Affiliation of Author(s):电子信息工程学院
Journal:JOURNAL OF LIGHTWAVE TECHNOLOGY
Key Words:Phase noise I/Q mixer frequency discriminator microwave photonics
Abstract:Digital phase demodulation can greatly simplify the calibration of microwave phase noise analyzers (PNAs) based on frequency discriminators, and avoid the use of feedback loops, but the required microwave in-phase and quadrature (I/Q) mixer always has a small operational bandwidth, leading to a limited phase noise measurement frequency range. In this paper, a novel photonic microwave PNA based on digital phase demodulation is proposed and investigated, using an all-optical microwave I/Q mixer that consists of a Mach-Zehnder modulator, a polarization modulator and two polarizers. Different from conventional electrical I/Q mixers, which rely on electrical hybrids to introduce a 90-degree phase difference between the I and Q channels, the all-optical microwave I/Q mixer achieves the 90-degree phase difference by properly setting the polarizers, ensuring a broad operational bandwidth. The major problems associated with the use of the optical mixer in the PNA, i.e., DC interference and I/Q mismatch, are solved by tuning a variable delay-line together with post signal processing. In addition, to improve the phase noise measurement sensitivity, the time delay required in the frequency discriminator is implemented by a span of low-loss fiber. Experimental results show that the I/Q mixer can maintain a good performance within a frequency range from 5 to 40 GHz, and the proposed PNA has a high sensitivity (<-100 dBc/Hz@1 kHz and <-130 dBc/Hz@ 10 kHz).
ISSN No.:0733-8724
Translation or Not:no
Date of Publication:2018-10-01
Co-author:Shi, Jingzhan,Ben, De,Shilong PAN
Correspondence Author:zfz
Date of Publication:2018-10-01