Design And Measurement Of Fiber True Time Delay Line In Optically Controlled Phased Array Antenna

In the past decades,time-delay line has been widely applied in amplifier,oscillator, decipherer,signal processing,radar and electronic countermeasures.Restricted by the aperture fill time of array,the conventional phased array antenna(PAA) only operates under the relatively narrow band signals.It is difficult to realize a high instantaneous bandwidth and a wide-angle beam-scanning,which makes it not suitable to more complex conditions and domains requiring high-performance.Optically controlled phased array antenna(OCPAA) with applied optical true time delay(OTTD) can remove the restriction by the aperture fill time of array.With the optically controlled beamforming network,OCPAA offers well-known advantages of high instantaneous bandwidth,low propagation loss,small- size and weight, immunity to electromagnetic interference(EMI),removing-capability,and squint free operation, so that it has become an important trend in the development of PAA.The paper mainly consists the design and measurement of fiber true time delay line in OCPAA,including the design and measurement of fiber true time delay line,the processing method of measurement data and the preliminary optimization of the measurement uncertainty.Firstly,the basic theory of the scanning of PAA and the time delay of the OTTD is introduced.Then the principle of several fiber true time delay lines is illustrated and their advantages and disadvantages are analyzed.The fiber true time delay line for certain application is designed and its anti-radiation performance is discussed.Thirdly,several modern measurement of time-delay are presented,with comparison of their characteristics.And the least square linear fitting with data processing is chosen as the method of time delay measurement.As the main research,the optimization of time delay measurement method is proposed to depress the measurement uncertainty and improve the time delay precision.In this paper,the true time delay measurement system is designed and built up using the vector network analyzer.Based on the system,the time delay of fibers with different lengths is measured and the phase-frequency characteristics of the test data is processed with the least square linear fitting method.The measurement uncertainty is analyzed and the method of improving the measurement uncertainty is proposed.Finally,the measurement uncertainty of around 0.013ns for the time delay range of tens ns is obtained.