A modified Levenberg-Marquardt (MLM) algorithm is proposed to substitute for modified G-S (mgs) algorithm in some situations of phase-diverse phase retrieval wavefront sensing (WFS), such as the obstructed pupil, in w...
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A modified Levenberg-Marquardt (MLM) algorithm is proposed to substitute for modified G-S (mgs) algorithm in some situations of phase-diverse phase retrieval wavefront sensing (WFS), such as the obstructed pupil, in which the second derivative information is specifically employed to eliminate the local minimum stagnation. Experiments have been performed to validate MLM algorithm in WFS accuracy (less than lambda/30 RMS) referring to ZYGO interferometer results and in WFS repeatability (less than lambda/200 RMS), even the dynamic range is more than 7 lambda PV. Moreover, experiments have shown the MLM algorithm is superior to the mgs algorithm both in WFS accuracy and repeatability. (C) 2009 Optical Society of America
In this work we propose a low complexity detector for hybrid MIMO space-time codes based on linear dispersion coding. This detector is designed for systems with fewer receiver than transmitter antennas. We also presen...
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ISBN:
(纸本)9781457706387
In this work we propose a low complexity detector for hybrid MIMO space-time codes based on linear dispersion coding. This detector is designed for systems with fewer receiver than transmitter antennas. We also present a fast, scalable hardware architecture (suitable for FPGA implementation) that performs the matrix inversion required by the detector. This architecture is based on the QR matrix decomposition, implemented with a low-complexity, parallel and pipelined CORDIC with fixed-point arithmetic. This results in a 60% reduction in complexity, compared with other reported algorithms. We show that the proposed detector achieves better bit-error rates than comparable double-space-time transmit diversity (DSTTD) fixed-point detectors.
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