I created a microstrip dipole antenna for my antenna class and whenever I feed it with a 50 ohm COAX cable, the antenna couples with the coax. In HFSS, the coax seems to resonate at certain frequencies. I do not know why the coupling in happening and how to remove it. Can someone explain it to me?
Remove COAX coupling
- Thread starter ateet101
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You are feeding a balanced load with unbalanced line. That's the short answer. Need more details about the specific antenna design and operating frequency.
Your dipole will resonate at the frequency its designed for with a very small percent of band width, where all the signal you feed it will radiate and little or no signal will be reflected back to the signal source. If you change frequency or feed it a signal wider than its inherent band width, some of the signal will reflect back to the signal source and some of the signal can travel as common mode currents on the outside of the coax and radiate. In this case the length of the coax will affect the results because the coax is now a radiating part of the antenna system when it has common mode current on the shield. I suspect your using HFSS to model the dipole and you have changed the frequency without re-scaling the dipole to the new frequency.
prcguy
prcguy
Just like those "magical" isotron antennas that people often don't realise that they haven't actually bought an antenna at all.
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