Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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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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 for various reasons, but the antenna usually…
Ci3
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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, since a transmitting antenna eventually should…
DK2AX
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How does an antenna radiate (how do currents flow through the wire)

I don't understand how antennas radiate a signal. I understand the basics of antennas (wavelength, electron E field, etc.), but I simply don't understand how a current can go through a wire that doesn't have negative pole. Can you please explain…
depecheSoul
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How can a 9mm square antenna pick up GPS?

I'm confused again. Per various antenna dipole calculators online, and if GPS uses 1.575 and 1.228 GHz signals, the dipole antenna needs to be on the order of 10 cm. Yet Adafruit has (or had) tiny GPS antennas of about 9mm square. And there's the…
user3303210
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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 you can't just stick a small tank circuit on a board…
Phil Frost
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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, and how they're manufactured. Can anyone provide…
Daniel Schuler
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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 immediately showed a 60.0Hz (peroid of 16.66ms),…
dpdt
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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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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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Is an omnidirectional antenna a must for a cell phone?

I have read somewhere (but unfortunately I am not able to remember where) that cell phones do need an omnidirectional antenna. If it is so, what are the reasons for that? Why a normal directional loop antenna could not be (efficiently) used ?
Standard Sandun
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Is it possible to generate light with an antenna?

An antenna (e.g. a dipole) is able to radiate at a certain frequency thanks to the EM field generated by a current provided by a signal generator at such a frequency. So, for instance: Voltage source at frequency f (representing an amplifier) +…
Kinka-Byo
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Is it possible to receive information if the received power is below the noise floor?

This relates to my previous question, which I think I have asked in the wrong way: How to insert background EM noise into pathloss equation? I wasn't really interested in detectability of the signal, and I have phrased that question very…
David K.
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True GPS Location - At the Antenna or Receiver Chip?

Suppose I have a GPS unit attached to an antenna through a 50 meter coax cable. How would the location as calculated by the GPS unit be affected by the cable length? As a bonus question, how would the time accuracy of the GPS be affected by the…
David Gardner
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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 breakout board of the same module, but the reference…
mux
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What is a 50-ohm antenna? How would you make one?

This is an intentionally very open ended question. What does it mean for an antenna to be a 50-ohm antenna at some frequency? How do you make a 50-ohm antenna for say 433.92MHz? What are the options? What are the consequences of it being different…
vicatcu
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