The precision of frequency signal is constantly improving, and the application of high-precision frequency signals requires an equally high-precision transmission method. So in this paper, we demonstrate an optical carrier radiofrequency phase stabilization transfer system based on a phase lock loop (PLL), applied to a 20 km spooled fiber link. The phase noise induced by optical fiber is suppressed by the PLL, and the transfer stability improved from 7.2×10-13@1 s to 8.9×10-15@1 s. In addition, the phase difference of peak-to-peak with compensation is less than 10 ps in a measurement of about 1 day. The phase study in antenna is with the compensation mode, so this work will lay the foundation for the phase synchronization of distributed coherent antenna system.
We proposed an ultra-wide-band microwave photonics flexible frequency conversion scheme for integrated electronic systems, meeting the requirements of frequency conversion for multifunctional signal without crosstalk. The reconfigurable microwave photonics filter is exploited to achieve the flexible segmentation of optical broadband microwave signal with different center frequency and elastic bandwidth. The LO optical signal adapted to the signal frequency and target IF frequency is provided by the signal optical carrier, and the carrier-suppression single sideband mode of DPMZM ensures the flexible frequency conversion function. The numerical simulation of the proposed scheme is introduced to verify the feasibility and effectiveness, and three analog wideband signals are flexibly and efficiently converted to the target frequency with almost no crosstalk interference.
The trend of modern radar signals towards multi format, multi frequency band, and large bandwidth has posed greater challenges to radar signal detection in electronic warfare, requiring receivers to have large instantaneous bandwidth, wide spectral coverage and high-frequency spectral resolution capabilities. Microwave photon technology, due to its advantages of low loss, large bandwidth, resistance to electromagnetic interference, and simple equipment structure, is matched with the demand for ultra wideband channelized reception. This article designs a parallel reconfigurable channelized reception scheme for high-frequency and broadband signals and conducts simulation verification. A coherent dual optical comb with 30 comb teeth is generated based on a cascaded electro-optic modulator, and a dual parallel Mach-Zehnder modulator is used to broadcast the broadband signals and frequency shifting of optical combs to achieve channel division of 17 channels. Finally, a filter was used to filter out the signal from a single free spectral region of the optical comb for down conversion, achieving information extraction of high-frequency broadband signals with a bandwidth smaller than the free spectral range of the optical frequency comb using a small free spectral region optical frequency comb.
In this paper, three algorithms are proposed to restore the fog-containing relative intensity image of lidar based on the atmospheric scattering model and dark channel prior theory. The algorithm was evaluated by analyzing the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) of the two data sets, including the fog-free relative intensity images and the fog-containing relative intensity images and standard fog-free relative intensity images. The experimental results show that the PSNR of the two groups of data can be improved by the three algorithms to varying degrees, and the highest PSNR can reach 35.6%. The structure similarity SSIM was significantly improved, and the effect was up to three orders of magnitude.
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