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Bandstop filter design

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Hello,
I am working on Biomedical Signal Acquisition from body.
A basic problem with all these types of signal is that they are of very low amplitude therefore noise comes in it.
Can anyone guide me how to remove it accurately without having any effect on amplitude and phase of the origional signal.
Thanks
 

The trick is to reduce the bandwidth as much as possible compatible with recovering your signal. One way is to use a chopper. So right at the input you short out your signal at some low frequency (much higher then your signal frequency), say 500 HZ. Then you know that all your signals characteristics are contained within the 500Hz waveform. This you then amplify and filter it with a bandpass 500Hz filter with a bandwidth of 1Hz or so. The resultant output is rectified and filtered to recover the signals characteristics.
Frank
 

I forgot to state that the noise is of 50Hz. And the signal frequency is in the range of 0-120Hz.
 

What about if one want to increase the order too.
 

Hello,
Applying the circuit gives me the following result with a change in the shape of the waveform regardless of what the frequency is.
2c696cfcb2.jpg
 

Attachments

  • filter 2.bmp
    1.3 MB · Views: 39

Here are some more pics
 

Attachments

  • filter 1.bmp
    1.3 MB · Views: 45
  • 70 hz response.bmp
    2.3 MB · Views: 39
  • 30HZ response.bmp
    2.3 MB · Views: 38

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