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Cryogenic isolators play an important role in low-noise receiver systems widely employed in millimeter and submillimeter telescopes. To enable a significantly wider Intermediate Frequency (IF) bandwidth, there is strong demand for a wideband, low-loss isolator in modern facilities like the Submillimeter Array (SMA) and Atacama Large Millimeter/submillimeter Array (ALMA). In this article, we present a novel cryogenic edge-mode isolator that incorporates an innovative circuit design. Operating at a cryogenic temperature of 4 K, this isolator delivers unprecedented performance, covering a frequency range from 4 GHz to 22 GHz. It exhibits insertion loss of less than 1 dB, together with return loss below -15 dB. In particular, it provides an isolation better than 17 dB across most of the band, a significant improvement over the previous generation of edge-mode isolators. This new isolator design is suitable for a wide array of low-noise receiver applications, from radio-astronomy to quantum computing.

Abstract The contribution of this work is to propose a novel circulator design using the substrate‐integrated coaxial line (SICL) structure. Conventionally, the circulator is composed of three‐dimensional waveguide components, and, in contrast, the proposed SICL circulator allows the 3‐D waveguide circulator to be built in a planar form using the printed circuit board (PCB) technology. The proposed SICL circulator is composed of three substrates with two parallel signal strips embedded in the central SICL tunnel. For better impedance matching, a widened section is inserted in each uniform feedline, and the Y‐junction joint on the bottom surface of the middle substrate is connected with three stubs and is loaded with a circular disk on the top surface of the middle substrate. A bandpass filter (BPF) can be embedded in each circulator's branch to improve signal selectivity and the out‐of‐band isolation. Experiments are conducted to verify the circuit design. Agreements are observed between the measured and simulated data.

The wetting and brazing of Y3Fe5O12 (YIG) ceramics with a Ag–8CuO–2TiO2 filler was investigated for the first time. For comparison, the wettability of a Ag–10CuO filler on YIG ceramics was similarly investigated. The Ag–8CuO–2TiO2 filler has an equilibrium contact angle of approximately 31 °C on the YIG substrate at 1000 °C; thus, its wettability is excellent. Moreover, its wettability exceeds that of Ag–10CuO. The microstructure and the interfacial structure between the filler and the substrate were determined using scanning electron microscopy, X-ray diffraction, EPMA and transmission electron microscopy. The liquid Ag–8CuO–2TiO2 filler can react with the YIG substrate by forming continuous Y2Ti2O7 layers with dotted CuFe2O4 and promote the wetting behavior and bonding performance. The average shear strength could exceed 30 MPa for the joints at a brazing temperature of 1000 °C. As rupture occurred adjacent to the seam at the ceramic side, the strengths of the interfaces were characterized via nanoindentation. The hardness of the interface with doped TiO2 exceeds that of Ag–10CuO, which is strengthened by the dotted CuFe2O4 among Y2Ti2O7.