Six-port transceiver for 6–9 GHz ultrawideband systems

Requirement for high speed wireless connectivity is propelling research in advanced communication systems. Low power and wide bandwidth of the ultra-wideband technology makes it a potential candidate for high speed data transmission. The six-port based radio systems and wideband antennas have been studied and presented in this dissertation for ultra-wideband applications. The six-port modulator operation with carrier leakage suppression was demonstrated at a center frequency of 7.5 GHz. The six-port correlator utilizes a quarter wavelength transmission line for carrier leakage suppression, together with diodes or eld effect transistors as variable impedance terminations. Especially, a differential six-port modulator was designed and veried through simulation and measurement. The prototype shows its capability of carrier leakage suppression and high speed data transmission with 256-quadrature amplitude modulation at 50 Msymbol/s at the center frequency of 7.5 GHz. Furthermore, a differential six-port demodulator was demonstrated with the 16 quadrature amplitude modulation at a data rate of 0.8 Gbit/s at the center frequency of 7.5 GHz. It uses zero-bias anti-parallel Schottky diodes as power detectors. Flexible antennas were designed such that they can be housed by folding it around in space limited environment with stable performance over a wide operation bandwidth. Measurement, on a exible dipole antenna with integrated balun, shows that it covers a frequency band from 6 to 11 GHz at a voltage standing wave ratio lower than 2.5 with the antenna eciency above 86%. A miniaturized monopole antenna that is not only capable of operating over an ultra-wideband but also for lower frequency bands was invented and veried. It covers a frequency range from 1.35 to 11.5 GHz. It gives a quasi-omnidirectional radiation pattern and high eciency. The antenna has a patent pending status with the United States Patent and Trademark Oce.