Who Can Solve this ADC Puzzle !!!

[ahmed osama]

Dear all

now suppose we have ADC12DL040 from www.national.com
with
Sample Rate : 40 MSPS
Full Power Bandwidth: 250 Mhz

indeed what i know that when the sample rate is 40Mhz so MAX MAX input freq should be 20 Mhz

SO what is the 250MHZ ???????

thanks all
bye

 

[Grig]

Hello
You can work with input signal up to 250 MHz
taking into account oversampling
For ex 250MHz will be like 10 MHz

 

[safwatonline]

i am not sure but i think this means when u use the ADC to digitize an IF signal, here u can use a signal on IF carrier higher than the Nyquist rate given that the BW is respecting the Nyquist rate.
i.e. u can demodulate a signal on a carrier of 200MHz as long as the signal BW < 40MHz/2

 

[ahmed osama]

i am not sure but i think this means when u use the ADC to digitize an IF signal, here u can use a signal on IF carrier higher than the Nyquist rate given that the BW is respecting the Nyquist rate.
i.e. u can demodulate a signal on a carrier of 200MHz as long as the signal BW < 40MHz/2

u can demodulate a signal on a carrier??? how ADC can do that ??


what i know
ADC just convert the analog singal to a samples to a digital stream ..??

 

[safwatonline]

sampling the signal forms images of the signal at every fs , so u can use the sampling process to get the image of the signal around DC while the main signal is modulated, this is called subsampling (undersampling)

 

[ahmed osama]

sampling the signal forms images of the signal at every fs , so u can use the sampling process to get the image of the signal around DC while the main signal is modulated, this is called subsampling (undersampling)

:idea: :idea: a very new info. for me thanks alot

 

[pcm159]

While previous posts are correct;

The device itself needs an input bandwidth to be much greater than the sampling rate to allow the input signal to settle during the acquisition time of the ADC. The accuracy of the device depends on acquiring the signal during the small time aperture during the acquisition phase of conversion. The input needs to have a bandwidth that allows the ADC input dynamic range of the converter to settle during that aperture so as to not distort the sampled signal.

Cheers,
Peter.

 

[mahgoub]

why it can not be just wrong

 

[ahmed osama]

why it can not be just wrong

with www.national.com !!!

may be with prob. 0.000000001% lol !

so so diff.

Thanks

 

[XNOX_Rambo]

why it can not be just wrong

Well, it works fine in a BTS project I once took part in...