Frequency (bandwidth) limits for the DFB?

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SuMa_296631
Level 5
Level 5
50 replies posted 25 replies posted 10 replies posted

(I hope this is the best forum for this question - apologies if not.)

   

I want to use the 2 channels of the DFB to create an LPF and HPF/BPF but I can;y find any information about the lower limits of the frequency response I can get from the DFB.

   

I'm currently sampling the signal at 1KHz and the LPF cutoff at 50Hz. The HPF (or BPF) wil have a lower frequency cutoff at about 0.8Hz.

   

I can use the DFB design tool to enter the various frequencies using vales such as 0.050KHz and 0.0008KHz and the graphs seem roughly correct (the scales are rather had to read with numbers like those) but I was more concerned if there was a practical lower limit for the DFB frequency response?

   

If there is, would lowering my sampling rate (for various reasons it can't go below about 400Hz as there are multiple samples that need to be taken each sampling period although not all of the items sampled wil pass through the filter) help or are there other techniques I can use to handle the bandwidth I need using the PSOC5 CY8C58LP family devices?

   

Susan

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Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Susan,

   

the sampling frequency affects the filter. At Nyquist you will not get a clean signal out. At high sampling rates the low frequencies would require a long filter chain to save all the values. My best experiences are at rates of 20-100 * Nyquist. Care must be taken so that the real taken sps matches the value set.

   

 

   

Bob

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Bob_Marlowe
Level 10
Level 10
First like given 50 questions asked 10 questions asked

Susan,

   

the sampling frequency affects the filter. At Nyquist you will not get a clean signal out. At high sampling rates the low frequencies would require a long filter chain to save all the values. My best experiences are at rates of 20-100 * Nyquist. Care must be taken so that the real taken sps matches the value set.

   

 

   

Bob

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Totally off topic but this thread gave me a laugh over the weekend.

   

Bob, the forum very kindly told me that you had replied to my question. You replied on 5/2/2016 and I had read the response shortly after you posted it. I get the email 14/2/2016 some 8 days later!

   

Susan

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