| Digital video signal and analog video signal are very important for video technology development.Video signal parameters metrology guarantees the quality of video signal,video system and relative equipment.Video signal parameters metrology includes measurement of video signal parameters,calibration of video signal measurement instrument,establishment of metrology standard,improvement of traceability,analysis and calculation of uncertainty of measurement.Serial Digital Interface Video Signal(SDI signal)is the key part of digital video signal,which is used to transmit signal among digital equipment in broadcast television studio,master control system,and broadcasting center system.In the recent years,to meet transmission of high definition and resolution video signal,transmission rate of SDI signal is increasing.Jitter is becoming the key factor of SDI signal quality.SDI signal is transformed from analog component video signal.Distortion of analog component video signal will have negative influence on SDI signal and decrease video signal quality.However,because of equipment,cable,and environment disturbance,analog component video signal will be distorted inevitably.Jitter of SDI signal and distortion of analog component video signal will have negative influence on video signal coding,decoding,modulating,demodulating and transmission,decreasing signal quality at receiving end.The study mentioned in this paper focuses on such two video signal parameters metrology.The main research contents are as follows:(1)Research on standard SDI signal jitter generatorSDI signal jitter generator can be used to calibrate video signal measurement instrument.Jitter parameter of commercial video signal generator cannot trace to metrology standard,which has negative influence on instrument calibration and value traceability of SDI signal's jitter parameter metrology.Research and develop a standard SDI signal jitter generator.Such generator is based on sinusoidal frequency modulated signal model and E8257 D signal generator.Video signal measurement instrument is employed to test SDI signal jitter generator.The result shows that such generator is suitable for instrument calibration.SDI signal with known jitter is output by generator,when measurement results exceed threshold values,video signal measurement instrument need to be adjust to improve its measurement accuracy.Develop a video measurement and analysis software which can control standard SDI signal jitter generator and process measurement data,improving the automation and convenience of instrument calibration.(2)Research on calibration method of SDI signal jitter generatorFor the developed standard SDI signal jitter generator,to have accurate and reliable output jitter parameter,research on several jitter calibration methods.A method is presented to calibrate standard SDI signal jitter generator with modulation index and relative power.Calibration system is built with SDI signal jitter generator,spectrum analysis,and frequency standard equipment.Analyse and evaluate measurement uncertainty of SDI signal jitter generator calibration: expand measurement uncertainty is 4.6×10-3UI for standard definition video signal and 7.8×10-3UI for high definition video signal.Compared with other commercial jitter generator under the same experiment condition,measurement uncertainties of developed generator are lower.Through standard SDI jitter generator and its calibration system,SDI signal jitter parameter is traced to atomic time primary standard,power primary standard,and attenuation primary standard.(3)Research on standard analog component video signal distortion generatorFor the calibration of analog component video instrument,several measurement points should be chosen because of the measurement range and measured signal.Standard measurement signal limits choice of measurement points.Research and develop a standard analog component video signal distortion generator which is based on TG700 video signal generator and SDP2000 software and can output test signal with distortion(such as: 5 step signal,color bar signal,multiburst signal,flat field signal).Video signal measurement instrument is employed to test such generator.The result shows that developed generator is suitable for calibration of analog component video signal instrument.Test signal with known distortion is output by the generator,when measurement results exceed threshold values,video measurement instrument need to be adjust to improve its measurement accuracy.(4)Research on calibration method of standard analog component video signal distortion generatorFor the developed standard analog component video signal distortion generator,to have accurate and reliable output parameter,calibrate the amplitude and rise time of the generator with oscilloscope.Analyse and evaluate measurement uncertainty of calibration: expand measurement uncertainty of standard definition signal DC amplitude is 0.090%,AC amplitude is 0.14%,and rise time is 0.38%;expand measurement uncertainty of high definition signal DC amplitude is 0.094%,AC amplitude is 0.16%,and rise time is 0.56%.Under the same experiment condition,compared with the amplitude and time calibration of MDW1862,measurement uncertainties of the developed generator are lower.Through standard analog component video signal distortion generator and its calibration system,analog component video signal distortion parameters are traced to impulse waveform parameter metrology primary standard.(5)Research on primary standard of video signal parameters metrologyVideo signal parameters can be trace to impulse waveform parameter metrology primary standard through oscilloscope.Such primary standard is realized by electro-optic sampling system.Chinese researchers have not built impulse waveform parameter metrology primary standard based on electro-optic sampling system,which has negative influence on traceability of video signal parameters metrology.To solve this problem,research electro-optic sampling theory,build impulse waveform parameter measurement system.Develop electro-optic modulating crystal and measurement and control software.Analyse and optimize lock-in amplifier time constant,chopper frequency,and femtosecond laser power.Measurement output electrical impulse signal from XPDV3120R-VF-FP photodiode.Rise time of such electrical impulse signal is 4.6ps. |
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