Complex logarithmic ALU

Abstract

The present invention relates to an ALU implements logarithmic arithmetic and describes a method and apparatus for performing logarithmic arithmetic with real and / or complex numbers represented in a logarithmic format. In one exemplary embodiment, an ALU implements logarithmic arithmetic on complex numbers represented in a logpolar format. According to this embodiment, memory in the ALU stores a look-up table used to determine logarithms of complex numbers, while a processor in the ALU generates an output logarithm based on complex input operands represented in logpolar format using the stored look-up table. In another exemplary embodiment, the ALU performs logarithmic arithmetic on real and complex numbers represented in logarithmic format. In this embodiment, the memory stores two look-up tables, one for determining logarithms of real numbers and one for determining logarithms of complex numbers, while the processor generates an output logarithm based on real or complex input operands represented in logarithmic format using the real or complex look-up tables, respectively.

Description

technical field [0001] The present invention relates generally to computing and digital signal processing, and more particularly to pipelined logarithmic operations in an arithmetic logic unit (ALU). Background technique [0002] The ALU is traditionally used to implement various arithmetic functions such as addition, subtraction, multiplication, division, etc. on real numbers and / or complex numbers. Conventional systems use fixed-point or floating-point ALUs. ALUs using real logarithms with limited precision are also known. See, for example, "Digital filtering using logarithmicarithmetic" (N.G. Kingsbury and P.J.W. Rayner, Electron. Lett. (Jan. 28, 1971), Vol. 7, No. 2, pp. 56-58). "Arithmetic on the European Logarithmic Microprocessor" (J.N. Coleman, E.I. Chester, C.I. Softley and J. Kadlec, (July 2000) IEEE Trans. Comput., Vol. 49, No. 7, pp. 702-715) provides a high Another example of a precision (32-bit) logarithmic unit. [0003] Fixed-point programming places a bu...

AI Technical Summary

Problems solved by technology

In this way, the Coleman process still includes the complexity associated with the multiplication

[0017] While the prior art describes various methods and apparatus for implementing logarithmic operations on real numbers, the prior art does not provide a look-up table solution for complex arithmetic, which is useful in radio signal processing

Moreover, the prior art does not provide an ALU with shared real and complex processing capabilities

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