Method and circuit configuration for generating filter coefficients

A method for generating correction signals in a transmission equipment for a duplex transmission of data signals via a two-wire line, which data signals assume a plurality W of different amplitude values and which correction signals function for suppressing echo signals relating to transmit data signals delivered to said two-wire line and superimposed on receive data signals coupled from said two-wire line, said method comprising the steps of:

• storing a plurality N of successive transmit data signals in a serial-in parallel-out storage arrangement having a plurality N of data signal storage cells;
• adding predetermined correction signal coefficients corresponding to the transmit data signals stored in said data signal storage cells individually for the W possible amplitude values and making available W corresponding partial sum signals;
• multiplying the partial sum signals individually by a factor corresponding to the particular amplitude value to form product signals;
• multiplying at least some of the product signals by an additional correction signal coefficient assigned to the particular amplitude value to form additional product signals;
• and
• adding the product signals and the additional product signals to form a correction signal.

A transversal filter for generating filter signals, to which data signals assuming a plurality W of different amplitude values are supplied as input signals, said transversal filter comprising:

• a serial-in-parallel-out storage arrangement having a plurality of N data signal storage cells for storing N successive data signals;
• a coefficient storage arrangement having a plurality of N coefficient storage cells for storing filter signal coefficients assigned to the N data signal storage cells;
• polling means connected to the serial-in-parallel-out storage arrangement and the coefficient storage arrangement for polling the data signal storage cells together with the coefficient storage cells;
• an accumulator arrangement with a plurality W of accumulators, each of which is assigned to one of the possible W amplitude values of said data signals and is individually selectable according to the data signals stored in the data signal storage cells at the polling of the data signal storage cells and the coefficient storage cells, thereby adding only the filter signal coefficients provided by the coefficient storage arrangement for the particular amplitude value and making available a corresponding partial sum signal;
• a multiplier arrangement with a plurality W of first multipliers, each of which is coupled to one of the accumulators for multiplying the partial sums signal supplied to it by a factor corresponding to the particular amplitude value and makes available a product signal resulting therefrom;
• a plurality of second multipliers succeeding at least some of the first multipliers for multiplying the product signal supplied to the particular second multiplier by an additional filter signal coefficient assigned to the particular amplitude value to form an additional product signal;
• and
• an adder responsive to the product signals and additional product signals made available by the first and second multipliers which adder adds these product signals and additional product signals to form a filter signal.

A transversal filter for generating filter signals, which is supplied with four-level binary encoded data signals of whose two possible amplitude values are symmetrical to a predetermined reference value and differ only with respect to sign, comprising:

• a serial-in-parallel-out storage arrangement having a plurality of N data signal storage cells for storing N successive data signals;
• a coefficient storage arrangement having a plurality of N coefficient storage cells for storing filter signal coefficients assigned to the N data signal storage cells;
• polling means connected to the serial-in-parallel-out storage arrangement and the coefficient storage arrangement for polling the data signal storage cells together with the coefficient storage cells;
• an accumulator arrangement with two accumulators, each of which is assigned to one of said possible two amplitude values deviating from each other with respect to magnitude and which is individually selectable according to the data signals stored in the data signal storage cells at the polling of the data signal storage cells and the coefficient storage cells, thereby, dependent upon the sign information contained in the binary encoded data signals, accumulating only the filter signal coefficients provided by the coefficient storage arrangement for the particular amplitude value and making available a corresponding partial sum signal;
• a multiplier arrangement including two first multipliers, each of which is coupled to one of the accumulators for multiplying the partial sum signal supplied to it by a factor corresponding to the particular amplitude value and makes available a product signal resulting therefrom;
• a second multiplier succeeding one of said first multipliers for multiplying the product signal supplied to the second multiplier by an additional filter signal coefficient assigned to the particular amplitude value to form an additional product signal;
• and
• an adder responsive to the product signals and the additional product signal made available by the first and second multipliers which adder adds these product signals and additional product signal to form a filter signal.