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RAP opportunity at Air Force Research Laboratory     AFRL

Onboard Satellite Synchronization for Frequency Hopping Spread Spectrum Waveforms


Space Vehicles Directorate, RV/Space and Planetary Sciences

opportunity location
13.40.01.C0065 Kirtland Air Force Base, NM 871175776


name email phone
Khanh Dai Pham 505.846.4823


Synchronization in satellite communications is the process of aligning the time and phase scales of satellite ground hubs, satellite transponders, and user terminals so that the equipment operations occur at correct times and correct phases in correct orders. First, time synchronization requires the clocks at receiver ends to acquire and track periodic timing information in transmitted signals. Second, phase synchronization requires receiver carrier tracking loops to acquire and track carrier phase information in transmitted signals. There are several methods to obtain time and phase information through commercial communications infrastructures, including both coherent and non-coherent frequency hopping demodulations. However, levels of trust, accuracy, and robustness of these mechanisms limit potential usefulness for military communications missions. Prospective onboard satellite synchronization paradigms ought to consider the following technical challenges: (1) analysis of time and phase errors associated with ground satellite system controllers, (2) technical requirements of modeling and characterization for time and phase errors at user terminals, (3) uncertainty quantification and management of onboard satellite transponder’s timing and phase errors, and (4) performance assessment of both open- and closed-loop synchronization techniques for phase and timing jitters per hop and/or potential onboard computation solutions for fast phase and time synchronizations in the presence of radio interferences.



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Minn H, Bhargava VK, Letaief KB: “A Robust Timing and Frequency Synchronization for OFDM Systems”. IEEE Transactions on Wireless Communications 2(4): 822-839, 2003

Tsang C-S, Nguyen TM: “Long Loop Time Tracking Performance for Satellite Communication System”. IEEE MILCOM Proceedings: 855-959, 1999

Duffett-Smith PJ, Hansen P: “Precise Time Transfer in a Mobile Radio Terminal”. Proceedings of the 2005 National Technical Meeting of the Institute of Navigation: 1101-1106, 2005

Nguyen TM, Hant J, Taggart D, Tsang C-S, Johnson DM, Chuang J-C: “Design Concept and Methodology for the Future Advanced Wideband Satellite System”. IEEE MILCOM Proceedings: 189-194, 2002


key words
Satellite communications; Radio interference; Frequency hopping spread spectrum; Timing synchronization; Phase synchronization; Timing jitter; Timing and phase errors; Transponder timing errors; Closed-loop synchronization; Open-loop synchronization;


Citizenship:  Open to U.S. citizens
Level:  Open to Postdoctoral and Senior applicants


Base Stipend Travel Allotment Supplementation
$80,000.00 $5,000.00

$3,000 Supplement for Doctorates in Engineering & Computer Science

Experience Supplement:
Postdoctoral and Senior Associates will receive an appropriately higher stipend based on the number of years of experience past their PhD.

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