High-precision high-time-resolution terahertz wave band tau radiation measuring device

Abstract

The invention provides a high-precision and high-time-resolution terahertz wave band tau radiation measuring device. The high-precision and high-time-resolution terahertz wave band tau radiation measuring device comprises an antenna module, a calibration assembly, a local oscillator signal source module, a refrigeration module, a superconducting receiver module, a data acquisition module and a system control module. Measurement of atmospheric opacity and atmospheric radiation temperature calibration in any direction of a station site are realized through the antenna module and the calibration assembly. The superconducting receiver module adopts a superconducting SIS mixer, the detection sensitivity is improved by one order of magnitude compared with that of a normal-temperature Schottky mixing receiver, and high-precision and high-time-resolution atmospheric opacity measurement can be realized by combining the narrow-band frequency gating and real-time spectrum data quick reading characteristics of a high-spectrum-resolution real-time FFT spectrum analyzer of the data acquisition module. And meanwhile, a real-time FFT frequency spectrograph of the data acquisition module of the device has high-frequency-resolution frequency spectrum processing capability, so that the device can be used as a spectral line receiver with high sensitivity and high frequency spectrum resolution, and terahertz astronomical molecule spectral line observation with high frequency spectrum resolution can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of terahertz radiometers and relates to a high-precision and high-time-resolution terahertz band τ radiation measurement device based on a superconducting SIS. Background Art

[0002] The terahertz (THz) band is generally defined as the range of 0.1 to 10 THz, covering the band from short millimeter waves to submillimeter waves (far infrared). This band is the last electromagnetic band to be fully developed and studied. It is an important supplement to the optical near-infrared and microwave bands, and is also a brand-new band with important scientific significance and broad application prospects. Because the terahertz band accounts for nearly half of the photon energy in the universe after the microwave background radiation, and there are rich molecular spectral lines, it is considered to be particularly suitable for carrying out the most important cutting-edge scientific research in modern astronomy.

[0003] Due to the strong interaction between terahertz waves and atmospheric molecules, terahertz waves are strongly absorbed by the atmosphere during their propagation, which greatly limits the observation efficiency of ground-based terahertz astronomical observation equipment to the conditions of ground-based astronomical stations. Currently, the excellent terahertz observatory sites that have been identified worldwide are located in very few high-altitude, low-temperature, and dry areas such as Antarctica, Chile's Atacama Desert, Hawaii's Mauna Kea, and Greenland. How to find a suitable terahertz observatory site has always been a topic of concern to astronomers.

[0004] The atmospheric opacity τ of the observatory site is the most direct and important parameter to characterize the characteristics of the terahertz astronomical observatory site. Atmospheric opacity is frequency-dependent, and the atmospheric opacity shows a change in window characteristics with frequency, that is, it has a lower atmospheric opacity in certain specific frequency bands, while in other frequency bands, it presents a high value or always maintains an ultra-high atmospheric opacity due to strong atmospheric absorption. Moreover, as the frequency increases, the opacity of the atmospheric window in a specific frequency band tends to increase, and the atmospheric conditions with greater opacity are less suitable for terahertz astronomical observations. In other applications of terahertz astronomical target imaging observations or terahertz interferometer interferometric observations, it is necessary to correct the influence of atmospheric disturbances on the image quality of the imaging area, or to correct the influence of the atmosphere on the interferometer line-of-sight phase delay. Therefore, it is necessary to measure the rapid fluctuation characteristics of the atmospheric opacity of the observatory site.

[0005] The atmospheric opacity measurement in the terahertz band is carried out for specific atmospheric window frequencies, which mainly include 0.23THz, 0.35THz, 0.46THz, 0.49GHz, 0.66THz, 0.85THz and 1.3~1.4THz, etc. The atmospheric opacity measurement equipment in the terahertz band is mainly a terahertz radiometer. In order to accurately understand the atmospheric characteristics of the frequency band where terahertz astronomical observations are located (specific atmospheric window frequency band), it is generally necessary to deploy terahertz τ radiometers in the corresponding frequency band to measure the atmospheric opacity, so as to characterize the characteristics of the terahertz observatory site, whether terahertz astronomical observations can be carried out in this frequency band, and the rapid fluctuation characteristics of the atmospheric opacity of the observatory site.

