CN-121978787-A - Local oscillator noise suppression device of superconducting tunnel junction mixer

CN121978787ACN 121978787 ACN121978787 ACN 121978787ACN-121978787-A

Abstract

The invention provides a local oscillator noise suppression device of a superconducting tunnel junction mixer, and belongs to the technical field of terahertz detection. The device comprises a local oscillation signal source, a local oscillation light path, a superconductive tunnel junction mixer and a quasi-optical filter, wherein the local oscillation signal source provides local oscillation signals for the superconductive tunnel junction mixer through the local oscillation light path, the quasi-optical filter is positioned between the local oscillation signal source and the local oscillation light path and used for attenuating local oscillation power and reducing reflection of signals in the local oscillation light path, the quasi-optical filter is formed by processing an integrated metal plate, circular grooves are arranged at symmetrical positions on two sides of the metal plate, and a through hole is formed in the center of each groove and used as an attenuation window. The invention has strong environmental adaptability, supports normal temperature/low temperature stable work, has the composite design of the conical structure and the blackbody absorption coating, effectively inhibits signal reflection and sideband noise, and realizes accurate power matching based on Gaussian beam theory.

Inventors

SHI SHENGCAI
ZHAO JINBIAO
LIU DONG
LI JING
LIN ZHENHUI

Assignees

中国科学院紫金山天文台

Dates

Publication Date: 20260505
Application Date: 20260115

Claims (8)

1. The device for suppressing local oscillation noise of the superconducting tunnel junction mixer is characterized by comprising a local oscillation signal source, a local oscillation light path, the superconducting tunnel junction mixer and a quasi-optical filter, wherein the local oscillation signal source provides local oscillation signals for the superconducting tunnel junction mixer through the local oscillation light path, the quasi-optical filter is positioned between the local oscillation signal source and the local oscillation light path and used for attenuating local oscillation power and reducing reflection of signals in the local oscillation light path, the quasi-optical filter is formed by processing an integrated metal plate, circular grooves are formed in symmetrical positions on two sides of the metal plate, and through holes are formed in the centers of the grooves and used as attenuation windows.
2. The device for suppressing local oscillation noise of the superconducting tunnel junction mixer of claim 1, wherein tapered structure arrays are symmetrically arranged in the grooves on two sides of the metal plate except for the through holes, the tapered structure arrays are formed by arranging a plurality of cone arrays, and black body absorption materials are coated on the surfaces of the tapered structure arrays.
3. The local oscillation noise suppression device of the superconducting tunnel junction mixer of claim 1, wherein the metal plate is an aluminum plate.
4. A local oscillation noise suppression device of a superconducting tunnel junction mixer as claimed in claim 1, wherein the radius of said groove is Satisfies the following formula: where for a fundamental film Gaussian beam propagating along the z-axis, the beam waist is located at At the position of the first part, The beam radius is indicated as such, The propagation distance is indicated as such, The wavelength is indicated as such, Representing the initial beam waist radius of the signal.
5. A local oscillation noise suppression device of a superconducting tunnel junction mixer as claimed in claim 4, wherein said via is formed in a region of said substrate Cutting out the position and radius of the through hole Satisfies the following formula: In the formula, Is the power transmittance, is equal to the power of the signal attenuated by the through hole And the original power Is a ratio of (2).
6. A superconducting tunnel junction mixer local oscillation noise suppression device as claimed in claim 2, characterized in that the height of said cone Satisfies the following formula: In the formula, Indicating the low frequency cut-off frequency of the blackbody absorbing material, In order to achieve the light velocity, the light beam is, A relative dielectric constant that is a blackbody absorbing material; The width of the bottom edge of the cone Height and height of The ratio of the two adjacent vertebrae is 0.7-1.2 , The wavelength corresponding to the highest frequency of the target.
7. The device for suppressing local oscillation noise of superconducting tunnel junction mixer as claimed in claim 2, wherein the blackbody absorbing material adopts silicon carbide particles as an absorbent, and the silicon carbide particles are uniformly dispersed in a mixed matrix of Stycast epoxy resin and Catalyst 9 curing agent, and are cured to form a composite wave-absorbing structure.
8. A local oscillation noise suppression device of a superconducting tunnel junction mixer as claimed in claim 7, wherein said silicon carbide particles have a particle size According to the target operating frequency The design is performed with the design criteria given by: In the formula, In order to achieve the light velocity, the light beam is, Representing the relative permittivity of silicon carbide in the terahertz frequency band.

