Complex signal with multiple features can not be decomposed sparsely in single feature over-complete dictionary,
so the idea of building the combined over-complete dictionary is proposed. The combined over-complete dictionary is
composed of many over-complete dictionaries with a single feature, and contains the information of every separate signal.
The complex signal has sparsity in the combined over-complete dictionary. The decomposition result of the complex signal
in a combined over-complete dictionary is contrasted with the decomposition result in an over-complete dictionary with a
single feature. Simulation results show the rationality and effectiveness of the proposed idea of the combined over-complete
dictionary.