[0006] At present, traditional τ-radiometer devices mainly use room-temperature Schottky mixers with low detection sensitivity as receivers (the system equivalent noise temperature is on the order of several thousand K). In the process of measuring atmospheric opacity, a larger intermediate frequency bandwidth is required to obtain more atmospheric radiation signal energy. At the same time, a chopper wheel is used to perform synchronous detection and long-term integration (each observation elevation position requires integration of more than 10-20s) on the broadband intermediate frequency total power to obtain sufficient detection signal-to-noise ratio. Therefore, it takes more than 10 to 20 minutes to complete an elevation scanning observation. The measurement time is long, which makes it difficult to meet the application scenarios of rapid changes in atmospheric opacity fluctuations required by terahertz interferometer observations. In addition, the need for a wider intermediate frequency will inevitably make the system more susceptible to interference from the external environment, resulting in reduced system stability. In addition, as the observation frequency increases, the atmospheric opacity in the terahertz high frequency band increases, which means that the difference in atmospheric radiation brightness temperature at different pitch angles is weaker. At the same time, the detection sensitivity of the room temperature Schottky mixer decreases significantly with the increase in frequency. Therefore, even if the synchronous detection time is increased, it is difficult to achieve a sufficient signal-to-noise ratio, which leads to a large system error in the measurement data, and the measurement is not accurate enough, and it is even impossible to carry out atmospheric opacity measurement. Therefore, the τ radiometer device with room temperature Schottky mixer as the core mainly focuses on low-frequency bands with low atmospheric opacity (most commonly such as 0.23THz band) to carry out atmospheric opacity measurement, but it is difficult to carry out high-precision and high-time resolution measurements in higher frequency bands such as 0.46THz and above. Summary of the invention

[0007] In order to overcome the technical problems that the existing terahertz τ radiation measuring devices are difficult to carry out high-precision and high-time resolution measurements in higher terahertz frequency bands, the present invention provides a high-precision and high-time resolution terahertz band τ radiation measuring device based on superconducting SIS.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a high-precision and high-time resolution terahertz band τ radiation measurement device, comprising an antenna module, a local oscillator signal source module, a refrigeration module, a superconducting receiver module, a data acquisition module and a system control module; the antenna module comprises an antenna and a reflection component, the antenna can perform atmospheric pitch scanning at any orientation, and the received signal is incident on a receiving end of the superconducting receiver module through a signal transmission path of the reflection component; the refrigeration module comprises a vacuum dewar, a cold head and a refrigerator, and the refrigerator provides refrigeration capacity for the vacuum dewar; the superconducting receiver module comprises a superconducting mixer, a low-temperature low-noise amplifier, a normal temperature amplifier and a low-pass filter connected in sequence, the superconducting mixer and the low-temperature low-noise amplifier are arranged in the vacuum dewar, The input signal from the antenna module enters from the Dewar window, and through the heat sink formed by the cold head, the superconducting mixer and the low-temperature low-noise amplifier operate in the 8K temperature zone; the room temperature amplifier and the low-pass filter are arranged outside the vacuum Dewar; the input signal of the antenna module and the local oscillator signal output by the local oscillator signal source module enter the superconducting mixer for mixing, and then the signal-to-noise ratio is improved by the low-temperature low-noise amplifier, the output signal is amplified by the room temperature amplifier, and then filtered by the low-pass filter; the data acquisition module is used to perform spectrum processing on the intermediate frequency signal from the superconducting receiver module; the system control module is respectively connected to the antenna module, the local oscillator signal source module, the refrigeration module, the superconducting receiver module and the data acquisition module, and is used to control the system operation.

[0010] Furthermore, the reflection assembly includes a first reflector, a second reflector and a third reflector; the first reflector and the second reflector are parallel to each other, with an inclination angle of 45°, and are distributed on the same horizontal plane; the third reflector is distributed below the second reflector and is mirror-symmetrical with the second reflector; the signal received by the antenna enters the second reflector through reflection by the first reflector, enters the third reflector through reflection by the second reflector, and finally enters the superconducting receiver module through reflection by the third reflector and is received by the superconducting mixer.

