<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.0 20120330//EN" "JATS-journalpublishing1.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article"><front><journal-meta><journal-id journal-id-type="publisher-id">INFORMATICA</journal-id><journal-title-group><journal-title>Informatica</journal-title></journal-title-group><issn pub-type="epub">0868-4952</issn><issn pub-type="ppub">0868-4952</issn><publisher><publisher-name>VU</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">inf23104</article-id><article-id pub-id-type="doi">10.15388/Informatica.2012.349</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research article</subject></subj-group></article-categories><title-group><article-title>A Forward–Backward Approach for Instantaneous Frequency Estimation of Frequency Modulated Signals in Noisy Environment</article-title></title-group><contrib-group><contrib contrib-type="Author"><name><surname>Kazlauskas</surname><given-names>Kazys</given-names></name><email xlink:href="mailto:kazys.kazlauskas@mii.vu.lt">kazys.kazlauskas@mii.vu.lt</email><xref ref-type="aff" rid="j_INFORMATICA_aff_000"/></contrib><contrib contrib-type="Author"><name><surname>Pupeikis</surname><given-names>Rimantas</given-names></name><email xlink:href="mailto:rimantas.pupeikis@mii.vu.lt">rimantas.pupeikis@mii.vu.lt</email><xref ref-type="aff" rid="j_INFORMATICA_aff_000"/></contrib><aff id="j_INFORMATICA_aff_000">Vilnius University, Institute of Mathematics and Informatics, Akademijos 4, LT-08663 Vilnius, Lithuania</aff></contrib-group><pub-date pub-type="epub"><day>01</day><month>01</month><year>2012</year></pub-date><volume>23</volume><issue>1</issue><fpage>65</fpage><lpage>76</lpage><history><date date-type="received"><day>01</day><month>02</month><year>2011</year></date><date date-type="accepted"><day>01</day><month>09</month><year>2011</year></date></history><abstract><p>In this paper a forward–backward basis function approach for instantaneous frequency estimation of the frequency-modulated signal in noisy environment is presented. At first, a forward–backward prediction approach is applied for least squares estimation of time-varying autoregressive parameters. A time-varying parameters are expressed as a summation of constants multiplied by basis functions. Then, the time-varying frequencies are extracted from the time-varying autoregressive parameters by calculating the angles of the estimation error filter polynomial roots. The experimental results are presented, which shows the superiority of the proposed method against the covariance (forward prediction) approach.</p></abstract><kwd-group><label>Keywords</label><kwd>instantaneous frequency estimation</kwd><kwd>forward–backward approach</kwd><kwd>basis functions</kwd><kwd>noisy environment</kwd></kwd-group></article-meta></front></article>