Multichannel Transmitting System Based on High-Temperature Superconducting Phase Shifter

Multichannel very high frequency (VHF) high-power transmission system, based on a 90^°, high-temperature superconductor YBa₂Cu₃O₇ (YBCO) hybrid coupler is presented. The small dimension coupler performs as a phase shifter utilized for matching several different channels into a single junction. The planar coupler was implemented in a microstrip geometry by patterning a thin layer of YBCO on a sapphire substrate. Superconductivity is essential for obtaining low losses and high-power capabilities. The system was tested for power transmission of up to 52.9 dBm over a period of several hours. No deterioration with time was recorded. Maximum losses of 0.8 dB per channel were measured. The proposed system shows high-precision tuning capabilities, a critical feature for multichannel systems.