| Popis: |
In this paper, we propose a new speedup method of frequency switching time of the prescaler PLL frequency synthesizer using (N+ {{1}\over {2}}) pulse swallow programmable divider. The (N+{{1}\over {2}}) pulse swallow programmable divider can set half the division ratio ({{D}\over {2}}) in comparison with the desired division ratio D. In the improved prescaler method, since the total division ratio including ({{1}\over {2}}) fixed prescaler becomes desired division ratio D, the reference frequency which is two times bigger than that of the conventional prescaler method can be used. Therefore, the loop gain, the natural angular frequency and the damping factor are increased, and the frequency switching time can be speeded up. By the experimental results, it is observed that the frequency switching time of the improved prescaler method is two times faster than that of the conventional prescaler method. |
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