Yagi-Uda Monopole Array with Folded Feed

Image of the Yagi-Uda Monopole Array with Folded Feed.

The standard Yagi-Uda dipole array is probably one of the most popular antennas dating back to 1920 and is mostly used in HF, VHF and UHF frequency bands. These antennas typically have low input impedance and narrow bandwidth which can be improved by replacing the dipole feed with a folded dipole.

The Yagi-Uda Monopole array with Folded-Feed replaces the dipoles with monopoles and uses a folded monopole instead of the folded dipole feed. This feed has half the impedance of the folded dipole version and does not require a balun. It can be used in applications where a ground plane is present and is consequently more rigid than dipole arrays.

Antenna Magus allows the user to design the The Yagi-Uda Monopole array with Folded-Feed for different parameter objectives like gain, beamwidth and frequency and number of elements. There is a trade-off between the performance characteristics when optimising for increased bandwidth which reduces the obtainable gain.

The following image shows a design comparison between the classic Yagi-Uda dipole array, Yagi-Uda Monopole Array with Folded-Feed and Yagi-Uda Dipole Array with Folded Dipole designed at a center frequency of 600 MHz, each plotted in its own reference impedance system. Note that the folded dipole version is ideally matched for twin flex or coax feed with Zo = 75 Ω where the other two antennas are matched at lower reference impedances.

Design comparison between the classic Yagi-Uda dipole array, Yagi-Uda Monopole Array with Folded-Feed and Yagi-Uda Dipole Array with Folded Dipole designed at a center frequency of 600 MHz, each plotted in its own reference impedance system.