## Antenna - Theory .com: The Antenna Site

antenna-theory.com :: View topic - Active input impedance
antenna-theory.com
Antenna Theory

Author Message
the_unforgiven
Antenna-Theory.com Newbie

Joined: 23 Jun 2009
Posts: 1

 Posted: Tue Jun 23, 2009 9:28 am    Post subject: Active input impedance Hi all, i have a question fou you. I need a formulation for the antenna input active impedance for a simple quadripole.... i mean when the two port are simultaneously feeded... sorry for my english Thank you

Joined: 03 Jan 2007
Posts: 203

 Posted: Tue Jun 23, 2009 10:30 pm    Post subject: Quadrupole Antenna I believe the quadrupole antenna is the same as the crossed dipole antenna or "crossed dipoles". I assume you mean basically 4 monopole antennas forming a plus sign (+) in this analysis. For half-wave dipoles, the impedance is roughly 72 Ohms if they are shortened to be resonant at about 0.49 lambda. If you feed two orthogonal dipoles with the same source, that is basically having two 72 Ohm antennas in parallel, so that the input impedance would be roughly 36 Ohms. To first order, the antennas are orthogonally polarized (or completely mismatched in terms of polarization - 1 dipole is vertical and the other dipole is horizontal). So from a far-field perspective, they won't influence each other to a huge degree. That said, I am not sure what the exact solution would be. For a back of the envelope calculation, use Zactive = Z_dipole/2
 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
 All times are GMT Page 1 of 1

 Jump to: Select a forum The Antenna Forum----------------Questions Related to Antenna TheoryNews
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum