Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Time-Frequency Analysis Using Warped-Based High-Order Phase Modeling | EURASIP Journal on Applied Signal Processing 2005 17 2856-2873 2005 Hindawi Publishing Corporation Time-Frequency Analysis Using Warped-Based High-Order Phase Modeling Cornel Ioana ENSIETA E3I2 Research Centre 2 rue Francois Verny 29806 Brest France Email ioanaco@ Andre Quinquis ENSIETA E3I2 Research Centre 2 rue Francois Verny 29806 Brest France Email quinquis@ Received 7 June 2004 Revised 27 June 2005 Recommended for Publication by Douglas Williams The high-order ambiguity function HAF was introduced for the estimation of polynomial-phase signals PPS embedded in noise. Since the HAF is a nonlinear operator it suffers from noise-masking effects and from the appearance of undesired crossterms when multicomponents PPS are analyzed. In order to improve the performances of the HAF the multi-lag HAF concept was proposed. Based on this approach several advanced methods . product high-order ambiguity function PHAF have been recently proposed. Nevertheless performances of these new methods are affected by the error propagation effect which drastically limits the order of the polynomial approximation. This phenomenon acts especially when a high-order polynomial modeling is needed representation of the digital modulation signals or the acoustic transient signals. This effect is caused by the technique used for polynomial order reduction common for existing approaches signal multiplication with the complex conjugated exponentials formed with the estimated coefficients. In this paper we introduce an alternative method to reduce the polynomial order based on the successive unitary signal transformation according to each polynomial order. We will prove that this method reduces considerably the effect of error propagation. Namely with this order reduction method the estimation error at a given order will depend only on the performances of the estimation method. Keywords and phrases high-order ambiguity function polynomial phase signal warping operator. 1.
