, comprising a microwave antenna, a microwave mixer, a microwave frequency multiplier, a digital synthesis microwave source, a high-speed acquisition card, a three-dimensional drive motor, a three-dimensional rotating platform, and a planar support structure. In terms of microwave signal processing, the present invention uses a difference frequency measurement method to reduce the frequency of a high-frequency microwave radio frequency signal to be measured to a low-frequency intermediate frequency signal, divides the microwave signal into two paths, namely, an "experimental channel" and a "reference channel", to eliminate the influence of the time-varying phase on the wavefront measurement, and increases the control of the three-dimensional angle of the microwave antenna to achieve effective measurement of the edge position of the microwave field; in terms of mechanical control, the present invention achieves control of the six-dimensional degrees of freedom of the microwave antenna through the effective cooperation of the three-dimensional drive motor and the three-dimensional rotating platform, and realizes the full-automatic measurement of the wavefront shape of the W band microwave by the six-dimensional platform through the self-developed measurement platform control software.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave diagnosis of magnetic confinement nuclear fusion plasma, and in particular relates to a six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal. Background Art

[0002] In magnetic confinement nuclear fusion plasma diagnostic technology, microwave diagnosis has been widely valued because of its wide detection range and non-invasive characteristics. One of the important diagnostic equipment is Microwave Imaging Reflectometry.

[0003] For general microwave reflectometers, the plasma density profile distribution and plasma density fluctuation information are measured by using the plasma cutoff characteristics of electromagnetic waves. An electromagnetic wave with a frequency of ω is emitted along the plasma density gradient as a detection beam. The detection wave has two independent propagation modes in the tokamak plasma environment: ordinary mode (O-mode) and extraordinary mode (X-mode). When the refractive index N of the electromagnetic wave in the plasma environment is zero or the wave number k approaches zero, the wave will be cut off. Generally speaking, the wave is reflected at the cutoff point. The dispersion relation of the electromagnetic wave propagating in O-mode in the plasma is:

[0004]

[0005] The dispersion relation for X-mode propagation is:

[0006]

[0007] According to the cut-off condition refractive index N = 0, the O-mode cut-off frequency and X-mode cut-off frequency of electromagnetic waves propagating in plasma are obtained:

[0008]

[0009]

[0010] The magnetic field strength is in Gauss units, ω R ,ω L The frequency is called the right-handed cutoff frequency and the left-handed cutoff frequency of the electromagnetic wave, ω ce =eB / cm e is the electron cyclotron frequency, ω UH 2 =ω ce 2 +ω pe 2is the high hybrid oscillation frequency. From formula 3, we can see that for electromagnetic waves propagating in O-mode, the plasma cutoff frequency is the plasma oscillation frequency, so the cutoff frequency only has a one-to-one correspondence with the electron density. It is cut off at the plasma density ne position that meets the electromagnetic wave cutoff condition. This density is generally called the "cutoff density of electromagnetic waves", and the surface with the same plasma density in space is called the cutoff surface or cutoff layer of electromagnetic waves. From formula 4, we can see that for electromagnetic waves propagating in X-mode, the cutoff of both left-handed cutoff wave and right-handed cutoff wave is related to the electron density and magnetic field strength. When the longitudinal current in the tokamak is given, the magnetic field strength and the large radius of the tokamak B∝1 / R, and the electron density ne is distributed in a gradient on the small radius of the plasma. Therefore, the cutoff frequency of the electromagnetic wave propagating in X-mode in the tokamak also corresponds to the position of the electron density. Therefore, the characteristic that electromagnetic waves of a specific frequency are reflected by the density cutoff layer when propagating in the plasma is used to detect the density information on the cutoff layer.

[0011] Microwave reflectometry uses the characteristic of plasma to cut off and reflect electromagnetic waves. By measuring the flight time of electromagnetic waves in plasma or the group phase delay of incident and reflected electromagnetic waves in plasma, the position of plasma cutoff layer corresponding to different frequencies is calculated, and the position of plasma density distribution is given. Due to the density fluctuation in plasma, the spatial position of the cutoff layer changes with time, causing the propagation optical path of electromagnetic waves in plasma to change with time, which ultimately affects the phase of the reflected signal. Therefore, by analyzing the phase fluctuation, the density fluctuation on the corresponding cutoff layer can be obtained.

