Terahertz receivers for astronomy

We give a review on the present status and perspectives of THz-receiver development for the new observatories going to cover this very important, but little explored frequency range. The rapid advances in all components along the signal chain, starting from the receiver optics and the THz-local oscillators and continuing with the heterodyne mixers, the IF-amplification and finally the backend spectrometers on one hand achieves very high sensitivities up to THz-frequencies across a broad IF bandwidth, and on the other hand allows for a compact enough design that makes possible the integration of modest focal plane arrays into a single receiver.