US 6,487,221 B1 · Digital device and method for filtering, decimation and transposition into distributed baseband and corresponding digital modulator

Abstract

The invention relates to apparatus for filtering, decimating and transposing into baseband, the apparatus being of the entirely digital type, and serving both to extract and transpose into baseband one of the channels, referred to as the “channel of interest”, of a frequency multiplex of channels, and also to reduce the oversampling factor of said channel of interest, each channel being associated with a distinct carrier. The said apparatus comprising at least two stages in cascade (401 to 40L), each stage comprising filter means (42) and decimation means (43), said filter means being placed upstream from said decimation means and enabling a portion of the spectrum to be purged at locations where the decimation means produce aliasing. According to the invention, each stage (401 to 40L) also comprises transposition means (41) placed upstream from said filter means (42) and associated with a transposition frequency (ft,i) previously selected from a set of N possible distinct transposition frequencies so as to transpose the carrier (p0) associated with said channel of interest as close as possible to zero frequency.

Claims15

Dependent claims

Apparatus for filtering, decimating and transposing into baseband, the apparatus being of entirely digital type, and serving both to extract and transpose into baseband one of the channels, referred to as the “channel of interest”, of a frequency multiplex of channels, and also to reduce the oversampling factor of said channel of interest, each channel being associated with a distinct carrier,

the said apparatus comprising at least two stages in cascade (401 to 40L), each stage comprising filter means (42) and decimation means (43), said filter means being placed upstream from said decimation means and enabling a portion of the spectrum to be purged at locations where the decimation means produce aliasing,
the apparatus being characterized in that each stage (401 to 40L) also comprises transposition means (41) placed upstream from said filter means (42) and associated with a transposition frequency (ft,i) previously selected from a set of N possible distinct transposition frequencies so as to transpose the carrier (p0) associated with said channel of interest as close as possible to zero frequency.

A method of filtering, decimating and transposing into baseband, the method being of the entirely digital type and enabling both a particular channel referred to as the “channel of interest” in a frequency multiplex of channels to be extracted and transposed into baseband, and also the oversampling factor of said channel of interest to be reduced, each channel being associated with a distinct carrier,

the method being characterized in that the operations of filtering, decimation, and transposition into baseband are performed in at least two successive processing stages (801 to 80L) where each processing stage comprises the following successive steps:
transposition (81) enabling the carrier associated with said channel of interest to be transposed as close as possible to zero frequency;
filtering (82);
and
decimation (83), said filtering step serving to purge a portion of the spectrum in locations where the decimation step produces aliasing.

2 more elements

Dependencies are inferred from the claim text.

Digital device and method for filtering, decimation and transposition into distributed baseband and corresponding digital modulator

Life of this patent

Digital device and method for filtering, decimation and transposition into distributed baseband and corresponding digital modulator

Life of this patent

Abstract

Claims15