Adaptive electronic filter

Claim 3

The method of claim 1, wherein step (e) comprises the step of: generating said new input vector using gray coding.

Claim 4

The method of claim 2, wherein step (i) comprises the steps of: converting said new input vector from a gray code to a binary code; and storing said new table value into a memory location indicated by said binary code.

Claim 5

A finite impulse response filter, comprising: a coefficient register for storing a set of weighting coefficients; an input vector generator for generating a plurality of input vectors, each input vector having a plurality of bits, each bit corresponding to one of the weighting coefficients in said coefficient register, said generator generating an initial input vector and a plurality of successive input vectors with each successive input vector differing from an immediately prior input vector by only one bit, this one bit in each input vector being referred to as the changed bit; means for deriving an initial table value to associate with said initial input vector, said initial table value representing the negative of the sum of the weighting coefficients; a temporary register for storing a most recently derived table value; means for generating, for each of said successive input vectors, a table value associated with the input vector, said generating means determining for each successive input vector whether the changed bit changed from a 1 to a 0, or from a 0 to a 1, and in response to a determination that the changed bit changed from a 1 to a 0, said generating means selecting the coefficient corresponding to the changed bit from the coefficient register and subtracting twice the corresponding coefficient from the table value currently stored in said temporary register to derive a table value for the input vector, and in response to a determination that the changed bit changed from a 0 to a 1, said generating means selecting the coefficient corresponding to the changed bit from the coefficient register and adding twice the corresponding coefficient to the table value currently stored in said temporary register to derive a table value for the input vector; means for storing each table value into said temporary register after each table value is generated; a memory; means for storing said table values into said memory, with each table value being stored in a memory location associated with the input vector corresponding to the table value; and means for receiving an actual input vector and accessing a memory location in said memory associated with said actual input vector to cause said memory to output the table value associated with said actual input vector, the outputted table value representing a filtered output for the actual input vector.

Claim 6

A finite impulse response filter, comprising: a coefficient register for storing a set of weighting coefficients; an input vector generator for generating a plurality of input vectors, each input vector having a plurality of bits, each bit corresponding to one of the weighting coefficients in said coefficient register, said generator generating an initial input vector and a plurality of successive input vectors with each successive input vector differing from an immediately prior input vector by only one bit, this one bit in each input vector being referred to as the changed bit; means for deriving an initial table value to associate with said initial input vector, said initial table value representing the negative of the sum of the weighting coefficients; a temporary register for storing a most recently derived table value; means for generating, for each of said successive input vectors, a table value associated with the input vector, said generating means determining for each successive input vector whether the changed bit changed from a 1 to a 0, or from a 0 to a 1, and in response to a determination that the changed bit changed from a 1 to a 0, said generating means selecting the coefficient corresponding to the changed bit from the coefficient register and subtracting twice the corresponding coefficient from the table value currently stored in said temporary register to derive a table value for the input vector, and in response to a determination that the changed bit changed from a 0 to a 1, said generating means selecting the coefficient corresponding to the changed bit from the coefficient register and adding twice the corresponding coefficient to the table value currently stored in said temporary register to derive a table value for the input vector; means for storing each table value into said temporary register after each table value is generated; a memory; means for storing said table values into said memory, with each table value being stored in a memory location associated with the input vector corresponding to the table value; and means for receiving an actual input vector and accessing a memory location in said memory associated with said actual input vector to cause said memory to output the table value associated with said actual input vector, the outputted table value representing a filtered output for the actual input vector.

Claim 7

The finite impulse response filter of claim 4, wherein said input vector generator is a gray counter for generating a gray code sequence.

Claim 8

The finite impulse response filter of claim 5, wherein said means for storing said table values into said memory comprises: means for converting said input vector from a gray code to a binary code; and means for storing the table value corresponding to said input vector into a memory location indicated by said binary code.

Claim 9

The finite impulse response filter of claim 6, wherein said means for receiving an actual vector comprises: means for converting said actual input vector into an actual binary code; and means for accessing a memory location indicated by said actual binary code to cause said memory to output the table value stored therein.

Claim 12

An adaptive digital filter, comprising: a coefficient register for storing a set of weighting coefficients; means for generating a plurality of possible sets of input samples and associated table values, each table value representing a sum of the products of the associated input samples and said weighting coefficients; a memory for use as a look-up table; means for storing said table values into said memory; means for applying input samples to said memory to cause said memory to output selected table values, these selected table values representing filtered outputs of the applied input samples; means for comparing said filtered outputs from said memory with a set of desired outputs to derive an error vector; means for generating a set of coefficient adjustments based on said error vector; means for combining said set of coefficient adjustments with said weighting coefficients to derive a set of revised weighting coefficients; means for storing said revised weighting coefficients into said coefficient register; means for generating another plurality of possible sets of input samples and associated revised table values, each revised table value representing a sum of the products of the associated input samples and said revised weighting coefficients; means for storing said revised table values into said memory; and means for applying input samples to said memory to cause said memory to output selected revised table values, these revised table values representing revised filtered outputs of the applied input samples.

Claim 13

An adaptive digital filter, comprising: a coefficient register for storing a set of weighting coefficients; means for generating a plurality of possible sets of input samples and associated table values, each table value representing a sum of the products of the associated input samples and said weighting coefficients; a memory for use as a look-up table; means for storing said table values into said memory; means for applying input samples to said memory to cause said memory to output selected table values, these selected table values representing filtered outputs of the applied input samples; means for comparing said filtered outputs from said memory with a set of desired outputs to derive an error vector; means for generating a set of coefficient adjustments based on said error vector; means for combining said set of coefficient adjustments with said weighting coefficients to derive a set of revised weighting coefficients; means for storing said revised weighting coefficients into said coefficient register; means for generating another plurality of possible sets of input samples and associated revised table values, each revised table value representing a sum of the products of the associated input samples and said revised weighting coefficients; means for storing said revised table values into said memory; and means for applying input samples to said memory to cause said memory to output selected revised table values, these revised table values representing revised filtered outputs of the applied input samples.

Claim 14

In an adaptive digital filter wherein an input digital stream is filtered using a set of weighting coefficients to derive a filtered output, an apparatus for correlating said input digital stream with an error vector derived from said filtered output, comprising: a coefficient register for storing said error vector; means for generating a plurality of possible sets of input samples and associated table values, each table value representing a sum of the products of the associated input samples and said error vector; a memory for use as a look-up table; means for storing said table values into said memory; means for applying said input digital stream to said memory to cause said memory to output selected table values, these selected table values representing coefficient adjustments for adjusting said weighting coefficients.

Claim 15

In an adaptive digital filter wherein an input digital stream is filtered using a set of weighting coefficients to derive a filtered output, an apparatus for correlating said input digital stream with an error vector derived from said filtered output, comprising: a coefficient register for storing said error vector; means for generating a plurality of possible sets of input samples and associated table values, each table value representing a sum of the products of the associated input samples and said error vector; a memory for use as a look-up table; means for storing said table values into said memory; means for applying said input digital stream to said memory to cause said memory to output selected table values, these selected table values representing coefficient adjustments for adjusting said weighting coefficients.

Claim 16

In an adaptive digital filter wherein an input digital stream is filtered using a set of weighting coefficients to derive a filtered output, an apparatus for correlating said input digital stream with an error vector derived from said filtered output, comprising: a coefficient register for storing said input digital stream; means for generating a plurality of possible sets of input samples and associated table values, each table value representing a sum of the products of the associated input samples and said input digital stream; a memory for use as a look-up table; means for storing said table values into said memory; means for applying said error vector as input to said memory to cause said memory to output selected table values, these selected table values representing coefficient adjustments for adjusting said weighting coefficients.

Claim 17

In an adaptive digital filter wherein an input digital stream is filtered using a set of weighting coefficients to derive a filtered output, an apparatus for correlating said input digital stream with an error vector derived from said filtered output, comprising: a coefficient register for storing said input digital stream; means for generating a plurality of possible sets of input samples and associated table values, each table value representing a sum of the products of the associated input samples and said input digital stream; a memory for use as a look-up table; means for storing said table values into said memory; means for applying said error vector as input to said memory to cause said memory to output selected table values, these selected table values representing coefficient adjustments for adjusting said weighting coefficients.