Development of a 70-110 GHz silicon corrugated horn for cosmic microwave background experiment

Next generation cosmic microwave background (CMB) polarization telescope will use large arrays of receiver with nearly 100 000 transition edge sensor (TES) detectors and receiving antennas. Such large TES and antenna array is a big challenge for the fabrication of TES and antennas. A 35-layers silicon-platelet corrugated horn for 70-110 GHz is designed and fabricated based on the micro electro mechanical system (MEMS) technology. Compared with the traditional corrugated horn, the last layer of the 35-layers silicon-platelet is designed with no corrugation to increase the beam symmetry. A parametric HFSS model of the horn was established to evaluate the performance of the horn and effect of fabrication process. The measured S11 and cross-polarization of the fabricated prototype horn are both below -20 dB while the sidelobe at 70 and 90 GHz is below -20 dB. The beam symmetry of the horn is good in 70-110 GHz band. The measured gain is greater than 15 dBi. These results show that the performance of the designed horn meets the requirement of CMB experiment.