A dual local oscillator submillimeter-wave superconducting detection system

Abstract

This invention relates to a dual-local-oscillator submillimeter-wave superconducting detection system. The system includes a first local oscillator source, a second local oscillator source, a first coupler, a second coupler, a housing, a superconducting mixer, a signal amplifier, and an intermediate-to-back-end processing system. Two local oscillator signals, generated by the first and second local oscillators, enter the housing through designated signal windows and are coupled by the first coupler to obtain dual-local-oscillator output signals. The detected signal enters the housing through a designated signal window and undergoes secondary coupling with the dual-local-oscillator output signals. The signals after the two couplings converge at the feed of the superconducting mixer, are mixed by the superconducting mixer, and output as an intermediate-frequency (IF) signal. This IF signal is then processed by the signal amplifier and output to the IF back-end processing system, completing the detection of the submillimeter-wave signal. Compared with existing technologies, this invention effectively avoids problems such as pointing, calibration, and instrument errors caused by discrete observations, and helps to achieve high-quality, wide-range spectral line observations.

Description

Technical Field

[0001] This invention relates to the field of astronomical detection instrument technology, and in particular to a dual local oscillator submillimeter-wave superconducting detection system. Background Technology

[0002] With approximately half of the photons produced by the Big Bang, interstellar molecules, and many characteristic spectral lines of cold, dark celestial bodies lying in the submillimeter range, and with the interstellar medium exhibiting far less extinction in this band than in the visible / near-infrared range, observations and studies in the submillimeter band are of paramount importance for understanding the overall structural evolution of the universe, galaxy formation and evolution, and galaxy and gas dynamics. Currently, astronomers have observed over a hundred types of molecules in the universe, with most transitions (including rotational and vibrational) occurring in the submillimeter band. Observations using these molecular spectral lines as probes can reveal the chemical characteristics, density, temperature, transmittance, and dynamic processes of gases in molecular clouds, which is crucial for exploring the formation and evolution of stellar and planetary systems.

[0003] Within the solar system, observations of cometary water molecules and their isotopes, especially measurements of the deuterium-to-hydrogen ratio (D / H), can reveal scientific questions such as the evolution of the solar system and the origin of Earth's water. The molecular transition spectra of water isotopes in comets are located in the submillimeter waveband, primarily containing HDO (I0.05) and other isotopes. 10 -I 01 The rotational transition of H2 17 O, H2 18 O(I 10 -I 01 The ground state transitions, etc. The HDO molecular spectral line is located at 509.3 GHz, and H2... 18 O is located at 547.7 GHz, H2 17 O is located at 552.0 GHz. Due to the extremely weak transition signal of the HDO molecule itself and the highly unstable gas release process of comets, how to measure its ultra-low noise D / H ratio is a current challenge.

[0004] Traditional methods for analyzing the water molecule isotopes HDO and H2 in comets 18 When observing comets, separate detectors are used. Due to the instability of cometary activity and gas release processes, the signal sources from two observations are difficult to keep consistent and therefore lack correlation. Furthermore, the noise, response, and efficiency parameters of the two separate detectors differ, making direct comparisons even for observations of the same signal source impossible. Complex calibration and instrument error correction are required. Therefore, simultaneous observation using the same terminal is crucial for achieving ultra-low noise and ultra-high correlation D / H ratio measurements of cometary water molecule isotopes.

[0005] With the development of ultra-wideband superconducting mixers integrating cryogenic low-noise amplifiers and cryogenic isolators, it may be possible in the future to use a single detector to simultaneously perform HDO and H2. 18 O and H2 17 The measurement of O. However, this ultra-wideband output detection technology has drawbacks:

[0006] (1) A second downconverter is needed to downconvert the output signal again before it can be sent to the back-end intermediate frequency processing system, which will increase additional noise.

