Research And Implementation Of High-precise Data Acquisition Technology In Phase Noise Analyzer

Phase noise analyzer is a kind of signal analyzer used to measure the frequency stability of a signal source.Its main function is to measure the phase noise spectrum of the signal source.Phase noise is the set of noises that appear as phase fluctuations in the near-carrier noise of the signal source.With the advancement of science and technology,the phase noise of high-quality signal sources is getting lower and lower.This puts forward higher requirements on the measurement accuracy of the phase noise analyzer acquisition system.Based on the principle of phase noise measurement and the theory of high-precision data acquisition,the circuit design and related noise reduction algorithms of the acquisition system of the direct digital phase noise analyzer is studied and implemented in this thesis.The main research contents of this thesis include:1.The overall architecture of the direct digital phase noise analyzer acquisition system is researched and designed.Direct digital phase noise analyzers abandon the traditional design of demodulating phase fluctuations on the analog circuit side.The separation of phase fluctuations is achieved through the digital phase demodulation algorithm,which reduces the scale of analog circuit and reduces the kinds of noise in the acquisition system.2.Circuit of high-precision acquisition system is designed.The noise floor of a phase noise analyzer with a direct digital architecture is basically determined by the noise of the instrument's data acquisition system.Therefore,this thesis theoretically analyzes and simulates the main noise in the multiple modules of the analog-to-digital converter,signal conditioning channel,sampling clock,power supply and reference voltage source in the acquisition system,and provides a theoretical proofs for the circuit design of the acquisition system and the selection of corresponding devices.And on this basis,the circuit of the acquisition system is designed in detail.3.Application of digital phase demodulation algorithm and cross-correlation algorithm in high precision phase noise measurement.A digital phase demodulation algorithm is an algorithm that separates phase fluctuations from the original signal data.This thesis studies the digital phase demodulation algorithm theory and its realization method,and verifies that the digital phase demodulation algorithm can realize the accurate separation of phase fluctuations.After the phase fluctuation is accurately extracted,the irrelevant noise introduced by the acquisition system in the phase fluctuation is suppressed by the cross-correlation algorithm,which reduces the noise floor of the system and increases the measurement accuracy.Finally,the corresponding phase noise power spectrum is obtained.4.The performance indicators of the prototype is tested and compared with the measurement results of foreign high-end instruments.The test results show that the broadband noise floor index of the prototype can reach the level of-174.7 d Bc/Hz@1MHz,which basically meets the design requirements of the project,and can measure the phase noise of the signal source normally.