[0012] Microwave imaging reflectometer (MIR) is based on the reflectometer principle. It captures two-dimensional (in the polar and annular) time frame images of density turbulence at a specified radial position based on large-lens optical imaging. It mainly focuses on the multi-directional scattering of the detection beam by the cutoff layer of the two-dimensional density fluctuation structure. It uses large-aperture optical devices to collect enough scattered waves on the cutoff surface, and images the complex interference pattern of the reflected wave of the cutoff surface on the detection array plane, so that the density information of the cutoff surface can be completely reconstructed. At this time, the formula can be used

[0013]

[0014] It represents the relationship between the measured signal phase fluctuation power spectrum and the density fluctuation power spectrum, and then inverts the information of density fluctuation on the cutoff surface to achieve two-dimensional imaging.

[0015] To realize the above-mentioned two-dimensional imaging function, it is necessary to spatially couple the wavefront of the illumination optical path, the "image plane" of the receiving optical path, and the shape of the cutoff layer. At this time, the signal is strong, there is no Doppler frequency shift, and the density fluctuations on the cutoff layer are well projected onto the MIR receiving antenna array.

[0016] The microwave wavefront shape in the MIR optical path is simulated by optical software in major international magnetic confinement fusion devices, and lacks actual measured data. Considering that the optical software simulation cannot fully take into account the experimental environment and the robustness of the experimental equipment installation, its simulation results are not convincing. In order to obtain a convincing microwave wavefront shape in the MIR optical path, we designed a six-dimensional test platform for measuring the wavefront shape of microwave signals.

[0017] There are three main difficulties in measuring the microwave wavefront shape in the MIR optical path:

[0018] 1. The microwave source of the microwave imaging reflectometer operates in the W frequency band (75-110GHz). To collect microwave signals, the sampling rate of the acquisition card must be at least twice the microwave frequency. Such a high-frequency acquisition card does not actually exist. Even if the signal can be collected, the amount of data is too much for the computer to bear.

[0019] 2. The phase of an electromagnetic wave not only changes with space but also with time, so it is impossible to measure the absolute phase value at a specific point in space.

[0020] 3. Microwave signals are essentially Gaussian beams, and their equiphase surfaces (wavefronts) have a certain curvature. The receiving capability of microwave receiving antennas is directional. The measurement effect is best when the receiving antenna is perpendicular to the microwave wavefront. When the detection point is at the edge of the wave field, the microwave receiver is no longer perpendicular to the microwave wavefront here, which will cause the detection effect to deteriorate, which also seriously affects the accuracy of microwave wavefront measurement. Summary of the invention

[0021] The purpose of the present invention is to measure the wavefront shape of a microwave radio frequency signal in a microwave imaging reflectometer (MIR) optical path to assist in realizing the two-dimensional imaging function of the MIR; at the same time, to solve the problems that the frequency of the microwave radio frequency signal to be measured is too high to be measured, the phase of the radio frequency signal varies both with space and with time, and the efficiency of microwave field edge detection is low.

[0022] In order to achieve the above object, the present invention adopts the following technical solutions:

[0023] In order to solve the problem that the frequency of the microwave RF signal to be measured is too high to be measured, the difference frequency measurement method is adopted. A digital synthetic microwave source is used to generate a high-frequency local oscillator signal, and a W-band microwave mixer is used to mix the RF signal with the local oscillator signal to obtain a lower frequency intermediate frequency signal. The acquisition card only needs to collect and process the intermediate frequency signal, so the sampling rate requirement of the acquisition card is greatly reduced, and the amount of signal data is also greatly reduced.

[0024] In order to solve the problem that the phase of the RF signal varies both in space and in time, we borrowed the principle of interferometer and added a "reference channel" in addition to the "experimental channel". For the "experimental channel", the microwave RF signal is emitted by the microwave source antenna, and is received by the microwave receiver after propagating a certain distance in space, and then mixed with the local oscillator signal to obtain the intermediate frequency signal, which is collected and recorded by the acquisition card; for the "reference channel", the RF signal of the microwave source does not propagate through space, but is directly connected to the microwave mixer through a coaxial cable, and is mixed with the local oscillator signal in the mixer to obtain the intermediate frequency signal, which is collected and recorded by the acquisition card. In this way, the only difference between the data recorded by the "experimental channel" and the "reference channel" is whether the RF signal is propagated through the air. By comparing the two data, the phase difference caused by air propagation can be obtained. It can be seen that this scheme can eliminate the influence of time-varying phase, making it possible to measure the absolute phase at the spatial coordinate.

