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US 4,734,875 AGranted
Log mixer circuit
AssigneeThe Singer Company
InventorsJudit K. Florence, Roy W. Latham
Life of this patent
Estimating the term…
Abstract
A logarithmic mixer circuit in the form of a conversion circuit for mixing digital representations of logarithmic values eliminating the usual mathematical processes of determining anti-logs, summing them and then determining the logs again, the invention using addition, subtraction and a look up table. Additional utiity is obtained by the use of scaled offset representations of logarithmic values for digital processing and separate representations for zero values. Also the final output values are limited to the range of the inputs in anticipation of further processing.
Claims3
A digital logarithmic mixer comprising:
- first add circuit means having first and second signal inputs, each of said first and second signal inputs representing a number, said first add circuit means having an output, the output signal representing the sum of said first and second signal inputs;
- second add circuit means having third and fourth signal inputs, each of said third and fourth signal inputs representing a number, said second add circuit means having an output, the output signal representing the sum of said third and fourth signal inputs;
- a subtractor circuit means, having first and second subtractor inputs, said first subtractor circuit means input being the output of said first add circuit means, and the second subtractor circuit means input being the output of said second add circuit means, said subtractor circuit means including a subtractor output;
- look up table means connected to the output of said subtractor circuit means for producing a look up table output;
- and
- third add circuit means having a first input from the output of the second add circuit means and a second input from the output of the look up table for producing a result corresponding to the logarithmic mix operation.
3 more elements
Dependencies are inferred from the claim text.