[0011] Furthermore, the first reflector and the antenna are jointly fixed on the mounting surface of the pitch drive motor, and can be jointly rotated in pitch under the drive of the pitch drive motor, and the pitch rotation angle is 0 to 90°; the second reflector, the first reflector, the antenna and the pitch drive motor are jointly fixed on the mounting surface of the azimuth drive motor, and can be jointly rotated horizontally under the drive of the azimuth drive motor, and the horizontal rotation angle is -270 to +270°.

[0012] Furthermore, the antenna module is also provided with a calibration component; the calibration component includes a room temperature calibration blackbody, which is an aluminum square cone array obtained by molding, and its radiation surface is attached with a high thermal conductivity silicon carbide powder layer by low-temperature Stycast glue; the room temperature calibration blackbody is arranged at the optical path waist plane in front of the superconducting receiver module, and the room temperature calibration blackbody is fixed on the driving motor, and can rotate 180° under the drive of the driving motor to switch the signal path through the on / off switch; the driving motor is connected to the system control module.

[0013] Furthermore, the local oscillator signal source module includes a microwave signal source and a frequency multiplication chain, the frequency multiplication chain includes at least one group of frequency multiplication amplifiers connected in sequence, the microwave signal source is used to output the local oscillator signal, the frequency and power of the microwave signal source are tunable, and the frequency multiplication chain is used to multiply the frequency of the local oscillator signal; wherein, the microwave signal source takes insulation measures, and the final frequency multiplication chain is arranged inside the vacuum dewar.

[0014] Furthermore, the superconducting mixer is a superconducting SIS mixer made of all NbN materials and capable of operating in the 8K temperature range, and the operating frequency band is the 0.5THz frequency band.

[0015] Furthermore, the refrigerator is a low-power (500-watt-level) high-frequency pulse tube closed-loop refrigerator, which provides the refrigeration power required for the superconducting SIS mixer made of all NbN materials to operate stably in the 8K temperature range.

[0016] Furthermore, the intermediate frequency gain of the normal temperature amplifier is above 30 dB, and the effective bandwidth of the low-pass filter is between 0 and 2.4 GHz; the normal temperature amplifier and the low-pass filter operate in a wide temperature range of -40°C.

[0017] Furthermore, the antenna is a card-type antenna, including a carbon fiber plate and a CNC aluminum antenna supported on the carbon fiber plate.

[0018] Furthermore, in the refrigeration module, the refrigerator and the cold head are connected via a vibration-isolating sealed bellows to reduce the vibration of the cold head.

[0019] Furthermore, the data acquisition module adopts a real-time FFT spectrometer for real-time FFT spectrum processing of broadband intermediate frequency signals; the system control module includes an embedded computer and system control software running on the embedded computer, the embedded computer operates in a wide temperature range of -40 to 50°C, and the system control software is used to set and control parameters of the entire system, including controlling the antenna pitch and azimuth scanning in the antenna module, the optical path on / off switching of the calibration black body, the tuning of the local oscillator signal source module, the superconducting mixer bias, the low-temperature low-noise amplifier bias, the vacuum dewar refrigeration start and stop, and the start and stop of the real-time FFT spectrometer.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention adopts a small card-type antenna capable of 0-90° pitch scanning and omnidirectional scanning, combined with an ultra-high sensitivity superconducting SIS mixer reception (the overall equivalent noise temperature of the device is better than 300K in the 0.5THz frequency band). Compared with the traditional Schottky mixer, the detection sensitivity can be improved by one order of magnitude. At the same time, combined with the real-time FFT spectrum analyzer with fast (10 milliseconds) data readout capability and narrower bandwidth frequency gating characteristics (the spectrum bandwidth of the spectrum analyzer channel is better than 100kHz), compared with the traditional total power readout method, it has higher flexibility and stronger anti-interference ability (convenient to eliminate the large interference signal spectrum in the band), so it can achieve high-precision and high time resolution (minutes) measurement of atmospheric opacity in the 0.5THz frequency band.

[0022] (2) The present invention integrates the antenna scanning and calibration components and separates them from other components of the device (including receiver components, local oscillator signal source components and system control components, etc.) for dynamic and static separation, thereby reducing the operating load of the antenna scanning and calibration components, avoiding the mechanical operation of non-operating parts, and improving the stability of the overall mechanical and electrical characteristics of the device.

