INTERFEROMETERS IN RADIO PERIMETER SECURITY SYSTEMS BASED ON SOFTWARE-CONFIGURED RADIO

Abstract

This paper investigates the implementation of Software-Defined Radio (SDR) technology in modern perimeter security systems with an emphasis on interferometric direction-finding (DF) methods. The study presents an analytical and simulation-based examination of correlation interferometry as an efficient approach to determining the direction of arrival (DoA) of radio emissions from potential threats, including unmanned aerial vehicles (UAVs). A mathematical model of a two-antenna interferometer was developed, and a numerical experiment was conducted to estimate the dependence between phase difference and signal arrival angle for parameters λ0 = 0.3 m and d = 0.15 m, corresponding to a frequency of approximately 1 GHz. This frequency range (800–1800 MHz) is characteristic of UAV control, telemetry, and navigation channels, making it highly relevant for perimeter monitoring applications.

The results confirm the nonlinear nature of the relationship between phase shift and incident angle, consistent with theoretical expectations. It was found that when the antenna spacing equals half the wavelength (d = λ0/2), the system provides an unambiguous angle estimation in the 0–90° range, with optimal precision observed for small angles (≤30°). The proposed SDR-based implementation of the interferometer offers adaptability, digital calibration, and real-time reconfigurability, allowing dynamic adjustment of processing algorithms and operating frequencies without hardware replacement.

Furthermore, the paper discusses practical aspects of system design, including the impact of antenna array geometry, synchronization of reception channels, and mitigation of multipath and interference effects. The obtained data substantiate that SDR-based interferometric DF systems combine the flexibility of digital signal processing with high angular accuracy, enabling effective detection and localization of unauthorized emitters. The results can be used in the development of integrated security infrastructures, drone countermeasure systems, and advanced radiomonitoring platforms that utilize artificial intelligence for signal classification and adaptive perimeter defense.