What is input signal bandwidth of ADC ?

[naisare]

input signal bandwidth

Hello,
Can any one explain me this..
What is input signal bandwidth of ADC. How this is related to the ADC throughput rate?

Thanks

 

[nl5]

adc input signal bandwidth

This is probably related to Nyquist theorem. Simply speaking, if ADC samples data with frequency f, the input signal spectrum should be limioted by f/2, otherwise the aliasing may occur.
An example: if sampling rate is 1 MHz, and input signal is 1 MHz sinewave, the sampled data will be a constant (depending on a phase shift between sampling and signal).
0.9 MHz signal will result in 100 kHz sampled data: "beating" of 1 MHz and 0.9 MHz.

Thanks.

 

[JoannesPaulus]

input signal bandwidth

The input signal bandwidth of an ADC is the maximum frequency that the adc can digitize with a loss of 3dB in SNDR (0.5 bit ENOB).
Note that this can be higher than the sampling frequency and it is not related with it. Of course, the Nyquist theorem still applies and you will have to be careful on where you place your signal bandwidth. Here is an example: your adc has a sample rate of 1MHz, therefore the input maximum bandwidth can be 0.5MHz. Your adc could still be able to sample a bandpass signal between 0.5MHz and 1MHz, or 1MHz and 1.5MHz, or 1.5MHz and 2MHz. These bands are called Nyquist zones. In this casa you are undersampling your signal.

 

[FvM]

Re: input signal bandwidth

I'm not sure about general validity of the SNDR -3dB criterion. Some manufacturers (e.g. Analog) specify simply signal bandwidth achieved in undersampling operation. The latter mainly depends on the S/H aperture window, SNDR/SINAD on additional properties. For typical high speed ADC, it's also considerably higher than nyquist frequency. A 12-Bit 50 MSPS ADC has e. g. 300 - 500 MHz signal bandwidth and 100 - 200 MHz SNDR bandwidth.

A typical application utilizing undersampling of a bandpass signal is IF processing in digital receiver designs.