Re: Synthesis Of WideBand Waveform




"yogesh_gharote" <yogesh_gharote@xxxxxxxxx> wrote in message
news:YMednQcXn7z5VbrXnZ2dnUVZ_gCdnZ2d@xxxxxxxxxxxxxxx
Hi all!
I have a 400MHz bandwidth analog real waveform & I want to digitise
it using ADC. So i need to sample it at least at 800MHz. But I dont have a
suitable ADC to do that (I need to maintain a high dynamic range of around
75dB requiring a ADC chip of around 16bits which can sample at 800MHz or
more which i dont have). What i have instead is a 4 channel ADC which can
sample at upto 200MHz (each channel) . My question is can I sample the
wideband waveform using 4 channels simultaneously sampling at 200MHz (each
channel), something akin to quadrature sampling , and then combine the 4
channel streams to get back my original wideband waveform ? Is there any
tangible literature which states how this can be done? ( I have read most
of the basic sampling theorms papers which give information about higher
order bandpass sampling and interpolants but had a hard time understanding
them)So i am looking around if any of u guys have done this before.

Note: The wideband waveform which i have mentioned is bandpass waveform
centred around some freq fc>>400MHz

Regards,
Yogesh


In principle, this can be done. In practice, matching or calibrating the
ADCs and the sampling
instants to the required precision for your dynamic range is a bear.

There was an article in the Agilent Technologies Measurement mag a couple of
years ago about this technique as used in their high speed scopes, it might
be on
the T&M section of their website. There's also a patent by Howard Hilton on
calibration of a pair of ADCs used like this (7049992).

Regards
Ian


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