What is the way you use to filter the noise of your signal?  - Page 1
Forum section: electronics / projects

author: Dhanushka
author_rank: Regular Contributor
timestamp: May 03, 2020, 11:30:48 am
content: When I design some hobbyist electronics, usually signals related stuff, if they have some noise, then I can take the FFT power spectrum, design filters to eliminate unwanted peaks. But this filtering path must goes beyond the hobbyists scope of view. I would like to know the your way related to your fields of experience such as audio, ECG, RF etc.Also, I think, it is better to tell us, if there are any great books, tutorials, websites etc. related to noise filtering you know.Thanks.

author: cdev
author_rank: Super Contributor
timestamp: May 03, 2020, 12:05:18 pm
content: Could you be a bit more specific as to what kind of signal, where.

author: Dhanushka
author_rank: Regular Contributor
timestamp: May 03, 2020, 06:36:38 pm
content: First of all, thanks for your reply.I was working about noise reduction of a audio signal due to ground looping on the matlab before use proper hardware DSP chip (I know, its not practical. But this is good project to learn most of the things about DSP.) When I take the FFT of the noise and the signals on matlab no huge difference. I have attached the FFT graphs as follos. Top one is Noise+Signal. Second is Noise only.Thanks

author: cdev
author_rank: Super Contributor
timestamp: May 03, 2020, 07:05:22 pm
content: You probably know more than I do.Is this helpful? there is good advice here on noise reduction in op-amp related circuits which is an appliction where noise is critical.https://www.analog.com/media/en/technical-documentation/application-notes/an47fa.pdfThis application note is a classic of the genre. Depending on the frequency another very useful technique for finding and getting rid of noise is to make a small shielded probe loop, you can make them yourself or buy them. I have a bunch of different ones I have made out of scraps of semirigid coax bought off of ebay. You can make a small square loop out of semirigid coax that loops around itself and at the tip, connect the tip to the coax shield, connect a female SMA or similar high bandwidth coaxial connector. Then you have a probe you can use to trade the noise path Depending on what frequency the noise is you should be able to use this as an H-field probe. (what you want for ground loops) A square shape is useful for getting it flat and close to the PCB.The way a board is laid out is all important. There are lots of people here who are very knowledgeable. I personally have never made a multilayer board. But what is done is basic, using ground planes to isolate a noisy signal traces and different sections with ground planes and vias to lower the impedance to ground - vias have significant impedance and inductance. Oftentimes people use multilayer boards to isolate noisy signals and protect sensitive inputs. An active device like an amplifier should be at groundyou often have multiple grounds read the parts notes over several times and take notes. make prototypes before you commit to a design. Amplifiers are great for learning on because they amplify mistakes as well as successes. See probe videos pic. Also Youtube uses sm5bsz has excellent videoson making and using a homemade h-field probe. There is no better way to learn getting rid of noise than that. You can make lots of other probe types too. I made one with a large clothes pin and two farrites that clips around wires for when you have noise that follows wires.