Passive components design for UWB-RFID systems.
Date of Issue2013
School of Electrical and Electronic Engineering
Positioning and Wireless Technology Centre
Recently, radio-frequency identification (RFID) systems emerge in many daily applications. However, their operation frequencies are narrowband which inherently limit their capabilities. To break this bottleneck, impulse radio based ultra-wideband (UWB) technology is a promising candidate. It enables the next-generation RFID system with powerful functions such as real-time location tracking with high accuracy. This PhD thesis presents some key passive components for UWB enabled RFID (UWB-RFID) systems. Filter is one of the passive components in a UWB-RFID system. This thesis presents novel UWB filters which employ composite right/left-handed transmission line (CRLH-TL) structures. To facilitate the filter designs, their circuit models are introduced and analyzed. Following a comprehensive theoretical analysis, design guidelines are given. Two different filters are then numerically simulated, experimentally measured, and practically integrated in UWB-RFID transmitter and receiver, respectively. These filters feature compact size, low in-band insertion loss, and also high out-of-band suppression to avoid interference. In addition, an absorptive filter is proposed to absorb the stop-band power rather than reflect it towards the UWB source. It therefore makes the UWB source operate with high stability.Antenna is another key component. This PhD thesis presents several planar antennas for different UWB-RFID tags. The first antenna is a two-port design for wireless-powered UWB-RFID tag. In the same volume, it physically integrates two antennas, i.e., a narrowband slot for energy harvesting and a circularly polarized (CP) quasi-spiral for UWB signal transmission. This two-port antenna features compact size and high electrical isolation. The second antenna is a CP square slot for active UWB-RFID tag. After simulating and measuring this UWB CP antenna in the frequency and time domains, it is then integrated with active circuits for demonstration. Moreover, this square slot is optimized to be embedded in Concrete for debris tracking. Following the above filters and antennas, this thesis also demonstrates a UWB-RFID system using chipless CP tag for the first time. The chipless tag adopts the above designed square slot. Its CP characteristic significantly benefits the UWB-RFID system by reducing amplitude ratio between structural and antenna modes, and also alleviates the mutual coupling between transmitter and receiver. In addition, the chipless tag uses short delay line which makes the chipless tag more compact, resulting in overlapped backscattered pulses. To avoid the latter side-effect, a novel four-step time-domain processing scheme is developed to extract both structural and antenna modes from the overlapped pulses. The proposed scheme also enables the system to operate at lower frequency and extends its detection range.Overall, this thesis presents filters and CP antennas for several different UWB-RFID systems. Following these designs, this thesis also demonstrates a UWB-RFID system using CP chipless tag and novel processing scheme. This thesis gives some new and broad insights for next-generation UWB-RFID systems.
DRNTU::Engineering::Electrical and electronic engineering::Antennas, wave guides, microwaves, radar, radio