Techniques for Highly Deterministic Sampling of Attenuated Microwave Signals Brian Wheelwright Optical Sciences and Engineering, Junior University of Arizona

ATOMMS Active Temperature, Ozone, and Moisture Microwave Spectrometer. Frequencies between 10GHz-183GHz Selected based on absorption properties in moisture and ozone.

Preliminary Tests Building to Building (Summer 2009) Flight Test in WB-57 (Fall 2009)

Data Acquisition Requirements Microwave signals are down-converted to 10-40KHz range. Deterministic Sampling (low jitter) 100KS/sec on 9 channels. 800KS/sec on 2 channels. Phase information is important. Very accurate time stamping Correlate data from each plane

NI LabVIEW Real Time 2 Compact RIO with FPGA 2 Multi-Processor Servers

Challenges: FIFO and Timestamping …[1][2][3][4][5][6][7][8][9][1][2][3][4][5][6][7][8][9][1][2]… FIFO has limited space Reading too fast or too slow will scramble data Lag between data acquisition and logging. Server FPGA

Worst Case

Solution Dynamically read from FIFO Run both RIO modules with phase locked 10MHz Oscillator [<1Hz Bandwidth] Add 10th channel that has PPS from GPS Rising edge of PPS is accurate to within less than 1μs.

Result Sampling jitter is less than 25ns. Correlate data between planes to within 1μs. ATOMMS A ATOMMS B

Thank You Acknowledgments: Questions? Rob Kursinski, Chris Groppi, Michael Schein, Steven Bell. Questions?