Large Horizontal Near-Field Scanner Based on a Non-Tethered Unmanned Aerial Vehicle

Abstract

A horizontal planar scanner with an approximate size of 40 m × 40 m has been implemented using the Unmanned Aerial Vehicle (UAV) technology. The UAV is not wired to the ground to maintain the flexibility and short setup time of a non-tethered flight. In this configuration, the UAV-mounted continuous-wave source is not phase-locked to the on-the-ground receiver. A dual-polarized reference antenna placed on the ground is hence used to retrieve the relevant phase information. The presented approach has been applied on the Pre -Aperture Array Verification System (Pre -AAVS1) of the Square Kilometre Array, which is a digital beamformed array with 16 active elements. An inverse source technique has been applied on measured Near-Field (NF) data acquired on two different sets of points (one for each electric field component) from all the receiver channels. In this way, Embedded Element Patterns (EEPs), array calibration coefficients and pattern have been determined from NF data only. The achieved results have been validated using a complementary set of Far-Field (FF) measurements and simulations.INDEX TERMS Antenna measurements, near-field measurements, unmanned aerial vehicle, digital beamforming array, phased-array radio telescopes, array calibration.

Improving the Performance of the Phaseless Sources Reconstruction Method for Antenna Diagnostics and Characterization

“…Concerning the number of measurements, extensive studies about sampling methods have been described in the literature [35]- [38], being recently introduced for the optimization of the flying path for UAV-based NF measurements [39]. Nevertheless, it must be pointed out that, in the case of UAV-based NF measurements, the effectiveness of these optimal sampling strategies would be conditioned by the 𝐹 ini = (𝑊)(𝑀 eq,ini )…”

“…It might require the UAV to fly at those different measurement surfaces, increasing acquisition time. • Use of a reference antenna placed in the vicinity of the AUT to create a controlled interference, usually referenced to as hologram, so that the phase of the NF can be retrieved through simple processing [13]- [15].…”

“…For example, the post-processing conducted in [16]- [18] is based on the fast irregular antenna field transformation algorithm (FIAFTA) [19]. A sources reconstruction method is considered in [9]- [12] (without imposing Love's condition of internal zero field, [20]) and in [13]- [15] (using Love's condition, [21]) for antenna diagnostics and NF-FF transformation.…”

A Cost-Effective Tethered-UAV-Based Coherent Near-Field Antenna Measurement System

“…This is of major interest when the environment of the antenna influences the radiated field as it might occur for broadcast [3], [4], aircraft navigation [5] or mobile communication [6] systems. On-site testing is also inevitable when the antenna is immobile or simply too large for any indoor measurement facility as is the case for the lowfrequency antenna array (LOFAR) radio telescope [7], [8] and the square kilometer array (SKA) [9]. Small hovering platforms are also suitable for field distribution measurements due to their minimal scattering behavior compared to conventional probe positioning systems.…”

A Cost-Effective Tethered-UAV-Based Coherent Near-Field Antenna Measurement System

“…This is of major interest when the environment of the antenna influences the radiated field as it might occur for broadcast [3], [4], aircraft navigation [5] or mobile communication [6] systems. On-site testing is also inevitable when the antenna is immobile or simply too large for any indoor measurement facility as is the case for the low-frequency antenna array (LOFAR) radio telescope [7], [8] and the square kilometer array (SKA) [9]. Small hovering platforms are also suitable for field distribution measurements due to their minimal scattering behavior compared to conventional probe positioning systems.…”