PROJECT TITLE :

Fundamental Study of Influence of Ripple Noise From DC–DC Converter on Spurious Noise of Wireless Portable Equipment

ABSTRACT:

Power offer noise could be a serious concern in noise-sensitive radio frequency or analog circuits. This paper presents an analysis of the influence of the synchronous rectification buck-sort dc–dc converters for power amplifiers. An output ripple noise equation of the converter and a spurious noise equation of the carrier output voltage of the category-A amplifier powered by the converter are derived to analyze basic characteristics of those noise parts theoretically. The amplifier's output spurious noise is calculated by these equations and measured by the analysis circuit board. The spurious noise variation caused by the parameter variations of the amplifier or the converter is mentioned primarily based on these experimental and theoretical results. The spurious noise will be suppressed by decreasing the channel length modulation coefficient of the n-channel MOSFET constituting the amplifier and the natural frequency of the converter output LC filter. The spurious noise is reduced to low level below − 60 dB compared to the carrier signal by setting the channel length modulation coefficient below 0.1 V−1 and therefore the natural frequency below 120 kHz. Furthermore, when the natural frequency is below 40 kHz, the spurious noise is − 80 dB below the carrier signal.