UC Irvine

The millimeter-wave frequency band spectrum represents a great opportunity for ultrahigh-speed, short-range wireless communications and a wealth of new applications such as target positioning or tracking. However, a number of challenges remain for this spectrum to be a viable solution for high-volume consumer applications.

One challenge is the determination of the electromagnetic properties of dielectric substrate packaging materials and metamorphic structures. This is vital for the optimal and robust design of beamforming mm-wave systems. In this thesis we present "The Covered Transmission Line Method", a new method to determine the complex permittivity of printed circuit and packaging materials at the mm-wave frequencies. This method is relevant in that it allows for testing of a variety of materials without changes on the setup and with minimal sample processing.

Some applications however, require more advanced materials, called metamorphic materials, which are able to change their response to electromagnetic waves. We present in here a unique electromagnetically metamorphic material that can undergo four distinct electromagnetic states (Perfect Electric Conductor, Perfect Magnetic Conductor, Perfect Amplification and Perfect Absorption). Fundamental mathematical and electromagnetic analysis has been used to obtain a full wave analytical model of the scattering properties of this novel composite material. For the first time, a truly metamorphic surface that can precisely be tuned to any electromagnetic state has been fabricated and tested. This is achieved by loading the basic elements (printed circular rings) of the surface with active devices (tunnel diodes) that can sweep their terminal resistance from a high negative to a high positive value.

The combination of small wavelength and large available bandwidth make mm-wave target positioning systems a viable option to achieve the desired accuracy. However, such systems require the use of beamforming mm-wave antenna systems to mitigate the high path losses (there are 21 dB more path losses at 60 GHz than at 5 GHz). In this work, we present a novel high-gain beam selection 60 GHz band Grid Array antenna that fulfills the requirements of beamforming, low-cost and small size for integration with mobile devices.

Regarding target positioning applications, we study the impact of using beamforming mm-wave antenna systems on the location precision of multiple targets in a realistic indoor environment. The positioning error is assessed when omnidirectional antennas are used at the receiving sensors and when they are substituted by beamforming antennas.