Presenter

Mr Barend Van Liempd - ETRO, Vrije Universiteit Brussel en IMEC [Email]

Abstract

Driven by the end-user's insatiable thirst for increased data throughput, wireless data networks today suffer from spectrum scarcity. As spectral resources become ever-more precious, on-going standardization effort results in more stringent specifications. As a result, the complexity of a radio's RF front-end (RFFE) increases to suit more bands, band combinations and schemes aimed towards improved spectral efficiency, such as carrier aggregation (CA) and MIMO. A clear need for tunable RF front-end circuits arises, to reduce size, cost and complexity, and enable new duplexing techniques, such as in-band full-duplex (IBFD).
This thesis presents six circuit designs that make significant steps towards the integration of tunable RFFEs. Two designs focus on solutions for IBFD and four designs focus on enabling tunable frequency-division duplexing (FDD)-capable RF front-ends. All the presented circuits are naturally tunable, relying on tunable impedance techniques to provide increased functionality or improved performance when compared to the state-of-the-art.
Key technical contributions elaborated in this thesis relate to the field of tunable impedance techniques, in particular electrical-balance (EB). A first electrical-balance duplexer implementation achieves sufficient linearity to support IBFD, achieving up to +70 dBm IIP3 and handling up to +30 dBm transmit (TX) power. A second tunable RFFE prototype combines an EB duplexer and a tunable surface acoustic-wave (SAW)-filter for dual-frequency TX-RX isolation. In addition, this work presents a highly tunable balance network, capable of synthesizing an impedance at two frequencies independently, key to enable EBDs that can support FDD operation. Furthermore, this work recognizes that balance can be achieved between two on-chip tunable balance networks instead of between only an off-chip antenna and a single on-chip balance network. Example demonstrations of this principle include a tunable phase shifter and a tunable filter, both of which are key building blocks for tunable RFFEs. Finally, an LNA is presented with tunable in- and output matching for 0.7 to 1 GHz, that achieves high linearity without the need for any adaptive tuning, achieving up to +15 dBm of IIP3 and showing insensitivity to supply variations.

Short CV

Master of Science in Electrical Engineering, Eindhoven University of Technology, 2011