Radio Systems – EE Master Specialisation
If I ask you now: if you want to put an antenna somewhere, where would you put it? – Well, I think outside, high... Ah, these two. You put it outside and you put it high.
But why, if I ask you? – I don't know, it's intuition. Intuition, yeah. Your intuition is completely correct.
We put it outside, we put it as high as possible. But when you study Radio Systems, you'll understand why we put it outside and why we put it as high as possible. When a regular person hears 'radio'... they immediately think about broadcasting radio, right? Things that we have in our cars. But, this is something that where radio started at the beginning of the 20th century. Now, when we talk radio systems, this is everything.
Any system that uses wireless signals of a given spectrum. Which basically means up to a few hundred of gigahertz. Because above that, you're talking already about semi-optical systems. So the scope is absolutely enormous. Anything from all the communication devices. You have smartphones, walkie talkies, satellite communications, to all sorts of sensing systems, including radar.
The world is moving towards wireless in everything. Like now we see that whenever you have the chance to get rid of a wire, they do it. You have two antennas. Which you have for a transmitter and a receiver. So we look actually at the antennas themselves. How do you design antennas? How you can make systems with multiple antennas.
You have antennas: transmitters and receivers. But, there is something in between which we call the channel. And the channel is also part of our research because you might have direct connections between the transmitter and the receiver, but you also might have reflections. So, we also look at the channel. How can we model it? How can we do measurements on it? And then later on, you have connections to some equipment from the antenna. And first of all, we have some analog parts at both the transmitters and receivers.
And out of the analog parts comes digital data, so to speak. And we have some digital processing there as well. If you look at the areas that we within our Radio Systems group cover... Then basically these are the areas: We look at the digital processing algorithms.
We do not look at the analog part, but we cover the antennas, the channel once again, and then we go back like this. And if you look at the analog part, that is being covered by the ICD group. So what you learn in our specialisation is: how do you design your entire link on the physical layer? The main blocks that are essential for the transmitter and receiver. Such as modulation, error correction coding, and then demodulation, decoding, synchronisation, with the view that you have to deal with the propagation channel between the two antennas, transmit and receive. And what is so special there: the complexity of that channel. If you imagine that you just have a wire between transmitter and receiver, everything is simple because your signal just travels along a single path that you designed, right? It's there.
When you imagine that now you have antennas and in between there is you, me, there is the tables, everything. Cars if you're outside. They all reflect the signal that's being transmitted. And at the receiver that creates a very dense picture of the different reflected paths that come together. We have four mandatory courses.
There is a mandatory course in each quarter of the first year. And I teach the first one, which is Wireless Communication Systems. This is actually the course that provides the basic structure of a wireless link. Which is, again, all the blocks from the transmitter, antenna, channel, antenna, receiver that you need to have to be able to transmit information and receive it reliably.
And of course also addressing those specific things that are related to the wireless channel. So if the channel is not very well. If it's noisy, then we have to use a different kind of modulation, to make sure that it's received correctly. You feel like you're doing a puzzle. You remember when we were children? Like, we used to put the number of the letter instead of the letter and write letters to our friends with it.
It reminds me of this kind of of things. So this is kind of an introductory course, that really gives you the full perspective of how the system on a physical layer is organised. And what are the challenges that one has to deal with as an engineer to be able to have a functioning system, essentially. Then in the later courses, we dive a little bit deeper of the different aspects of a communication system. So in the second quarter, we have Smart Antennas. So in that course, we learned all the different types of antennas.
What are the fields of these antennas? How do they look like? What type of antenna to use in different applications? You basically just get to know all the antennas and then you learn how to join them in arrays, for example, to elevate the performance of that single antenna. Like when you put them all together and you put them in a specific design or a specific spacing, then you have a completely different outcome. So, Smart Antennas was a nice course. At the beginning, you feel like... For me, at least, I felt like at the beginning I was a bit lost.
But after you get the fundamental concepts, you can follow up. Then in the third quarter, we have a course which is called 5G/6G Wireless Communication and Sensing Channels. And that is actually all about: how does a channel behave? How can we model a channel? And this channel can be used for two purposes: for communication aspects, but also for sensing. So, actually related to radar and localisation. And then the last course, which is called Advanced Communication and Radar System.
This is where I participate as well. That's where we actually dive into advanced aspects such as multi-antenna systems. Which is extremely important nowadays with the development of fifth generation and sixth generation communication systems.
We combine that with also using antenna arrays for sensing purposes. The traditional realm of radio systems, wireless systems, has been communications. That's how systems essentially developed. Even from the radio, the broadcasting, it's to communicate the information.
