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US 5,703,801 AGranted
Logarithm/inverse-logarithm converter utilizing second-order term and method of using same
AssigneeMotorola, Inc.
InventorsShaoWei Pan, Shay-Ping Thomas Wang
Life of this patent
Estimating the term…
Abstract
A converter which may be used for implementing either logarithmic or inverse-logarithmic functions is disclosed. The converter includes a memory, a multiplier, and two adders. The memory stores a plurality of parameters and second-order terms which are derived using a least squares method to estimate a logarithmic or inverse-logarithmic function over a domain of input values. A method of computing the parameters and second-order terms is also disclosed.
Claims30
A logarithm converter, which comprises:
- a memory for storing a plurality of parameters and a plurality of second-order terms, wherein the parameters are calculated using a least squares method to estimate a logarithmic function over a domain of input values, the memory providing as output ones of the parameters and a second-order term which correspond to an input value;
- and
- arithmetic means, operatively coupled to the memory, for generating a log value by performing arithmetic operations on the input value, the ones of the parameters, and the second-order term.
A logarithm converter for generating a log value corresponding to an input value, the logarithm converter comprising:
- a memory for storing a plurality of second-order terms and a plurality of parameter pairs, wherein each of the parameter pairs is calculated using a least squares method to estimate a logarithmic function over an interval of input values, the memory providing as output a parameter pair and a second-order term which correspond to the input value, wherein the parameter pair has a zero-order parameter and a first-order parameter;
- a multiplier for multiplying the first-order parameter by a bit slice of the input value to produce a proportional term;
- a first adder for summing the proportional term and the second-order term to produce a first sum;
- and
- a second adder for summing the first sum and the zero-order parameter to produce the log value.
2 more elements
A computing device, which comprises:
- a processing unit for executing a computer operation which utilizes a log value;
- a computer memory for storing a computer program which includes the computer operation;
- a bus for connecting the processing unit and the computer memory;
- and
- a logarithm converter which receives an input value and includes:
- a memory for storing a plurality of parameters and a plurality of second-order terms, wherein the parameters are calculated using a least squares method to estimate a logarithmic function over a domain of input values, the memory providing as output ones of the parameters and a second-order term which correspond to the input value;
- and
- arithmetic means, operatively coupled to the memory, for generating the log value by performing arithmetic operations on the input value, the ones of the parameters, and the second-order term.
5 more elements
An inverse-logarithm converter, which comprises:
- a memory for storing a plurality of parameters and a plurality of second-order terms, wherein the parameters are calculated using a least squares method to estimate an inverse-logarithmic function over a domain of input values, the memory providing as output ones of the parameters and a second-order term which correspond to an input value;
- and
- arithmetic means, operatively coupled to the memory, for generating an inverse-log value by performing arithmetic operations on the input value, the ones of the parameters, and the second-order term.
An inverse-logarithm converter for generating an inverse-log value corresponding to an input value, the inverse-logarithm converter comprising:
- a memory for storing a plurality of second-order terms and a plurality of parameter pairs, wherein each of the parameter pairs is calculated using a least squares method to estimate an inverse-logarithmic function over an interval of input values, the memory providing as output a parameter pair and a second-order term which correspond to the input value, wherein the parameter pair has a zero-order parameter and a first-order parameter;
- a multiplier for multiplying the first-order parameter by a bit slice of the input value to produce a proportional term;
- a first adder for summing the proportional term and the second-order term to produce a first sum;
- and
- a second adder for summing the first sum and the zero-order parameter to produce the inverse-log value.
2 more elements
A computing device, which comprises:
- a processing unit for executing a computer operation which utilizes an inverse-log value;
- a computer memory for storing a computer program which includes the computer operation;
- a bus for connecting the processing unit and the computer memory;
- and
- an inverse-logarithm converter which receives an input value and includes:
- a memory for storing a plurality of parameters and a plurality of second-order terms, wherein the parameters are calculated using a least squares method to estimate an inverse-logarithmic function over a domain of input values, the memory providing as output ones of the parameters and a second-order term which correspond to the input value;
- and
- arithmetic means, operatively coupled to the memory, for generating the inverse-log value by performing arithmetic operations on the input value, the ones of the parameters, and the second-order term.
5 more elements
Dependencies are inferred from the claim text.