Iterative method for synthesizing digital filters for shaping a signal

• US 9,425,996 B2
• Filed: 12/11/2014
• Issued: 08/23/2016
• Est. Priority Date: 12/11/2013
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Baptiste, Francois
• Primary Examiner(s): Fan, Chieh M
• Assistant Examiner(s): Koeth, Michelle M
• Application Number:
  US14/566,970
• Publication Number:
  US 20150163076A1
• Time in Patent Office: 621 Days
• US Class Current: 1/1
• CPC Class Codes: H04L 2025/03611 Iterative algorithms
• CPC Class Codes: H04L 2025/037 Detection of convergence state
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03853 Shaping by digital methods other than look up tables or up/down converters
• CPC Class Codes: H04L 25/03885 adaptive
• CPC Class Codes: H04L 25/03949 equalizer selection or adaptation based on feedback multiple signaling inclusive of a precoding command for adapting the transmitter H04L1/0031; feedback for transmit diversity systems H04B7/0619; selection of codebook or precoding matrix for MIMO diversity systems H04B7/0456
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005

Abstract

An iterative method for synthesizing digital filters comprises the following steps: generation of a transmit filter intended to be applied to a signal to be transmitted; and generation of a receive filter intended to be applied to a received signal. The method comprises the following iteratively executed steps: convolution of the transmit filter and the receive filter in order to generate a transmission filter; determination of a criterion that is representative of the level of intersymbol interference on said transmission filter and whether the level of intersymbol interference is higher than a given level; calculation of an equalizing filter for the intersymbol interference; replacement of the transmit filter with the convoluted transmit filter having the equalizing filter or the replacement of the receive filter with the convoluted receive filter having the equalizing filter.

Claims

1. An iterative method for synthesizing digital filters, the method comprising:

generating an emission filter to be applied to a signal to be transmitted, and

generating a reception filter to be applied to a received signal,

wherein the method further comprises the following iteratively executed steps;

a first convolution of the emission filter and the reception filter to generate a transmission filter,

determination of a criterion representative of a level of intersymbol interference on the transmission filter, and

if the level of intersymbol interference is higher than a given level,

calculating an equalizing filter for the intersymbol interference, and

replacing, at a next iteration, selectively either the emission filter with a second convolution of the emission filter and the equalizing filter or the reception filter with a third convolution of the reception filter and the equalizing filter,

wherein a choice between replacing the emission filter with the second convolution of the emission filter and the equalizing filter or replacing the reception filter with the third convolution of the reception filter and the equalizing filter is done based on a proximity of the emission filter or the reception filter to a desired frequency template for the emission filter or the reception filter.

2. The iterative method for synthesizing digital filters according to claim 1, further comprising stopping the iteratively executed steps when the level of intersymbol interference is below a given threshold.

3. The iterative method for synthesizing digital filters according to claim 1, wherein the criterion that is representative of the level of intersymbol interference on the transmission filter is taken to be equal to a ratio between a sum of absolute values of coefficients of the transmission filter except a central coefficient and an absolute value of the central coefficient of the transmission filter.

4. The iterative method for synthesizing digital filters according to claim 1, wherein the equalizing filter is multiplied by a weighting window, a type of weighting window is selected based on a desired speed of convergence of the iterative method.

5. The iterative method for synthesizing digital filters according to claim 1, wherein the emission filter and the reception filter are root raised-cosine filters.

6. The iterative method for synthesizing digital filters according to claim 5, wherein the root raised-cosine filters are multiplied by a weighting window.

7. A non-transitory computer-readable medium including a computer program having instructions for executing the iterative method for synthesizing filters according to claim 1 when the computer program is executed by a processor.