On-Chip RF Directional Coupler
The purpose of this project is to design and implement an on-chip RF directional coupler for full duplex RF systems that can simultaneously transmit and receive with one antenna.
A typical transformer-based wideband RF directional coupler comprising two identical, uncoupled transformers (T1 and T2) is shown below. The antenna is denoted as ANT. RF signal cancellation (left) in transformer-based couplers isolates the receiver (RX) from the transmitter (TX).
Ports A (TX), B (ANT), C (RX), and D are referred to as input, coupled, isolated, and direct ports, respectively. The inductive coupling between the primary and secondary windings of each transformer is M (k(L1L2)1/2), where k is the coupling coefficient and L1 and L2 are the self-inductances of the windings. A passive only solution consumes no power. However, monolithic transformers are lossy and require large die area.
In this project, the candidate will investigate existing technologies and then propose a wideband (6-11 GHz), differential circuit solution (passive and/or active) in sub-micron CMOS that fulfills the required specifications over PVT variations. The RF coupler must present low insertion loss (direct coupling) with high power handling capability.
Lumped-elements circuits: http://www.artechhouse.com/uploads/public/documents/chapters/bahl_ch12.pdf
Monolithic transformers for silicon RF IC design: http://ieeexplore.ieee.org/document/741890/
Full duplex radios: http://web.stanford.edu/~skatti/pubs/sigcomm13-fullduplex.pdf