[0007] (2) Using broadband low-temperature low-noise amplifiers and low-temperature isolators will introduce more mid-frequency noise, which will reduce the detection sensitivity to some extent. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a dual-local oscillator submillimeter-wave superconducting detection system that can simultaneously observe wide-range spectral lines in submillimeter-wave astronomical observations, obtain the precise molecular and atomic content ratio of the observed spectral lines, have ultra-high detection sensitivity, do not require secondary frequency reduction, and can perform four-sideband detection.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] This invention provides a dual local oscillator submillimeter-wave superconducting detection system, which includes a first local oscillator source, a second local oscillator source, a first coupler, a second coupler, a housing, a superconducting mixer, a signal amplifier, and a mid-to-back-end processing system;

[0011] The two local oscillator signals generated by the first and second local oscillator sources enter the enclosure through the provided signal windows. After being coupled by the first coupler, dual local oscillator output signals are obtained. The signal to be detected enters the enclosure through the provided signal window and is coupled twice with the dual local oscillator output signals. The signals after the two couplings are converged to the feed of the superconducting mixer. After being mixed by the superconducting mixer, the intermediate frequency signal is output. Then, after being processed by the signal amplifier, it is output to the intermediate frequency back-end processing system to complete the detection of submillimeter wave signals.

[0012] Preferably, the signal coupling adopts a quasi-optical mode; both the first coupler and the second coupler are beam combiners, and their signal coupling process is as follows:

[0013] The two local oscillator signals, with their propagation directions perpendicular to each other, are generated by the first and second local oscillator sources. They enter the housing through signal windows on the housing and are then combined via optical transmission to a first combiner placed at a 45° angle to the propagation direction of the first local oscillator signal, where they are coupled to obtain a dual local oscillator output signal. The signal to be detected enters the housing through the signal window, and its propagation direction is perpendicular to the direction of the dual local oscillator output signal. The two signals are then combined via optical transmission to a second combiner placed at a 45° angle to the signal to be detected, where they are coupled a second time.

[0014] Preferably, the enclosure includes a drying chamber connected to a cryogenic thermostat and a cryogenic vacuum chamber formed by a cryogenic thermostat, wherein the secondary coupling process is located inside the drying chamber and the superconducting mixer mixing process is located inside the cryogenic vacuum chamber formed by the cryogenic thermostat.

[0015] Preferably, the inner wall of the drying chamber is covered with a microwave-absorbing material to absorb residual submillimeter wave signals and eliminate ambient moisture.

[0016] Preferably, both the first and second bundlers are Mylar film bundlers.

[0017] Preferably, the signal coupling adopts waveguide mode; the first coupler and the second coupler are both waveguide-type directional couplers, or both are duplexers; the enclosure is a low-temperature vacuum enclosure formed by a cryogenic thermostat.

[0018] Preferably, the signal amplifier includes a low-noise amplifier housed in a low-temperature vacuum chamber and a room-temperature amplifier housed at room temperature; the intermediate frequency signal is amplified by the low-noise amplifier and the room-temperature amplifier respectively, and finally output to the intermediate frequency back-end processing system to complete the detection of the submillimeter wave signal.

[0019] Preferably, the two local oscillator signals formed by the first local oscillator source and the second local oscillator source are specifically as follows: the first local oscillator source and the second local oscillator source are respectively provided with basic signals by two signal generators, spurious and harmonic signals are filtered by YIG filters, and then obtained by passing through multi-stage frequency multipliers and power amplifiers respectively.

[0020] Preferably, the signal window is a submillimeter-wave antireflection and anti-reflection film made of multilayer polymer.

[0021] Preferably, the superconducting mixer is a superconducting tunnel junction (SIS) mixer or a superconducting thermoelectronic (HEB) mixer, used for mixing submillimeter-wave signals and outputting intermediate frequency signals.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1) This invention uses a dual local oscillator coupled signal as the local oscillator signal source of a submillimeter-wave heterodyne receiver. After secondary coupling with the signal to be detected, the signal is mixed by a superconducting mixer and then output as an intermediate frequency signal. After processing by a signal amplifier, the signal is output to the intermediate frequency back-end processing system to complete the detection of the submillimeter-wave signal. This invention enables simultaneous observation of broadband spectrum lines in submillimeter-wave astronomical observations, i.e., simultaneous observation by the same terminal. It has a simple structure, low cost, and effectively avoids the problems of pointing, calibration, and detector errors caused by discrete observations. It helps to achieve high-quality observation of broadband spectrum lines.