Nowadays, we see in the past maybe decade or so that using wireless systems for sensing so, basically not for transmitting information, but inferring parameters of the surroundings based on the wireless signals, becomes more and more important and relevant. So we want to do all sorts of sensing. Sometimes, with dedicated systems such as radar-like systems. And sometimes, just using the communication infrastructure that is there. Which is also possible.
And that's where the 'radar' part in the Advanced Communication and Radar Systems comes from. Where we try to give also a feel of what else is possible beyond transferring information. What we also think is very important, is that the courses are not purely theoretical. So we think it's very important to have also practical aspects in each course. To have the students doing experiments with the equipment that we have. If you do our specialisation, then you should be familiar with spectrum analysers, network analysers and these kinds of equipment.
I like in all the courses that you have to do assignments. And these assignments actually make you understand what was being studied in theory. When you do assignments or design...
Like, for example, we designed kind of a modulator and we put a signal at the input and we expect something at the output that we learned in theory. So if we did not get what we expected, we know that we did something wrong in building that modulator. So you see exactly how a parameter can change the whole signal at the output. So it was very nice. Essentially, we use our lab facilities where we have the equipment that's required. For instance, if we do something closer to a project, we can use, for instance, software defined radio.
Which is a radio that can be reconfigured in software. So on your on your PC to perform different tasks. So everything can be reconfigured. The frequency, the waveforms, what you do, and the receiver. So that's very nice. Because then you can actually emulate various systems.
You don't have to have a specific purpose hardware. You have a general transceiver and everything else is done in software, essentially. We use those quite extensively in our practical sessions.
Furthermore, there is five EC, which is mandatory and spent on academic skills. From the year 2025-2026 onwards, the course electromagnetic compatibility will be mandatory as well. This is a great addition, since the mandatory courses that have been mentioned mainly deal with wanted radiation. Unwanted radiation, which disturbs the proper operation of electronic devices, is discussed in the electromagnetic compatibility or EMC course. The remaining 30 credits can be spent on elective courses.
On the web page of Radio Systems there's a list of electives that you can choose from. Some of them are actually recommended to be taken in combination with some of the courses that we need to take as Radio Systems students. So, for example, microwave techniques is a very important course for for us because it has to do with how to connect an antenna to its feeding line. How the electromagnetic fields can be affected. When we wanted to take Smart Antennas, it was recommended that we follow that Microwave Techniques course beforehand. But you also are free to choose whatever you find interesting.
And once you form your study programme, you show it to your supervisor and then he can approve it. From my perspective, there are two different possibilities. You can either say I really want to dive into one specific aspect and follow all kinds of courses that are related to that specific aspect. One example, could be that if you are really interested in 'how can I implement a communication system on chips' then you can follow all kinds of courses related to chip design.
What I think is also interesting is to say: 'No, I really would like to have a broader view.' So, having different topics that are related to communication systems. So you could, for example, say that, I'm not going to look at the design of chips, but you could also say... 'I could just look at software development in the context of software defined radio.' Or you could even say: 'I also want to know a little bit about artificial intelligence.'
– So, how did you approach your electives? Yeah, actually, I like mathematics. So I tried to choose some courses that are about, for example, statistics and probabilities. I also went a bit for the general networking courses. So I did some courses in mobile networking. I did a course that I actually really, really enjoyed. And it was Performance Evaluation.
And it's basically about queuing techniques. For example, if you have multiple users to serve and they need to wait, for example, in a queue to get served. What is the best queuing technique to use in every situation? Depending on if you have a priority for some services, or if you have like different number of queues.
I learned from that course to think critically. So in principle, the second year is filled with an internship and also the graduation process: the master thesis project. I did my internship in a consultancy company. What I did in my internship is kind of an electromagnetic compatibility study in the wireless systems. So how can we ensure that a wireless control system that is being used in a water lock to open and close the gate of that lock... How can we ensure that this system can work properly in the existence of the electromagnetic fields from all the electric systems? What if we put it inside a room? What if the weather was rainy or snowy? How does that affect the performance of that system? I combined my theoretical knowledge from all the courses that I took and put them in that research.
So it was a way to wrap up what I learned in my Radio Systems courses. You have quite some companies where you can do your internship. So, for example, one of our students went to an antenna design company and designed an antenna.
So, from scratch, with specifications from the company using the design tools to design it. But also the company manufactured the antenna and measurements were being done by the student in order to verify the behaviour of the antenna. So that is one of the examples. And the thesis is in the group? The thesis, it is in principle in the group. We also have the opportunity to do master thesis projects within companies as well, but it's always under supervision of the university.
