Variable-Cutoff Ramp Wave Filter for ADC Linearity

The low-pass filter transitions from a fixed cutoff frequency to a dynamic, time-variable cutoff frequency. The filter operates at a first cutoff frequency for a predetermined time period after receiving the ramp wave, then switches to a second cutoff frequency (larger than the first) after the predetermined time period has passed. This dynamic adjustment allows the filter to adapt its characteristics based on the timing relative to the ramp wave start, thereby removing glitch noise while correcting waveform distortion at the starting point.

The invention changes the parameter of cutoff frequency over time. By varying the cutoff frequency parameter according to the timing after ramp wave reception, the filter can optimize its performance at different stages: using a lower first cutoff frequency initially to remove glitch noise, then switching to a higher second cutoff frequency later to maintain waveform linearity and reduce distortion at the starting point.

The low-pass filter is designed to perform multiple functions: it removes glitch noise from the ramp wave and simultaneously corrects waveform distortion at the starting point. By making the cutoff frequency time-variable, a single filter circuit achieves what would traditionally require separate noise removal and waveform correction circuits, thereby improving waveform accuracy without proportionally increasing circuit complexity.

The dynamic cutoff frequency mechanism allows the filter to automatically adapt to different operational phases without requiring external control circuits for waveform correction. The predetermined time period can be implemented using simple timing circuits, and the switch between first and second cutoff frequencies is automatically triggered by the timing mechanism, avoiding the need for complex external control systems.