| 摘要 |
PROBLEM TO BE SOLVED: To reduce phase distortion of a teletext signal. SOLUTION: A modulation wave is generated by permuting a rising edge and a falling edge of digital data with a rising waveform and a falling waveform of a sine wave at a frequency f1 (f1=1/2 transmission rate of digital data), respectively. Specifically, Δθ (Δθ=360×f1/f2) is cumulatively added synchronously to a clock signal at a frequency f2 (f2>f1) to sequentially calculate a first phase value, and a level corresponding to the first phase value is selected for each first phase value. In selection, while defining a time point, when the first phase value exceeds an integer multiple of 180°, as a waveform determination point, it is determined at each waveform determination point whether to select a HIGH level or a LOW level or to select the rising waveform or the falling waveform is determined in accordance with the current bit and the next bit of the digital data, from the waveform determination point to just before the next waveform determination point. COPYRIGHT: (C)2010,JPO&INPIT |
