A multi-mode w-band radar/radiometer for experimental studies

This paper describes a 75-110 GHz millimeter-wave system with versatile functionality, for studying fundamental scattering, emission and absorption behaviors in the laboratory or in restricted field conditions. The primary studies of interest currently concern absorption spectra of behavior of pollutant gases and particulates; scattering and emission from clouds and fog; scattering, absorption and emission from snow and other natural dense media; and the reflection-transmission behavior of periodic structures such as waveguide gratings. A block diagram level design of the instrument is presented. The 75-110 GHz spectrum is monitored by using 2 receiver IF sections and dividing the region into 9 GHz wide segments. Frequency stability is maintained by locking all oscillators to a high quality ovenized crystal oscillator. Preselection is done at the input using quasioptical techniques in order to reduce insertion loss which would be encountered in waveguide filters. The system operates as a spectrometer, pulse radar, step frequency radar and radiometer.