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

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

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

5. 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

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

7. Challenges: FIFO and Timestamping
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FIFO has limited space
Reading too fast or too slow will scramble data
Lag between data acquisition and logging.
Server
FPGA

8. Worst Case

9. 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.

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

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