Hardware-Accelerated Real-Time Spectrum Analyzer With a Broadband Fast Sweep Feature Based on the Cost-Effective SDR Platform

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.