[0025] In order to solve the problem that the edge curvature of the Gaussian beam wavelength affects the detection efficiency, this wavefront measurement platform is designed to have six degrees of freedom. In addition to the three-dimensional spatial coordinates, there are three more degrees of freedom corresponding to the three-dimensional rotation angle of the microwave receiver. The six degrees of freedom are precisely controlled by the motor. At each detection point in the three-dimensional space, the platform control program will control the motor to automatically scan the three-dimensional angle. Through real-time analysis of the detected microwave signal, the angle with the strongest signal is automatically selected, which automatically realizes the alignment of the microwave receiver with the wavefront normal direction of the microwave radio frequency wave field, making it possible to measure the microwave wavefront shape over a large spatial range.

[0026] As a further description of the above technical solution:

[0027] The microwave components of the six-dimensional test platform include an experimental channel microwave processing unit, a digital synthetic microwave source, a microwave source, a reference channel microwave processing unit, and a coaxial cable; there are two radio frequency signals emitted by the microwave source, one of which is emitted into a three-dimensional space through a microwave antenna, and is received by a microwave receiver in the experimental channel microwave processing unit after propagating a certain distance; the other is directly transmitted to a mixer in the reference channel microwave processing unit through a coaxial cable; for the experimental channel microwave processing unit, a frequency multiplier receives a local oscillator signal from a digital synthetic microwave source, and obtains a local oscillator signal close to the radio frequency frequency after frequency multiplication, and then the local oscillator signal is mixed with the radio frequency signal received by the microwave receiver in the mixer to obtain an experimental channel intermediate frequency signal, and then the intermediate frequency signal is transmitted to an acquisition card through a coaxial cable to be collected and recorded; for the reference channel microwave signal processing unit, a frequency multiplier receives a local oscillator signal from a digital synthetic microwave source, and obtains a local oscillator signal close to the radio frequency frequency after frequency multiplication, and then the local oscillator signal is mixed with the reference channel radio frequency signal in the mixer to obtain a reference channel intermediate frequency signal, and then the intermediate frequency signal is transmitted to an acquisition card through a coaxial cable to be collected and recorded.

[0028] As a further description of the above technical solution:

[0029] The three-dimensional drive motors in the six-dimensional test platform include an X-axis drive motor, a Y-axis drive motor, and a Z-axis drive motor. The guide rails of the three groups of drive motors are perpendicular to each other, wherein the guide rail of the X-axis drive motor is fixed on the platform bracket, the guide rail of the Y-axis drive motor is fixed on the slider of the X-axis drive motor guide rail, and the guide rail of the Z-axis drive motor is fixed on the slider of the Y-axis drive motor guide rail, forming a spatial rectangular coordinate system. By controlling the three groups of motors, the slider of the Z-axis drive motor can be moved in three-dimensional space.

[0030] As a further description of the above technical solution:

[0031] The three-dimensional rotating table in the six-dimensional test platform includes a yaw-axis electric rotating table, a pitch-axis electric rotating table, and a roll-axis electric rotating table. The guide rail of the yaw-axis electric rotating table is fixed on the slider of the Z-axis driving motor, the guide rail of the pitch-axis electric rotating table is fixed on the rotating block of the yaw-axis electric rotating table, the guide rail of the roll-axis electric rotating table is fixed on the rotating block of the pitch-axis electric rotating table, and the microwave receiver is fixed on the rotating block of the roll-axis electric rotating table. The detection angle of the microwave receiver in space can be controlled by controlling the motors of the three groups of rotating tables.

[0032] As a further description of the above technical solution:

[0033] The planar support structure in the six-dimensional test platform includes a platform bracket and Foma casters. The platform bracket is made of aluminum profiles or other supporting materials and is used to install and fix the main part of the six-dimensional test platform. The Foma casters are installed at the four corners below the platform bracket to realize the movement of the six-dimensional test platform.

[0034] As a further description of the above technical solution:

[0035] The three-dimensional drive motor, three-dimensional rotating table, acquisition card and other electronic control components are remotely controlled by the independently developed "W band wavefront automatic measurement platform control software", which can realize the automatic alignment of the microwave receiver to the normal direction of the RF signal wavefront and the automatic scanning measurement of the wavefront shape, and can also manually fine-tune the six-dimensional degrees of freedom of the microwave receiver.

