Spectral baseline ripple in hot-electron bolometer mixers due to local oscillator phase and amplitude instabilities
Abstract
High resolution millimeter and submillimeter wave astronomical spectrometers using hot-electron bolometer mixers as detectors often show marked 'standing wave patterns' in the spectral baseline. LO phase noise contributes through two mechanisms: the phase noise sidebands may be converted to amplitude noise in the source because of the power-frequency characteristic of the source, or they can be converted to in-band amplitude noise through the action of the quasi-optical discriminator formed by the mixer, beam-splitter and telescope structure. The baseline ripple components due to each of these mechanisms have different characteristic periods, and under some circumstances can dominate the spectrometer baseline. The ripple levels estimated using the theory agree well with those observed in practice. It is shown that with careful design systematic effects due to this cause can be reduced to a negligible level.
- Publication:
-
International Journal of Infrared and Millimeter Waves
- Pub Date:
- October 1992
- DOI:
- 10.1007/BF01009231
- Bibcode:
- 1992IJIMW..13.1471P
- Keywords:
-
- Astronomical Spectroscopy;
- Bolometers;
- Hot Electrons;
- Millimeter Waves;
- Submillimeter Waves;
- Beam Splitters;
- Indium Antimonides;
- Noise Reduction;
- Standing Waves;
- Electronics and Electrical Engineering