Oral Presentation

Investigation of optimal dielectric lens for a new 7-beam receiver in 72–116 GHz on the Nobeyama 45-m telescope

Author(s): Yasumasa Yamasaki (Osaka Prefecture University), and the NRO45-m 7beam team

Presenter: Yasumasa Yamasaki (Osaka Prefecture University)

We are conducting the development of a new 7-beam heterodyne receiver in 72–116 GHz band for the Nobeyama 45-m telescope to understand the early stage of star formation by the deuterium fraction. The receiver system based on the cooled LNA can efficiently perform simultaneous observations of various lines such as N2D+, N2H+, and CO.
The optics for this receiver employs wideband corrugated horns covering 67–116 GHz band and dielectric lenses to couple with the telescope optics. One of the important points is anti-reflection coating (AR) of the lens. The triangular shape has been optimized to achieve a return loss of better than 20 dB and to keep the symmetry of the beam pattern. The lens performances with different AR designs were compared by measurements and simulations in terms of beam pattern, reflection/transmission, and receiver noise temperature. As a result, it was found that the AR with straight grooves has much better performances in all respects than that with concentric grooves.