A Compact Wideband Active Two-Dipole HF Phased Array

The design and construction of an upgraded HF quarter-wavelength two-dipole active array with 90(circle) difference feed was implemented in the course of a research project to perform a directional (azimuthal) investigation of interference at HF. The lack of affordable compact antennas to meet the project requirements was the incentive to develop a compact unidirectional antenna, with the maximum possible front-to-back ratio at frequencies of 20-30 MHz, where the dimensions of traditional passive antennas are enormous. By installing a low-noise very-high-input impedance amplifier in each dipole of the array, the effect of the mutual coupling between the two dipoles was reduced, improving the front-to-back (F/B) ratio over a wide frequency range. Electronic steering, easy polarization adjustment, and fast and easy deployment were the key requirements for the construction of the antenna. Therefore, a light and compact design was of the utmost importance to meet the space limitations at the monitoring site, which did not allow the deployment of a traditional HF directional antenna that employs a very long boom and elements.

Automated summary

In a research project investigating HF interference, an upgraded HF antenna array was designed and constructed to overcome the issue of traditional antenna size. By optimizing the design and installing amplifiers, the antenna performance was improved. The antenna needed electronic beam steering and easy polarization adjustment, while also being lightweight and compact to fit space constraints at the monitoring site.