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1

Generation of chirped microwave signal with any central frequency based on a nonuniformly spaced finite impulse response filter

Chen D., Wang R., Pu T., Xiang P., Fang T., Zheng J., Xiong J.

Optica Applicata

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2016

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Vol. 46, nr 3

399--408

EN

A novel optical approach to generating a chirped microwave signal by using a nonuniformly spaced finite impulse response filter is proposed and demonstrated. In this scheme, a narrowband Gaussian pulse is used as the original chirped-free signal, which is easy to be acquired. To eliminate the need of a wideband chirped-free signal, a mixer and a radio frequency signal are used to up-convert the spectrum of the original Gaussian signal. Therefore, the required frequency response can be calculated and reconstructed by a finite impulse response filter with nonuniformly spaced taps. Besides, a dual drive Mach–Zehnder modulator is used to realize single sideband modulation of the chirpedfree signal. Thus, the transfer function induced by the fiber dispersion is eliminated and the chirped microwave signal with any central frequency can be generated. In this paper, a design example of a filter with a central frequency of 10GHz is provided, and generation of the target chirped microwave signal is also demonstrated by numerical simulations.

2

A novel approach to photonic generation of periodic triangular radio frequency waveforms

Xiang P., Guo H., Chen D., Zhu H., Wu C.

Optica Applicata

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2015

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Vol. 45, nr 3

381--391

EN

A novel approach to photonic generation of triangular radio frequency waveforms with a tunable repetition rate is proposed and analyzed. In the proposed system, a continuous-wave light is modulated by a reference microwave signal through a polarization modulator, and then its output optical sidebands are manipulated by a microwave photonic filter with a negative tap. By properly adjusting the system parameters, full-duty-cycle triangular radio frequency waveforms can be generated after optical-to-electrical conversion, and its repetition rate (frequency) can be tuned in a wide range. A model describing the proposed system is derived, which is verified via computer simulations.

3

Optical generation of ultra-wideband signals with a reconfigurable spectral notch-band

Xiang P., Chen Y., Chen D., Zhao J.

Optica Applicata

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2014

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Vol. 44, nr 3

411--419

EN

A novel method for optical generation of ultra-wideband signals with a reconfigurable spectral notch-band is proposed. In the proposed system, ultra-wideband signals are generated in the optical domain and an optical tunable delay line is deployed to introduce a notch-band to the spectral profile of the generated ultra-wideband signals, which can effectively avoid the signal interference between ultra-wideband signals and pre-planned narrowband wireless signals used in wireless local area networks (WLAN). A theoretical model describing the proposed system is derived; the optical generation and fiber transmission of ultra-wideband signals with a reconfigurable notch-band are demonstrated via computer simulations.

4

Photonic generation of phase-coded microwave signals based on optical pulse shaping and time delay

Xiang P, Zheng X, Zhang H, Li Y, Wang R

Optica Applicata

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2012

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Vol. 42, nr 4

835--843

EN

A novel approach to photonic generation of phase-coded microwave signals based on optical pulse shaping and time delay is proposed. In the proposed approach, an optical short pulse train is inserted with a specified amount of time-delay to certain pulses, and then converted into super-Gaussian microwave pulses based on the optical pulse shaping technique. By properly adjusting the time-delay, phased-coded microwave signals with a desired code pattern can be generated. A model to describe the signal generation is developed, and the generations of phase-coded microwave signals with frequencies up to 50 GHz are demonstrated.

5

Heat transfer in a turbulent channel flow with a permeable wall

Kuznetsov A. V., Xiang P.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 3

705-713

EN

A problem of turbulent flow in a channel with a permeable wall recently considered in Hahn and Choi (2002) is extended to include heat transfer. A model is utilized to investigate this problem numerically. The modeling is based on the assumption that the flow in the channel is turbulent while in the porous block the flow remains laminar. The wall functions approach is utilized to determine the boundary conditions for the k and equations. The dependence of the Nusselt number on the Darcy and Reynolds numbers is investigated.