Questions tagged [antenna]

Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g. TV or radio) waves. -Wikipedia

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Antenna: Impedance matching vs. tuning

I always try to tune my pcb antennas in length, so they operate in resonance, by cutting the antenna with a scalpel and then matching the tuned antenna to the transmitter. But recently an RF engineer ...
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What's the purpose of such weird wiring inside this smart card?

Here's a scan of a stripped MIFARE Ultralight smart card That's some plastic film with (I assume aluminum) foil wiring acting as the antenna for both powering the chip and providing radio ...
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Why is an inductor not a good antenna?

[An antenna must have] current flowing along its length, so that the resulting fields radiate that energy into space. (Receiving antennas are just this process in reverse). [This] explains why ...
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Via fences for noise reduction of a chip antenna?

I'm working on a 4-layer PCB that has a wifi module and a chip antenna, the antenna is placed at the corner of the PCB and the copper beneath it is removed, I see that via fences are used on the ...
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Why does 1/4 wavelength have a ground plane and 1/2 wavelength needs none?

Why does 1/4 wavelength have to have a ground plane and 1/2 doesn't? I know that an antenna that has half a wavelength does not need the ground plane (example a dipole antenna) and when using a ...
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434MHz PCB Trace Antenna Design

Can anyone provide a reference design for a 434 MHz PCB Trace Antenna? Is it just a matter of creating a snake trace pattern about 17cm long and slapping a ground plane under it (with a trace ...
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RFID Antenna Array

Is it possible to connect more than one antenna to a single RFID reader module in order to pick up two different RFID chips at once? I would like to create an arduino project like this..
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how much power is radiated by cell towers?

I want to know how much power is radiated by cell towers of GSM (1.8 Ghz), 3G (2.1 Ghz), 4G (2.6 Ghz) ? I want links to references if exist.
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Antenna coupling via capacitor

Assume we have following section of a more or less elementary receiver circuit consisting of an resonant circuit L1 & C2 and an antenna coupled via capacitor C2 to the resonant circuit (source: ...
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How does a chip antenna work?

There are many guides to using chip antennas, with and without baluns, PCB layout considerations, etc., but I've been unable to find any information on how chip antennas work at a fundamental level, ...
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3 answers
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What does the radiation from an antenna look like?

Just out of curiosity, I searched for antenna on Google Images, and what usually shows is something like this. So I really thought that an antenna radiates in a circular and equal pattern. But as I ...
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Simulate bad cell phone reception in the lab

I'm currently developing an internet of things device that utilizes a uBlox SARA-U260 gsm/3G modem. In field testing, we have had significant software/firmware issues due to poor cell phone reception ...
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What is the physical model for energy flow in or around a lossless conductor during transient analysis? (Veritasium Electricity in Wires)

Context Veritasium - The Big Misconception About Electricity - Energy Doesn't Flow in Wires Note I do not agree with the answer (D) given by Veritasium which is only plausible if any tiny current ...
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Oscilloscope Output with its positive terminal touching human's body and negative terminal left open

it once happened that when I touched the positive terminal of the Oscilloscope input probes letting its negative terminal open, I observed sinusoidal voltage signals with 0.5V peak to peak and of ...
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1 answer
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XBee short wire antenna replacement to longer wire?

Is it possible to extend the 1mW wire antenna XBees from the short wire antenna, to a longer wire antenna? Will this harm the output stage of the XBee? The point being that I have an XBee in a metal ...
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Why is a coaxial cable unbalanced?

Let's consider a coaxial cable which supplies a dipole antenna. My reference for all my statements is here. My reference says: Note that the current along a transmission line should be of equal ...
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FM transmitter circuit working?

