Cryogenic Ka-Band 180 $^{\circ}$ Phase Switch Based on Schottky Diodes

A Ka-band hybrid 0/180
$^{\circ}$
phase switch working at cryogenic temperature is presented. The circuit is designed on an alumina substrate using uniplanar hybrid technology, combining air-bridged coplanar waveguides and slotlines. Schottky diodes are used as switching elements, taking advantage of their cryogenic behavior, with low equivalent series resistance and low capacitance. Cryogenic performance at 15 K shows a phase difference response of
$177 \pm 2^{\circ}$
, average insertion losses of 1 dB and amplitude imbalance of less than 0.2 dB between states in the frequency range from 24 to 37 GHz (40% relative bandwidth) with a low-power consumption of 10.5 mW. The low insertion loss and small phase error make the designed phase switch suitable to be used on radioastronomy receivers (QUIJOTE experiment 26–36 GHz band) minimizing the total system noise temperature.