[0036] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0037] The present invention effectively solves the problems of "too high frequency", "phase changes with time" and "low efficiency of wavelength edge detection" in the measurement of the wavefront shape of W-band RF signals, and can realize automatic measurement of the wavefront shape of W-band RF signals in combination with the test platform control program. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A three-dimensional diagram of a six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal proposed by the present invention;

[0039] Figure 2 It is a front view of the present invention;

[0040] Figure 3 It is a side view of the present invention;

[0041] Figure 4 It is a top view of the present invention;

[0042] Figure 5 It is a schematic diagram of microwave signal processing;

[0043] Figure 6 It is the main interface of the measurement platform control software;

[0044] Legend:

[0045] 1. Electric rotating table for yaw axis; 2. Electric rotating table for pitch axis; 3. Electric rotating table for roll axis; 4. Drive motor for x axis; 5. Drive motor for y axis; 6. Drive motor for z axis; 7. Acquisition card; 8. Platform bracket; 9. Forma casters; 10. Experimental channel microwave processing unit; 10(1) Mixer for experimental channel microwave processing unit; 10(2) Frequency multiplier for experimental channel microwave processing unit; 10(3) Microwave signal receiver for experimental channel microwave processing unit; 11. Digitally synthesized microwave source; 12. Microwave source; 13. Reference channel microwave processing unit; 13(1) Mixer for reference channel microwave processing unit; 13(2) Frequency multiplier for reference channel microwave processing unit; 14. Coaxial cable. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0047] The present invention relates to the field of microwave diagnostic technology for magnetic confinement fusion plasma, and in particular to a six-dimensional test platform for measuring the wavefront shape of Wband microwave signals, including a microwave antenna, a microwave mixer, a microwave frequency multiplier, a digital synthesis microwave source, a high-speed acquisition card, a three-dimensional drive motor, a three-dimensional rotating platform, and a planar support structure. In terms of microwave signal processing, the present invention uses a difference frequency measurement method to reduce the frequency of a high-frequency microwave radio frequency signal to be measured to a low-frequency intermediate frequency signal, divides the microwave signal into two paths, "experimental channel" and "reference channel", eliminates the influence of time-varying phase on wavefront measurement, and increases the control of the three-dimensional angle of the microwave antenna (receiver) to achieve effective measurement of the edge position of the microwave field; in terms of mechanical control, the present invention realizes the control of the six-dimensional degrees of freedom (three-dimensional spatial coordinates + three-dimensional rotation angle) of the microwave antenna (receiver) through the effective cooperation of the three-dimensional drive motor and the three-dimensional rotating platform, and realizes the full-automatic measurement of the wavefront shape of the W-band microwave by the six-dimensional platform through the self-developed measurement platform control software. The present invention effectively solves the problems of "too high frequency", "phase changes with time" and "low efficiency of wave field edge detection" in the measurement of the wavefront shape of W-band radio frequency signals. The automatic measurement of the wavefront shape of W-band radio frequency signals can be realized by matching with the test platform control software.

[0048] To solve the problem that the frequency of microwave RF signal to be measured is too high to be measured, we adopt mixing technology, use digital synthetic microwave source to generate high-frequency local oscillator signal, and use W-band microwave mixer to mix RF signal with local oscillator signal to obtain lower frequency intermediate frequency signal. The acquisition card only needs to collect and process the intermediate frequency signal, so the sampling rate requirement of the acquisition card is greatly reduced, and the amount of signal data is also greatly reduced.

[0049] To solve the problem that the phase of the RF signal varies both in space and in time, we use the interferometric measurement method to add a "reference channel" in addition to the "experimental channel". For the "experimental channel", the microwave RF signal is emitted by the microwave source antenna, propagates a certain distance in space, is received by the microwave receiver, and then mixed with the local oscillator signal to obtain an intermediate frequency signal, which is collected and recorded by the acquisition card; for the "reference channel", the RF signal of the microwave source does not propagate through space, but is directly connected to the microwave mixer through a coaxial cable, and is mixed with the local oscillator signal in the mixer to obtain an intermediate frequency signal, which is collected and recorded by the acquisition card. In this way, the only difference between the signals recorded by the "experimental channel" and the "reference channel" is whether they are propagated through the air. By comparing the two signals, the phase difference caused by air propagation can be obtained. It can be seen that this scheme can eliminate the influence of time-varying phase, making it possible to measure the absolute phase at the spatial coordinate.

[0050] In order to solve the problem that the edge curvature of the Gaussian beam wavelength affects the detection efficiency, this wavefront measurement platform is designed to have six degrees of freedom. In addition to the three-dimensional spatial coordinates, there are three more degrees of freedom corresponding to the three-dimensional rotation angle of the microwave receiver. The six degrees of freedom are precisely controlled by the motor. At each detection point in the three-dimensional space, the platform control program will control the motor to automatically scan the three-dimensional angle. Through real-time analysis of the detected microwave signal, the angle with the strongest signal is automatically selected, which automatically realizes the alignment of the microwave receiver with the wavefront normal direction of the microwave radio frequency wave field, making it possible to measure the wavefront shape over a large spatial range.

