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How to buid virtual antenna with controllable SWR?

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goxy

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I want to build series of virtual antennas with different SWR on 2.4Ghz.
For example with SWR: 1.1, 1.15, 1.2, 1.25, 1.3, 1.35 etc. ,like etalons.
Anybody has some ideas?
 

S

sick_man

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to change the standing wave ratio

introduce a missmatch
in the feeder
or adjust the lengh of the radiator element to give a different resonant frequency

swr is a measure of N the impedance of Z match between the feeder and the radiator

the feeder will always and should be 50 or 75 R

50R is the route of 1-1 golden circle
75R " " " 1-1.5 golden circle

so best just too adjust the radiator lengh
 

goxy

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This etalons will be in room without EM apsorbers.
If I buid simple microstrip antenna, reflection will change SWR and will not be like in open air. Can I simulate antenna with resistor (max. output power from transmitter is 20mw)?
 

flatulent

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Standard method

The standard method to do this at these frequencies is to set the SWR with a resistor different than 50 Ohms (new R = 50 times SWR) and change the phase with different line lengths. You can see the effects of this on a Smith chart. In days gone by a lab would have a trombone section of coax which could change its length mechanically. You may have to have a set of striplines or coax sections to set the length. The set of different lengths should be made up of one cable for each length so tha you do not have to put a bunch together and add the unknown problems of connector effects. All lines should be 50 ohms.
 

egliu

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terminal ports

just terminal ports are required for this purpose
 

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