Versatile Conical Conformal Array Antenna Based on Implementation of Independent and Endfire Radiation for UAV Applications

This paper proposed an integrated conical conformal array antenna (CCAA) for versatile application to the unmanned aerial vehicles. The CCAA consists of five flexible linear gradient subarrays with a uniform circumferential arrangement around the conical surface. It is also embedded with a pyramid reflective back-cavity (PRBC) within the conical carrier. The implementation for the three different elements of the linear gradient subarray toward impedance match and high isolation was investigated, and their identity resonant frequency (9.8 GHz) principle was developed and demonstrated. Furthermore, the PRBC was presented to improve the radiation null of the elements. A numerical 5-bit phase shifter manipulating phase difference of 72° was then combined with an 8-way power divider to obtain a fixed beam with a half power bandwidth (HPBW) of less than 24°, which indicated the backward endfire direction (θ = 180°) in terms of three circumferential arrays (R#X). Finally, the measurements with the aid of the designed phase shifter and power divider (model SHPDW4-040140S) were conducted. The experimental results show one omnidirectional coverage (360°) in the H-plane through the switching working mode of the elements with a wide scanning solid angle (≥72°) when these elements of the subarray hold an identity resonant frequency and exhibit a uniform performance in the point-to-point communication. The measurements of a narrow HPBW of less than 27.5° and the gain over 10.7 dBi in the endfire direction of the three circumferential arrays show great potential in backward blind space detection simultaneously.