Linear Incoherent Antenna Arrays Focused in the Near Radiated Field Zone

Introduction. Antenna systems designed for operation in the near-radiated field zone,
using the principle of in-phase addition of electromagnetic waves emitted by individual sections of an aperture at the focal point, are gaining increasing attention. From the perspective of conveniently forming the required amplitude-phase distributions of partial currents, antenna arrays are commonly employed as radiating systems. An alternative approach to achieving focused spatial distributions of
electromagnetic fields involves the synchronous addition of energy from short pulses with durations on the order of a nanosecond. In this case, synchronicity at the focal point is ensured by controlling the emission timing of individual pulses based on the distances between each radiator in the antenna array and the focal point. In this initial exploration of the properties of incoherent focused antenna arrays, we limit our analysis to the behavior of the radio pulse envelope. The aim of the article is to is to
examine the main properties of incoherent focused radiation formed by the synchronous addition of individual pulses at the focal point. The research methods are grounded in established principles of electrodynamics and radio wave propagation, implemented through mathematical models simulating the propagation of a set of partial pulses in the near-radiated field zone, while accounting for the
focusing effect. The simulation results indicate that effective incoherent focusing can be achieved for focal lengths approximately equal to the linear size of the antenna array. As the focal point distance increases, the disparity in distances between the outer and central emitters to the focal point diminishes. This leads to near-synchronous pulse emission by individual emitters, ultimately reducing the focusing effect. The maximum transverse deviation of the focal point from the normal axis to the center of a linear antenna array is determined to be half the array's linear size. When the focal point shifts transversely from the normal axis, the size of the focused area increases. Conclusion. By appropriately controlling the emission timing, it is possible to steer the focal point within the bounds of the aperture size. Additionally, optimizing the coordinates of individual emitters in an incoherent antenna array, transitioning to flat or volumetric antenna arrays, and exploring arrays with complex
spatial geometries hold significant promise for achieving desired spatio-temporal distributions. These advancements will enhance the potential applications of antenna arrays focused in the near-radiated field zone for various radio engineering purposes.