A compact size six-port correlator using bandwidth enhancing stubs for the 69 GHz ultra wideband radio is presented. The proposed six-port has a center frequency of 7.5 GHz with 50% relative bandwidth. The correlator is based entirely on microstrip technology for low cost and simple circuit implementation.

A triplexer for ultra-wideband radio implemented entirely with distributed microstrips is presented. The triplexer is composed of a triplex junction network and three bandpass filters. The circuit is integrated in a flex-rigid printed circuit board. Three flat 1 GHz sub-bands in the frequency band 6-9 GHz have been achieved. The group delay variation within each 1 GHz sub-band was measured to be less than 0.4 ns. A good agreement between simulation and measurement was obtained, e.g., less than 0.3 dB difference in the forward transmission in the majority of the frequency band.

The use of six-port correlators to implement six-port receivers has been intensively studied. The six-port receiver can also be modified to a five-port or a four-port receiver. However, the six-, five-, or four-port receiver solution requires different baseband processing to recover the baseband In-phase (I) and Quadrature-phase (Q) data. A unified mathematical model for the six-, five- and four-port receivers is presented in this article. Possible solutions to recover the baseband data are discussed and compared. The investigation shows that the six-port receiver has advantages over the five- and four-port receivers in terms of complexity when analog baseband processing is used. Simulations are conducted to verify the model and to estimate the error vector magnitude versus frequency; the simulation also shows that the six-port receiver operates over a wider bandwidth than the five- or four-port receiver.

A differential six-port demodulator for the 7-8 GHz band is reported for the first time. It is composed of a differential six-port correlator on the two sides of the substrate and zero-bias antiparallel Schottky diodes acting as power detectors. It is theoretically analyzed and also simulated. A prototype has been fabricated and data transmission at 0.8 Gbit/s (but not the maximum) with the 16 quadrature amplitude modulation (QAM) is experimentally demonstrated.

A differential six-port demodulator for the 7-8 GHz band is reported for the first time. It is composed of a differential six-port correlator on the two sides of the substrate and zero-bias antiparallel Schottky diodes acting as power detectors. It is theoretically analyzed and also simulated. A prototype has been fabricated and data transmission at 0.8 Gbit/s (but not the maximum) with the 16 quadrature amplitude modulation (QAM) is experimentally demonstrated.

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.

A fully integrated dipole antenna with a balun fot ulna wideband (UWB) radio in the band 6-9 GHz utilizing a flexible and rigid printed count board is presented in this at tide The balun utilizes broadside coupled microstrips and is integrated in the rigid part of the printed coma boat d whereas the radiator is placed in the flexible pat! The antenna with the balun covets the frequency band 6 0-8 5 GHz at voltage standing mate ratio (VSWR) andlt;2 0 and 55-110 GHz at VSWR andlt; 2 5 Moreover simulated and measured radiation patterns and antenna efficiency above 860% are observed

This paper presents a direct carrier six-port modulator. To allow arbitrary load impedances to be used and for suppression of carrier leakage, a new circuit architecture with a technique to suppress carrier leakage is proposed and implemented. A theoretical model of the proposed modulator is derived. A prototype modulator utilizing diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz for verification of the proposed technique. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 100 Msymbol/s is generated, as well as good carrier leakage suppression.

In six-port modulators a phase shifting network on specific ports can be used to suppress the carrier leakage that may be present if this network is not present. A model is derived to predict the carrier leakage suppression and error vector magnitude (EVM) as a function of the phase shifting network Sparameters. Both carrier leakage suppression and EVM can be expressed by the same error function. The error function can be used to find the allowed amplitude and phase mismatch in the phase shifting network, or to optimize the performance of a phase shifting network over a given frequency range. A broadband phase shifting network, based on a loaded transmission line, is designed and optimized to operate at a relative bandwidth of 60% for an EVM < 10%. This should be compared to a phase shifting network based on a single transmission line with a corresponding bandwidth of only 12%. The broadband phase shifting network is useful for six-port modulators with carrier leakage suppression, targeting UWB applications.

The use of Schottky diodes as high-speed variable impedance loads in six-port modulators are proposed and analyzed in this paper. The impedance dependency of diode parameters and local oscillator power are investigated by theoretical analysis and simulations. A prototype for a direct carrier six-port modulator using Schottky diodes for impedance generation is designed and fabricated for a center frequency of 7.5 GHz. Measurements show good modulation properties when a 16 quadrature amplitude modulation signal at 300 Msymbol/s is generated, i.e., at a data rate of 1.2 Gbit/s, validating the use of Schottky diodes as high-speed variable impedance loads in six-port modulators.