Noise Temperature Reduction Study of Filtering Metasurfaces in Radio Telescopes

Radio astronomical telescope is a key system in astronomical observation, deep space exploration and other researches. It is of great significance to improve its sensitivity and reduce the system noise temperature. However, because the frequency band allocated to radio astronomy research is limited and often shared with other businesses, radio astronomy telescopes are vulnerable to strong radio frequency interference. After these interferences enter the RF receiver, intermodulation interference, amplifier saturation and other problems will occur in the low-temperature amplifier, raising its noise background and reducing the detection sensitivity of the radio telescope to weak signals. The filtering metasurface technology can effectively suppress radio astronomy radio frequency interference, but the additional introduced noise needs to be controlled. In this paper, we propose a method to reduce the noise temperature of filtering metasurface in radio astronomical telescope. We study the relationship between the dissipative loss and reflection loss of filtering metasurface and its noise temperature, and minimize the noise temperature by restricting the direction of mismatched reflections. Using the method proposed in this paper, the system noise temperature can be reduced by 35.4%. If the filtering metasurface is set in the cooling chamber, an additional noise temperature of only 0.11 K can be achieved.