A 400-MHz Bandwidth Autocorrelation Spectrum Analyzer

Autocorrelation spectral analysis has demonstrated excellent stability, flexibility, and noise floor levels in radio astronomy applications, largely due to its predominantly digital signal processing. Extending this approach to the wide bandwidths required in millimeter-wave stratospheric remote sensing requires advances in fast digital signal processing techniques. To reach a target bandwidth of 400 MHz requires an 800-MHz digitizer sample rate and processing throughput. We have produced in quantity the required delay-multiply-count digital building block (or node) operable above 400 MHz We have demonstrated logic of the speed required for the 800-MHz digitizer and the distributor which divides the data into multiple slower streams for processing by the node cascades, but have not yet completed these faster portions. The completed instrument will offer 2% spectral resolution to 400 MHz total instantaneous bandwidth, and 1% resolution for all total bandwidths below 200 MHz. Observation time penalty due to the 3-level signal representation used is 57%.