Research On Phase Determining In Frequency Domain For Multisine Signals

Advances in measurement instrumentation now make it feasible to accurately measure both the magnitude spectrum and the phase spectrum of wide-bandwidth microwave signals. Even though it is routine to accurately measure wide-bandwidth magnitude spectrum, it is challenging to accurately measure the corresponding phase spectrum. In a practical measurement, the spectrum is obtained over a finite window of time. For a periodic signal, the spectrum magnitude is independent of the position of this time-domain window, allowing straightforward comparison of measurements made at different times. The spectrum phase is dependent on the position of the time-domain window, resulting the phase spectrums to differ between repeated measurements of an identical waveform. So it is difficult to measure the spectrum phase and to compare multiple phase spectrum measurements with different starting time of the time-domain window, or to incorporate several measurements into a model.Accurate vector-signal analysis needs high dynamic range measurement instrumentations, accurate calibration methods and feasible phase analysis methods. Firstly, this research introduces several phase analysis methods proposed for determining the phase spectrum so that multiple measurements can be effectively compared and utilized in models. Secondly, some researches is done about several existing frequency domain alignment algorithm. The methods are reviewed in terms of the running time and memory space required. Then, on the base of analysis of frequency domain alignment algorithm for measured multisine signals, We present a novel method called frequency domain alignment based linear phase, which solve the problem that existing frequency domain alignment algorithm is difficult to deal with phase variation from -180 degree to +180 degree. Thirdly, we discuss measuring two-port network using the new algorithm. Finally, Some experiments have been done. We analyze the spectrum of the vector source signal. Experimental data processing results of inverting amplifier verify the efficiency of this new method. And we acquire the actual initial phase at different times of the vector signal generator using this new method.Through this research work, the improved phase analysis methods will enable the development of next generation, wide-bandwidth, high data-rate systems.