[0024] 2) The dual local oscillator submillimeter-wave superconducting detection system has the characteristics of simple structure, no need for secondary frequency reduction, and ultra-high detection sensitivity. It can perform four-sideband detection and obtain the precise molecular atomic content ratio of the observed spectral lines.

[0025] 3) Signal coupling using quasi-optical mode is performed through a beam combiner for secondary coupling. Quasi-optical mode avoids the processing difficulties and transmission losses caused by waveguide mode for high-frequency signals.

[0026] 4) The submillimeter-wave superconducting detection system of the present invention can achieve all the functions of single local oscillator detection using only one local oscillator;

[0027] 5) The drying chamber can effectively eliminate the influence of water vapor in the atmosphere on the detection;

[0028] 6) The inner wall of the drying oven is covered with absorbing material, which can effectively absorb residual submillimeter wave signals;

[0029] 7) The Mylar membrane combiner has a semi-transparent and semi-reflective characteristic for submillimeter wave signals injected into it, which can more effectively couple dual local oscillator signals and couple the probe signal with the dual local oscillator signals.

[0030] 8) In view of the shortcomings of existing technologies, such as low-temperature low-noise amplifiers and low-temperature isolators introducing more intermediate frequency noise, which reduces the detection sensitivity to a certain extent, the low-temperature low-noise amplifier of this invention is placed in a low-temperature vacuum chamber formed by a low-temperature thermostat for signal amplification, thereby reducing intermediate frequency noise and improving detection sensitivity.

[0031] 9) The signal window uses a multilayer polymer submillimeter-wave antireflection coating, which has high transmittance and low reflectance for submillimeter-wave signals, and has good toughness. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the dual local oscillator submillimeter-wave superconducting detection system in quasi-optical mode in Example 1;

[0033] Figure 2 This is a schematic diagram of the dual local oscillator submillimeter-wave superconducting detection system in waveguide mode in Example 2;

[0034] Figure 3 This is a schematic diagram of the detection sideband of the dual local oscillator submillimeter-wave superconducting detection system in the embodiment. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1 As shown in the figure, this embodiment presents a dual-local-oscillator submillimeter-wave superconducting detection system, mainly including: two local oscillator signal sources, two beam combiners, an optical transmission system, a drying chamber, absorbing materials, a signal window, a cryostat, a superconducting mixer, a low-noise amplifier, and a room-temperature amplifier, etc. Details are as follows:

[0038] The two local oscillators are provided with base signals (typically 10-30 GHz) by two signal generators. Spurious and harmonic signals are filtered out by YIG filters, and then two stable submillimeter-wave local oscillator signals (with a wide frequency difference, tens of GHz, such as 500 GHz and 550 GHz) are obtained by connecting multiple stages of frequency multipliers and power amplifiers.

[0039] Both combiners are Mylar films (a type of polyester film), which exhibit semi-transmissive and semi-reflective properties to submillimeter-wave signals incident upon them. Considering their submillimeter-wave spectral characteristics, the first combiner can use a 75μm Mylar film to achieve coupling of the dual local oscillator signals; the second combiner can use an 8.5μm Mylar film to achieve coupling of the probe signal and the dual local oscillator signals.

[0040] The signal window employs a multilayer polymer submillimeter-wave antireflection coating, such as a thin film with a Zitex / LDPE / HDPE / LDPE / Zitex structure (Zitex is porous Teflon), which exhibits high transmittance and low reflectance for submillimeter-wave signals, along with good toughness. The optical transmission system includes the local oscillator signal transmission system and the probe signal transmission system within the drying chamber, as well as the coupled signal transmission system within the cryostat, primarily composed of planar and parabolic mirrors.

