I am busy with Dynamic Range of an ADC including Programmable Gain Atmplifier. I try to calculate maximum Dynamic range level of my measurement system. How can i calculate Dynamic range? I have read these equations:
"SNR (dB) = 6.02x(ENOB) + 1.76 (dB)" ENOB: (efficient number of bits) also
total DR can be found by this formula; DR = SNR of ADC (dB) + Gain of PGA (dB)" According to these formulas where is the nyquist frequency? I don't understand how can Nyquist Frequency increase SNR? Can anyone explain me?
How to Nyquist Frequency increase SNR
snr
Related Solutions
If you have a multi-input ADC and can have it select among inputs that are amplified by different amounts, that's generally the cleanest approach. In some cases, one might also adjust gain by scaling down the reference voltage to an ADC.
The effectiveness of those approaches, versus simply scaling up the values read from the ADC, will vary significantly based upon the ADC design. Some kinds of ADC have a noise floor which is independent of the strength of the incoming signal, but some kinds of converters, especially delta-sigma ones, have a noise floor which varies with signal amplitude. An ideal 16-bit converter would have an SNR of about 96dB on a full-strength signal, but that would drop to 48dB on a -48dB signal. A cheaper 16-bit converter designed for audio, by contrast, might have only a 60dB SNR on a full-strength signal but still manage a 36dB SNR on a -48dB signal (reducing the signal by 48dB would only reduce the SNR by 24dB). On such a converter, feeding in a signal at -12dB and multiplying the readings by four would yield results that were not as good as feeding in a clean signal that was 12dB higher, but may degrade the SNR by a lot less than 12dB.
The cleanest way to scale signals is to use analog scaling before the ADC. Scaling digitally won't be as good, but the amount of degradation will depend upon the kind of converter used, and may or may not be objectionable.
Assuming the PIC has an analog input capable of operating at 32MHz or significantly higher than 9kHz (Nyquist Frequency), then yes it is possible to use averaging to increase the SNR.
It is important to consider the issues with respect to your SNR. For example, if the SNR is low due to transmission distance (attenuation), then averaging may not be very effective, whereas if transient spikes or emi are the source of your issues the averaging could be very helpful. In both cases, you may decide you need a hardware solution such as a pre-amlifier or a bandpass filter respectively.
I suggest you use an oscilloscope to look at the eye diagram, this will help reveal the specific problem with your received signal.
Silabs have a useful note on oversampling and averaging here.
Best Answer
I think you actually mean how can increasing the sampling rate (and by inference the nyquist rate) increase the resolution of an ADC.
I also think you meant SNR(dB) = 6.02 N + 1.76 rather than 6.02ENOB + 1.76.
Just going thru the errors in your question....
Dynamic range has also nothing to do with gain - it has everything to do with the bandwidth of your signal, the ADC sampling rate and the ADC bit-resolution. For instance, if the BW of your signal is 20 kHz the minimum sampling rate is 40kHz but, if you over sample by 4 (160 kHz) then you effectively increase the resolution of your ADC by 1 bit. Oversample by 4 times again and you retrieve another bit of resolution. This is basically the theory behind sigma delta ADCs but applies equally to any ADC.
I'd urge you to read this document by analog Devices entitled "Understand SINAD, ENOB, SNR, THD, THD + N, and SFDR so You Don't Get Lost in the Noise Floor".