Multi-source Excited Bowtie Loaded Meander Antenna for Series Superconducting Josephson Junction THz Mixer

For some applications, the performance of the high-temperature superconducting (HTS) devices is limited by the fairly low impedance of the Josephson junction (JJ). Series JJ structure is a good choice to improve the impedance of the device so as to realize the impedance matching with the coupled antenna, in addition to solve saturation problem at terahertz (THz) band. In this work, a bowtie loaded meander antenna (BLMA) with the multi-source excitation is presented for a series superconducting JJ THz harmonic mixer. F-parameters, surface current distribution, and far-field radiation patterns are investigated to prove the validity of this multi-source excited BLMA. Numerical simulations show that two or four series junctions embedded at appropriate positions in the BLMA keep a good antenna performance and form a good impedance matching with this antenna. Also, the embedding series junctions with the resistances of 20 Ω in the antenna work well at a THz window around 0.22 THz. Furthermore, key parameters of the antenna are studied to explore the effect of embedding JJs with different numbers and at different positions on the impedance matching. This work provides an experimental guidance for multi-source excitation in a single antenna and shows a good antenna design scheme for series JJ devices.