CMOS Beamforming Techniques
Duration: Sep 2007 - Dec 2011
Satellite receivers with a dish antenna receive signals that fall within the so-called “beam” of the antenna. Every antenna has a characteristic "beam pattern", which is determined by the mechanical construction of the dish antenna. When using an array of antenna elements, the beam-pattern can also be defined electronically. Such beamforming can be realized via an antenna array combined with electronics,making the array direction sensitive via phase shifters or time delays. Beamforming is the basis for realizing “smart antenna’s”, which intelligently adapt their antenna beam pattern to the local environment, e.g. to maximize received signal quality and minimize interference.
Until now, beamforming is mainly applied in military applications, and more recently in base stations for telecommunication. Applications in consumer electronics are scarce, despite of the many potential advantages. This is because beamforming is typically implemented using specialized microwave and Radio Frequency (RF) technologies with hybrid module assembly techniques, and many RF-cables and connectors, unsuitable for cost-effective mass production. For consumer electronics, a high level of integration, preferably in mainstream CMOS technology, is desired. However, CMOS technology is also increasingly important for military and high-end telecom applications, because of the large amount of digital signal processing involved in smart antennas. Thus a convergence in IC-technology for telecom, military and consumer applications can be observed, leading to the observation: "If CMOS technology can, it will". From a functionality, size and cost point of view, it would be very attractive to also realize the radio interface of a beamforming system in CMOS.
In this project we want to explore fundamental options for beamforming, aiming to find new mixed analog-digital beamforming techniques suitable for CMOS. Concretely, we propose to study techniques suitable for satellite receivers in the 10-12GHz band. This is scientifically very challenging, as virtually all known beamforming systems heavily rely on high quality RF components and on microwave structures with physical sizes related to the wavelength of the radio frequency. At 10GHz the wavelength is 3cm, making microwave component sizes too large to fit on a CMOS chip. Inductors can be realized but are not very attractive as they take large chip area and have relatively poor quality. On the other hand, recent research shows that multi-GHz samplers are becoming feasible in CMOS, while jitter in samplers is less of a problem that often thought. This might open the door to new CMOS compatible beamforming techniques, using no or only a few traditional RF components. In this project we want to explore the possibilities for such techniques, focusing on the RF and mixed analog/digital signal processing.
This project is a coorporation between the Computer Architecture for Embedded Systems (CAES) and Integrated Circuit Design (ICD) group.
- Marcel van de Burgwal: Digital Processing & Correction (CAES)
- Kasra Garakoui: RF System Design (ICD)
- Michiel Soer: RF Circuit Design (ICD)
- Andre Kokkeler (CAES)
- Eric Klumperink (ICD)
- Frank van Vliet (ICD)