African VLBI Network Training Site


Invited Talk: Thursday 23 May 2019 - Dr Arnold de Beer


23 May 2019 10:00 - 11:00

Title: RFI and EMI in VLBI:
         Unintentional RFI – the threat of everyday electronics to Radio Astronomy

Author: Dr Arnold de Beer
              Electronic Energy Processing (Power Electronics) Group and Centre for Telecommunication 
              University of Johannesburg (UJ)

Radio Astronomy relies on the detection of very faint radio signals from celestial bodies. Because these signals are so faint, they are prone to man-made interference. Interference obscures natural signals and masks the radio waves from the processes radio astronomers want to study. This is called Radio Frequency Interference (RFI) and is a by-product of modern human technology. That is why Radio Astronomy is done in so-called radio quiet zones where no intentional radio waves (transmissions) are made.

RFI is either intentional or unintentional. Intentional RFI comes from radio transmitters such as TV and radio stations, remote controls, two-way communication, Wi-Fi and Bluetooth devices. Unintentional RFI comes from electronic products that are not intentionally transmitting a radio signal, such as computers, cameras, MP3 players etc. Although not made to radiate, they do emit radio frequency energy due to internal switching and oscillations in the electronics. If close enough to a Radio Astronomy receiver, they cause RFI.

This lecture focuses on how everyday electronics can be a threat to Radio Astronomy.The mechanisms of how electronics create radio emissions will be explained. These include switching and oscillation frequencies of operation and their spectra. Other topics to be addressed are the effect of distance, the sensitivity of radio telescopes and the effect of cables. To understand how everyday electronics emit, the concept of differential mode to common mode (antenna mode) conversion will be introduced. Lastly, mitigation techniques such as distance, filtering and shielding will be introduced.

More about the author:


Dr Arnold de Beer specialises in the study of Electromagnetic Compatibility (EMC) – especially in the field of power and digital electronics. His interest is in the design of converters and digital circuits which will produce a minimum of electrical and electromagnetic interference (EMI), also known as RFI (Radio Frequency Interference). He started his professional career at the Rand Afrikaans University in Johannesburg, South Africa, where he obtained a bachelors, masters and PhD in Electrical and Electronic Engineering. He studied under the renowned professors Daan van Wyk and Braham Ferreira. After more than a decade in industry, he returned to academia as senior lecturer at the University of Johannesburg (UJ), where he lectures High Speed Electronics and Electromagnetics.

He is active in two research groups at UJ. The Group on Electronic Energy Processing (Power Electronics) and the Centre for Telecommunications where he investigates the role of power and digital electronics on Power Line Communications (PLC). One of his research interests is the role technology (especially power electronics, digital electronics and PLC) plays in generating unintentional RFI that is a threat to Radio Astronomy. Dr De Beer is a member of the South African Institute of Electrical Engineers as well as the IEEE and is a US Certified iNarte EMC Engineer. He is the author of a 2-day Introductory Course on EMC and has presented on EMC to audiences worldwide.