1：Experimental Design and Method Selection:

The study involves measuring the double sideband (DSB) receiver noise temperature (Trec) of a log-spiral antenna coupled

2：1-5 THz NbN superconducting HEB mixer across different frequencies and bath temperatures. Sample Selection and Data Sources:

The superconducting HEB mixer consists of a 2-μm wide,

3：2-μm long and 5-nm thick NbN microbridge, and a self-complementary log-spiral planar antenna fabricated on a highly resistive and natively oxidized Si substrate. List of Experimental Equipment and Materials:

The measurement setup includes a close-cycled cryostat, different frequency multiplier chains for LO signal, a Mylar beam splitter, a high-density polyethylene (HDPE) window, a Zitex G104 infrared filter, a bias-tee, an isolator, cryogenically cooled and room-temperature amplifiers, and a square-law detector.

4：Experimental Procedures and Operational Workflow:

The HEB device is mounted into a copper mixer block on the 4 K cold plate of the cryostat. The LO signal is coupled into the cryostat, and the IF output signal is amplified and recorded.

5：Data Analysis Methods:

The IF output signal is filtered and recorded, with the noise temperatures corrected by calibrating the RF noise including beam-splitter, window, and infrared filter.