Design and Characterization of 275-500 GHz Corrugated Horns and Optics for a Wideband Radio Astronomy Receiver

As a technical demonstration of an astronomical receiver working in a frequency range of 275-500 GHz, we are developing such a wide-band one, called as band 7 + 8 receiver. The splined corrugated horn and corresponding quasi-optics in the receiver designed for ASTE telescope in Chile are described. The fabricated horn has < -20 dB of return loss and < -23 dB of cross-polarization over the frequency range. Based on the measured beam field propagating through the fabricated optics illuminated by the horn, aperture efficiency is estimated to be $\gt 80$ % at all frequencies.