Sun Tianchi, Zhang Li, Daryoush Afshin S
IEEE Trans Ultrason Ferroelectr Freq Control. 2020 Jan;67(1):217-223. doi: 10.1109/TUFFC.2019.2944425. Epub 2019 Sep 30.
Optoelectronic oscillators (OEOs) with their demonstrated low phase noise are popular due to the increasing demand of very clean local oscillator and clock signal sources. A forced technique of self-injection locked and phase-locked loop (SILPLL) reduces phase noise and suppresses side mode observed in long fiber delay of the standard OEO. A frequency synthesizer working at X -band is developed using an electrically coarse-tuned YIG filter cascaded with an optical wavelength fine-tuned dispersive optical transversal filter by tuning the oscillation frequency of the synthesized OEO frequency, as a replacement for fixed-frequency narrowband filter using high- Q aluminum cavities. A close-to-carrier phase noise of -115 dBc/Hz at 1 kHz is reported by the V operation of a Mach-Zehnder modulator (MZM) over 8-12 GHz with a frequency tuning step as small as 2.6 kHz. Phase noise introduced by a photodetector is also explored at a very close-to-carrier frequency. It shows 10-dB phase noise degradation at PD reverse bias voltage of 3 V compared with 6 V at close to the V operation of an MZM. A 19-in rack mount frequency synthesizer system is also realized at X -band with a demonstrated long-term (up to 60 min) frequency drift stability of 3 kHz over whole X -band working frequencies.
由于对非常纯净的本地振荡器和时钟信号源的需求不断增加，具有低相位噪声的光电振荡器（OEO）很受欢迎。一种自注入锁定和锁相环（SILPLL）的强制技术可降低相位噪声，并抑制在标准OEO的长光纤延迟中观察到的边模。通过调整合成OEO频率的振荡频率，开发了一种工作在X波段的频率合成器，它使用电粗调的YIG滤波器与光波长微调的色散光学横向滤波器级联，以替代使用高Q铝腔的固定频率窄带滤波器。据报道，马赫-曾德尔调制器（MZM）在8-12 GHz范围内以2.6 kHz的小频率调谐步长进行V操作时，在1 kHz处的载波附近相位噪声为-115 dBc/Hz。还在非常接近载波频率的情况下研究了光电探测器引入的相位噪声。结果表明，与MZM的V操作附近6 V时相比，在3 V的光电探测器反向偏置电压下，相位噪声恶化了10 dB。还在X波段实现了一个19英寸机架安装频率合成器系统，在整个X波段工作频率范围内，其长期（长达60分钟）频率漂移稳定性为3 kHz。