[0023] (3) The real-time FFT spectrometer used in the present invention has the spectrum processing capability of high frequency resolution, and the device can be used as a high-sensitivity and high-spectrum-resolution spectrum line receiver to achieve high sensitivity and high spectrum resolution (R~10 6 )'s terahertz astronomical molecular spectral line observations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram of the high-precision and high-time resolution terahertz band τ radiation measurement device of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are 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 making creative work are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, a high-precision and high-time resolution terahertz band τ radiation measurement device includes an antenna module, a local oscillator signal source module, a cooling module, a superconducting receiver module, a data acquisition module and a system control module.

[0027] The antenna module includes an antenna and a reflector assembly, and the antenna can scan the atmosphere in any direction. The received signal is incident on the receiving end of the superconducting receiver module through the signal transmission path of the reflector assembly. The refrigeration module includes a vacuum dewar, a cold head and a refrigerator, and the refrigerator provides refrigeration for the vacuum dewar. The superconducting receiver module can realize high-sensitivity reception and mixing of atmospheric signals, including a superconducting mixer, a low-temperature low-noise amplifier, a normal temperature amplifier and a low-pass filter connected in sequence. The superconducting mixer and the low-temperature low-noise amplifier are arranged in the vacuum dewar, and the input signal from the antenna module enters from the dewar window. Through the heat sink formed by the cold head, the superconducting mixer and the low-temperature low-noise amplifier work in the 8K temperature zone; the normal temperature amplifier and the low-pass filter are arranged outside the vacuum dewar; the input signal of the antenna module and the local oscillator signal output by the local oscillator signal source module enter the superconducting mixer for mixing, and the signal-to-noise ratio is improved by the low-temperature low-noise amplifier, and the output signal is amplified by the normal temperature amplifier, and then filtered by the low-pass filter. The data acquisition module is used to perform spectrum processing on the intermediate frequency signal from the superconducting receiver module. The system control module is respectively connected with the antenna module, the local oscillator signal source module, the cooling module, the superconducting receiver module and the data acquisition module to control the operation of the system.

[0028] The antenna adopts a 30cm card antenna, which includes a carbon fiber plate and a CNC aluminum antenna supported on the carbon fiber plate.

[0029] like Figure 1 As shown, the reflective assembly includes a first reflector (M1), a second reflector (M2) and a third reflector (M3), and the first reflector, the second reflector and the third reflector are all metal reflectors. The three metal reflectors are used to realize the folding and beam adjustment of the received signal transmission path to match the superconducting SIS mixer antenna beam in the receiver assembly. The first reflector and the second reflector are parallel to each other, with an inclination angle of 45°, and are distributed on the same horizontal plane; the third reflector is distributed below the second reflector and is mirror-symmetrical with the second reflector; the signal received by the antenna enters the second reflector through reflection from the first reflector, enters the third reflector through reflection from the second reflector, and finally enters the superconducting receiver module through reflection from the third reflector and is received by the superconducting mixer.

[0030] Considering the convenience of azimuth rotation and pitch scanning of the antenna, the first reflector and the antenna are fixed together on the mounting surface of the pitch drive motor, and can be driven by the pitch drive motor to perform pitch rotation together, so as to achieve antenna pitch scanning and keep the signal beam transmission characteristics between the first reflector and the second reflector unchanged. The pitch rotation angle can be set to 0 to 90°. The second reflector, the first reflector, the antenna and the pitch drive motor are fixed together on the mounting surface of the azimuth drive motor, and can be driven by the azimuth drive motor to perform horizontal rotation together. By rotating the azimuth drive motor, the azimuths of the second reflector, the first reflector and the antenna change in unison, while ensuring that the signal beam transmission characteristics folded vertically downward by the second reflector remain unchanged, so as to achieve azimuth scanning. The horizontal rotation angle can be set to -270 to +270°.

[0031] like Figure 1 As shown, the antenna module is also provided with a calibration component, which is a normal temperature calibration black body, which is used for calibration of the observed signal source, helps to understand the error caused by the stability problem of the measurement, and is also used for calibration of the system sensitivity during the system performance test. The normal temperature calibration black body is an aluminum square cone array obtained by molding, and its radiation surface is attached with a high thermal conductivity silicon carbide powder layer through a low-temperature Stycast glue. The normal temperature calibration black body is set at the optical path waist plane in front of the superconducting receiver module, and is equipped with a high-precision temperature sensor, and the normal temperature calibration black body is fixed on the drive motor, and can be driven by the drive motor to rotate 180° to switch the signal path through / out, and the drive motor is connected to the system control module.

