Development of octave band planar ortho mode transducer with kinetic inductance detector for LiteBIRD
We demonstrate a design of octave band circular waveguide coupled planar ortho mode transducer (OMT) with Microwave Kinetic Inductance Detector (MKID) for LiteBIRD mission, a small size satellite for cosmic microwave background (CMB) polarization signal full sky mapping. In our 4 pixel prototype design, each single pixel is sensitive to two frequency bands (90 GHz and 150 GHz) corresponding to atmospheric window. Silicon on insulator (SOI) has been selected for OMT structure and a broadband coplanar waveguide (CPW) 180 degree hybrid is designed to cancel higher modes of a circular waveguide and add two signals from the fundamental mode together. After a microstrip bandpass diplexer, a microstrip line to coplanar waveguide transition structure couples signal to MKID. MKIDs are designed with Nb ground plane and Al/Ti bilayer center strip line to achieve low frequency response and high sensitivity. A 4 pixel module is under test and we plan to deploy these multi chroic polarimeters on Nobeyama 45m telescope.
Astronomical Telescopes Instrumentation