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how to choose ADC for a signal frequency 150 KHz?

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ADC Selection

Hi,

Can any please explain how to choose ADC for a signal frequency 150 KHz. Considering Nyquist criteria, say Sampling Frequency, Fs = 400KHz.

What factors should I take into accound before making the selection ? How much bit resolution I would need to sample my data properly ?

I will appreciate your help.

Regards,
EE
 

ADC Selection

The ADC resolution depends on your system/application. Some need 3 bits others need 16 bits...
The choice of your sampling frequency goes the same way: if you need low resolution, you might just go with a Nyquist ADC, if you need high resolution you might use oversampling (since your signal is very low frequency).

These are just very general statements. You basically need to evaluate your system to set the ADC specifications.
 

Re: ADC Selection

JoannesPaulus said:
The ADC resolution depends on your system/application. Some need 3 bits others need 16 bits...
The choice of your sampling frequency goes the same way: if you need low resolution, you might just go with a Nyquist ADC, if you need high resolution you might use oversampling (since your signal is very low frequency).

These are just very general statements. You basically need to evaluate your system to set the ADC specifications.
Click to expand...


Thanks Joannes for your kind attention.

I didn't understand the relation between sampling frequency and bit resolution, I mean to say if I choose an ADC for my application which is 400KHz, how would I select the bit resolution ?

Will the sampling rate of ADC matter or bit resolution ? Can you please make me understand if you have to choose ADC for signal with frequency 150KHz ?
 

ADC Selection

The higher the sampling frequency the more difficult it is to achieve higher and higher resolutions with Nyquist ADCs. If your signal bandwidth is low, you can use oversampling and noise shaping in order to resolve more bits. That is the relationship between sampling rate and resolution.

Again, the choice of the resolution of your ADC depends on your system. If you need help with that, you need to say something about the system.
 

Re: ADC Selection

JoannesPaulus said:
The higher the sampling frequency the more difficult it is to achieve higher and higher resolutions with Nyquist ADCs. If your signal bandwidth is low, you can use oversampling and noise shaping in order to resolve more bits. That is the relationship between sampling rate and resolution.

Again, the choice of the resolution of your ADC depends on your system. If you need help with that, you need to say something about the system.
Click to expand...

Hey Joannes, I still didn't get my answer that how could I select an ADC if my signal has a frequency of 400KHz, how would I select the bit resolution ?

About the system, I would like to build a realtime FFT spectrum analyser display for signal ranging from 3KHz to 150Khz. Before doing FFT in DSP, I need to sample it. According to Nyquist, I should sample the signal with sampling frequency twice the higher frequency component of the signal. In this case, lets suppose, Fs = 400KHz, now how should I procees with ADC selection?
 

ADC Selection

You are now getting somewhere!
Your system is an FFT processor. Your sample rate choice is correct but you also need to consider an anti-aliasing filter in front of your ADC to limit the input signal bandwidth (unless you are sure that there is no signal above 150kHz). A higher sample rate simplifies your filter.
The next step is the resolution you want to achieve with yor FFT. Im most applications, 8 bits is enough but it really depends on your final goal.
Try to use a system model using matlab, for instance, to understand how the resolution of the ADC affects the FFT output.
 

Re: ADC Selection

JoannesPaulus said:
You are now getting somewhere!
Your system is an FFT processor. Your sample rate choice is correct but you also need to consider an anti-aliasing filter in front of your ADC to limit the input signal bandwidth (unless you are sure that there is no signal above 300kHz). A higher sample rate simplifies your filter.
The next step is the resolution you want to achieve with yor FFT. Im most applications, 8 bits is enough but it really depends on your final goal.
Try to use a system model using matlab, for instance, to understand how the resolution of the ADC affects the FFT output.
Click to expand...

Thanks for your reply.

Is it possible to model ADC in Simulink ?
 

ADC Selection

you can use the quantizer block in the "discontinuities" library. Just set the quantization interval appropriately.
 

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