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Low-cost System with Handheld Analyzer for Optimizing the Position of Indoor Base Stations
( C. C. Lee ),( Degang Xu ),( George Chan ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.2
In this paper, an automatic system of locating the indoor area with weak or no mobile signal was proposed and demonstrated experimentally by using the Internet of Things (IoT) technology. Nowadays, the technicians of mobile services providers need to go along with numerous heavy equipment to measure and record the mobile signal strength at outside environment. Recently, there are systems proposed to do such measurement at outdoor area by using the IoT technology automatically. However, these works could not be applied in the indoor area since there are difficulties to do the indoor mapping and positioning. In this work, the Bluetooth Low Energy (BLE) was used to tackle these two difficulties. After a proper placement of BLE in the testing site, while the technician walk around with a handheld analyzer, the data can be obtained accordingly for further analysis in the proposed system which includes the construction of floor plan, detection of mobile signal strength and suggestion of indoor base stations. The gift wrapping and centroid algorithms were used during the analysis. The experimental results showed that the proposed system successfully demonstrated the indoor mapping, positioning of weak mobile signal area and suggestion of indoor base stations for the normal rectangular rooms with an area of 100 m2 on single floor.
Frequency Tuning Characteristics of a THz-wave Parametric Oscillator
Zhongyang Li,Pibin Bing,Degang Xu,Jianquan Yao 한국광학회 2013 Current Optics and Photonics Vol.17 No.1
Frequency tuning characteristics of a THz-wave by varying phase-matching angle and pump wavelength in a noncollinear phase-matching THz-wave parametric oscillator (TPO) are analyzed. A novel scheme to realize the tuning of a THz-wave by moving the cavity mirror forwards and backwards is proposed in a noncollinear phase-matching TPO. The parametric gain coefficients of the THz-wave in a LiNbO3crystal are explored under different working temperatures. The relationship between the poling period of periodically poled LiNbO3 (PPLN) and the THz-wave frequency under the condition of a quasi-phasematching configuration is deduced. Such analyses have an impact on the experiments of the TPO.
Zhongyang Li,Pibin Bing,Shengyuan Xu,Degang Xu,Jianquan Yao 한국광학회 2015 Current Optics and Photonics Vol.19 No.3
Terahertz (THz) wave generation from bulk and periodically poled LiTaO3 (PPLT) with a Cherenkovphase matching scheme is numerically investigated. It is shown that by using the crystal birefringenceof bulk LiTaO3 and a grating vector of PPLT, THz waves can be efficiently generated by differencefrequency generation (DFG) with a Cherenkov phase matching scheme. The frequency tuning characteristicsof the THz wave via varying wavelength of difference frequency waves, phase matching angle, polingperiod of PPLT and working temperature are theoretically analyzed. The parametric gain coefficient inthe low-loss limit and the absorption coefficient of the THz wave during the DFG process in the vicinityof polariton resonances are numerically analyzed. A THz wave can be efficiently generated by utilizingthe giant second order nonlinearities of LiTaO3 in the vicinity of polariton resonances
Zhongyang Li,Kai Zhong,Pibin Bing,Sheng Yuan,Degang Xu,Jianquan Yao 한국광학회 2016 Current Optics and Photonics Vol.20 No.1
Terahertz (THz) generation by a GaP ridge waveguide with a collinear modal phase-matching schemebased on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascadedStokes interaction processes and the cascaded anti-Stokes interaction processes are investigated fromcoupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared withnon-cascaded DFG processes, THz intensities from 11-order cascaded DFG processes are increased to 5.48. The quantum conversion efficiency of 177.9% in cascaded processes can be realized, exceeding theManley-Rowe limit.
Investigation of Stimulated Polariton Scattering from the B₁-symmetry Modes of the KNbO₃ Crystal
Zhongyang Li,Mengtao Wang,Silei Wang,Bin Yuan,Pibin Bing,Degang Xu,Jianquan Yao 한국광학회 2018 Current Optics and Photonics Vol.2 No.1
Stimulated polariton scattering from the B₁-symmetry modes of a KNbO₃ crystal to generate a terahertz wave (THz-wave) with a noncollinear phase-matching scheme is investigated. The frequency-tuning characteristics of the THz-wave by varying the phase-matching angle and pump wavelength are analyzed. The expression for the effective parametric gain length under the noncollinear phase-matching condition is deduced. Parametric gain and absorption characteristics of the THz-wave in KNbO₃ are theoretically simulated. The characteristics of KNbO₃ for a terahertz parametric oscillator (TPO) are compared to those of MgO:LiNbO₃. The analysis indicates that KNbO₃ is an excellent optical crystal for a TPO, to enhance the THz-wave output.