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Negative impedance for an antenna at 1 GHz (and 50 Hz)

Posted: Wed 08 Apr 2020, 04:53
by jjmaloss
Hello. I am running a simulation where an antenna is made of an external wire and a coaxial wire. These two wires are connected through an active and passive lumped ports. Each port has a resistance of 50 ohms. The antenna is approximately 190 mm long. The frequency that I use is is 1 GHz. The passive port has an *negative* impedance of -50 ohms. This does not make much sense. Moreover, a test performed with a frequency of 50 Hz also shows a negative impedance of -50 ohms. It looks like that I am not using the software properly because in the later case, the antenna should actually behave like a basic electric circuit. I would really appreciate if someone could point to the mistake that we are making. Thank you very much in advance.

I attach the 2 simulations.

Jean-Jacques Malosse