WEBVTT

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Hello, my name is
Russell Hoppenstein,

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and I'm the High Speed
Data Converter Application

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Manager at Texas Instruments.

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In this RF Sampling
Series, we're

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going to look that
why RF sampling.

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And I'm going to give
you a hint to the answer,

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it's going to be bandwidth.

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But we're going to look
at a few different cases

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to see how it manifests itself.

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Now, first, we'll look at
the bandwidth considerations

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related to pulses.

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Now, if we had an
ideal impulse function

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and we did a Fourier
transform on that,

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that would convert it
into infinite frequency.

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But that's not very realistic.

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If we look at something a
little bit more realistic,

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a finite pulse in time,
like a boxcar function,

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and we translate that
into the frequency domain,

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it translates into
a sinc function.

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And what we see here
is the pulse width

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T will translate to the main
lobe width that is inversely

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proportional to T. So 1 over T.

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Now, if we take the case as
those pulses gets smaller,

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the bandwidth and the frequency
domain is now getting larger.

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And you can see the
[? extend ?] here

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as we get smaller and
smaller, that bandwidth is

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going to get higher and higher.

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And the need for an
RF sampling converter

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sampling at a very high speed
is going to be required.

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Now, looking at bandwidth
considerations related

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to frequency, sampling
theorem dictates

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that a minimum sampling rate
must be at least 2x the desired

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bandwidth.

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Now, in practice more
is generally required.

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But looking at one
case, where we're

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talking about one
large signal bandwidth,

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and so we need a
sampling converter

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that's capable of capturing
that entire bandwidth.

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But we can also look at
another case in which it's not

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one contiguous frequency space.

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But it's broken up
into two or more bands.

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And if we take both
of those together,

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and we look at the
entire system bandwidth,

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we can now capture both
of those simultaneously.

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So before we might have to have
a separate receiver for each

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of those bands.

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Now we can capture both
of them at the same time.

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And this leads me into
kind of the flexibility

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and the tunable nature of
the RF sampling architecture.

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Previously, we would have a
mixer within a synthesizer.

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We would convert that
down to the baseband or IF

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and then capture with ADC.

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But now with the
RF sampling ADC,

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we don't need to know the
exact location of our signal

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in the RF space.

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We have a bit of
tunability, if you will,

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because we can capture it no
matter where that signal is.

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And we don't even really
need to know where it lies.

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We can capture the
entire bandwidth

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and in digital
signal processing,

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we can find out where the
relevant information is

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and process from there.

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Well, thank you for listening.

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If you have any further
technical questions

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on this topic, feel free to
contact our application experts

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at e2e.ti.com.

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