Description

Local oscillator noise suppression device of superconducting tunnel junction mixer Technical Field The invention belongs to the technical field of terahertz detection, and particularly relates to a local oscillator noise suppression device of a superconducting tunnel junction mixer. Background A superconducting tunnel junction (Superconductor-Insulator-Superconductor, SIS) mixer is a quantum limit sensitivity coherent detector and is widely applied to the fields of astronomical detection, space remote sensing, deep space detection and the like from millimeter wave to terahertz wave bands. The mixer operates in a manner that requires a Local Oscillator (LO) signal source to provide a highly stable reference signal, the sensitivity of which is typically characterized by an equivalent noise temperature. Early superconducting SIS mixers generally used local oscillator signal sources based on gunn oscillator and frequency multiplier architecture, and had small sideband noise ratio, which was negligible in practical applications. However, such LO signal sources have problems of narrow bandwidth, limited output power, reliance on mechanical tuning, and the like, which limit the application in complex systems of interferometric arrays. In recent years, a new generation of local oscillation signal sources composed of a microwave reference source, a frequency multiplier and a power amplifier have become the mainstream. The architecture has the advantages of large bandwidth, high power, no need of mechanical tuning, convenience in use and the like, but more remarkable local oscillator sideband noise is introduced. The noise is down-converted to an intermediate frequency during the mixing process, directly affecting the system detection sensitivity. The noise formation mechanism is complex and is mainly influenced by factors such as reference signal phase noise, working state of a power amplifier, nonlinearity and efficiency of a frequency multiplier and the like. In addition, researches also find that a return signal generated by signal reflection of an optical device in the local oscillation optical path system can cause part of local oscillation energy to be re-coupled to a signal link, so that the sideband noise level is obviously aggravated. The above problems have become a non-negligible factor in practical applications. The conventional method for suppressing local oscillation noise mainly comprises the steps of 1, placing a local oscillation signal source in a low-temperature environment, wherein local oscillation thermal noise can be suppressed, but system complexity, power consumption and volume are remarkably increased, the overall sideband noise suppression effect is limited, 2, a power amplifier works in a driving saturation region and can reduce noise introduced by the power amplifier, but when the sideband noise of a microwave reference source is high, the noise of the power amplifier and a frequency doubling link can deteriorate the sideband noise of a final output signal to cause unsatisfactory suppression effect, 3, a narrow-band tunable filter is introduced at the output end of the microwave reference source, although the out-of-band noise can be effectively suppressed, two main problems are that firstly, larger insertion loss is introduced, the input driving capability of the frequency multiplier is weakened, and secondly, as an active device, the control difficulty and the circuit complexity are high, and frequency characteristics are possibly changed due to temperature drift under long-term operation, so that the overall stability risk of the system is increased. In summary, although the existing methods suppress sideband noise to some extent, there are significant performance limitations or high system costs. Therefore, there is a need for a device for suppressing local oscillator sideband noise of a superconducting tunnel junction mixer. Disclosure of Invention Aiming at the defects in the prior art, the invention provides a local oscillator noise suppression device of a superconducting tunnel junction mixer, which is suitable for the suppression of local oscillator sideband noise of the high-sensitivity superconducting tunnel junction mixer and the optimization of system performance. In order to achieve the above purpose, the present invention adopts the following technical scheme: A local oscillation noise suppression device of a superconducting tunnel junction mixer comprises a local oscillation signal source, a local oscillation light path, the superconducting tunnel junction mixer and a quasi-optical filter, wherein the local oscillation signal source provides local oscillation signals for the superconducting tunnel junction mixer through the local oscillation light path, the quasi-optical filter is positioned between the local oscillation signal source and the local oscillation light path and used for attenuating local oscillation power and reducing reflection of signals in the local oscil