Planar antenna arrays for CMB polarization detection

A novel slot antenna array architecture is presented for cosmic microwave background (CMB) polarization detection. Future CMB polarization detection instruments will require large focal planes with thousand of detectors to have large throughput improving overall sensitivity of the instrument. Field of view of these detectors needs to be restricted to reduce stray radiation pickup. Current technology of using metal horn antennas are found impractical for very large arrays. Although planar antennas solve many of the problems of horn antenna, they require substrate lens to have a narrow beam required for CMB polarization detection. We have designed and developed dual-polarized antennas producing a narrow beam without any substrate lenses and is compatible with large focal plane architecture. The antenna array output for each polarization is combined in phase and detected using transition edge sensors (TES). These dual- polarized slot antennas provide approximately 20-25% fractional bandwidth with better than 20 dB cross polarization.