Research On Digital Measurement Method For Time-Frequency Signal And Hardware Design

Digital measurement method for time-frequency signal and hardware design are studied in this paper. The concept of instantaneous frequency and its physical significance are analyzed, and the Hilbert-Huang Transform Technology (HHT) has been introduced. Starting from the concept of the instantaneous frequency, the intrinsic mode functions which made the instantaneous frequency meaningful, and the way how to realize the Empirical Mode Decomposition (EMD) has been introduced. An instantaneous frequency measurement system built up by TS201 basing on Hilbert-Huang transform is proposed in this paper. The hardware design and software design are introduced and the critical circuit is presented in detail. This system can detect instantaneous frequency which consists of one frequency or more frequencies.Frequency and phase difference measurement method based on multi-layer correlation is proposed. Because the sinusoidal signal has a particular autocorrelation trait, it is possible to detect the phase difference of two unknown weak signals in powerful noise by multi-layer autocorrelation and the frequency of weak signal. This method can achieve higher precision than conventional measurement methods, especially in the condition of low signal-to-noise ratio. A new method for time and frequency based on time axis digitization is proposed and also several typical cases are given. Theory analysis and experiment show that this method has an advantage over conventional methods...