>> Hello, this is Dr. Cynthia Furse of the University of Utah.
Today, I would like to show you how capacitors and
inductors are used in this microwave circuit.
This is the receiver for a wireless local area network,
that's able to transmit signals from one computer to the other.
Computers talking digital code,
they use ones and zeros to represent letters,
numbers and so on.
But we can't transmit a one or a zero through the air.
Instead, this circuit uses two frequencies to represent the one and the zero.
The zero is 2.4 gigahertz,
and one is 2.6 gigahertz.
So we transmit one or the other of
those frequencies representing the one or the zero.
Now here's how this circuit works.
First, you start with the antenna.
The antenna is going to receive the signal,
transmit it to an amplifier that's going to
amplify the signal because it's too little when it comes in at the antenna.
It's then going to split that signal into two equal parts.
We don't know if it's a 2.4 or 2.6 gigahertz signal at this point,
but the signal is going to end up here
and here when it passes through this splitter.
Now we have two band pass filters,
one passes 2.4 gigahertz and the other passes 2.6,
and those are going to tell us which of the two frequencies we have.
There's going to be an output voltage either here,
if it's 2.4 or here,
if it's 2.6 gigahertz.
Then, it's going to come into a diode detector.
The way a diode detector works,
is it makes it so only the positive part
of the signal can be transmitted through,
and then it averages it to be able to see which of these has a voltage.
So by the time we get to the end,
there's going to be a DC voltage here,
or a DC voltage there but not both.
That will tell us if it's a zero or a one,
and then that can be brought into the computer.