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Cellular Phones and You! (How does a cell phone work?)

Cellular Phones and You! (How does a cell phone work?)


Everyone carries around a cell phone, but
do you know how they work? Believe it or not, they work in a similar
manner as smoke signals and telegraphs. Never played with fire? Well done! Safety
first. However, instead of dots and dashes, or that
dangerous smoke, cell phones use electromagnetic waves. That’s all well and good, Professor, but
what’s an electromagnetic wave? Well, Jimmy, I’m glad you asked! An electromagnetic
wave is exactly what it sounds like. It’s a wave of electric and magnetic fields. But what’s a wave?! Oh, Jimmy… A wave is simply an oscillation that travels
through space or matter. For example, when you are out taking a hike and stop to toss
a rock in the pond, ripples form on the surface and expand outward. Those ripples are waves.
As we are all aware, you can describe a wave by the height of its ripple–its amplitude–and
by how many ripples cross a given point every second–that is its frequency. In cell phones, instead of rocks forming ripples
in the pond water, moving electrons form waves in the electric and magnetic fields. Now,
unlike the ripples in the water which oscillate very slowly, electric and magnetic fields
and the electrons oscillate very quickly: billions of times every second. Whenever this
occurs, we refer to that electromagnetic wave as a microwave. Microwaves are able to propagate
very long distances at literally light speed, satisfying the demands of our society for
long-distance high-speed communication. That’s great, Professor! How do I speak
microwave? Oh, Jimmy, you can’t speak microwave! But
we can use microwaves to communicate through something called “modulation.” Mod-u-la-tion? Isn’t that a Commie trick? Oh, Jimmy, not since the war. No, “modulation”
you may think sounds similar to “modify,” and you’d be correct, because modulation
is simply modifying an electromagnetic wave–for example, changing its amplitude, or its frequency,
or its phase–in order to carry data. It’s similar to when I speak to you I use volume
and tone and pitch to connote information to you. Like I say, “Oh, great! Jimmy!”
But what I’d really like to say is, “Oh, great… Jimmy.” So, by modulating electromagnetic
waves we embed information in them to transmit. Now that we understand electromagnetic waves,
let’s look inside a cell phone. Jimmy, what you see here is a futuristic iPhone
4S. There are many chips connected on a board that work together to convert your voice,
or text message, into a microwave signal flying through the air. Let’s follow a voice signal
through the phone to see how it’s processed. First, your voice, which is just a pressure
wave, is converted by a microphone to an electrical signal. This electrical signal is then digitized
so that it can be modified by software in whatever way we deem necessary. Once it is
modified, it is transformed into an analog signal, but this signal is very low frequency.
And remember, we want to operate at the microwave level. So, we must convert it up to a high
frequency. Once it’s been converted this signal is not very strong, but we want to
pump, pump, pump the power in so that we have enough strength to send that signal all the
way to the cell phone tower via the antenna. It will become an electromagnetic wave on
its way through the air. Now let’s say you want to have someone talk
to you or send you a message. Then the process is reversed. The signal is sent to your antenna
and then converted all along the way back to the speaker where it becomes an audio signal
once again. And now, Jimmy, you know how a cell phone
works! But, Professor, it’s 1957. What’s a cell
phone?

9 thoughts on “Cellular Phones and You! (How does a cell phone work?)”

  1. if that's the case could any random person with a microwave receiver eavesdrop on any coversation going on?

  2. this is how informative videos should be made with excellent explainations but a little humor too so its not boring to the audience . great job

  3. I must be from the stone age but when I look at one electronic brick and another one, understanding that the two can hear the other one talk without any wires connecting, I had to know just how it really works at the simplest level. What invisible matter connects these two communication devices together that they can instantly hear noise that is put into it? I Appreciate this video for making it clearer. I can only imagine what it was like to be the person who invented the first telephone. Before that it would have been sorcery to imagine 2 rocks held up to an ear and what is said in one could be heard in the other. I also assume that the cup string trick was done long before phones existed.
    To me I'm so fascinated that what is invisible to the naked eye, such as electromagnetic waves, sounds and signals are vital to making such devices work. I'm clearly not well educated on this subject, and I would love to learn more.

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