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Axial Ratio measurements.

Question asked by akutty on May 19, 2015
Latest reply on May 19, 2015 by akutty

Hi, 
    I am trying to simulate a Quadrifilar Helical Antenna, using the FDTD simulator in EMPro. I use four independent 50 Ohm voltage sources as feeds to the 4 ports of the antenna. The relative phase shift between successive ports must be 90 degrees. So I use the phase shift parameter in the voltage source and choose 0 deg, 90 deg, 180 deg and 270 deg as the phase shift values for each voltage source. I use broadband waveform as excitation. I am using a far zone sensor to get the field measurements.

    In the simulation setup, I choose not to get any S-parameter measurements and choose to collect steady state data for far zone sensor. This simulation log shows that all the four ports are active in this simulation. Now I have the following questions.

1. Do you see any possible issue with the above setup in order to get the needed circular polarization? (for instance, is it possible to have relative phase shift between the different independent voltage sources, by just specifying the phase shift?).

2. How to read the Axial ratio measurement? It seems to be give results in a scale of -1000s to 1000s, without any specific units. 

Thanks & Regards,
Ajith.

 

Edited by: akutty on May 19, 2015 10:46 PM

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