If we want to filter out noise at 120Hz and keep a signal at 10Hz, what kind of filter should we use?
- StevenLv 71 month ago
I will assume that the 120Hz is constant power line noise and the 10Hz carries some kind of intelligence, ie is some how modulated, which means that you need to pass more than just 10Hz. So the solution is a narrow rejection/notch filter of 120Hz. Typical implementations include twin-t analog filters but there are many others. A digital trick is to sample at the noise frequency so that every sample hits the same noise voltage.
- PhilomelLv 71 month ago
Go to here:
use a narrow band twin T notch filter.
This is a 120hz notch filter.
- qrkLv 71 month ago
You have the option of using a low-pass filter, a notch filter, or both. If implemented in the analog world, a notch filter will give you more rejection for a given amount of parts.
- roderick_youngLv 71 month ago
40 years ago, I would have said a low pass butterworth filter - inductors in series, and capacitors to ground. If this is a course question, than that's probably what they're looking for.
If this is a real design, the data rate is quite slow, and the signal could be easily digitized. You could buy a very low end processor such as a PIC for less than a dollar, and implement the filter digitally, which gives you other options in addition to a lowpass filter. You could anti-correlate the noise, removing it even if its frequency changes, or even if the signal frequency changes. This kind of adaptive filter can't be done with fixed analog components.
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- ElizabethLv 71 month ago
A low-pass filter ... switched capacitor filters can have extremely rapid rolloffs ... Linear Technologies used to make them but Analog Devices took them over ...