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.

There is an increasing demand for high-speed wireless data communications to support consumers’ need for, among other things, real time streaming of high definition video and fast file transfers. One radio architecture that has a potential to meet the increasing demand for high-speed data communications is a radio technique based on the six-port architecture. In addition to high-speed, the six-port radio also allows low power consumption and low cost. In this thesis, a comprehensive study of the six-port radio technique for high data rate (> 1 Gbit/s) and low complexity are presented.

Firstly, a technique to suppress the carrier leakage was proposed, analyzed and verified by measurements. The proposed technique uses only a phase shifting network between the six-port correlator and its variable impedance loads, hence it is easy to implement. When the proposed carrier leakage suppression technique is used together with differential control signals, it also has the benefit of both improving the linearity and increasing the output power of the modulator. The same carrier leakage suppression technique can also be used in a six-port demodulator (receiver) to improve its performance.

Secondly, Schottky diodes were proposed to be used as high-speed variable impedance loads. A six-port modulator operating at 7.5 GHz, using the carrier leakage suppression technique together with Schottky diodes as variable impedance loads, was manufactured. Measurements on a 16 quadrature amplitude modulated (QAM) signal with a symbol rate of 300 Msymbol/s, i.e., a data rate of 1.2 Gbit/s, have proved high-speed operation, good modulation properties as well as carrier leakage suppression.

Thirdly, a six-port demodulator was built for high data rate applications and measurements were conducted to characterize its performance. Demodulation of a 16-QAM signal at a data rate of 1.67 Gbit/s results in an acceptable bit error rate and error vector magnitude (EVM) performance.

Last but not least, new diode configurations were proposed, analyzed and verified for use in six-port demodulators. Using the proposed diode configurations, the use of differential amplifiers, as commonly used in a six-port demodulator, can be avoided. Avoiding the use of differential amplifiers allows high-speed processing and at the same time reduces the power consumption and implementation complexity. In the context of the new diode configurations, it was shown that a six-port receiver has better EVM vs frequency performance and lower implementation complexity, compared to a five-port or four-port receiver.