[0051] The microwave processing part of the present invention is shown in the "microwave signal processing schematic diagram", which includes an acquisition card 7, an experimental channel microwave processing unit 10, a digital synthesis microwave source 11, a microwave source 12, a reference channel microwave processing unit 13, and a coaxial cable 14. The RF signal emitted by the microwave source 12 has two paths, one of which is transmitted into three-dimensional space through a microwave antenna, and is received by a microwave receiver 10 (3) in the experimental channel microwave processing unit 10 after propagating a certain distance; the other path is directly transmitted to the mixer 13 (1) in the reference channel microwave processing unit 13 through the coaxial cable 14. For the experimental channel microwave processing unit 10, the frequency multiplier 10 (2) receives the local oscillator signal from the digital synthesis microwave source 12, and obtains a local oscillator signal close to the RF frequency after frequency multiplication. Then, the local oscillator signal is mixed with the RF signal received by the microwave receiver 10 (3) in the mixer 10 (1) to obtain the experimental channel intermediate frequency signal, and then the intermediate frequency signal is transmitted to the acquisition card 7 through the coaxial cable 14 to be collected and recorded. For the reference channel microwave signal processing unit 13, the frequency multiplier 13 (2) receives the local oscillator signal from the digital synthetic microwave source 12, and obtains a local oscillator signal close to the radio frequency after frequency multiplication. The local oscillator signal is then mixed with the reference channel radio frequency signal in the mixer 13 (1) to obtain a reference channel intermediate frequency signal. The intermediate frequency signal is then transmitted to the acquisition card 7 via the coaxial cable 14 to be collected and recorded.

[0052] The mechanical control part of the present invention is shown in the "front view", "side view", "top view" and "three-dimensional view" figures, and includes: a yaw axis electric rotating table 1, a pitch axis electric rotating table 2, a roll axis electric rotating table 3, an x-axis driving motor 4, a y-axis driving motor 5, a z-axis driving motor 6, a platform bracket 8 and a Forma caster 9. The spatial position and angle of the microwave receiver 10 (3) are controlled by the three-dimensional driving motor and the three-dimensional rotating table, and the signals output by the experimental channel microwave processing unit 10 and the reference channel microwave processing unit 13 are collected and recorded by the acquisition card 7. In addition, all the electric control components of the six-dimensional test platform can be programmed and controlled. During the experiment, only a few buttons need to be pressed in the program to realize the precise adjustment of the spatial position and angle of the microwave receiver 10 (3), the automatic recording of the detection signal and the automatic measurement of the entire table experiment.

[0053] The three-dimensional drive motor part is composed of an x-axis drive motor 4, a y-axis drive motor 5, and a z-axis drive motor 6. The guide rails of the three groups of drive motors are perpendicular to each other, the guide rails of one group of motors are fixed on the platform bracket, the guide rails of the second group of motors are fixed on the sliders of the first group of guide rails, and the guide rails of the third group of motors are fixed on the sliders of the second group of guide rails, forming a spatial rectangular coordinate system. By controlling the three groups of motors, the sliders of the third group of motors can be moved in three-dimensional space, thereby driving the microwave receiver 10 (3) to complete the measurement of the phase of the radio frequency signal at any position in space.

[0054] The three-dimensional rotating platform is composed of a yaw axis electric rotating platform 1, a pitch axis electric rotating platform 2, and a roll axis electric rotating platform 3. The guide rails of one group of rotating platforms are fixed on the slider of the third group of driving motors, the guide rails of the second group of rotating platforms are fixed on the rotating block of the first group of rotating platforms, the guide rails of the third group of rotating platforms are fixed on the rotating block of the second group of rotating platforms, and the experimental microwave signal processing unit 10 is installed on the rotating block of the third group of rotating platforms. The detection angle of the microwave receiver 10 (3) in space can be controlled by controlling the motors of the three groups of rotating platforms, and the microwave receiver 10 (3) can be automatically aligned with the wavefront normal direction of the microwave radio frequency wave field in combination with the test platform control software.

[0055] The platform support structure consists of a platform bracket 8 and a Foma caster 9. The platform bracket 8 is used to install and fix the main part of the six-dimensional test platform. The Foma caster 9 is installed at the bottom of the bracket, which can realize the arbitrary movement of the six-dimensional test platform. The support column in the Foma caster 9 can be dropped to fix the position of the six-dimensional test platform. By adjusting the height of the support column in different casters, the placement level of the platform can be adjusted, so that the six-dimensional test platform can work normally when the ground is slightly tilted.

[0056] In summary, the present invention effectively solves the problems of "too high frequency", "phase changes over time" and "low efficiency of wavelength edge detection" in the measurement of the wavefront shape of W-band RF signals. When combined with the test platform control program, the automatic measurement of the wavefront shape of W-band RF signals can be realized.

