| 摘要 |
<p>A local oscillation circuit for loop frequency conversion used to realize an AV transmission system adopting 64 QAM modulation/demodulation scheme for, e.g., a digital cable system in a mobile body involving vibration, such as an aircraft. Conventionally phase variation is caused by microphonic noise attributed to vibration, and hence the bit error rate in modulation/demodulation and transmission increases because of the phase vibration. To reduce the phase variation, (a) the phase comparison frequency being set in a PLL synthesizer used as a local oscillation circuit for frequency conversion is raised, (b) the values of components of a loop filter section of the PLL synthesizer are determined so that the natural angular frequency (φn) of the loop filter section may be above the frequency range of the vibration, and (c) the loop filter section is provided with a plastic film capacitor hardly producing shock noise.</p> |
