Adaptive equalizer with decision directed constant modulus algorithm
US6337878B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 3, 1999 |
| Grant date | Jan 8, 2002 |
| Priority date | — |
| Expiry date | Mar 3, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2025/0363
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
An adaptive equalizer for use in blind equalization systems to compensate for transmission channel distortion and noise in a digital communication system quantizes the input signal samples to generate a quantized implementation of the Constant Modulus Algorithm (CMA). To quantize the input signal samples, a nearest-element decision device (a slicer), that is typically present in a digital receiver, is used to pre-compute the quantized CMA error function. The number of unique values for the CMA error term is thereby reduced, and the reduced number of CMA error term values are stored in a lookup table. By greatly reducing the number of received signal values used in the CMA error calculation a relatively small lookup table can be used to compute the CMA error function. Passband implementation is accommodated by incorporating the signal de-rotation factor into the lookup table entries. In one embodiment the CMA multiply operation is replaced with shifts and adders. To make efficient use of shift and add operations to achieve multiplication in the adaptation process, the lookup table values are selected to be either a power of 2 or a minimal sum of powers of 2.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.