Research On Generation Of Waveform-shaped Signal And Time-stretched Analog-to-digital Conversion Technology

In recent years,waveform-shaped signal generator and analog-to-digital converter(ADC)are essential components for radar,communication and information processing equipment,with signal generation and processing developing continuously in the direction of high frequency,high speed and high precision.The operation of using photonic technology to generate up to dozens of GHz waveform signals is simple,and can effectively avoid the electrical complex structure and reduce the high frequency electromagnetic interference.Due to its excellent performance,the photonic technology has been used to update the ADC.Among the schemes,the photonic assisted analog-to-digital converter has been the point since it was proposed.Photonic processing structure exquisitely uses dispersion to stretch the input signal by the optical pulse envelope.After the photoelectric conversion,the stretched signal of which the band is compressed in frequency domain,can be obtained.Then the ADC is used to deal the stretched signal.The excessive demand in band for the signal processing equipment can be reduced while maintaining high accuracy at the same time.At present,it is difficult to output simultaneously multiple waveforms for many waveform-shaped generation schemes which need local resource in high performance.Photonic time-stretched scheme modulates the signal to optical pulse envelope,therefore,the backend needs to obtain stretched signal by removing the pulse envelope.The differential algorithm is a kind of linear technology.However,in order to keep coherence,two complement signals need to be transmitted in the same segment of optical fiber and this way reduces the performance.In order to deal with the above problems,this article discuss waveform-shaped generation and photonic time-stretched scheme by analysis and simulation.The detailed content is as following:1.A multifunctional waveform generation scheme is proposed which can fully utilize the polarization-dependence of two modulators in modulation efficiency.In this paper,the scheme is verified by theoretical analysis and simulation.The result shows that the proposed scheme can generate triangular wave,square wave,half-duty sawtooth wave and full-duty sawtooth wave.2.A novel scheme is proposed to generate triangular-shaped waveform with frequency doubling.In principle,a balanced detector is used to eliminate the generated 4th harmonic and enhance the 2nd and 6th harmonics.A 10-GHz full-duty triangular-shaped waveform is successfully generated by using a 5-GHz signal in simulation and experiment.3.A time-stretched scheme is designed which utilizes the dual-polarization modulator to generate two complement signals and utilizes the differential algorithm to remove the optical pulse envelope.The complement signals with orthogonal polarization are sent to the same optical fiber for transmission.After that,the two signals are split through polarization beam splitter to remove the envelope by differential algorithm.All in all,the performance of scheme is improved.