| Start Date: | 6/12/2014 | Start Time: | 2:00 PM |
| End Date: | 6/12/2014 | End Time: | 3:30 PM |
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Event Description
Title: Opto-electronic Frequency Stabilization Techniques in Forced Oscillators
Advisor: Dr. Afshin Daryoush
Date: Thursday, June 12, 2014
Time: 2:00 p.m.
Location: Biomed Seminar Room, Room 709, 7th Floor, Bossone Research Enterprise Center
Abstract
Oscillator phase noise is the short-term random fluctuation in the frequency (or phase) of an oscillator signal. In many cases, the noise level may be above system demands or system performance can be enhanced if the noise level is reduced. Therefore, frequency stabilization techniques must be applied in forced oscillators for phase noise reduction when high spectral purity is required.
Forced frequency stabilization techniques of self-injection locking (SIL) and self-phase locked loop (SPLL) have been demonstrated to be effective for phase noise reduction. Investigations of published literature and reported patent have revealed that SIL and SPLL are only being used independently, whereas in this thesis self-injection locking and phase locked loop (SILPLL) is introduced for the first time by simultaneously combining SIL and SPLL; the control theory based modeling for SIL, SPLL, and SILPLL techniques are developed and the simulation results have indicated that phase noise of the oscillation signal is enhanced as injection locking removes phase noise in far-out offset frequencies, while phase locking effectively reduces the close-in to carrier phase noise. Optimum delay length and delay parameters are identified for the most effective performance using the modeling.
Moreover, since both SIL and SPLL techniques require long fiber optic delay lines to provide substantial phase noise reduction, the long delay generates undesirable sidemodes that appear in offset frequencies of 20kHz to 200kHz away from carrier for fiber optic delays of 1km to 10km. These close-in to carrier sidemodes are difficult to be filtered out electrically and optical filtering using transversal filters are employed in this thesis to have them effectively suppressed. In this dissertation, dual self-injection locking (DSIL) and dual self-phase locked loop (DSPLL) employing short and long delays have been proposed for this sidemode suppression while maintaining same amount of phase noise reduction provided by the long delay. As an example of DSIL, sidemode suppression of more than 20dB for fiber delay links of 1km and 5km have been experimentally achieved compared to a single 5km long SIL. The DSIL also provides a phase noise reduction of 40dB (in reference to free running oscillator) at 10kHz offset from a 10GHz carrier; for DSPLL using fiber delay lines of 3km and 5km, a sidemode suppression of 29dB have also been experimentally achieved compared to SPLL of 5km. Phase noise reduction of DSPLL is 30dB (in reference to free running oscillator) at 10kHz offset from a 10GHz carrier. Experiment results that demonstrate the benefit of SILPLL incorporating dual delays have been reported for the first time corroborating analytical predictions. A dual SILPLL (DSILPLL) system with 3km and 5km fiber delay has been implemented, and measured phase noise reduction of 40dB provided by DSILPLL is the same as DSIL at 10kHz offset. However, at 1kHz offset, DSILPLL provides a phase noise reduction of 52dB which is 11dB higher than DSIL; at 300Hz offset, DSILPLL provides 70dB reduction while DSIL provides only 42dB reduction.
In summary, DSILPLL is effective for sidemode suppression and phase noise reduction. Due to the advances in low noise electronics and broad bandwidth of the optical components used in the DSILPLL system, the DSILPLL technique has the potential to create highly stable RF oscillators approaching 100GHz.
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Location:
Biomed Seminar Room, Room 709, 7th Floor, Bossone Research Enterprise Center |
Audience:
Current StudentsFacultyStaffGraduate Students |
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