[0057] A specific implementation example is as follows:

[0058] First, install the three-dimensional rotating platform. As shown in the "front view", "side view", "top view" and "three-dimensional view", the three-dimensional rotating platform consists of a yaw axis electric rotating platform 1, a pitch axis electric rotating platform 2 and a roll axis electric rotating platform 3. The guide rail of the pitch axis electric rotating platform 2 is fixed on the rotating block of the yaw axis electric rotating platform 1, and the guide rail of the roll axis electric rotating platform 3 is fixed on the rotating block of the pitch axis electric rotating platform 2. By controlling the motors of the three rotating platforms, the three-dimensional angle rotation of the rotating block of the roll axis electric rotating platform 3 can be achieved.

[0059] Then install the three-dimensional drive motor. As shown in the "front view", "side view", "top view" and "three-dimensional view", the three-dimensional drive motor part is composed of an x-axis drive motor 4, a y-axis drive motor 5 and a z-axis drive motor 6. The guide rails of the three groups of drive motors are perpendicular to each other, wherein the guide rail of the x-axis drive motor 4 is fixed on the platform bracket, the guide rail of the y-axis drive motor 5 is fixed on the slider of the x-axis drive motor 4, and the guide rail of the z-axis drive motor 6 is fixed on the slider of the y-axis drive motor 5, forming a spatial rectangular coordinate system. By controlling the three groups of motors, the slider of the z-axis drive motor 6 can be moved in three-dimensional space.

[0060] Then assemble the microwave signal processing component. As shown in the "Microwave Signal Processing Schematic Diagram", it includes an acquisition card 7, an experimental channel microwave processing unit 10, a digital synthesis microwave source 11, a microwave source 12, a reference channel microwave processing unit 13, and a coaxial cable 14. The coaxial cable 14 is used to connect the microwave source 12 and the mixer 13 (1) in the reference channel microwave processing unit 13 to provide a radio frequency signal for the reference channel. The coaxial cable 14 is used to connect the digital synthesis microwave source 11 and the frequency multiplier 13 (2) in the reference channel microwave processing unit 13 to provide a local oscillator signal for the reference channel. The coaxial cable 14 is used to connect the signal output interface of the mixer 13 (1) in the reference channel microwave processing unit 13 and the input interface of the acquisition card 7 to realize the acquisition of the reference channel intermediate frequency signal by the acquisition card 7. The coaxial cable 14 is used to connect the digital synthesis microwave source 11 and the frequency multiplier 10 (2) of the experimental channel microwave processing unit 10 to provide a local oscillator signal for the experimental channel. A coaxial cable 14 is used to connect the signal output interface of the mixer 10 (1) in the experimental microwave processing unit 10 and the input interface of the acquisition card 7, so that the acquisition card 7 can collect the experimental intermediate frequency signal.

[0061] Then assemble the three-dimensional rotating table, three-dimensional driving motor and microwave signal processing components. As shown in the "front view", "side view", "top view" and "three-dimensional view", the guide rail of the yaw axis electric rotating table 1 in the three-dimensional rotating table is fixed on the slider of the z-axis driving motor 6. At this time, by controlling the three-dimensional driving motor and the three-dimensional rotating table, the movement of the rotating block of the roll axis electric rotating table 3 in three-dimensional space and the rotation of three-dimensional angles can be realized. The experimental microwave processing unit 10 is fixed on the rotating block of the roll axis electric rotating table 3, so as to realize the movement of the microwave receiver 10 (3) in the experimental microwave processing unit 10 in three-dimensional space and the rotation of three-dimensional angles.

[0062] Next, set the frequency of the microwave device. In this example, the RF frequency of the microwave source 12 is set to 91 GHz, and the signal is divided into two paths. The experimental channel signal is transmitted into space through the microwave antenna, and the reference channel signal is output through the RF interface; the local oscillator frequency of the digital synthesis microwave source 11 is set to 15.165 GHz; the frequency multiplier 10 (2) and the frequency multiplier 13 (2) are six-fold frequency multipliers of the same manufacturer, model and batch; the mixer 10 (1) and the mixer 13 (1) are mixers of the same manufacturer, model and batch; the sampling rate of the acquisition card 7 is set to 1.25 GSamples / s.

