Frustum-Shaped Conformal Antenna Array for Air-to-Ground Communication

In this work, a frustum-shaped conformal antenna array for Direct Air-to-Ground Communication (DA2GC) is designed and studied. The requirement calls for an omnidirectional radiation pattern, however the simple monopole or dipole is constrained only to the azimuth plane/yaw and might have deep null in elevation plane due to the aircraft body effect. This work proposes an eight elements conformal array operating at C band frequency covering 4.4 to 5.0 GHz, whose substrate has the shape of a frustum, which provides a solution that meets all the requirements. This design achieves less than 5 dB gain variation across azimuthal coverage and ensures sufficient gain at shallow elevation angles. A passive conformal array on a frustum fed with a microstrip-based $1: 8$ power divider design with results are presented first. Later, an active conformal array with switchable beam is explained. Further, a comprehensive analysis of implementation brought out, indicating that the proposed will be better switchable sectoral coverage is acceptable. This analysis also indicates that the active array configuration requires reduced power due to the increased gain of the array and as it covers only a sector at a given time.

I. Introduction

Conformal array antennas are very popular in aircraft, satellites, unmanned aerial vehicles, aerial weapons, and rockets for Radar and communication. The conformal array can also used in Direct Air-to-Ground Communication (DA2GC) for high-throughput, reliable data communication link between aircraft and ground stations. The choice between omnidirectional and directional beams depends on the sector coverage and the antenna gain requirements in a given application. Electronic scanning in a conformal array provides flexibility, removes bore sight errors, and covers a wider range of scan angles compared to planar antennas as in [1] and [2]. When designing antennas for DA2GC systems, several critical factors, such as aerodynamics, space constraints, potential interference issues, signal coverage and beamforming, durability and environment conditions, payload weight, and regulatory compliance, need to be taken into account to ensure optimal performance and reliability. Conventionally, cylindrical conformal antennas are commonly preferred, considering the ease of design and manufacturing. However, the advent of 3D printing and additive manufacturing has significantly expanded the possibilities for antenna design and fabrication. This offers good material efficiency, customized complex geometry with lightweight structures, and integrated functionality, allowing the designer to have compact and highly efficient antenna designs.