A Dual H-Shaped Ultrawideband Antenna for AAV-Based Ground Penetrating Radar

For VHF-band unmanned aerial ground penetrating radar (UAV-based GPR) applications, a novel dual H-shaped dipole antenna (DHDA) is proposed in this paper. The DHDA comprises a resistor-capacitor loading folded dipole antenna, a split director (SD), and tuning stubs. For capacitive loading requirements in VHF and lower frequency bands, conventional slit-based approaches face practical implementation challenges due to the required extremely narrow gaps. The developed RC-loading folded technique provides an optimal solution for low-frequency antenna bandwidth expansion. To further enhance the antenna gain, SD is introduced above the radiator. The near-field induction of the SD structure enables in-phase stack of the induced and primary field, and this enhancement extends into the far-field region, thereby increasing the antenna gain. Furthermore, the integrated tuning stub effectively compensates for the imaginary component of the input impedance, extending the bandwidth to higher frequencies. A prototype of the antenna is fabricated and tested, exhibiting |S11| < − 10 dB across the 30-170 MHz frequency range, while maintaining a low profile of 50 mm (0.017λ0 at 100 MHz). The antenna system is successfully integrated onto a UAV and demonstrated promising performance in subsurface geological detection.