Dynamic Real-Time Radio Frequency Spectrum Analysis Based On Temporal Talbot Effect

The temporal Talbot effect,also known as the temporal self-imaging effect,is an optical phenomenon.It occurs when a sequence of periodic optical pulses propagates through a dispersive medium,resulting in the output signal self-imaging in the temporal,where the output pulse maintains the same envelope shape as the input pulse.The effect has the advantages of a simple structure,system stability,and low noise introduction,making it widely used in high-speed optical communication,optical signal processing,and frequency synthesis.Notably,the temporal Talbot effect can achieve dynamic frequency analysis of high-speed RF waveforms,offering a new technical option for the demand of broadband real-time spectrum analysis in the fields of communication,radar,and radio astronomy.This article begins by introducing the current research status of photon-assisted spectrum analysis technology and the Talbot effect,and briefly describes the basic principles and research findings of several typical schemes.The article then focuses on the working principle and application scenarios of the temporal Talbot effect and proposes two new real-time broadband radio frequency spectrum analysis systems combined with microwave photonics technology,while elaborating on their working principles.Finally,the article verifies the effectiveness and reliability of these two systems through relevant experiments and numerical simulations,and discusses their application prospects in the field of optical signal processing.The main academic contributions and research results of this paper are summarized as follows:1.A high-precision dynamic waveform spectrum analysis scheme based on the inverse temporal Talbot effect is presented in this paper.The scheme achieves high-precision real-time spectrum analysis by completing the frequency-time mapping of RF signals through a sampling and dispersive medium structure,and utilizing the inverse temporal Talbot effect process.The feasibility of the system is verified through simulations and experiments.The proposed scheme first phase modulates the input periodic optical pulse sequence to meet specific conditions.Then,the signal to be measured is introduced into the photonic link with the help of an electro-optical modulator.Finally,the spectral information of the signal is mapped into the time domain using a section of dispersive medium that satisfies the temporal Talbot effect.The inverse temporal Talbot effect allows the period of the output pulse sequence to be increased to a multiple of the input pulse,thus effectively improving the frequency resolution of the scheme.Numerical simulations and experimental results show that the proposed scheme can achieve ns-level real-time spectrum analysis with a bandwidth above GHz and a frequency resolution of tens of MHz.2.A high-bandwidth,real-time spectrum analysis scheme based on the fractional-order temporal Talbot effect is proposed.The system extends the frequency measurement range by utilizing the pulse frequency multiplication property of the fractional-order Talbot effect,and experiments and simulations confirm the scheme’s potential for enhancing bandwidth.First,the periodic optical pulse sequence is processed through a dispersive medium satisfying the fractional-order Talbot effect,followed by sampling of the signal to be measured and another segment of dispersive medium with matching dispersion to the first.This results in a Fourier transform pair relationship between the output signal and the RF signal to be measured.The fractional-order Talbot effect scales the frequency-time mapping of the output and input signals,thus resolving the issue of limited bandwidth in existing integer-order Talbot effect-based frequency measurement schemes.Experimental results demonstrate the scheme’s ability to achieve RF signal spectrum analysis with a bandwidth of 29.7GHz at the ns level.