arXiv subjects

Alexander H. Paulus

Publications and source records attributed to Alexander H. Paulus.

4 recordsLinked to original sources

arXiv2026

High Speed High Signal-to-Noise Ratio Antenna Measurements -- Demonstration for UAV-Based Near-Field Measurements of Modulated Terrestrial Navigation Signals

Antenna measurements with high signal-to-noise ratio (SNR) require long measurement or integration times of the receiver and can, thus, lead to a very long duration of the measurements, especially if many frequency and spatial samples need to be collected. In order to speed up such measurements, an approach is presented, which collects all measurement samples with short measurement times, performs a Fourier transform of the measurement samples, bandpass filters the desired measurement signals with a small bandwidth, and obtains high-SNR measurement samples according to the short measurement times by inverse Fourier transform. This approach can be utilized with single-frequency continuous wave (CW) transmit signals, but also with transmit signals containing several discrete frequency components, as, e.g., found for periodically modulated CW carriers. The approach is first worked out and demonstrated for simulated test data. Next, it is utilized for the processing of modulated near-field (NF) measurement data collected via an uninhabited aerial vehicle (UAV) at a Doppler high-frequency omnidirectional radio range (DVOR) and at the localizer of an instrument landing system (ILS). The extracted CW NF data is transformed into the far field (FF) and diagnostic information is obtained from the underlying inverse source solutions.

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arXiv2026

An Indoor Localization Technique Utilizing Passive Tags and 3-D Microwave Passive Radar Imaging

A privacy-compliant indoor localization approach utilizing a 3-D near-field (NF) passive radar imaging technique is presented. This technique leverages ubiquitously radiated electromagnetic fields for imaging, with passive tags introduced to enhance the strength of scattering fields, thereby enabling precise localization at the imaging level. The method also supports localization in non-ideal imaging scenarios, such as for limited bandwidth or in highly-reflective environments. Based on their geometrical properties the simple and low-cost passive tags enable intuitive differentiation between individuals or objects. Associated privacy protection mechanisms are discussed, where the frequency-varying properties of the passive tags provide additional flexibility and potential applications under privacy and ethical considerations. Several forms of passive tags are presented, where both simulation and experimental results validate the effectiveness of the proposed passive tag designs.

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arXiv2026

Fast Full-Wave Simulation of Indoor RSS Maps for Pre-Measurement Validation in Device-Free Localization

Human localization is gaining momentum in security, healthcare, logistics, and smart spaces applications. While global navigation systems are unreliable indoor, device-free (a.k.a. passive) localization methods that exploit human-induced perturbations of radio propagation can be effectively used. This paper investigates the use of a compact full-wave electromagnetic (EM) setup as a fast and reliable tool to simulate indoor Wi-Fi propagation for human sensing. The goal is to provide a practical baseline for validating simplified propagation models, such as diffraction-based descriptions, and to reduce the need for costly measurement campaigns. Two-dimensional attenuation maps from received signal strength are generated and compared in controlled environments, focusing on attenuation statistics and interference patterns. The simulations reproduce the main spatial features, though discrepancies remain due to simplified material characterization. Diffraction-aware refinements are proposed to mitigate these effects. Overall, the approach provides an efficient pre-measurement reference to support device-free system design and to guide experimental planning.

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arXiv2026

Phase-Corrected Near-Field Microwave Imaging via Inverse Source Reconstruction with Modulated Signals

An inverse source reconstruction (ISR) based 3-D near-field (NF) passive radar microwave imaging method utilizing modulated signals is presented. The modulated signals from a non-cooperative transmitter are scattered by the targets of interest and captured by a fixed reference antenna together with an NF scanning probe at different positions. By normalizing with the reference signals, spatial coherence of the NF observations is obtained, and a single-frequency inverse source solver is subsequently utilized for ISR and image generation. A corresponding phase correction method is proposed for the coherent superposition of multi-frequency images and verified through simulations. In addition, it is shown that for realistic narrowband signals, an incoherent imaging approach is sufficient. The presented technical scheme is validated using a planar scanning system in a typical office room, where software-defined radios are employed for the transmitting and receiving of narrowband orthogonal frequency-division multiplexing signals at Wi-Fi operating frequencies. With the aid of background subtraction and reference signals, images of a mannequin placed in the office room are successfully obtained.

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