PhD Students: Francois Maasdorp – Commensal Radar

13 Apr 2014 - 16:30

We recently interviewed Francois Maasdorp about his PhD proposal on the topic of “Doppler Only Tracking in Commensal Radar Applications”.

Please tell us a bit about yourself?

Francois Maasdorp Francois Maasdorp

I was born and raised in Pretoria. In 1997, I matriculated from “die Hoërskool Menlopark” and enrolled at the University of Pretoria for my undergraduate studies in 1998 in the field of Electronic Engineering. I received my B.Eng (Electronics) from the University of Pretoria in 2001, and in 2008, I completed my M.Eng (cum laude), also at the University of Pretoria, in the field of Space-Time coding for communication applications. In a nutshell, my dissertation described how multiple transmit antennas can improve a communication system’s capacity and throughput.

I started my career at the University of Pretoria (2003 to 2005), where I lectured in undergraduate courses in Digital Communications and Linear System Analysis.

Since 2006, I’ve been employed at the CSIR in Pretoria, where I am a researcher in the competency area of Radar and Electronic Warfare (EW) within the business unit, Defence, Peace, Safety and Security (DPSS).

What is your current area of study?

My current research focus lies in communications, EW, Global Navigation Satellite Systems (GNSS), Commensal Radar (CR), and I’m currently studying towards a PhD at the University of Cape Town, South Africa in the field of CR. (You can read more about the Commensal Radar Project at UCT here:

CR is a class of radar, which makes use of 3rd party illuminators of opportunity (not their own) as their source of electromagnetic (EM) energy.

As illustrated in Figure 1, target detection is established by cross-correlating the reference signal from the illuminator of opportunity with the reflected signal from the target. As FM transmitters are widely deployed over Africa, we opt to exploit FM broadcast stations and hence refer to this as a FM band CR system.

The aim would then be to detect and track commercial aircraft using FM transmitters of opportunity and deploying many cost-effective receiver units in an area of interest.

Tracking would be accomplished by measuring only the Doppler information at the respective receiver nodes, hence the topic of my PhD proposal, “Doppler only tracking in Commensal Radar applications”.

FM Band Commensal Radar System using multiple receivers.

Figure 1: FM Band Commensal Radar System using multiple receivers.

Is this a collaborative effort?

The development of a local South African prototype CR system currently involves a joint collaboration between the Council for Scientific and Industrial Research (CSIR), the University of Cape Town (UCT), which is the research partner and, lastly, Peralex Electronics, the industry partner.

The first stage in radar is usually to detect the presence of a target and secondly to track the target. My PhD focuses on target tracking and follows on the work of another UCT PhD student, Craig Tong, which addressed the target detection problem. Also, the tracking filter to be used for my PhD is the Recursive Gauss Newton Filter, developed by another UCT PhD student, Roaldje Nadjiasngar.

Why did you choose this particular project?

Given my position at the DPSS within the CSIR, this project was in-line with our long-term goals; this project also has significant signal processing opportunities as well as mathematical solutions to be addressed. That is why I chose it.

What are the real-world applications of your project?

In developing nations, Air Traffic Control (ATC) radar systems are not an economically viable solution at small airfields, as they are very expensive in both procurement and maintenance costs.

CR systems, in contrast, could be deployed at low cost due to several factors: the absence of a transmitter subsystem and its associated high power consumption, the fact that there is no need for dedicated spectrum allocation, and that there are typically no moving parts. Therefore, my PhD research will investigate a cost-effective alternative solution to expensive ATC radar systems. Also, DPSS (which is where I work) is looking into using this technology for security purposes as well.

PhD Students: Francois Maasdorp – Commensal Radar


Tell us a bit about the practical experiment that was scheduled for July 2014?

In July 2014, we deployed four receivers spread over a geographical area around the Tygerberg transmitter; one of these will be the Malmesbury receiver site. The aim is to detect and track commercial airliners approaching and leaving Cape Town International Airport using Doppler only information gathered from the four respective receiver sites – Malmesbury, Boyes Drive, Tygerberg and Blouberg. If we can achieve this, it will be a first within the International CR community.


What challenges did you anticipate?

In theory, we should be able to track the incoming and departing airliners; however, theory and practice always take time to align, usually because you tend to neglect some critical points in the theory. Thus, I foresee that the main challenge after the experiment will be to converge the theory and practice

You can read more about the field testing of the commensal radar project here: Field Tests.


 Thank you very much for participating in this interview, Francois. We wish you much success.