Currently I'm doing the last steps, which are the master thesis. I began with it a couple of weeks ago. And I hope to be finished within the next six months.
– OK. And how do you like your thesis so far? It's an interesting topic, actually. I'm doing it with the Rijksinspectie Digitale Infrastructuur which is basically the inspection department in the Netherlands.
They do regular spectrum monitoring. So, they measure data continuously. And what I will be doing in my thesis is finding the best fit model that is provided by the ITU, the International Telecommunication Union.
So they have models to predict the received fields. And what I'll be doing is: to find the best model that fits the measured data. And later on, they want to automate the process of finding the illegal signals or the signals that are deviating from the licence they have.
Or if any provider is transmitting with more power or using more spectrum than is allowed for that provider. – What kind of career perspectives do you have, if you are specialised in Radio Systems? So there are different options you have. So, you can go to industry. Many students go to industry. There are quite a lot of companies that are looking for our students. Companies like Thales, but also manufacturers of measurement equipment like Rode and Swartz.
Also other companies in this area which are a little bit smaller but really specialised governmental institutions. For example, quite some students work at RDI at this moment. That's the former Agentschap Telecom.
We also have examples of students afterwards working in companies that do all sorts of, for example, sport tracking systems. Where you want to know where the players are. On top of that sensing their conditions.
Perspiration, the heart rate and so on. And the third option is of course that you start a PhD. We do a lot of research in various applications. The ones that I'm particularly interested in have to do with all sorts of sensing type of tasks. For instance, we all know about radar systems Where you have a signal that is being generated at the transmitter.
That signal is being reflected from various objects in the environment and received back at the receiver. So nowadays you see that this kind of sensing radar type systems they enter into all sorts of critical applications. For example in healthcare, where you can estimate the breath rate or even a heartbeat of a person remotely. In a non-contact way.
These kind of systems also are used in assistant driving. where you want to detect various objects along the road: pedestrians, bicycles. For example that we work on insect tracking. The number of insects is decreasing quite rapidly and actually biologists don't know why this is the case.
And actually they don't know the behaviour of insects that well. So what they really would like to do is study the behaviour of insects. That can be done by attaching a very small antenna on an insect. And by means of radar, tracking movements of insects.
The tags that we put on the insects are very simple. In essence it's just an antenna with a diode and a small loop across the diode to provide a path for the direct current. And also to assist the matching between the antenna impedance and the diode impedance. What happens is... Imagine you have an antenna and you have a diode.
A diode is a non-linear device. Which means that the relationship between the output and input is not a linear one. So when a signal arrives at the tag antenna the antenna intercepts a portion of the signal and that is basically a voltage that comes to the diode. So if there is enough of that signal to forward bias the diode, then it starts operating as a regular diode.
And what you see as an output on an input you have a sinusoidal wave. At the output you have a rectified wave. Which means that you have a signal for half the time and then for the other half of the time there is nothing. If you do the math, it turns out that if you just compute a Fourier transform of that rectified output of the diode. Then that output contains harmonics. So that is your non-linearity.
You had an input at one frequency and then suddenly you have an output at all those harmonic frequencies. And if you design your tag, meaning antenna with the diode together, such that it's optimised to receive the signal at given frequency and then re-radiate back a signal at another frequency. Usually it's a second harmonic because it's just the strongest.
Then you get yourself a non-linear frequency multiplier. And your return signal is now at a different frequency. So this is how the tag really works. They're still pretty large for practical application.
This is because we do prototyping at higher frequencies just for convenience purposes. If you have something that's a few millimetres in size it's really difficult to handle it. And of course also to manufacture. But the goal is to having these prototypes now to scale them up in frequency. And as you might know and you will learn in the Radio Systems specialisation the higher the frequency, the smaller is the antenna that you can make.
Our goal is to shrink that tag that you see right now about three times to a size of five times five millimetres. And that would be already quite useful for a lot of insect species. You can really work on hardware, software, mathematical modelling. And use that in order to make a wireless system. I think right now... Well maybe it's always like that.
But I feel that it's a very exciting time, because the amount of different use cases and really different applications is just increasing very quickly. Because the technology... Well, the cheap technology has come to the level where you can do a lot of things: quick, cheaply, with low power consumption. And that allows us, as more kind of system engineers, to enter into the domains, in the application areas where such systems haven't been possible before. Right? The mobile, compact...
Enabling remote non-contact monitoring, tracking, detection, sensing of all sorts of things. And that's very exciting. So that's what what's nice about Radio Systems. That's what I like about Radio Systems, is that you actually understand the things that you do when you talk about wireless communication that everybody does.
But quite a few people know why we do it. So, that's what I like about it.
2025-02-16 05:52
