The development of Unmanned Aerial Vehicles (UAVs), commonly referred to as drones, has introduced revolutionary changes in many areas over the past few years. However, aside from opening new possibilities, the usage of drones in an irresponsible and dangerous manner leads to many hazardous incidents. This paper presents a drone detection sensor with a continuous 2.400 GHz-2.483 GHz operational frequency range for detection methods based on passive radio frequency imaging techniques. The implementation based on Software Defined Radio (SDR) and Field Programmable Logic Array (FPGA) hardware that overcomes the 40 MHz real-time bandwidth limit of other popular SDRs is presented utilizing low-cost off-the-shelf components. Furthermore, hardware realization of the signal processing chain for specific detection algorithms is proposed to minimize the throughput between SDR and the companion computer and offload software computations. The device validation is made in a laboratory and real-life scenario and presented in relation to the sensor used in other works. The measurements indicate some detection sensitivity reduction compared to the reference receiver, consistent with hardware specifications. The final analysis demonstrates the proposed device's relevance as a sensor for obtaining machine learning datasets and as a part of a final anti-drone system.

Radio Frequency (RF) spectrum monitoring and broadband signal analysis have multiple application areas, especially in the era of a constantly growing number of wireless devices. One of the essential challenges for a spectrum sensor is to achieve an adequate measurement rate over a wide bandwidth to detect signals of short duration so that a low latency response can be provided. In procedures that require field measurements, and some compromise in accuracy is acceptable, low-cost Software Defined Radio (SDR) devices can be used instead of expensive and bulky professional spectrum analyzers. This paper introduces a real-time swept spectrum sensor based on LimeSDR-USB with custom embedded Field Programmable Gate Array (FPGA) firmware, designed to outperform similar software implementations. The Welch's spectral density estimation is implemented in hardware to minimise the USB transfer rate and offload the host PC signal processing. Furthermore, the frequency tuning state machine and cache calibration memory are also managed by the FPGA to reduce the blind time during broadband sweep. The performance of the proposed solution indicates up to 96 MHz of real-time bandwidth along with a capability of less than millisecond cumulative sweep time per gigahertz. The characteristics of various design elements are investigated and refined during simulation and laboratory measurements, whereas the final prototype implementation is verified in real-world scenarios. The results demonstrate the effectiveness of the proposed device as a sensor for propagation studies, multiband spectrum utilisation monitoring, and spectral white spaces detection.INDEX TERMS Electromagnetic analysis, field programmable gate array, radio frequency, software defined radio, surveillance.

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