Application of frequency estimation method based on Hilbert-Huang transform to non-cooperative information source

Frequency estimation in passive location based on non-cooperative information sources plays an important role. And existing methods such as wavelet transform (WT) can´t satisfy the precision of frequency estimation what is needed in location. In order to solve the puzzle, the Hilbert-Huang transform(HHT) is adopted in this article. HHT is based on the local characteristics of signals, which is an adaptive and efficient transformation method. It can not only overcome the disadvantages of quantitative time and frequency analysis in WT, but also it is particularly suitable for analyzing the nonlinear and non-stationary signals such as broadcasting signal, GSM signal etc. In this paper, we choose three typical kinds of signal to estimate their frequency. The original signal is first decomposed by Empirical Mode Decomposition(EMD), all intrinsic mode functions (IMF) will be acquired. Secondly we perform Hilbert Transform for them and gained signal´s Hilbert amplitude spectrum, and signal´s frequency component needed in location will be drawn and found in the end. The analysis results from simulated signals and experimental signals have verified the feasibility and precision of the method in frequency measurement of sine signal along with Gauss complex circle flat noise, the noiseproof feature is also wonderful, in the condition of which Signal-to-noise Ratio is greater than or equal to 5dB, for all kinds of modulation signal of the location technology, the estimated accuracy is suitable for the project.