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Centre for Array Technology (CAT)

Prof. dr. ir. Bram Nauta, dr.ir. André Kokkeler


CAT is an expertise centre for antenna array technology and processing. Beamforming is the essential functionality at the heart of sensor and imaging systems which combines signals from an arbitrary number of antenna elements into a limited number of high quality directional beams. Antenna arrays not only replace mechanically steered dish antennas but also offer opportunities to develop new techniques like e.g. multi-beaming and adaptive beamforming, exploiting digital processing capacities. Within the CAT, the focus is on ‘power efficiency’, ’flexibility’ and ‘Electro Magnetic Interference (EMI) robustness’ in the context of antenna arrays.

Research on antenna arrays comprises both the analog and digital domains and requires an integrated approach to discover solutions for multiple applications in e.g. telecommunications, radar and radio astronomy. To effectively search for these solutions, three groups of the University of Twente have joined forces: the Integrated Circuit Design (ICD) group, the Telecommunications Engineering (TE) and Computer Architectures for Embedded Systems (CAES) group.


Three focus areas are identified as the current forefront of technology: (1) beamforming, (2) cognitivity and (3) reconfigurability. Beamforming is at the heart of the node, and determines how signals are added and for example spatial selectivity is implemented. A shift from analogue to digital beamforming is strived for, with bandwidth, dynamic range and price/performance trade-offs as the current challenges. Digital beamforming on transmit is pursued as the next breakthrough. Cognitivity strives to introduce awareness of the environment and use this to adapt the performance of the array. Challenges include a low-power awareness based on spectral analysis, wideband (linear!) front-ends and intricate processing that is flexible enough to include system behaviour. Reconfigurability allows us to introduce agility into array systems so that functionality and performance can be adapted at arbitrary time-scales. Solving reconfiguration for the bottleneck functions, through filtering, switching, re-allocation or by other means, is key to reducing development cost, increasing flexibility and allowing multi-standard operation.

Research Agenda and Scientific Goals

The state-of-the-art research in the area of antenna arrays is reflected by the results of joint projects that have been, and are currently being carried out by the groups. Within the CMOS Beamforming project (STW) the use of antenna arrays in the context of a mobile satellite receiver (e.g. on top of a car) was investigated. An analog beamforming circuit has been realized in CMOS while at the same time, digital beamforming on a heterogeneous multi-core processor was implemented, realizing a hybrid beamformer. Furthermore a digital algorithm was developed to automatically steer a beam in the direction of a moving transmitter. In the context of Cognitive Radio, the AD-REM project (STW) has shown the feasibility of an extremely linear receiver for power detection through the combination of a highly linear analog receiver and a digital cross-correlator. Interference rejection performance is further improved by incorporating a flexible notch filter that was developed within the project. Another joint project of CAT partners is the WALNUT project where Noise-based Ultra-wideband transmission is exploited to effectively mitigate interference. Furthermore, CAT is heavily involved in the STARS project (FES) where reconfigurable sensor technology, both analog and digital, is researched in the context of security.

On a long term, the CAT aims at

  • Establishment of an integrated research community at the UT around the research subject ‘antenna arrays’.
  • The development of a long-lasting relation with the industry in the area of antenna array technology, with governmental bodies and service industry, culminating in multiple joint projects.
  • International visibility of the CTIT in general and the CAT more particularly with yearly publications at top conferences like e.g. ISSCC, ICC, and DAC/DATE and contributions to top journals (IEEE and ACM transactions).
  • But, the main aim is to create highly innovative technical solutions for real problems!

Core researchers

Integrated Circuit Design (ICD)
Prof. dr. Bram Nauta - analog and RF circuit design  
Prof. dr. Frank van Vliet - phased-array technology, advanced measurement techniques, MMIC’s
Dr. Eric Klumperink - analog and RF circuit design

Telecommunication Engineering (TE)
Dr. Mark Bentum - short range radio communications, novel receiver technologies, sensor networks

Computer Architecture for Embedded Systems (CAES)  
Prof. dr. Gerard Smit - low power, reconfigurable digital hardware
Dr. A.B.J. Kokkeler - analog-digital co-design, efficient realization of digital signal processing