[0063] Next, you can use the "W band wavefront automatic measurement platform control software" to remotely control the test platform. The software interface is shown in the "Main interface of the measurement platform control software". After the software is started, first click the buttons "board switch" and "serial port switch" in sequence. The "board card on status" and "serial port connection status" indicators light up, indicating that all motors of the test platform have started successfully. Then click the "pitch axis zero return button", "yaw axis zero return button", "roll axis zero return button", "circumferential zero return button", "polar zero return button", and "radial zero return button" in sequence to make the motors controlling the six degrees of freedom return to the zero position calibrated by the photoelectric switch. When the data display boxes "pitch axis current angle", "roll axis current angle", "yaw axis current angle", "circumferential axis current position", "polar axis current position", and "radial axis current position" are all 0, it means that the motors controlling the six degrees of freedom have returned to zero successfully. Next, you can set the positive direction of movement, step distance / angle, movement speed, and number of scanning coordinate points of each axis in the input box below. After the settings are completed, click the button "automatic scanning switch" to start the microwave wavefront shape automatic scanning function of the test platform. At this time, for each coordinate point in the space, after the three-dimensional driving motor sends the microwave receiver 10 (3) in the experimental microwave processing unit 10 to the detection position coordinate, the three-dimensional rotating table will first scan the three-dimensional angle. The number of scanning points in each dimension is controlled by the value in the scanning point input box of the dimension. After the angle scanning is completed, the software will automatically compare the microwave data of all angles, and the signal with the best signal strength will be used as the microwave radio frequency signal of the spatial detection point. The 91GHz radio frequency signal received by the microwave receiver 10 (3) in the experimental microwave processing unit 10 will be transmitted to the mixer 10 (1) in the experimental microwave processing unit 10. At the same time, the 15.165GHz local oscillator signal generated by the digital synthetic microwave source 11 is multiplied by 6 times by the multiplier 10 (2) in the experimental microwave processing unit 10 to reach 90.99GHz. The two signals are mixed in the mixer 10 (1) to generate a 10MHz experimental intermediate frequency signal. The intermediate frequency signal is transmitted to the acquisition card 7 through the coaxial cable 14 to be collected and recorded. At the same time, the 91GHz reference channel radio frequency signal generated by the microwave source 12 is transmitted to the mixer 13(1) in the reference channel microwave processing unit 13 via the coaxial cable 14. The 15.165GHz reference channel local oscillator signal generated by the digital synthesis microwave source 11 is multiplied by 6 times by the multiplier 13(2) in the reference channel microwave processing unit 13 to reach 90.99GHz. The two signals are mixed in the mixer 13(1) to generate a 10MHz reference channel intermediate frequency signal, which is transmitted to the acquisition card 7 via the coaxial cable 14 to be collected and recorded. At this time, the detection of the spatial detection point is completed, and the three motors in the three-dimensional rotating table automatically return to the starting angle to prepare for the next angle scan. Then the three-dimensional drive motor automatically delivers the microwave receiver 10(3) to the next detection position in the space to start the next automatic detection.By analogy, after all the spatial coordinate points set at the beginning of the software startup are detected, the three-dimensional drive motor automatically returns to the starting position to prepare for the next round of automatic scanning. In the above-mentioned automatic scanning process, the experimental channel and reference channel data of each detection point in the space are named and saved according to the coordinate data of the point, so as to be automatically read during data processing. It is easy to find that the only difference between the experimental channel and the reference channel data in the present invention is whether the radio frequency signal propagates in space. Therefore, in the later data processing, it is only necessary to compare the experimental channel and the reference channel data of each spatial detection point, and the phase difference obtained is the phase difference caused by the propagation of the radio frequency signal in space. Therefore, the phase difference of all detection points in space can be obtained based on this, and the wavefront shape of the microwave radio frequency signal in space can be obtained by fitting the surface.

[0064] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A six-dimensional test platform for measuring the wavefront shape of W-band microwave signals, characterized in that: The microwave processing component comprises an experimental channel microwave processing unit (10), a digital synthesis microwave source (11), a microwave source (12), a reference channel microwave processing unit (13), a coaxial cable (14), and an acquisition card (7); the radio frequency signal emitted by the microwave source (12) has two paths, one of which is emitted into a three-dimensional space through a microwave antenna and is received by a microwave receiver in the experimental channel microwave processing unit (10) after propagating a set distance; the other is directly transmitted to a mixer in the reference channel microwave processing unit (13) through a coaxial cable (14); for the experimental channel microwave processing unit (10), a frequency multiplier receives the local signal from the digital synthesis microwave source (12) The local oscillator signal is received by the digital synthesis microwave source (12), and after frequency doubling, a local oscillator signal close to the radio frequency frequency is obtained. The local oscillator signal is then mixed with the radio frequency signal received by the microwave receiver in a mixer to obtain an intermediate frequency signal of the experimental channel. The intermediate frequency signal is then transmitted to the acquisition card (7) via a coaxial cable (14) to be collected and recorded. For the reference channel microwave signal processing unit (13), the frequency multiplier receives the local oscillator signal from the digital synthesis microwave source (12), and after frequency doubling, a local oscillator signal close to the radio frequency frequency is obtained. The local oscillator signal is then mixed with the reference channel radio frequency signal in a mixer to obtain an intermediate frequency signal of the reference channel. The intermediate frequency signal is then transmitted to the acquisition card (7) via a coaxial cable (14) to be collected and recorded.

