PERFORMANCE OF NBN LATTICE-COOLED HOT-ELECTRON BOLOMETRIC MIXERS

The heterodyne performance of lattice-cooled hot-electron bolometric m ixers is measured at 200 GHz. Superconducting thin-film niobium nitrid e strips with similar to 5 nm thickness are used as waveguide mixer el ements. A double-sideband receiver noise temperature of 750 K at 244 G Hz is measured at an intermediate frequency centered at 1.5 GHz with 5 00 MHz bandwidth and with 4.2 K device temperature. The instantaneous bandwidth for this mixer is 2.6 GHz. The local oscillator power requir ed by the mixer is about 0.5 mu W. The mixer is linear to within 1 dB to an input power level 6 dB below the local oscillator power. A recei ver incorporating a hot-electron bolometric mixer was used to detect m olecular line emission in a laboratory gascell. This experiment unambi guously confirms that the receiver noise temperature determined from Y -factor measurements reflects the true heterodyne sensitivity. (C) 199 6 American Institute of Physics.