Photonic microwave synthesizer based on optically referenced sub-sampling phase-locked optoelectronic oscillator

Wideband and low phase noise microwave synthesizers are of critical significance for various applications. Phase-locked loop (PLL) based microwave synthesizers are widely used. Normally, the phase noise of the PLL based microwave synthesizer is limited by the phase noise of the reference, phase dete...

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Veröffentlicht in:Optics communications 2021-11, Vol.499, p.127304, Article 127304
Hauptverfasser: Peng, Huanfa, Liu, Naijin, Xie, Xiaopeng, Chen, Zhangyuan
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Sprache:eng
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Zusammenfassung:Wideband and low phase noise microwave synthesizers are of critical significance for various applications. Phase-locked loop (PLL) based microwave synthesizers are widely used. Normally, the phase noise of the PLL based microwave synthesizer is limited by the phase noise of the reference, phase detector, frequency divider and voltage-controlled oscillator (VCO). It is challenging to achieve a pure electronic microwave synthesizer with wide frequency coverage and low phase noise, simultaneously. Here, we propose a photonic microwave synthesizer which incorporates an ultra-low phase noise fiber mode-locked laser (MLL) based reference and a wideband frequency tunable optoelectronic oscillator (OEO) based VCO in a hybrid optoelectronic sub-sampling PLL. The frequency of the OEO can be locked to the harmonics of the repetition-rate of the fiber MLL, which combines the distinct advantages of the low phase noise of MLL and the wideband frequency tuning of OEO. A sub-sampling phase detector formed by a balanced optical microwave phase detector (BOMPD) eliminates the use of RF frequency divider and maintains low residual phase noise. We attain an X- and Ku-band photonic microwave synthesizer with over an octave frequency coverage from 8 GHz to 18 GHz, frequency synthesis step of 60.74 MHz and phase noise of -80 dBc/Hz at 100 Hz offset and -100 dBc/Hz at 1 kHz offset for 10 GHz output. The characteristics of the optoelectronic sub-sampling phase detector, the phase-locking dynamics of the hybrid optoelectronic PLL, and the phase noise of the synthesized RF signals are both theoretically and experimentally investigated. The experimental results agree well with the theoretical models. Our approach is promising to achieve wideband and low phase noise microwave synthesis. •A photonic microwave synthesizer by using an optoelectronic PLL is demonstrated.•A fiber mode-locked laser and a wideband optoelectronic oscillator are synchronized.•The performance of the synthesizer is theoretically and experimentally investigated.•X- and Ku-band signals with phase noise of -100 dBc/Hz at 1 kHz offset are achieved.
ISSN:0030-4018
1873-0310
DOI:10.1016/j.optcom.2021.127304