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How to measure a dipole antenna

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samtsui

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I would like to ask that how to measure a dipole antenna that don't have gnd plane?
 

elkimhoc

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you want to measure what :?:

adaptation :?: :?:
 

spikeyang

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To measure antenna radiation pattern,efficiency,you should use a full-wave microwave chamber.
 

jabidof

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If you want to measure the input impedance (S11) of the dipole, you'll have to use (or design) a balun. The dipole is a balanced antenna and cannot be measured as a single-ended device, e.g. a resistor, etc. Once the balun is ready, the "easiest" way is to design a TRL calibration kit and enter its data into the network analyzer.

Hope this helps
 

VSMVDD

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i think he askes how to calculate its lengh ????

its easy

(300 / freq)
= size of full wave
(*.96) {velocity factor}
then (/ 4) for a quarter wave size

size in meters of each element = (((300/freq)*.96)/4)

a dipole has an impedance of 75R
so look in a 50R system for ~ 1:1.5 standing wave ratio
 

jallem

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The equation could be

Length[mts] = 0.95*(1/2)*300/f[MHz]
for a dipole in the "air"

For dipole in PCB(FR4 or close) I would say the
lenght could

Length[mts] = (α)(0.95)(1/2)(300)/(f[MHz])

where α is between 0.5 to 0.7 depending of the
dielectric.
Example: fo=2450 MHz(802.11), FR4(ε=3.48)-->α=0.66
Length[mts]= 0.66*0.95*0.5*300/2450 = 3.83 cm
 

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