1 FSK WLAN overview

This is a receiver for an FSK WLAN. In this set of videos, I will show you how capacitors and inductors play a role in this particular circuit.

>> 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.