A Low-Cost Multicopter Based Near-Field Antenna Measurement System Employing Software Defined Radio and 6-D Laser Metrology

Abstract

A near-field antenna measurement system is presented that consists of components that are rather unusual compared to conventional antenna measurement setups. Instead of a vector network analyzer (VNA), a dual-channel wideband software defined radio (SDR) is used to measure the signals at the ports of a dual-polarized probe antenna. Instead of an exact multi-axis positioner for the antenna under test (AUT) or the probe antenna, a multicopter moves the probe along a predefined trajectory on a surface around the AUT. Instead of using expensive laser interferometry equipment, the position and orientation of the probe antenna are determined by a 6-D tracking system that was originally developed for virtual reality (VR) applications. Still, the first measurement results show the usability of the low-cost system for antenna measurements in the frequency range of mobile communication services.

Reliable Linearized Phase Retrieval for Near-Field Antenna Measurements with Truncated Measurement Surfaces

“…Suppose that we have measured an AUT twice, once with a single probe antenna and a single-channel receiver yielding 𝒃 1 ∈ C 𝑚 1 , and a second time with a two-element probe antenna array connected to a two-channel receiver resulting in 𝒃 2 ∈ C 𝑚 2 and 𝒃 3 ∈ C 𝑚 2 , where the two elements of the probe array are placed at the same set of sample locations with the number of locations 𝑚 2 . We further require that the twochannel receiver measuring 𝒃 2 and 𝒃 3 is able to observe the phase difference between its two channels -which is possible with scalar receivers via linear combinations (LCs), e.g., [29], [30], [39], or a vectorial device with coherent channels, e.g., a standard multi-channel vector network analyzer or a suitable software defined radio [42]. It follows that the phase differences between the 𝑘th entries in 𝒃 2 and 𝒃 3 for 𝑘 ∈ {1, ..., 𝑚 2 } is, thus, known.…”

“…TRANSFORMATION OF DRONE-BASED DATA WITH PARTIAL The effect of truncated NF measurements and the inherent null space in the forward operator on the performance of the linearized phase retrieval solver in (4) for PC is investigated for synthetic data on a real-world UAV flight trajectory. A simulation model of the aluminum tapered-slot antenna (ALUTSA), described in [47], was employed to generate NF data, and the sampling locations were placed on a UAV flight trajectory acquired with the multicopter and positioning system described in [42]. In this way, NF data for arbitrary probe antennas at realistically and irregularly distributed acquisition points could be generated.…”

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

“…The fused measurements form the input for the fast irregular antenna field transformation algorithm (FIAFTA) [41], [43], [44] that transforms the irregular distributed near-field measurements to the far field. Preliminary results from the initial version of the measurement system have already been given in [50], [51]. The experiences gained therein led to the evolved system in this work with improved RF and pose tracking performance.…”

Versatile Low-Cost and Light-Weight RF Equipment for Field Measurements

“…One issue in all these facilities is the signal distribution over long distances, at high frequencies, or to antennas without explicit feeding port. This is usually tackled by phaseless field measurements [4] or innovative measurement systems [5]- [11]. However, some of these solutions may be expensive or not very reliable; hence, we follow the idea of using a radio-frequency over fiber (RFoF) connection to mitigate problems with the measured phase.…”

“…Consider the scenario of in-situ measurements to verify the behavior of a device in its respective operating environment, e.g., a base station [1] or a flight navigation system [12]. A promising and flexible way to measure the radiated fields is to use unmanned aerial vehicles (UAVs) [11] or manually oper-ated handheld equipment [13]. Here, additional requirements arise due to the special needs of the measurement environment.…”