Dualband LPDA antenna

Image of the Dualband LPDA antenna.

The single-band LPDA antenna is one of the most popular broadband antennas due to its simple, light-weight, construction and low-cost. The dual-band LPDA consists of two single-band LPDA antennas in a cascade arrangement facilitating dual-wide-band operation with a single feed. This configuration is specifically useful where the desired upper and lower operating bands are far apart, and the dualband configuration results in a structure that it physically shorter than a single band LPDA that covers both required bands. Within the bands of operation, the dual-band LPDA has a single linearly polarized main lobe with gains ranging between 6 and 12 dBi. Out of band performance typically results in increased backlobe levels and sidelobe levels are generally more than 10 dB down from the main lobe for a well-designed structure.

The performance graphs shown below are for an LPDA designed to work in the normalised frequency range from 0.5 to 1.5 and then from 3.5 to 4.5. It is designed for a gain of 8 dBi and a resistance of 150 Ω.

Radiation patterns at two center design frequencies.
Gain vs frequency.
Typical S11 vs frequency.