[0041] The drying chamber is cleaned with high-purity nitrogen to maintain an internal water molecule content of less than 3%, effectively eliminating the influence of atmospheric moisture on the detection. The inner walls of the drying chamber are lined with absorbing material, specifically Eccosorb blackbody material, which effectively absorbs residual submillimeter-wave signals.

[0042] The cryostat provides a cryogenic vacuum environment for the superconducting detector, while also providing signal input and output channels. The superconducting mixer, which can employ a superconducting tunnel junction (SIS) mixer or a superconducting thermionic (HEB) mixer, achieves submillimeter-wave signal mixing and outputs an intermediate frequency (IF) signal. The low-noise amplifier, with ultra-low return loss, noise, and high gain, initially amplifies the IF output signal at cryogenic temperatures. The room-temperature amplifier, with lower noise and higher gain, further amplifies the IF output signal at room temperature.

[0043] The two local oscillator signals propagate perpendicularly and enter the drying chamber through signal windows. They are then transmitted optically and converged to a 45°-positioned combiner, achieving coupling between the two local oscillator signals. The detected signal enters the drying chamber through a signal window, its propagation direction perpendicular to the dual local oscillator output signals. Both signals are then transmitted optically and converged to a second 45°-positioned combiner, achieving coupling between the detected signal and the dual local oscillator signals. The coupled signals continue transmission, entering the cryogenic thermostat through signal windows. They are further transmitted optically and converged to the feed of a superconducting mixer. After mixing by the superconducting mixer, a four-sideband intermediate frequency (IF) signal is output. The IF signal is amplified and processed by a low-noise amplifier and a room-temperature amplifier, and finally output to the IF back-end processing system to complete the detection of the submillimeter-wave signal.

[0044] This dual local oscillator detection system can simultaneously observe wide-range spectral lines in submillimeter-wave astronomical observations, effectively avoiding problems such as pointing, calibration, and detector errors caused by discrete observations. At the same time, the dual local oscillator detection system has the characteristics of simple structure, no need for secondary frequency reduction, and ultra-high detection sensitivity. It can perform four-sideband detection and obtain the precise molecular atomic content ratio of the observed spectral lines.

[0045] Figure 3 This diagram illustrates the sideband detection of a dual-local-oscillator submillimeter-wave superconducting detection system. LO1 and LO2 represent the frequencies of local oscillator 1 and local oscillator 2, respectively; LSB1 and USB1 represent the lower and upper sidebands output by local oscillator 1, respectively; and LSB2 and USB2 represent the lower and upper sidebands output by local oscillator 2, respectively. This system achieves four-sideband detection and enables simultaneous observation of wide-range spectral lines in submillimeter-wave astronomy.

[0046] Example 2

[0047] like Figure 2As shown in the figure, this embodiment presents a dual-local oscillator submillimeter-wave superconducting detection system in waveguide mode. The system includes a first local oscillator, a second local oscillator, a first coupler, a second coupler, a housing, a superconducting mixer, a signal amplifier, and a mid-to-back-end processing system.

[0048] The two local oscillator signals generated by the first and second local oscillator sources are transmitted into the enclosure through waveguides. After being coupled by the first coupler, dual local oscillator output signals are obtained. The signal to be detected enters the enclosure through a signal window and is coupled twice with the dual local oscillator output signals. The signals after the two couplings are transmitted through waveguides to the mixer chip, mixed, and then output as intermediate frequency signals. After being processed by the signal amplifier, the signals are output to the intermediate frequency back-end processing system to complete the detection of submillimeter wave signals.

[0049] The first coupler and the second coupler are both waveguide-type directional couplers, or both are duplexers; the enclosure is a low-temperature vacuum enclosure formed by a low-temperature thermostat.