[0032] In the present invention, the azimuth scanning and elevation scanning of the antenna are both driven by a harmonic deceleration elevation drive motor and an azimuth drive motor, and the normal temperature calibration black body is switched by the drive motor, so that the movement of the antenna scanning and calibration components and the static state of the subsequent superconducting receiver components are effectively separated, thereby minimizing the moving parts, saving the system energy consumption, and contributing to the improvement of the system working stability.

[0033] The local oscillator signal source module adopts a microwave reference source combined with a solid-state local oscillator signal source design of frequency multiplication amplification, which is convenient for system integration. The local oscillator signal source module includes a microwave signal source and a frequency multiplication chain, and the frequency multiplication chain includes at least one group of frequency multiplication amplifiers connected in sequence. The microwave signal source is used to output the local oscillator signal. The frequency and power of the microwave signal source are tunable, and the frequency multiplication chain is used to multiply the local oscillator signal. Since the local oscillator signal source is a relatively temperature-sensitive component, in order to improve the stability of the signal source, the microwave signal source adopts insulation measures, and at the same time, the final frequency multiplication chain is set inside the vacuum dewar (smaller temperature change) to avoid the problem of stability of the local oscillator signal source caused by environmental temperature changes.

[0034] The superconducting mixer operates in the 0.5THz frequency band, covering the 0.46THz and 0.492THz atmospheric windows, and can carry out atmospheric opacity measurements in the 0.46THz and 0.492THz frequency bands. Considering the low-temperature energy consumption, a superconducting SIS mixer made of all NbN (niobium nitride) materials that can operate in the 8K temperature range is used. Compared with the 4K temperature range, the all-NbN superconducting SIS mixer operates in the 8K temperature range, which greatly reduces the demand for Dewar cooling and the requirements for the operation of the Dewar refrigerator, thereby greatly reducing the overall energy consumption of the system.

[0035] The low-temperature low-noise amplifier adopts discrete components and achieves high gain through multi-stage cascade, making full use of the low mixing loss characteristics of the superconducting SIS mixer to improve the system sensitivity while reducing the noise coefficient requirements for the room-temperature intermediate frequency. The room-temperature amplifier and low-pass filter operate in a wide temperature range of minus 40°C, the room-temperature amplifier intermediate frequency gain is above 30dB, and the low-pass filter has an effective bandwidth of 0 to 2.4GHz to match the bandwidth and power requirements of the subsequent spectrum analyzer input.

[0036] In the refrigeration module, the cold plate of the 8K vacuum dewar that provides a low-temperature working environment for the superconducting SIS mixer adopts a multi-level support method to reduce the overall size (height), which also helps to fully utilize the space of the vacuum dewar. In order to reduce the impact of the 8K dewar cold head on the refrigeration cycle vibration of the closed-loop refrigerator, the refrigerator and the cold head are connected through a vibration-isolating sealed bellows to reduce the vibration of the cold head, thereby reducing the fluctuation of the refrigeration temperature and improving the working stability of the superconducting SIS mixer.

[0037] The refrigerator uses a high-frequency pulse tube closed-loop refrigerator with a vacuum pump to provide the 8K Dewar with long-term continuous cooling capacity. The 8K closed-loop refrigerator has the advantage of long-term cooling and is suitable for applications where long-term continuous observation is carried out. Considering the system's need to operate under field conditions, since the superconducting SIS mixer uses all-NbN materials, its high transition temperature characteristics mean a high operating temperature range, which reduces the cooling power requirements of the high-frequency pulse tube closed-loop refrigerator. The closed-loop refrigerator uses a low-power (500W power consumption) and single-phase power supply high-frequency pulse tube refrigerator, which greatly reduces the power demand and complexity of the energy supply platform for the field, and improves the system's miniaturization and integration as well as the convenience of system transportation and installation.

