Questions tagged [wavelength]
23 questions
19
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4 answers
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 wavelength of 1/4 it is usually necessary to have the…
LUFER
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What is the meaning of "longer electrical length = more wavelengths"?
Reading a Keysight-note, not sure what is the following selected line means?
I read and understood the meaning of electrical length, how it is related to bit in flight and wavelength is not clear.
student7
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3
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Why does lumped discipline not hold as dimension approaches operating signal wavelength?
I'm studying some basic introduction to the lumped matter discipline on my own. I completely understand where the first two constraints come from (i.e. lumped matter can only interact through their terminals, which is consistent with KVL and KCL),…
Ramin
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3
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1 answer
Blocking RF on same side as PCB antenna?
I have a penta-band GSM transciever on a 4-layer board, along with a matched chip antenna. Similar concept to EE.SX/questions/35836/how-do-components-on-a-ground-plane-of-monopole-pcb-antenna-effect-radiation-eff.
First few prototypes placed most…
rdtsc
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How to calculate far field distance from an antenna
I understand the formula for calculating the far field distance from an antenna is:
Distance = (2D2)/λ
Is the D in the above equation the length of the antenna under test (antenna under test is a small PCB antenna)? In which direction (1 or 2 in the…
MRB
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Reflection in low frequency conductors (not transmission line)
Is the reflection phenomenon common in RF work with unmatched source/load pairs also present at low frequencies? Or are the wavelengths so much longer than the physical conductor lengths that reflections do not matter? I.e, are reflections strictly…
jrive
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Antenna conterpoise or ground plane. Confused about length requirements
I have an appliation where i need to mount a multiband (VHF/UHF/700/800/900 MHZ) mobile antenna (picture 2) on a tower. The spec sheet for the antenna says it used a 4 foot diameter ground plane for testing. I'm considering using a mobile to base…
Frank
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1 answer
Antennas- Spacing between Reflectors & Directors in Wavelengths
I’m building an antenna and I want it to connect to channel 6 on the spectrum allocation chart (2.437 GHz). I’ve calculated the lengths of the reflectors and directors but im just a bit stuck on the spacing between the reflectors and directors.
I’ve…
Neamus
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Selection of wavelength for optical reflective sensing
Most of the reflective sensors in the market use either red or near IR wavelength and have a very short range (in the range of mm). Given the reflectance of the Si at different wavelengths and reflective material used for reflection, i need to…
KPK
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0
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1 answer
Ultrasonic phased array speaker spacing for high directivity and efficiency
(Short version of question(s) below.)
I want to make an ultrasonic parametric speaker at 40kHz, I want to drive them all at the same constant frequency to keep the electronics cheap.
When simulating the wave behavior in GIMP on one axis (so 2D), I…
TeD van Loon
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How to change the wavelength of LEDs in Proteus?
I have a problem in designing a circuit for my project.
Can anyone explain how to simulate an LED with 940, 1550, and 1650 nm in Proteus software?
Dors the emission coefficient of LEDs in Proteus help to change or control the eavelength of light…
0
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1 answer
Tuning current limitation for VCSEL laserdiode
Recently, we have bought a VCSEL laser diode, in which we can vary the wavelength by tuning the voltage and/or tuning current. Also, we got an application note in which it states as follows: "Set a current limit to 100 uA". I assume that this is a…
Kwok
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Why dimension of antenna's elements can be 1/2 and 1/4 or wave length and what about 1/3 or 1/8?
I'm an amateur and looked to the calculators of TV/3G/WiFi antennas.
All articles state I can get away with all sizes divided by 2 or 4 (for biquad antenna & the range 400MHz - 2.1GHz dividing by 4 makes antennas compact enough to keep it indoor…
gavenkoa
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How do we tell distance to target at the receiver from frequency modulation?
Was thinking about radar and how to tell distance using FM. If you send a wave with a consistent wavelength of 1 meter, and it hits a target 1000 meters away and then comes back, it will have gone 2000 meters and done 2000 oscillations. But how…
Af91
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What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave-length long?
What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave long? I have been told that this the the basis of what is known as a wave guide "Choke Joint" can someone explain the usefulness of…
Vinmann
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