A High Speed Digital Autocorrelator and Its Application to Mesospheric Water Vapor Detection.

Abstract : The emission and absorption spectrum of stratospheric and mesospheric water vapor are to be detected and analyzed. In both cases the method of detection requires a 22 GHz radiometer, and the data analysis requires a high speed, high resolution spectral analyzer. The basic radiometer fundamentals are discussed here, then the various techniques of spectral analysis are considered, which include both digital and analog versions of filter banks and autocorrelators. A prototype 2 x 1 bit digital autocorrelator was then designed and constructed. The system was designed to operate at a sampling rate of up to 100 MHz, with a resolution dependent on the number of autocorrelation points used. The system was then interfaced to a Nova 1200 minicomputer for data accumulation and transfer of data to nine track magnetic tape for standard processing. An IBM 370 computer system was available for final data reduction and analysis. The final system was a 16 point autocorrelator, two points of which were constructed. Future goals include completing the 16 points and using the system for a ground based measurement of upper atmosphere water vapor. (Author)