I am trying to understand FM transmitter circuit working basically on how a signal is imposed on to the carrier signal. I would like to get an acknowledgement on whether my understanding is correct or ...
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1 answer
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Cable length vs obstructions

tl;dr For minimal signal loss: a longer cable is better than solid obstructions. Right? I would like to enhance (the non-existing) phone signal indoors and have been thinking of connecting an ...
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Wireless water level sensor, in sump. Installation best-practices for longivity

My wireless water-level sensor is working fine, and when deployed in the sump-well, it is giving me periodic readings quite well. At this stage, I have the circuit still on a breadboard, and now plan ...
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nrf52 and Chip antenna Layout Questions

I am designing a four layer stack up PCB having nrf52832 SoC with chip antenna (2450AT18B100 Johanson Technology).It is BLE ...
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2 answers
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Shared antenna on multiple 2.4Ghz receivers

I want to use several 2.4 Ghz transcievers (not sure which IC yet, either Atmel AT86RF*** or TI CC) in order to build a simultaneous multi-channel sniffer. The transciever output is differential. I am ...
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Are the same type of antennas used for receiving and transmitting?

Short version: Is the same antenna type used for transmitting as is used for receiving if the frequency is the same? Long version: My garage door opener uses 433 MHz to receive signals from the ...
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1 answer
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How to match RF output of (30+j10) Ohms to 50 Ohm antenna with matching network?

I'm designing a matching network for a 2.4 GHz inverted F antenna on a PCB that I am also designing. I am using an ESP32-D0WDQ6 MCU, and reading from the datasheet, the output impedance for the RF pin ...
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Why are patch antennas used instead of planar dipole antennas?

As far as I know, the major advantage of patch antenna over dipole antenna is its directivity. If the planar dipole antenna can achieve the same directivity then why do we use patch antennas? Are ...
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Is this how you PCB trace a 50 ohm impedance transmission line for an RF antenna?

I am trying to use LoRa with a RFM95W module. I added this 3mm trace on the opposite side of the ground plane to try to create a 50-ohm impedance. I want to use a wire antenna to J4. I also included ...
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42 votes
8 answers
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Why is 50 Ω often chosen as the input impedance of antennas, whereas the free space impedance is 377 Ω?

In order to efficiently deliver power to a different part of a circuit without reflection, the impedances of all circuit elements need to be matched. Free space can be regarded as a further element, ...
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3 answers
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How does a Theremin "antenna" work?

I always assumed that the shape of the antennas was important; a vertical monopole for pitch and a horizontal loop for volume, thinking that this minimized their interference with each other. But it ...
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45 votes
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Why does an antenna trace have this shape?

I'm wondering why an antenna has a board trace that follows a certain "squiggly" shape. This doesn't have to apply to only antennas; I'm sure that there are other components that have changing paths ...
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Can people act like antennas?

I was watching my oscilloscope as I was holding a very short wire attached to the probe. It was showing about 0 voltage (small spikes) until I touched the metal. When I touched the metal, the scope ...
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19 votes
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What do I need in order to build and test a ferrite rod antenna for a specific frequency?

I am trying to piece together what I'd need for a small hobby project. I'd like to build something that is basically the equivalent to a home made avalanche beacon finder. Avalanche beacons transmit ...
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13 votes
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Antennas and Ground Planes

I'm looking at this datasheet for the ANT-433-HETH antenna. In the box labeled "Suggested Board Layout" I see a dimension labeled "Minimum Distance to Ground Plane" of 0.5 inches. I always thought ...
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Why is "wavelength" used as a unit for the length of an antenna?

We often refer to antenna size relative to wavelength. For example: a 1/2 wave dipole is approximately half a wavelength long. Wavelength is the distance a radio wave travels during one cycle. (...
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What power is measured by a spectrum analyzer?

Is the signal level that is shown in a spectrum analyzer power of the signal being measured. If yes then what power is it: average power, true power or peak power? Also when using a power meter for ...
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9 votes
1 answer
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PCB antenna: ground plane layers and dimensions?

I'm using an Inverted-F antenna on a Bluetooth Low Energy peripheral/device I'm designing and I'm not sure how I should design the ground plane. The ground plane should not be "too big" nor "too ...
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15 votes
5 answers
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Are antennas specified for a certain frequency?

