Delft-C3: The student nanosatellite

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Due to limited available space for solar cells, The Delfi -C3 satellite has limited power available. Often the power system cannot provide the transmission power required by the antenna, especially because of the limited effi ciency of the power amplifi er (PA) in the transceiver. Methods exist to optimize the effi ciency of the PA, but they tend to limit the operating bandwidth of the amplifi er and the choice of modulation scheme. This makes application of these PA’s in nanosatellites problematic. Furthermore, nanosatellites may perform a mission together in close cooperation. This implies that apart from communication to a ground station at various frequencies and data rates and apart from internal wireless communication with the on-board payloads, there will also be inter-satellite communication at variable frequencies and data rates. So there will be many frequencies, bandwidths and modulation schemes in use in one nanosatellite formation. Restrictions on mass, volume and power consumption make it impossible to fl y separate radios for each of the wireless links. One transceiver should be able to accommodate for all wireless communication. A crucial part in this is the availability of a wide-band, highly effi cient and very linear PA. In this mission a PA will be tested that utilizes over-all double loop negative feedback, using integrated transformers in the feedback network and in the frequency compensation network. It has been shown that integrated transformers work very well in a wide-band when used as feedback element. Since negative feedback is a very powerful means to linearize an amplifi er, the more non-linearity

of the active part - especially the power stage - can be tolerated. When more non-linearity can be tolerated, it is possible to increase the effi ciency of the power stage. Several experiments have shown that both a higher effi ciency and a higher linearity can be obtained using this technique. Space-qualifi cation of this technique, where integrated transformers are optimized for wide-band use in feedback amplifi ers, is crucial. Avery student’s who would like to know more about this new technology, please do come by at our Delfi -C3 room at the 18th _{fl oor in the EWI-faculty.}

Finding the right graduation assignment is quite important for every graduate, at least it is for me. My name is Faisal Ali Mubarak and I am a 23 year old Electrical Engineering student at Polytechnic Institute

Delfi -C3

The student nanosatellite

Faisal Ali Mubarak

When being asked about the Delfi -C3 nanosatellite, most of our students respond with

a mysterious look in their eyes. This gave us, members of the Delfi -C3 team, the reason

to provide the Maxwell readers with an article informing about what the Delfi -C3 is, and

how it is to work within our team. The Delfi -C3 nanosatellite is completely built by a

team of students from Electrical Engineering, Aerospace Engineering, Mathematics

and Information Technology departments. It is going to be the fi rst Dutch University

satellite ever to be fl own and is scheduled to launch in the year 2007. Providing equally

inquisitive as challenging thesis assignments to M.Sc. and B-Eng. students, it is in my

opinion a great opportunity for our Electrical Engineering students to get fi rst hand

experience and insight in designing electronics for our Delfi -C3 satellite. Delfi -C3 is

going to function as a test platform for a number of new technologies. Which are, Thin

Film Solar Cell Experiment, Autonomous Wireless Sun Sensor Experiments and the

Advanced Transceiver Experiments.

Figure 1: Delphi-C3 satellite rendering Delfi -C3

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it can be quite a task to get the satisfying assignment. Some just want to graduate, for them it doesn’t matter what the assignment really is, some know precisely what they want, but we all have one thing in common and that is to graduate. For me it is a little different story, as I want to get more then just experience and insight in electronic designing. The eagerness to wanting to know more than known has its own challenge and having so much to learn, who would ever like to stop learning? Delfi -C3 provided me with the answer. Working in a multidisciplinary team has its own challenges. Here at EWI-faculty we are located on the 18th _{fl oor in room} 130, where most of our Electrical Engineering Delfi -C3 colleagues work.

Students at Polytechnic Institute are thaught how things work, but why those things worked like that remained a great mystery for us. This is the main reason for me, to continue my study at Delft University of Technology

after graduating from Polytechnic Institute Rijswijk. Finding the right internship assignment wasn’t a very big problem for me, as I exactly knew what I wanted from my internship and Delfi provided me the opportunity for it. Under supervision of Dr. Chris Verhoeven, who supervises all Electrical Engineering students involved in the Delfi -C3 project, I completed my internship in April 2005. The internship provided experience and insight of its own. I was responsible for the Delfi -C3 ground station setup, satellite tracking & safety system and Doppler measurement system. Both applications were developed in visual programming environments, using National Instruments’ “LabView” and Hewlett Packard’s “Vee”. The goal of the security application is to park the antennas in a safe position if the wind speed exceeds certain speed limit. This application also allows users to control our antennas through TCP/IP-protocol from anywhere in the world and is developed within National Instruments’ “LabView” environment. The Doppler measurement application was developed within Hewlett Packard’s “Vee” environment, this due to the fact that it allowed much easier implementation of the GPIB-protocol needed to control our spectrum analyzer. The Doppler shift on its own turn was used to calculate the satellites’ orbit. Hereby I would like to thank Mr. Bert Belzer for providing me with his enthusiastic support and experience in HP Vee. Most important aspect of working within the Delfi -C3 team is its great learning environment. Normally it’s always nice to learn new things, but within the Delfi -C3 project learning is made fun and that’s what I liked the most about our satellite project.

Delft University of Technology provides 4th _{year students} from Polytechnic Institutes an opportunity to complete their graduation assignment and attending pre-master

Figure 2: Delphi-C3 communications architecture

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class lectures at the same time. This opportunity has been provided to students who would like to continue their study at Delft University of Technology after graduating for their B-Eng. course. At the moment I am working on my B-eng graduation assignment. Besides graduating I am also attending lectures for microelectronics pre-master class. Having decided to complete my graduation assignment within Delfi -C3 as well, not only because a great RF assignment of my interest was offered to me, it was a great opportunity to gain experience in structured electronic designing. Having this great opportunity to get real insight and experience in RF-circuit designing, as I want to specialize in RF during my M.Sc. at Delft University, I started my graduation in Delfi -C3 in February 2006. At the present moment I am designing a UHF-receiver. This receiver is part of the Radio Amateur Platform (RAP). The advanced transceiver is a payload and it is not a space proven device, so the RAP will serve as a backup communications device. The RAP must feature three communication options. These are a telecommand uplink for commanding the Delfi -C3 satellite, a telemetry downlink for transmitting the measured values to earth and a linear transponder to allow radio amateurs to communicate with each other.

The RAP is designed in two different sections: the receiver and the transmitter. Our receiver is based on the well known super heterodyne architectures as shown in fi gure 3.