Zhejiang University

Other

Xiaofeng Jin

Xiangdong Jin

Xianmin Zhang

Shilie Zheng

Xianbin Yu

Bo Cong

Yi Chen

Qinggui Tan

Kang Xiao

Hao Chi

Han Zhao

Guanghui Jia

Liuqing Yang

Yijie Du

Changqiao Liu

Yinfang Xie

Jichen Qiu

Donglin Qin

Zhiwei Cheng

Chenghui Zhang

Jianhai Ou

A transfer impedance calibration device for transducers based on spatial frequency domain smoothing technology is provided. The calibration device comprises a signal transmitter, a power amplifier, a transducer pair, a measurement amplifier, a signal collector, a measurement processor and a current sampler. The device extracts acoustic channel information through the sound filed spatial information or measurement method to design a spatial domain smoothing filter, and then comprehensively processes the transmitted current signal and the received signal through the spatial frequency domain smoothing technology to obtain the transfer impedance of the transducer pair.

Transducer transfer impedance calibration device based on spatial frequency domai smoothing technology

A method of free-field broadband calibration of hydrophone sensitivity based on pink noise, relating to the field of free-field underwater acoustic measurement, and is mainly used for broadband measurements of hydrophone sensitivity in free-field. The method of the present disclosure is to transmit a broadband pink noise signal by controlling the signal source, and to perform the synchronous processing and FFT to the transmitted current signal and the received voltage signal, such as interception and zero padding, and finally obtain the transfer function in the frequency domain; by analyzing the direct wave and the reflected wave in the water tank, the transfer function is averaged by a rectangular window to eliminate the influence of the reverberation of the reflected wave in the water tank, so as to obtain the broadband transfer function of the free-field between the transmitting transducer and the hydrophone.

Method of free-field broadband calibration of hydrophone sensitivity based on pink noise

A frequency modulation demodulator based on fiber grating sensor array comprises: a laser, radio frequency signal source, acousto-optic modulator, delay fiber pair, Mach-Zehnder modulator, optical filter, optical amplifier, optical isolator, circulator, fiber grating sensor array, photodetector and data acquisition card. By the cooperation of delay fiber pair and the fiber grating, the reflected optical pulses of the two gratings (the front grating and the back grating) are overlapped in the time domain to form interference, and thereby achieving multi-point array interference demodulation.

Frequency modulation demodulator based on fiber grating sensor array

A measurement device for polarization-maintaining optical fiber spindle difference delay is provided. The measurement device comprises a polarization-maintaining fiber (PM) Sagnac interferometer, a signal generator, a microwave detector, a microprocessor. The PM Sagnac interferometer comprises a laser, a photoelectric modulator, and a PM fiber coupler that are connected in sequence. The PM Sagnac interferometer further comprises an optical fiber interface Jand an optical fiber interface Jarranged at the two output ends of the PM fiber coupler, a PM fiber to be measured located between the fiber interface Jand the fiber interface J, and a photodetector arranged at the other output end of the PM fiber coupler.

Measuring device for polarization-maintaining optical fiber spindle differential delay

A frequency chirp correction method for the photonic time-stretch system comprises acquiring the stretching signal, i.e. acquiring the time-domain data after the time-domain stretching. First, the time-domain data of the stretching signal is Fourier transformed to obtain the spectral distribution. The spectral distribution is then convoluted with the first frequency-domain correction factor, and then multiplied with the second frequency-domain correction factor to obtain the modified frequency spectrum. Finally, the modified frequency spectrum is performed by the inverse Fourier transform to obtain the time-domain signal after the frequency chirp correction.

Frequency chirp correction method for photonic time-stretch system

A photonic radio-frequency receiver with mirror frequency suppression function, in which a single modulator is utilized to form a photoelectric oscillator so as to generate high-quality and low-phase-noise optically generated local oscillators, without the need for an external local oscillator source, and at the same time, another radio-frequency port is used as a radio-frequency signal input port, thereby allowing a compact structure. By properly setting a bias point for the two-electrode modulator and orthogonally synthesizing two branches of intermediate frequency signals respectively generated by the upper and lower sideband beat frequencies of the modulated optical signal, the photonic radio-frequency receiver realizes the functions of receiving radio-frequency signals and suppressing mirror frequency signals. The present disclosure can realize a photonic mirror-frequency suppression receiver.

Photonic radio-frequency receiver with mirror frequency suppression function

An optical sensing device applicable to two dimensional electric field, includes sequentially connected input polarization maintaining fibers, a sensing unit, an output single mode fiber, a photodetector and a signal processing unit, the sensing unit includes a lithium niobate substrate; a first Y optical waveguide and two Mach Zehnder structure optical waveguides are arranged on the lithium niobate substrate; the input of the first Y optical waveguide is connected with the output of the laser source, the output is respectively connected to the inputs of the two Mach Zehnder structure optical waveguides; the outputs of the two Mach Zehnder structure optical waveguides are connected to the photodetector; dipole antenna is arranged at any single waveguide arm of each Mach Zehnder structure optical waveguide, the polarization directions of the two dipole antennas are in orthogonality with each other. The invention realizes measurement of two dimensional electric field utilizing one sensing head device, which has the benefits of high sensitivity, high measuring accuracy and easy processing.

Optical sensing device for two-dimensional electric field measurement

A traveling-wave loop antenna based on a metal ring cavity for generating a radio frequency OAM beam includes a main structure which is the metal ring cavity whose top surface has an annular slot circumferentially opened. Two openings, &#xbc; of a perimeter of the metal ring cavity apart, are two excitation source ports of the antenna, for connecting a metal waveguide. When the two ports are inputted with microwave sources having the same frequency and a phase difference of &#xb1;90&#xb0;, an electromagnetic field in the metal ring cavity exhibits a traveling-wave distribution propagating circumferentially clockwise or counterclockwise. The annular slot constitutes the antenna. A reasonable design of a size of the metal ring cavity and a position of the annular slot realizes a conversion from a microwave guided-wave mode to an OAM mode and a generation of the radio frequency OAM beams with different orders l in free space.

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Hangzhou, China

Xiaofeng Jin