High and Low-Temperature Experiments of the Micro-Coaxial Directional Coupler

This paper presents the design of a micro-coaxial directional coupler with a working frequency range of 18-50 GHz and a coupling level of 10 dB. The coupler is fabricated using the micro-structure electrochemical fabrication (MEFAB) process. During the measurement process, the coupler was assembled with a coplanar waveguide ground (CPWG) transmission line using a custom fixture for measurement. The coupler demonstrated excellent performance during the measurement, meeting the design specifications. Additionally, to verify the coupler's performance stability under extreme conditions, high and low-temperature experiments were conducted. In the low-temperature experiment, under conditions of -196° C, the coupler's performance remained stable. In the high-temperature experiment, the coupler performed stably at temperatures below 150° C, with no noticeable performance degradation. However, when the temperature exceeded 150° C, the coupler's performance began to deteriorate.