[0050] The other settings in this embodiment are the same as in Embodiment 1.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dual-local-oscillator submillimeter-wave superconducting detection system, characterized in that, The system includes a first local oscillator, a second local oscillator, a first coupler, a second coupler, a housing, a superconducting mixer, a signal amplifier, and a mid-to-back-end processing system; The two local oscillator signals generated by the first and second local oscillator sources enter the enclosure through the provided signal windows. After being coupled by the first coupler, dual local oscillator output signals are obtained. The signal to be detected enters the enclosure through the provided signal window and is coupled twice with the dual local oscillator output signals. The signals after the two couplings are converged to the feed of the superconducting mixer. After being mixed by the superconducting mixer, the intermediate frequency signal is output. Then, after being processed by the signal amplifier, it is output to the intermediate frequency back-end processing system to complete the detection of submillimeter wave signals.

2. The dual-local-oscillator submillimeter-wave superconducting detection system according to claim 1, characterized in that, The signal coupling adopts a quasi-optical mode; both the first and second couplers use beam combiners, and their signal coupling process is as follows: The two local oscillator signals, with their propagation directions perpendicular to each other, are generated by the first and second local oscillator sources. They enter the housing through signal windows on the housing and are then combined via optical transmission to a first combiner placed at a 45° angle to the propagation direction of the first local oscillator signal, where they are coupled to obtain a dual local oscillator output signal. The signal to be detected enters the housing through the signal window, and its propagation direction is perpendicular to the direction of the dual local oscillator output signal. The two signals are then combined via optical transmission to a second combiner placed at a 45° angle to the signal to be detected, where they are coupled a second time.

3. The dual-local-oscillator submillimeter-wave superconducting detection system according to claim 2, characterized in that, The enclosure includes a connected drying chamber and a low-temperature vacuum chamber formed by a low-temperature thermostat. The secondary coupling process is located inside the drying chamber, and the mixing process of the superconducting mixer is located inside the low-temperature vacuum chamber formed by the low-temperature thermostat.

4. The dual-local-oscillator submillimeter-wave superconducting detection system according to claim 3, characterized in that, The inner wall of the drying chamber is covered with microwave absorbing material to absorb residual submillimeter wave signals and eliminate ambient moisture.

5. A dual-local-oscillator submillimeter-wave superconducting detection system according to claim 2, characterized in that, Both the first and second bundlers are Mylar film bundlers.

6. The dual-local-oscillator submillimeter-wave superconducting detection system according to claim 1, characterized in that, The signal coupling adopts waveguide mode; the first coupler and the second coupler are both waveguide-type directional couplers, or both are duplexers; the enclosure is a low-temperature vacuum enclosure formed by a low-temperature thermostat.

7. A dual-local-oscillator submillimeter-wave superconducting detection system according to claim 3 or 6, characterized in that, The signal amplifier includes a low-noise amplifier housed in a low-temperature vacuum chamber and a room-temperature amplifier housed at room temperature. The intermediate frequency signal is amplified by the low-noise amplifier and the room-temperature amplifier, and finally output to the intermediate frequency back-end processing system to complete the detection of the submillimeter wave signal.

8. The dual-local-oscillator submillimeter-wave superconducting detection system according to claim 1, characterized in that, The two local oscillator signals formed by the first local oscillator source and the second local oscillator source are specifically as follows: the first local oscillator source and the second local oscillator source are respectively provided with basic signals by two signal generators, and spurious and harmonic signals are filtered by YIG filters. Then, they are respectively passed through multi-stage frequency multipliers and power amplifiers to obtain two submillimeter wave local oscillator signals.

9. The dual-local-oscillator submillimeter-wave superconducting detection system according to claim 1, characterized in that, The signal window is a submillimeter-wave antireflection and anti-reflection coating made of multilayer polymer.

10. A dual-local-oscillator submillimeter-wave superconducting detection system according to claim 1, characterized in that, The superconducting mixer is a superconducting tunnel junction (SIS) mixer or a superconducting thermoelectronic (HEB) mixer, used for mixing submillimeter-wave signals and outputting intermediate frequency signals.

Images