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Combs filtering: improving acquisition and tracking in GNSS receivers / A. Dempster in GPS world, vol 20 n° 3 (March 2009)

Public [article]  inGPS world > vol 20 n° 3 (March 2009) . - pp 44 - 49 Titre : Combs filtering: improving acquisition and tracking in GNSS receivers Type de document : Article/Communication Auteurs : A. Dempster, Auteur Année de publication : 2009 Article en page(s) : pp 44 - 49 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] bruit (théorie du signal) [Termes IGN] filtrage du bruit [Termes IGN] filtre numérique [Termes IGN] récepteur GNSS Résumé : (Editeur) [...] In the electronic world, we are often faced with noisy signals. Fluctuating electrical currents or electromagnetic waves have two components: one of interest, called the desired signal, and one which is not, called the noise. The noise typically is unwanted and we usually seek ways to reduce its presence or level compared to that of the desired signal. The noise may or may not be random. The 50 or 60 Hz power-line hum picked up by an improperly grounded amplifier is an example of the latter, whereas the static on a weak radar return is an example of the former. We can reduce an undesirable component in a signal, analog or digital, by using a filter. A filter enhances or attenuates a particular frequency or range of frequencies in the input signal. There are a wide variety of filters, each designed to operate on a given input to produce a desired output. Common generic filters are the lowpass, highpass, and bandpass filters where the designations indicate the frequency range of the output signal. A special type of filter can be used where the desired signal or the noise has equally spaced frequency components. This filter has a frequency response with equally spaced passbands or stopbands resembling the teeth of a comb. Accordingly, it is called a comb filter. Comb filters are used in analog and digital televisions, for example, to reduce picture artifacts that otherwise result from incomplete separation of the luminance and chrominance signals in composite video. Comb filters have also been used to attenuate the power-line fundamental and its harmonics in audio signals and to separate solar and lunar variations in electron-content data. The pseudorandom noise codes transmitted by GNSS satellites repeat in the time domain, which results in equally spaced spectral components in the frequency domain. So, could comb filters in GNSS receivers enhance acquisition and tracking of satellite signals ? In this month's column, we find out. Copyright Questex Media Group Numéro de notice : A2009-051 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=29681 [article]

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