Mitigating interference from switch-mode power supplies in sampling receivers

This paper presents the research and development of techniques to mitigate interference from switch-mode power supplies (SMPS) in sampling receivers and also more specifically for FMCW radar receiver applications. During the system testing phase of an FMCW Radar at Reutech Radar Systems (RRS), it was found that a large false target was emerging on the Range-Doppler Map (RDM). It was concluded that the problem was originating from interference caused by the SMPS, which supplies DC power to the radar receiver subsystem. This created the need for a new DC power supply, which is able to minimize the interference itself, and mitigate the effects of the interference caused by the switching of the power supply. The study was divided four main sections, namely, research, simulation, design and evaluation. The research involved obtaining background information on sampling receivers, sampling theory, Range-Doppler Processing, SMPS’s, their effects and mitigation thereof. In the simulation phase, the research was utilised to simulate the various interference mitigation techniques. A power supply PCB was designed in the design phase to practically illustrate the techniques being utilised. Lastly, during evaluation, this PCB was evaluated against the criteria set out in the research phase. The results demonstrated that the techniques of synchronising the PWM clock to the Sampling frequency and Sweep Repetition Frequency yielded a significant reduction in the SMPS noise on the RDM. This technique may also be applied in other electronic sampling systems which perform digitisation of the input data, such as Analog to Digital Converters etc