Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [rf]

Short for Radio Frequency, i.e. frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.

Note that RF radiation is regulated in most, if not all, countries.

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What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances

What's the cheapest way to link a few microcontrollers wirelessly at low speeds over short distances. I'm looking to keep it ultra-cheap, use common discrete parts and keep it physically small. I don't care about bands and licensing so long as it…
Toby Jaffey
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What is impedance?

This is presented as both a resource for the community and a learning experience for myself. I have just enough knowledge of the subject to get myself into trouble, but I don't have the best grasp of the subject's details. Some helpful responses…
Jesse
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Can a radio transmitter somehow detect the number of receivers in its area?

During conversation, a colleague proposed that over-the-air television and radio broadcasters can determine the number of viewers or listeners based on the "load" on their signal. This seems to me like total bupkis, but he's piqued my curiosity and…
ghaberek
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What is wrong with my 50 Ω grounded coplanar waveguide?

I've been working on a 4-layer design built around the EFR32BG13 Bluetooth Low Energy SoC. While trying to measure the impedance of the antenna to build a matching circuit, I discovered that my short grounded coplanar waveguide (GCPW) transmission…
Michael Cooper
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What do I need for a basic RF circuit?

I'm looking for any resource that can help me build a very very basic RC circuit. I'm talking as simple as using RF to turn on/off an LED. The purpose of this circuit is for research and education. If anyone knows where I can get parts for simple RF…
Digital Brent
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Why do characteristic impedances matter only when traces are longer than half a wavelength?

Why are characteristic impedances of traces not considered when the traces are shorter than half a wavelength? I've had the same issue with light diffraction, which happens when pinholes are smaller than half a wavelength - it sort of makes sense…
user42875
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How come radio signals don't interfere with each other all the time?

I'm a newbie on wireless technologies and I'm trying to understand how they work. One thing I don't understand is this: How come transmissions from different devices don't interfere with each other all the time? For example, I'm living in a dense…
Ram Rachum
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Why don't we use lenses for RF?

Radio waves are a class of electromagnetic waves. Light also is a class of electromagnetic waves. By shaping a material in which the speed of light changes, we can bend the propagation direction of light, we call this a lens, and we call the speed…
valerio_new
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Why do some EMI/RF shields have holes on the top and some don't?

I am not talking about cutouts for tall components. I don't think they are for ventilation as they are often covered with manufacturer labels.
Dojo
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Can I build a camera that is sensitive at 2.4GHz?

I want to build a camera obscura as an art project that produces photos of WiFi signals. The idea for now is to build a 125cm x 125cm x 125cm Faraday cage (using fine copper mesh) with a centered hole (diameter of 12.5cm) and 20 x 20 disc shaped…
Lenar Hoyt
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FCC and CE Testing / Failure Resolution

I'm seriously thinking about (practically committed to) taking one of my products through FCC and EC testing and it's my first time doing so. It's Arduino based electronics running off a 16MHz crystal with an Ethernet Controller running off a 25MHz…
vicatcu
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At what frequencies does PCB design get tricky?

I have designed many mixed-signal PCB's where the highest-frequency component is the microcontroller's crystal oscillator itself. I understand the standard best practices: short traces, ground planes, decoupling caps, guard rings, shielding traces,…
bitsmack
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What happens at the end of a transmission line?

Let's say I wanted to make a widget containing a relay to switch between two antennas. There is a coax transmission line coming in from the transmitter, and two going out, each to a separate antenna. Inside is a relay which switches the center…
Phil Frost
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Why solder mask are not applied to RF PCBs

I've gone through some of the RF PCB designs. In which solder masking on the traces are not present. Like this one Is there a specific reason or performance issue to remove that?
Abhishek Parikh
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Why does radio reception consume so much energy?

On low-power radios, the current consumption for reception is similar to the consumption for transmission. For example, the Texas Instruments CC2652 System-on-Chip datasheet claims these values: Active-Mode RX: 6.9 mA Active-Mode TX 0 dBm: 7.3…
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