Fast real-time digital monitoring of signal waveform quality using an FPGA

The real-time or offline monitoring of signal waveform quality is important in many applications, such as electrical power quality monitoring, measurement of waveform distortion in recording systems and monitoring of electrical excitation in active measurement systems. This study presents a signal monitoring system based on a Field-Programmable Gate Array (FPGA), which receives digitized samples of analogue voltage developed across a sense resistor and performs signal processing in real time. The symmetry of the signal in both amplitude and time are calculated and used to form an overall symmetry parameter that quantifies the 'quality' of the signal, which ought to be sinusoidal. In addition, the signal frequency and amplitude are calculated. The value of the overall symmetry parameter as well as the signal amplitude are checked against predefined limits and accordingly flagged. The results show an optimum compromise among three parameters: code execution time, usage of FPGA resources and accuracy of results. The principles and implementation of the system discussed here may find application in fields where FPGA-based detailed waveform analysis is high priority.