2. A six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal according to claim 1, characterized in that: The difference frequency measurement method is used in the processing of high-frequency RF signals. The RF signal and the local oscillator signal are mixed by the mixer in the microwave processing unit, so that the ultra-high frequency W-band RF signal is downconverted to a lower frequency intermediate frequency signal, reducing the difficulty of signal acquisition and processing. The frequency of the intermediate frequency signal is adjusted by adjusting the frequency of the local oscillator signal involved in the mixing.

3. The six-dimensional test platform for measuring the wavefront shape of W-band microwave signals according to claim 1, characterized in that: In the processing of the experimental signals of the "experimental channel" and the "reference channel", the interferometer principle is used to limit the difference between the two signals to whether the radio frequency signal is transmitted through the air. In the subsequent data processing, the time-varying phase can be eliminated by "phase comparison" between the two, and the absolute phase of the microwave signal in space can be obtained by decoupling.

4. A six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal according to claim 1, characterized in that: The three-dimensional coordinates and three-dimensional detection angle of the microwave receiver in space are controlled by a mechanical component, which includes a three-dimensional drive motor, a three-dimensional rotating table, and a planar support structure. The three-dimensional drive motor and the three-dimensional rotating table are used to control the position coordinates and three-dimensional detection angle of the microwave receiver in three-dimensional space; The three-dimensional drive motor is composed of a plurality of drive motors, and controls the position of the microwave receiver in three directions of X, Y and Z in three-dimensional space; The three-dimensional rotating platform controls the angles of the microwave receiver in three directions: the yaw axis, the pitch axis and the roll axis.

5. A six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal according to claim 4, characterized in that: The three-dimensional drive motor comprises an X-axis drive motor (4), a Y-axis drive motor (5), and a Z-axis drive motor (6); the guide rails of the three groups of drive motors are perpendicular to each other, wherein the guide rail of the X-axis drive motor (4) is fixed on a platform bracket (8), the guide rail of the Y-axis drive motor (5) is fixed on a slider of the guide rail of the X-axis drive motor (4), and the guide rail of the Z-axis drive motor (6) is fixed on a slider of the guide rail of the Y-axis drive motor (5), forming a spatial rectangular coordinate system, and the movement of the slider of the Z-axis drive motor (6) in a three-dimensional space can be achieved by controlling the three groups of motors.

6. A six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal according to claim 4, characterized in that: The three-dimensional rotating platform comprises a yaw axis electric rotating platform (1), a pitch axis electric rotating platform (2), and a roll axis electric rotating platform (3); the guide rail of the yaw axis electric rotating platform (1) is fixed on a slider of a Z-axis driving motor (6); the guide rail of the pitch axis electric rotating platform (2) is fixed on a rotating block of the yaw axis electric rotating platform (1); the guide rail of the roll axis electric rotating platform (3) is fixed on a rotating block of the pitch axis electric rotating platform (2); a microwave receiver is fixed on a rotating block of the roll axis electric rotating platform (3); and the detection angle of the microwave receiver in space can be controlled by controlling the motors of the three groups of rotating platforms.

7. The six-dimensional test platform for measuring the wavefront shape of W-band microwave signals according to claim 4, characterized in that: The planar support structure includes a platform bracket (8) and a Foma caster (9). The platform bracket (8) is made of aluminum profiles or other supporting materials and is used to install and fix the main part of the six-dimensional test platform. The Foma caster (9) is installed at the four corners below the platform bracket (8). The support column in the Foma caster (9) falls down to fix the position of the six-dimensional test platform.

8. A six-dimensional test platform for measuring the wavefront shape of a W-band microwave signal according to claim 1 or 4, characterized in that: The electric control components of the three-dimensional drive motor, the three-dimensional rotating stage and the acquisition card (7) are all remotely controlled by the "W band wavefront automatic measurement platform control software" to control the microwave receiver to automatically align the normal direction of the radio frequency signal wavefront and automatically scan and measure the wavefront shape, or manually fine-tune the six-dimensional degrees of freedom of the microwave receiver.

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