Annals of Biomedical Engineering

, Volume 33, Issue 11, pp 1582–1594 | Cite as

Estimation of Time-Varying Coherence Function Using Time-Varying Transfer Functions

Article
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Abstract

We introduce a new method to estimate reliable time-varying coherence functions (TVCF) for causal systems. The technique is based on our previously developed method to estimate time-varying transfer functions (TVTF), known as the time-varying optimal parameter search algorithm [Zou, R., H. Wang, and K. H. Chon. A robust time-varying identification algorithm using basis functions. Ann. Biomed. Eng. 31: 840–853, 2003]. The TVCF is estimated by the multiplication of two TVTFs. The two TVTFs are obtained using signal x as the input and signal y as the output to produce the first TVTF, and signal y as the input and signal x as the output to produce the second TVTF. Demonstration of the feasibility and efficacy of the proposed approach is provided with both simulation examples and application to renal blood flow and pressure data. The proposed approach provides higher time-frequency resolution TVCF than afforded by the short time Fourier transform based TVCF.

Key Words

Time-varying transfer function Time-varying coherence function ARMA Time-varying Renal autoregulation 
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Copyright information

© Springer Science + Business Media, Inc. 2005

Authors and Affiliations

  • He Zhao
    • 1
  • Sheng Lu
    • 1
  • Rui Zou
    • 2
  • Kihwan Ju
    • 1
  • Ki H. Chon
    • 1
    • 3
  1. 1.Department of Biomedical EngineeringState University of New York at Stony BrookStony Brook
  2. 2.Department of NeurosurgeryChildren's HospitalBoston
  3. 3.Department of Biomed. Eng.SUNY at Stony BrookStony Brook

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