"LTE 868 MHz Antenna" Why does 868 MHz stand for? Are antennas specified for a certain frequency or is it necessary for something like input type? For example, I want to transmit a 40 MHz RF ...
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15 votes
2 answers
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Through-Glass WiFi Antenna

I used to install a lot of in-car UHF radios & hands-free cell phone kits. I mostly worked on trucks & commercial utility vehicles fitted with bull bars, upon which I would mount a big, bulky, ...
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10 votes
3 answers
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Directionality and gain: yagi versus parabolic antenna

I have a very remote cabin at 1000m (3000f), where I have close to no phone reception, so lately I have been trying to research as much as I can fathom of radio basics, but still without being able to ...
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10 votes
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Difference between Hirose U.FL and IPEX connectors

Both these connectors are used to connect antenna to Mini PCI cards. Wikipedia does not explain the difference between those naming issues: U.FL, IPEX, IPAX, IPX,[1] AMC, MHF and UMCC is a ...
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6 votes
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Design of an electronic device to disable remote access ability of contactless payment cards without visible alterations and damage to the card

Question: How could I build an electronic device which disabled the remote interaction functionality of contactless payment cards while not affecting the functions which are accessed via the on-card ...
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4 votes
1 answer
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How does having more antenna help in a networking router

When I look at networking routers on the market, those that provide external antenna connections offer at least 2 connections. What is the reason for having 2 antenna? Most if not all, have their ...
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Reducing EMC from a long trace where one end is normally floating

Following on from this question about a PCB layout with EMC issues, I'm currently reworking the design to minimise breaks in the ground plane and try and identify any other EMC issues. One thing that ...
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7 votes
3 answers
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What will it take to build a DIY 2km (city conditions) RF transmitter (433Mhz)?

This is my first question on this site. I am not an electronics/electrical engineer so pardon my depth of knowledge. I am trying to build an RF transmitter/receiver. These are my end goals : a text (...
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6 votes
2 answers
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Cheap 2.4GHz Antenna Tuning

I am planning on making a board which will have some 2.4GHz RF capabilities, and would like to know if there is a cheap way to tune an IFA cheaply. If I had access to the right equipment I could ...
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6 votes
2 answers
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How to compare a magnetic loop antenna to a conventional antenna

I want to build a compact 1 MHz receive coil (antenna for very near field). For that I need to make a choice on whether to build a simple RF coil only consisting of wire and capacitors or using a coil ...
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High Altitude Balloon Communication

Our team is planning to make a HAB (High Altitude Ballon) project for our university. We are planning to use XBee pro 868 RF modules (we are in Europe so we can not use 900 MHz band). We have to ...
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4 votes
3 answers
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What is the bandwidth of an antenna ? and what happens when a narrow bandwidth is used?

I'm trying to understand the bandwidth of an antenna in order to choose the right one for my next project which involves a Nordic 2.4GHz radio transceiver (NRF24 series) that operates from 2400MHz to ...
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4 votes
2 answers
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adding a yagi antenna to a bluetooth dongle

I want to set up a Bluetooth link between devices that are over 2000 feet apart. Yagi antennas for 2.4GHz that can connect to routers are available. A cheap Bluetooth dongle that can be easily taken ...
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1 answer
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How does this FM transmitter work?

I'm an electronics student and I have been trying to understand this FM transmitter diagram (taken from electronicshub.org) for a long time. I had put efforts to learn it by surfing the web but parts ...
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2 votes
1 answer
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At which point and how to connect VNA on the PCB for antenna tuning?

I am working on a 2.45 GHz(Bluetooth) project. I have used a ceramic chip antenna with 50 Ω impedance for this board. I've placed a Pi network close to the antenna and also I have used an integrated ...
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1 vote
2 answers
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Why does the length of an antenna, relative to the wavelength, matter?

I cannot understand following wikipedia illustration: It shows the antenna at right angles to the direction of travel of the EM wave. The wavelength is measured in the direction of travel. So why ...
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