>>>>> "Kulwinder" == Kulwinder Atwal <[EMAIL PROTECTED]> writes:
Kulwinder> How many channels do you need? I have done sampling of RF
Kulwinder> at 900 MHz. I sampled I and Q of the signal after it was
Kulwinder> demodulated from the carrier and sent through a mixer to
Kulwinder> produce separate I and Q channels.
Kulwinder> Do you need two channels? One for I and one for Q?
Kulwinder> Also, since your carrier is 1 GHz and your IF 10 MHz there
Kulwinder> is a mod/demod stage between your 1 GHz RF and your 10 MHz
Kulwinder> IF. It is not all done at a 'digital level'. The
Kulwinder> mod/demod of your IF is all digital.
Kulwinder> Your answer to the I and Q question will determine the
Kulwinder> type of ADC you need. - Kal Atwal.
>> Again ...our application is not the traditional analog ones as u
>> think....we do digitize the whole band and do the mod/demod at the
>> digital level....
>> 1. Physical parameter...?? Say a wideband signal centred at
>> 1Gc.....(10Mhz bandwidth...)...to be more specific let it be a
>> wideband CDMA signal.... 2. If I say 20Msps at 10 bits....
If your bandwidth is 10 MHz, then the min sampling rate you need is 20
Ms/s. Since your carrier is at 1 GHz, the sample/hold and analog
input stages of the A/D have to have sufficient bandwidth for that,
but it doesn't mean you have to sample at rates anywhere near there.
If you can do this -- and with modern A/Ds I believe you can, since
they are aimed at this exact application -- then you can do direct RF
sampling, no analog mixing to a lower IF is needed.
"Undersampling" is the term that describes this process. I remember
some nice apps notes on the subject from Harris, related to their
HSP50214 digital receiver ASIC.
paul
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