Small-Sized Broadband Antenna for Unmanned Aerial Vehicles Positioning

In the paper the results of the development of a low-profile broadband small-size antenna for spatial positioning of an unmanned aerial vehicle, characterized by simplicity of design, high-quality polarization characteristics, low wind load, and high vibration resistance are presented. The developed antenna is a loop emitter made in the form of a wide strip conductor on a dielectric substrate and placed above the screen for the creation unidirectional radiation. The antenna is feed by antiphase currents at two points located on the same diagonal of loop emitter. Matching in the frequency band is provided by two groups of half-loop non-emitting stubs placed on the same dielectric substrate with loop emitter. The stubs provide the minimum reactive and most constant active input impedance in the frequency band. The design of stubs in the forms of the half-loops allows minimizing the radiation of the stubs themselves. This is due to the presence of antiphase currents of almost the same amplitude on opposite parallel sections of each stub in the case when the length of the stubs does not exceed the half-wavelength. The developed antenna is characterized by the axis-symmetric radiation patterns and matching with VSWR no worse than 1.5 in the frequency band 500–900 MHz. The width of the radiation pattern main lobe in the E-plane is 90°-100°, in the H-plane is 80°-90°. The level of cross-polarizing radiation does not exceed -25 dB in the entire operating frequency band. In this case, the antenna gain does not change much, taking values of 6–8 dBi.