[0038] The data acquisition module adopts a real-time FFT (Fast Fourier Transform) spectrometer for real-time FFT spectrum processing of broadband intermediate frequency signals, and the data acquisition of the intermediate frequency signal spectrum is used for system performance testing and atmospheric opacity measurement. The data acquisition module adopts a real-time FFT spectrometer as a fast (10 milliseconds) data readout method. Compared with the traditional total power readout method, it has a fast (10 milliseconds) data readout capability and a narrower bandwidth frequency gating characteristic (the spectrum bandwidth of the spectrum analyzer channel is better than 100kHz), so it has higher flexibility and stronger anti-interference (convenient to remove the large interference signal spectrum in the band), combined with the superconducting SIS mixer signal reception with ultra-high detection sensitivity, to achieve higher precision and higher time resolution atmospheric opacity measurement.

[0039] The system control module includes an embedded computer and system control software running on the embedded computer. The embedded computer works in a wide temperature range of -40 to 50°C. The system control software is used to set and control parameters of the entire system, including controlling the antenna pitch and azimuth scanning in the antenna module, the optical path on / off switching of the calibration black body, the tuning of the local oscillator signal source module, the biasing of the superconducting SIS mixer, the biasing of the low-temperature low-noise amplifier, the start and stop of the 8K vacuum dewar refrigeration, and the start and stop of the real-time FFT spectrometer.

[0040] In addition to setting the parameters of each component and controlling the start and stop, the application software also includes monitoring of the key status information of each component. In addition, since the atmospheric opacity measurement requires antenna azimuth setting and elevation scanning, the application software accurately records the azimuth, the elevation angle corresponding to different times, and the observation data corresponding to different elevation angles, and saves the data and pre-processes the subsequent measurement data. The embedded computer reserves a remote control interface, and the application software has the function of remote control and data interaction with the outside world to meet the unattended operation of the equipment under suitable field conditions.

[0041] The overall structure layout of the terahertz band τ radiation measurement device of the present invention is divided into three layers. From top to bottom, the top layer is the antenna module and the calibration component, the second layer is the refrigeration module (8K refrigerator and 8K Dewar), the local oscillator signal source module, the superconducting mixer and the low-temperature low-noise amplifier, and the third layer is the vacuum pump (for Dewar vacuuming), the normal temperature amplifier, the low-pass filter, the data acquisition module, the system control module and the DC bias power supply of each component of the system. The second and third layers are encapsulated with thermal insulation materials.

[0042] In the second and third layer structures, the thermal control adopts a one-way air duct design and uses an adjustable speed fan to exhaust air, ensuring that the refrigerator located at the air inlet has a relatively low temperature working condition, while the fan is in a higher temperature environment. At the same time, a preheating unit is designed for preheating before the device is started, and for temperature compensation during normal operation. The structural layout and thermal control are intended to take into account the full use of the waste heat of the refrigerator and maintain the working temperature zone of the electronic components in the internal temperature system to prevent damage to the electronic components under extremely low temperature conditions. The thermal control layout of the device structure of the present invention is reasonably designed to ensure that the heat-generating refrigerator has a relatively low temperature working condition, and to make full use of the waste heat of the refrigerator to provide temperature compensation for electronic components under extremely low temperature conditions.

[0043] The terahertz band τ radiation measuring device of the present invention has two interfaces on the structural frame, including a 220V mains input interface for an external mains access device, and a gigabit network RJ45 interface for high-speed operation between an embedded computer and an external remote device.

[0044] Example 1: Measurement of atmospheric opacity at the zenith

[0045] Step 1: Place the terahertz band τ radiation measurement device horizontally in the test field, connect it to the 220V and Gigabit network cables, and start the external power supply. After the system control module is powered on, it automatically starts the system, enters the system control software interface, and waits for the next manual operation. At the same time, the bias power supply of the superconducting SIS mixer, low-temperature low-noise amplifier, room temperature amplifier, low-pass filter, real-time FFT spectrometer, and local oscillator signal source components of the superconducting receiver assembly are powered on at the same time. The portable computer outside the device switches to the system control software user interface of the embedded computer through the remote desktop.

[0046] Step 2: Start the vacuum pump of the refrigerator assembly through the user interface of the system control software running on the embedded computer to evacuate the 8K Dewar. When the vacuum degree reaches the target value (10 -4 mBar level), start the refrigerator and start cooling.

