arXiv subjects

C. Gao

Publications and source records attributed to C. Gao.

26 records · Page 2Linked to original sources

arXiv2016

Accurate and fast fiber transfer delay measurement based on phase discrimination and frequency measurement

An accurate and fast fiber transfer delay measurement method is demonstrated. As a key technique, a simple ambiguity resolving process based on phase discrimination and frequency measurement is used to overcome the contradiction between measurement accuracy and system complexity. The optimized system achieves a high accuracy of 0.3 ps with a 0.1 ps resolution, and a large dynamic range up to 50 km as well as no dead zone.

physics.ins-det↗

arXiv2015

Highly accurate fiber transfer delay measurement with large dynamic range

A novel and efficient method for fiber transfer delay measurement is demonstrated. Fiber transfer delay measurement in time domain is converted into the frequency measurement of the modulation signal in frequency domain, accompany with a coarse and easy ambiguity resolving process. This method achieves a sub-picosecond resolution, with an accuracy of 1 picosecond, and a large dynamic range up to 50 km as well as no measurement dead zone.

physics.ins-det↗

arXiv2015

Square Kilometer Array Telescope - Precision Reference Frequency Synchronisation via 1f-2f Dissemination

The Square Kilometer Array (SKA) is an international effort to build the world's largest radio telescope, with one square kilometer collecting area. Besides its ambitious scientific objectives, such as probing the cosmic dawn and cradle of life, SKA also demands several revolutionary technological breakthroughs, with ultra-high precision synchronisation of the frequency references for thousands of antennas being one of them. In this report, aimed at applications to SKA, we demonstrate a frequency reference synchronization and dissemination scheme with the phase noise compensation function placed at the client site. Hence, one central hub can be linked to a large number of client sites, forming a star-shaped topology. As a performance test, the 100 MHz reference signal from a Hydrogen maser clock is disseminated and recovered at two remote sites. Phase noise characteristics of the recovered reference frequency signal coincides with that of the hydrogen-maser source and satisfies SKA requirement.

physics.ins-det↗

arXiv2015

Dissemination stability and phase noise specification of fiber-cascaded RF frequency dissemination

Over the past decade, fiber based frequency dissemination has achieved significant progresses in following aspects. To study the dissemination stability and phase noise specifications of the fiber-cascaded RF frequency dissemination system, we perform a lab-top experiment using three sets of RF modulated frequency dissemination systems. They are linked by 50 km + 50 km +45 km fiber spools. The dissemination stabilities of each segments and whole system are measured simultaneously. After that, the phase noise of each segment is also measured and the result shows that the phase noise spectrums of recovered frequency signal can be optimized via narrow band phase lock loop.

physics.ins-det↗

arXiv2015

Fiber-based Radio Frequency Dissemination for Branching Networks with Passive Phase Noise Cancellation

We demonstrate a new fiber-based radio frequency dissemination scheme for branching networks. Without any phase controls on RF signals or usages of active feedback locking components, the highly stable reference frequency signal can be delivered to several remote sites simultaneously and independently. Relative frequency stability of 6E-15/s and 7E-17/1E4s is obtained for 10km dissemination. The proposed low cost and scalable method can be applied to some large-scale frequency synchronization networks.

physics.optics↗

arXiv2013

Fiber Based Multiple-Access Optical Frequency Dissemination

We demonstrate a fiber based multiple-access optical frequency dissemination scheme. Without using any additional laser sources, we reproduce the stable disseminated frequency at an arbitrary point of fiber link. Relative frequency stability of 3E10^{-16}/s and 4E10^{-18}/10^4s is obtained. A branching fiber network for highly-precision synchronization of optical frequency is made possible by this method and its applications are discussed.

physics.optics↗

arXiv2011

Coexistence of Ferroelectric Triclinic Phases and Origin of Large Piezoelectric Responses in Highly Strained BiFeO3 films

The structural evolution of the strain-driven morphotropic phase boundary (MPB) in BiFeO3 films has been investigated using synchrotron x-ray diffractometry in conjunction with scanning probe microscopy. Our results demonstrate the existence of mixed-phase regions that are mainly made up of two heavily tilted ferroelectric triclinic phases. Analysis of first-principles computations suggests that these two triclinic phases originate from a phase separation of a single monoclinic state accompanied by elastic matching between the phase-separated states. These first-principle calculations further reveal that the intrinsic piezoelectric response of these two low-symmetry triclinic phases is not significantly large, which thus implies that the ease of phase transition between these two energetically close triclinic phases is likely responsible for the large piezoelectric response found in the BiFeO3 films near its MPB. These findings not only enrich the understandings of the lattice and domain structure of epitaxial BiFeO3 films but may also shed some light on the origin of enhanced piezoelectric response near MPB.

cond-mat.mtrl-sci↗

arXiv2007

Bidding Strategy with Forecast Technology Based on Support Vector Machine in Electrcity Market

The participants of the electricity market concern very much the market price evolution. Various technologies have been developed for price forecast. SVM (Support Vector Machine) has shown its good performance in market price forecast. Two approaches for forming the market bidding strategies based on SVM are proposed. One is based on the price forecast accuracy, with which the being rejected risk is defined. The other takes into account the impact of the producer's own bid. The risks associated with the bidding are controlled by the parameters setting. The proposed approaches have been tested on a numerical example.

q-fin.GN↗