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LC Filters

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I only let in the radio waves you need.
The name “LC filter” comes from the way these electronics combine an inductor (L) and capacitor (C).
LC filters can be made to handle all kinds of radio waves!

The Power of LC Filters

A skilled inspector that chooses which radio waves get past.

The world is full of invisible radio waves from all kinds of devices, like video game consoles, laptops, smartphones, and more.
LC filters can tell what kind of radio wave is coming right away. They only let in one kind of radio wave, and get it to its target.

An illustration of an LC filter at work. Inside a smartphone, it only lets in the radio waves it needs, ignoring the radio waves from the video game console, laptop, and so on.

The Secret of the Power of LC Filters

Tiny size, made to match radio waves!

LC filters are made from many layers of thin sheets.
They can be made very small because the coil and capacitor are made from thin sheets.
One type of LC filter only lets through one type of radio wave. You need an LC filter for each type of radio wave you want to use.

This is the inside of an LC filter. It is made of layers of square sheets. Each sheet has electrodes at its edges, as well as dielectric ceramics and a capacitor (C) in the middle. There is an inductor (L) shaped like a round pillar in the center. It goes through the overlapping sheets.

Friends of Inductors

Combinations of L and C

Aside from LC filters, other electronics can also combine an inductor (L) and capacitor (C).
“Couplers” do it to check if radio waves are sent at the right strength.
“Baluns” do it to make interfering radio waves (noise) less of a problem.

Trivia

What are the units?

The unit of frequency is “Hz” (hertz). “MHz” (megahertz) and “GHz” (gigahertz) are often used for LC filters. One megahertz is 1 million hertz, and one gigahertz is 1 billion hertz.
The numbers generally match with the type of radio waves. For Wi-Fi™, the numbers are 2.4 GHz or 5 GHz, and for TV a lot of LC filters are 470 to 710 MHz.

Do they have different names?

LC filters sort radio waves by frequency (the number of waves per second). LC filters that only let low-frequency waves through are called “low pass filters,” and LC filters that only let high-frequency waves through are called “high pass filters.”

Think it out!

QUESTION

The L stands for the inductor, and the C stands for the capacitor.

Find the LC Filter!