[0047] Step 3: Wait until the temperature of the 8K Dewar cold plate reaches the target temperature zone (8K temperature zone), set the superconducting SIS mixer operating point, adjust the output power of the room temperature amplifier, set the observation frequency (such as 0.46THz) and power of the local oscillator signal source component, and set the integration time (on the order of 10ms) of the real-time FFT spectrometer.

[0048] Step 4: start the azimuth drive motor of the antenna module, rotate the antenna azimuth to the observed azimuth, and start the atmospheric opacity observation program on the user interface of the system control software of the embedded computer.

[0049] Step 5. The atmospheric opacity observation program performs an atmospheric pitch scan (Sky-tipping) at a preset pitch angle (15 pitch angles are preset between 10 and 85 degrees), and reads the observation values ​​at each pitch angle point by point from the real-time FFT spectrometer to form a set of atmospheric opacity Sky-tipping. The observation program of the system control module pre-processes the observation data to obtain an observed atmospheric opacity τ in the zenith direction (a set of observation processes is on the order of minutes).

[0050] Step 6: Repeat step 5 until the atmospheric opacity observation program is stopped, and a series of atmospheric opacities τ in the zenith direction during the observation period can be obtained.

[0051] Example 2: Astronomical molecular spectral line observation

[0052] The device can also be used for astronomical molecular spectral line observation, and the specific method includes the following steps:

[0053] Step 1: Place the device horizontally on the test site, adjust the level of the device, and adjust the orientation of the antenna module and calibration components of the device to ensure that the device orientation zero point points to the due north direction.

[0054] Step 2: Connect the radiometer device to the 220V and Gigabit network cables and start the external power supply. After the system control module is powered on, it automatically starts the system, enters the system control software interface, and waits for the next manual operation. At the same time, the superconducting SIS mixer, low-temperature low-noise amplifier, room-temperature amplifier, low-pass filter, real-time FFT spectrum analyzer, and bias power supply of the local oscillator signal source component of the superconducting receiver component are powered on at the same time. The portable computer outside the device switches to the system control software user interface of the embedded computer through the remote desktop.

[0055] Step 3: Start the vacuum pump of the refrigerator assembly through the user interface of the system control software running on the embedded computer to evacuate the 8K Dewar. When the vacuum degree reaches the target value (10 -4 mBar level), start the refrigerator and start cooling.

[0056] Step 4: Wait until the temperature of the 8K Dewar cold plate reaches the target temperature zone (8K temperature zone), set the superconducting SIS mixer working point, adjust the output power of the room temperature amplifier, set the astronomical molecular spectral line observation frequency of the local oscillator signal source component to around (such as 0.461THz), and set the basic integration time (1s) of the real-time FFT spectrometer.

[0057] Step 5: Start the astronomical molecular spectrum line observation program on the user interface of the system control software of the embedded computer and input the coordinates (right ascension and declination) of the observation antenna.

[0058] Step 6: The astronomical molecular spectrum line observation program will start the azimuth drive motor and the pitch drive motor of the antenna module to track the astronomical target, and at the same time perform position modulation to observe and integrate the data of a set of calibration processes of celestial signal source-cold sky background-black body calibration body.

[0059] Step 7. Repeat step 6 until the astronomical molecular spectral line observation program is stopped, and a series of astronomical molecular spectral line observation spectrum data for the observation period can be obtained. Subsequently, each set of observation data (including three sets of observation data of celestial signal source-cold sky background-blackbody calibration body) is amplitude calibrated in turn to obtain a series of astronomical molecular spectral line intensity information.

[0060] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A high-precision and high-time resolution terahertz band τ radiation measurement device, characterized in that: It includes an antenna module, a local oscillator signal source module, a cooling module, a superconducting receiver module, a data acquisition module and a system control module; The antenna module includes an antenna and a reflective component. The antenna can perform atmospheric pitch scanning at any orientation. The received signal is incident on the receiving end of the superconducting receiver module through the signal transmission path of the reflective component. The refrigeration module includes a vacuum dewar, a cold head and a refrigerator, and the refrigerator provides refrigeration capacity for the vacuum dewar; The superconducting receiver module includes a superconducting mixer, a low-temperature low-noise amplifier, a normal-temperature amplifier and a low-pass filter connected in sequence. The superconducting mixer and the low-temperature low-noise amplifier are arranged in a vacuum dewar. The input signal from the antenna module enters from the dewar window, and the superconducting mixer and the low-temperature low-noise amplifier are operated in the 8K temperature zone through the heat sink formed by the cold head; the normal-temperature amplifier and the low-pass filter are arranged outside the vacuum dewar; the input signal of the antenna module and the local oscillator signal output by the local oscillator signal source module enter the superconducting mixer for mixing, and then the signal-to-noise ratio is improved by the low-temperature low-noise amplifier, the output signal is amplified by the normal-temperature amplifier, and then filtered by the low-pass filter; The data acquisition module is used to perform spectrum processing on the intermediate frequency signal from the superconducting receiver module; The system control module is respectively connected with the antenna module, the local oscillator signal source module, the cooling module, the superconducting receiver module and the data acquisition module, and is used for controlling the operation of the system.

2. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1 is characterized in that: The reflective assembly includes a first reflector, a second reflector and a third reflector; The first reflector and the second reflector are parallel to each other and are distributed on the same horizontal plane; the third reflector is distributed below the second reflector and is mirror-symmetrical with the second reflector; the signal received by the antenna enters the second reflector through reflection from the first reflector, enters the third reflector through reflection from the second reflector, and finally enters the superconducting receiver module through reflection from the third reflector and is received by the superconducting mixer.

3. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 2 is characterized in that: The first reflector and the antenna are fixed together on the mounting surface of the pitch drive motor, and can perform pitch rotation together under the drive of the pitch drive motor; The second reflector, the first reflector, the antenna and the pitch drive motor are fixed together on the mounting surface of the azimuth drive motor, and can be horizontally rotated together under the drive of the azimuth drive motor.

4. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1 is characterized in that: The antenna module is also provided with a calibration component; The calibration component includes a normal temperature calibration black body, which is an aluminum square cone array obtained by molding, and a high thermal conductivity silicon carbide powder layer is attached to the radiation surface through low temperature Stycast glue; The normal temperature calibration black body is arranged at the optical path waist plane in front of the superconducting receiver module, and the normal temperature calibration black body is fixed on the driving motor and can rotate 180 degrees under the drive of the driving motor to switch the signal path through / out; the driving motor is connected to the system control module.

5. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1 is characterized in that: The local oscillator signal source module includes a microwave signal source and a frequency multiplication chain, the frequency multiplication chain includes at least one group of frequency multiplication amplifiers connected in sequence, the microwave signal source is used to output the local oscillator signal, the frequency and power of the microwave signal source are tunable, and the frequency multiplication chain is used to perform frequency multiplication amplification on the local oscillator signal; Among them, the microwave signal source adopts insulation measures, and the final frequency doubling chain is set inside the vacuum dewar.

6. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1 is characterized in that: The superconducting mixer is a superconducting SIS mixer made of all NbN materials and can operate in the 8K temperature range, and the operating frequency band is the 0.5THz frequency band.

7. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1 is characterized in that: The intermediate frequency gain of the normal temperature amplifier is above 30dB, and the effective bandwidth of the low-pass filter is between 0 and 2.4GHz; The constant temperature amplifier and the low-pass filter operate in a wide temperature range of -40°C.

8. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1 is characterized in that: The antenna adopts a card antenna, which includes a carbon fiber plate and a CNC aluminum antenna supported on the carbon fiber plate.

9. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1, characterized in that: In the refrigeration module, the refrigerator and the cold head are connected through a vibration-isolating sealed bellows to reduce the vibration of the cold head; The refrigerator is a high frequency pulse tube closed loop refrigerator.

10. The high-precision and high-time-resolution terahertz band τ radiation measurement device according to claim 1, characterized in that: The data acquisition module uses a real-time FFT spectrum analyzer for real-time FFT spectrum processing of broadband intermediate frequency signals; The system control module includes an embedded computer and system control software running on the embedded computer. The embedded computer works in a wide temperature range of -40 to 50°C. The system control software is used to set and control parameters of the entire system, including controlling the antenna pitch and azimuth scanning in the antenna module, the optical path on / off switching of the calibration black body, the tuning of the local oscillator signal source module, the biasing of the superconducting mixer, the biasing of the low-temperature low-noise amplifier, the start and stop of the vacuum dewar refrigeration, and the start and stop of the real-time FFT spectrometer.

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