| 摘要 |
PROBLEM TO BE SOLVED: To generate high-frequency RF pulse by using a low-speed D/A converter. SOLUTION: An envelope curve shape is read out in the frequency area memorized on a table. Next, considering the output of D/A converter reduced by aperture effect, the envelope curve shape is corrected with the value of sinc function. At this time, when the sampling frequency is fs and the center frequency is fo of the basic wave, it is considered that the alias shape of n×fs-fo (n is natural number) inverts to the envelope curve shape at the low-frequency side and the high-frequency side. Additionally, the corrected envelope curve shape undergoes the inverse Fourier transformation to measure the digital value of the basic wave shape within the time domain. The digital value of this basic wave shape is converted to analog wave shape by using the D/A converter, and the predetermined alias is extracted with a band pass filter from the group of alias included in the analog wave shape. The extracted alias is transmitted as RF pulse. COPYRIGHT: (C)2008,JPO&INPIT
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