The optimization of binary group sequences generated by the nonlinear code multiplexing

This paper presents the challenge of optimization of binary group sequences obtained from the nonlinear code multiplexing. It shows that at optimal element wise methodology for group sequences in a full system of orthogonal Walsh functions, a maximum criterion for the minimum distance of group sequences is equal to a maximum criterion for the minimum correlation response for the information orthogonal Walsh functions which contain group sequences. After a nonlinear code multiplexing group sequences are often contained errors, that makes using this method of multiplexing more difficult. To eliminate this source of errors the algorithm of optimization of group sequences was suggested. In this algorithm some elements of group sequences can be replaced with the opposite elements. Additionally, the algorithm of receiving of the entire group sequence among the nearest group sequences was developed. This algorithm provides considerable increasing of immunity while group sequence receiving unlike the other algorithm of element-to-element receiving in a full system of orthogonal Walsh functions.

Multiband SHEPWM Control Technology Based on Walsh Functions

The drawback of modulation ratio limitation in selective harmonic elimination pulse width modulation (SHEPWM) technology based on Walsh function transformation. In order to solve this problem, a multiband SHEPWM control technology method for a multilevel inverter based on Walsh functions is proposed. By analyzing multiband SHEPWM for multilevel inverter voltage waveforms under a Fourier series transform, the unified nonlinear multiband SHEPWM equations for a multilevel inverter with a modulation index varying from 0 to 1 can be generalized. The equations can be solved by Walsh function transform. In this way, the difficulties faced in expanding the modulation index, online calculation, and real-time control are resolved simultaneously. A seven-level inverter is taken as the example, for which the piecewise linear equations of Walsh functions under different bands and the trajectories of switching angles are given. Meanwhile, the conditions for multiple sets of solutions at such a point where the modulation index is switched over are also taken into account. The feasibility of the proposed method is verified by simulation based on MATLAB and SIMULINK. Finally, the feasibility of the practical application is proved by the experiment based on Digital Signal Processor (DSP).