Yagi-Uda Antenna Input Impedance

[Zangetsu57]

Hello everyone,

I've written some MATLAB code to calculate the radiation pattern and directivity of a Yagi-Uda antenna. The code is similar to that which described in the Antenna Theory by Balanis text on p. 586, but written from scratch.

I'm trying to find out how to calculate the input impdance of the driven element, but haven't found any good sources on how to do this. My hunch is I need to use the matrix of current modes Inm and solve a system of equations involving voltage and impedance.

Does anyone know how to accomplish this? The best lead I have is here: **broken link removed** but it isn't specific enough.

Thanks!

 

[flatulent]

You will discover that it is relatively low compared to a dipole. This is why it is frequently the case that a folded dipole driven element is used to 4x the impedance.

 

[Zangetsu57]

flatulent,

While this is true, it is my understanding that you can tune the spacing between the driven element and the reflector to change the input impedance. I'd like to do a parameterized sweep in MATLAB, but so far have no way of accomplishing this without a way to calculate the input impedance.

 

[Antenna_Guy]

You can download a copy of NEC2 for free from locations on the internet. It will take some time to get it up and running, but it is designed for analyzing wire antennas. NEC4 is also available for purchase.

 

[kekosat300]

Hi, you could also use **broken link removed**. However, you could get the input impedance inverting the array matrix and calculating the current intensity at the driven element.