Six-port technology for millimeter-wave MIMO systems

Presently, the data rates in modern wireless communication systems are becoming higher and higher and new frequency bands and technologies are being exploited in support of high data transmissions. The millimeter-wave band is a candidate of choice to support Gbps data transmission. In addition, Multiple-Input Multiple-Output (MIMO) technology will open the way for low-cost reliable communication systems that require even higher data rates.;While the conventional heterodyne receiver has been widely applied in many kinds of communication systems due to its high selectivity and sensitivity, the direct-conversion receiver allows higher-level circuit integration by reducing the number of circuit components. Among these direct-conversion receivers, six-port scheme presents a passive circuit that acts as an interferometer. The additional diversity is produced by the quadrature outputs of the six-port circuit that are linear combinations of the unknown input signal and the reference signal. Substrate integrated waveguide (SIW) can be integrated with planar circuits easily. The design procedure is obviously simplified as a result of the existing typical design methods for the rectangular waveguide. Based on the above techniques and discussions, the millimeter-wave MIMO system based on SIW six-port circuit is presented in this dissertation.;First, the SIW power divider and hybrid coupler are presented. The implementation of those circuits is based on the SIW design rules, according to the working frequency band of interest. Several critical parameters can be manipulated to control performances of the SIW power divider and hybrid coupler. An SIW to microstrip line transition is designed for measurement purposes. Simulation results of the circuits show good performances.;Second, based on the studied and designed SIW power divider and hybrid coupler, the six-port circuit is presented. Three types of six-port architecture are compared, with one of them chosen to work in our millimeter-wave MIMO system demonstration. Simulation and measurement results agree well and guarantee a good performance of the proposed circuit itself and wireless high-speed communication system in which the circuit is embedded.;Finally, the 2 x2 millimeter-wave MIMO system is presented. There will be no crosstalk between two receiver array responses when the line-of-sight (LoS) propagation Rayleigh criterion is satisfied. Multiple quadrature outputs of the six-port circuits ensure that the performance of the MIMO system will stay acceptable when some parameters are changed. This can be proven by the bit error rates (BER) in different cases.