WEBVTT

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>> Hello, this is Dr. Cynthia Furse
of the University of Utah.

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Today, I would like to show
you how capacitors and

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inductors are used in
this microwave circuit.

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This is the receiver for
a wireless local area network,

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that's able to transmit signals
from one computer to the other.

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Computers talking digital code,

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they use ones and zeros
to represent letters,

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numbers and so on.

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But we can't transmit a one
or a zero through the air.

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Instead, this circuit uses two frequencies
to represent the one and the zero.

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The zero is 2.4 gigahertz,

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and one is 2.6 gigahertz.

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So we transmit one or the other of

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those frequencies representing
the one or the zero.

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Now here's how this circuit works.

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First, you start with the antenna.

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The antenna is going to receive the signal,

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transmit it to an amplifier that's going to

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amplify the signal because it's too
little when it comes in at the antenna.

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It's then going to split
that signal into two equal parts.

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We don't know if it's a 2.4 or 2.6
gigahertz signal at this point,

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but the signal is going to end up here

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and here when it passes
through this splitter.

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Now we have two band pass filters,

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one passes 2.4 gigahertz
and the other passes 2.6,

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and those are going to tell us which
of the two frequencies we have.

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There's going to be
an output voltage either here,

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if it's 2.4 or here,

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if it's 2.6 gigahertz.

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Then, it's going to come
into a diode detector.

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The way a diode detector works,

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is it makes it so only the positive part

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of the signal can be transmitted through,

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and then it averages it to be able
to see which of these has a voltage.

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So by the time we get to the end,

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there's going to be a DC voltage here,

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or a DC voltage there but not both.

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That will tell us if it's a zero or a one,

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and then that can be
brought into the computer.