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AssigneeNxtwave Communications, Inc.
InventorsThomas J Endres, Samir N Hulyalkar, Christopher H Strolle, Troy A Schaffer
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An adaptive equalizer for use in blind equalization systems to compensate for transmission channel distortion and noise in a digital communication system uses multiple quantization levels for implementation of the Constant Modulus Algorithm (CMA). Different quantization levels are used in different regions of the CMA error function for both passband and baseband equalizers. In one embodiment, a quantizer with a step rise having logarithmic scale is used to digitize the CMA error function. In particular, a quantizer with a step rise in which each level of the quantizer step rise is a power of 2 is used to digitize the CMA error function. In another embodiment, a quantizer with a step rise in which each level of the quantizer step rise is the sum of two or more logarithmic scales is used to digitize the CMA error function. In particular, a quantizer with a step rise wherein each level of the quantizer step rise is the sum of two or more numbers each of which is a power of 2 is used to digitize the CMA error function. The use of logarithmic scales, the sum of logarithmic scales, powers of 2, or the sum of powers of 2 for the quantizer step rise size to digitize the CMA error function make efficient use of shift and add operations to achieve multiplication in the adaptation process.
In a digital communications receiver including an equalization filter having a plurality of adjustable parameters, and an error term calculator for updating said plurality of adjustable parameters, said error term calculator responsive to a received digital signal and the error in said received digital signal, said error being proportional to an error function, a quantization method comprising:
In a digital communications receiver including an equalization filter having a plurality of adjustable parameters, and an error term calculator for updating said plurality of adjustable parameters, said error term calculator responsive to a received digital signal and the error in said received digital signal, said error being proportional to an error function, a quantization apparatus comprising:
In a digital communications receiver including an equalization filter having a plurality of adjustable parameters, and an error term calculator for updating said plurality of adjustable parameters, said error term calculator responsive to a received digital signal and the error in said received digital signal, said error being proportional to an error function, a quantization method comprising:
In a digital communications receiver including an equalization filter having a plurality of adjustable parameters, and an error term calculator for updating said plurality of adjustable parameters, said error term calculator responsive to a received digital signal and the error in said received digital signal, said error being proportional to an error function, a quantization apparatus comprising:
An equalizer for a digital communications receiver for receiving digital symbols, said equalizer comprising:
An equalizer for a digital communications receiver for
Dependencies are inferred from the claim text.