Electrothermal Design of Bidirectional Wide-Boom Log-Periodic Antennas

A wide-boom, microstrip-fed planar bidirectional log-periodic (LP) antenna is proposed and improvements in its impedance match, radiation, and thermal performances are demonstrated. The boom width of each arm is increased by moving its virtual apexes into the other arm while preserving the small flare angle and self-complementarity. This modification widens the ground plane for the microstrip feed line and results in enhanced impedance match and gain. In addition, electrothermal multi physics analysis demonstrates that the wide-boom mitigates hot spots logarithmically developed on LP's active regions. The impedance and far-field measurements show that the fabricated antenna achieves VSWR ≤ 2 and flat gain around 5 dBi over a decade bandwidth. A non contact thermal imaging system is used to measure temperature response of the antenna under a ~5 W input power over 1.71-1.85 GHz range. The measured temperature images correlate well with the multi physics simulations, therefore validating the conclusions obtained via electrothermal analysis.