Tsinghua University

Xiaoping Zheng

Nan Hua

Zhijie Li

Shangyuan Li

Yihao Li

Xiaoxiao Xue

Xiaojiao Deng

Yiwei Bai

Ruijie Luo

Guanyu Han

A method for processing a radar signal based on a photonic fractional Fourier transformer comprises: transmitting a linear frequency modulation signal to targets to be detected, receiving echo signals of the targets to be measured, and loading the linear frequency modulation signal and the echo signals onto a single-frequency optical wave by an electro-optical modulator (S); respectively biasing a sub-modulator and a parent modulator of the electro-optical modulator at different bias points, modulating the single-frequency optical wave by the electro-optical modulator based on the linear frequency modulation signal and the echo signals, and outputting a modulated optical signal (S); converting the modulated optical signal by a photoelectric detector to a photocurrent (S); and performing Fourier transform on the photocurrent to obtain a fractional Fourier spectrum, and obtaining distance information of the targets to be measured according to peak positions of each pulse signal in the fractional Fourier spectrum (S).

Method and system for processing radar signal based on photonic fractional fourier transformer

A terahertz gas spectrometer detection system is provided. The system includes: a terahertz generation module, a gas module, a terahertz detection module and a program-control and acquisition module. terahertz generation module is configured for generating and transmitting terahertz signals with different frequencies; gas module is configured for setting and storing to-be-detected gas, so that terahertz signals with different frequencies pass through the to-be-detected gas; terahertz detection module is configured for detecting amplitude signals of terahertz signals after passing through the to-be-detected gas through field effect transistor detector; program-control and acquisition module is configured for controlling the terahertz generation module to generate and transmit frequency of terahertz signal, and is further configured for acquiring amplitude detection signals of terahertz signals after passing through the to-be-detected gas, and generating spectrogram of to-be-detected gas.

Terahertz gas spectrometer detection system

The present disclosure provides a high-precision time synchronization method. With the method, a traditional time synchronization protocol of a traditional IEEE 1588 network can be improved by introducing a periodic perturbation time between any two nodes in the time synchronization network, the perturbation time can be caused by changing the lengths of transmission paths or introducing clock phase perturbation due to different clock frequencies in the transistor and the receiver. With the method, the relevance of resulting errors of multiple synchronizations can be eliminated, and the perturbation can be compensated by means of statistical averaging, such that the synchronization error due to the low clock resolution of the synchronization node can be decreased. The method may realize the time synchronization at the precision of nanosecond, having significant advantages over the traditional time synchronization method based on IEEE 1588 protocol.

High-precision time synchronization method

An all-optical time slice switching method based on time synchronization is provided. With the method, continuous data streams in an optical network are assembled to time domain periodic optical time slices and are transmitted in an asynchronous transmission mode. Network nodes obtain high precision synchronization time via a network and control optical switches to switch arriving optical time slices to a target port at precise time points periodically, therefore all-optical switching is implemented. When a connection request arrives, an available path, a wavelength and time slots to be occupied are calculated by a source node according to information on available time slots of the optical network, and the time slots are reserved by a connection management module. After the time slots are reserved, the source node send optical time slices carrying services periodically at reserved time slots. A destination node restores the optical time slices to the data streams.

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Beijing, China

Xiaoping Zheng