Sb. Rozanov et al., LOW-NOISE COOLED PLANAR SCHOTTKY DIODE RECEIVERS FOR GROUND-BASED SPECTRAL OZONE MEASUREMENTS AT 142 GHZ, International journal of infrared and millimeter waves, 19(2), 1998, pp. 195-222
Two new low-noise cooled receivers based on planar Schottky diode mixe
rs were designed and built for the Lebedev Physics Institute (LPI) spe
ctrometer for ground-based measurements of the atmospheric ozone spect
ral line of 142.175 GHz central frequency. The receivers differ in the
intermediate frequency (IF) bands, of around 3.7 and 1.5 GHz. Review
description of the spectrometer equipped with the 3.7-GHz IF receiver
is given, and its performance is compared with other millimeter-wave g
round-based ozone spectrometers. Special attention was paid to design
of the input Gaussian optics and the mixers. Techniques of laboratory
tests of the receivers and results of the tests through all 2-mm wavel
ength range are considered and discussed. SSB mixer noise temperature
of 460+/-60 K was obtained at 151 GHz for room temperature mixer, and
the value of 180+/-30 K was measured at 134 GHz under cooling to 85 K
in liquid nitrogen cryostat. SSB mixer conversion losses were less tha
n 5.5 dB in both the cases. SSB noise temperature of the spectrometer
is less than 1500 K without cooling and less than 700 K at cryogenic o
peration at 142 GHz. This provides sensitivity of about 0.2 and 0.1 K
for the narrowest spectral channel width of 0.1 MHz and signal integra
tion time of 1 hour. Using the optimized spectrum analyzers delivers d
ata on high-accuracy retrieval of the ozone vertical profile in the at
mosphere at altitudes about from 15 to 75 km. Examples of the ozone ob
servation data are given.