A diffraction grating device for splitting or coupling light beams permits the divergence of the light beams to be minimized easily. A multi-channel PWM apparatus and method can reduce noise from amplifying PCM-based audio signals having adjacent signal processing paths. The flexible pipe is provided with a substantially sequential spiral shaped concavities and convexes about the periphery of the pipe along a length of the pipe. The transmission signal is multiplied by an intracell common scrambling code used in common among sectors in a same cell in addition to or in place of the multiplication of the first code. In some embodiments, the method does not affect the font of the text.