Note: innovative demodulation scheme for coherent detectors in cosmic microwave background experiments.
We propose an innovative demodulation scheme for coherent detectors used in cosmic microwave background polarization experiments. Removal of non-white noise, e.g., narrow-band noise, in detectors is one of the key requirements for the experiments. A combination of modulation and demodulation is used to extract polarization signals as well as to suppress such noise. Traditional demodulation, which is based on the two-point numerical differentiation, works as a first-order high pass filter for the noise. The proposed demodulation is based on the three-point numerical differentiation. It works as a second-order high pass filter. By using a real detector, we confirmed significant improvements of suppression power for the narrow-band noise. We also found improvement of the noise floor.
Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Oho, Tsukuba, Ibaraki 305-0801, Japan. koji@awa.tohoku.ac.jp
K
K
Ishidoshiro
Y
Y
Chinone
M
M
Hasegawa
M
M
Hazumi
M
M
Nagai
O
O
Tajima