RFID Antennas for Biomedical Applications

Abstract

In this current technological trend, radio frequency identification (RFID) can provide the solution for modern wireless data transmission and reception for a broad range of identification, tracking, and surveillance applications. The RFID technology can be a potential competitor to the optical barcode technology by introducing the chipless RFID tags. The fully printable chipless RFID technology can reduce the manufacturing cost to a great extent and might be useful in a vast range of applications. This dissertation is aimed at building design methodology, analysis, and ideas regarding RFID antennas required for biomedical applications. It focuses on the limitations associated with the technology and the design challenges. It also aims to overcome the above-discussed drawbacks as well as enhancing overall microwave system performance by proposing new structures. In this research work, the design of chipless RFID reader and tag antennas are investigated for biomedical applications. Both linearly polarized (LP) and circularly polarized (CP) reader antennas are investigated with mathematical modeling and analysis. The radiation characteristics are evaluated along with the full-wave analysis and physical measurement. The first LP antenna design presented in this thesis can be used as an RFID reader having a wide bandwidth of 64.86% for vital sign monitoring applications. The planar monopole antenna comprises of a primary radiating element having one half of a Koch snowflake fractal geometry, and a partial ground plane. The analytical model provides a comprehensive understanding of the antenna operation. Measurement of the fabricated prototype confirms that the design possesses an operational bandwidth from 4􀀀7.84 GHz with a peak realized gain of 3.4 dBi at 7.2 GHz with omnidirectional radiation characteristics. The proposed antenna has a dimension of 0.33__0.49__0.03_, at 5.8 GHz and is found compact compared to some recently reported designs. Similarly, a Pythagorean-tree fractal monopole RFID reader antenna is analyzed for sleep apnoea applications. The antenna is fed by the coplanar waveguide (CPW) feeding method with the filleted ground plane. The lumped element circuit of proposed design is validated with full-wave simulation model to understand the operation of the structure. The measurement results show a wide bandwidth in the frequency range of 4.22􀀀7.52 GHz and a peak realized gain of 2.9 dBi at 5.8 GHz. The use of fractal geometry is mainly to reduce the metallic footprint size, along with to obtain a wider bandwidth. The LP antenna is having an overall dimension of 0.36__0.43__0.015_ at 5.8 GHz covering the industrial scientific and medical (ISM) band. In this thesis, a planar monopole antenna having a slotted ground plane is also presented. The antenna is energized by a 50-Ω feedline having a sigma-shaped radiator. The proposed design resonates at 5.8 GHz with an operational bandwidth from 5.71􀀀5.9 GHz. The radiation characteristics of the structure show the realized gain value greater than 3.6 dBi in the entire operating frequency range. The antenna has an overall dimension of 0.55__0.55__0.03_ at 5.8 GHz and can be a suitable RFID reader in the ISM band. In another LP antenna design, the analysis of a meandered line monopole antenna with a defected ground structure (DGS) for RFID applications is investigated. In the proposed antenna, the linearly polarized meandered line acts as the main radiator whereas the inverted C-shaped patch acts as a parasitic element. The defects on the ground plane are responsible for providing low pass filter performance. From the measurement, it is found that the antenna operates over the 5.74–6 GHz with a resonance at 5.82 GHz. The designed antenna structure shows omnidirectional radiation characteristics with the realized gain value greater than 4 dBi in the entire operating frequency range. It has an overall dimension of 0.55_ _ 0.55_ _ 0.03_ at resonating frequency which is effectively fit for use in RFID readers operating at 5.82 GHz ISM band. In this thesis, a single-feed, miniaturized, CP microstrip patch antenna (MPA) using Koch fractal geometry for RFID applications is presented. The design consists of a probe-fed slotted square-shaped patch with the fractal edge and two pairs of capacitively coupled
grounded metal strips. The proposed design methodology is validated by designing two prototypes (Antenna 1 and Antenna 2), which are operating at 2.435 GHz and 5.78 GHz respectively. Both antennas show right-hand circular polarization (RHCP) characteristics with 3 dB axial ratio bandwidth (ARBW) covering 2.433–2.439 GHz and 5.75–5.8 GHz respectively. This design offers a compact antenna to meet the demands of portable wireless devices. The thesis also describes the design, modeling, and analysis of a two-bit retransmission-based chipless RFID tag operating in the microwave ISM band. The chipless RFID tag has cross-polarized transmitting and receiving antennas along with open-stub resonators. The fabricated prototype confirms 2-bit data encoding in which the simulation results are strongly related to the experimental outcomes. The proposed tag occupy an overall size of 0:53__0:53__0:012_ (at f = 2:4 GHz) and can be suitable for biomedical applications. At the end of this research work, the broad idea of a chipless RFID system is provided in the Appendix section. It includes the overview of a complete reader system to read the encoded data from a chipless RFID tag. This investigates each of the elements of the reader system and the functionality. In this current technological trend, radio frequency identification (RFID) can provide the solution for modern wireless data transmission and reception for a broad range of identification, tracking, and surveillance applications. The RFID technology can be a potential competitor to the optical barcode technology by introducing the chipless RFID tags. The fully printable chipless RFID technology can reduce the manufacturing cost to a great extent and might be useful in a vast range of applications. This dissertation is aimed at building design methodology, analysis, and ideas regarding RFID antennas required for biomedical applications. It focuses on the limitations associated with the technology and the design challenges. It also aims to overcome the above-discussed drawbacks as well as enhancing overall microwave system performance by proposing new structures. In this research work, the design of chipless RFID reader and tag antennas are investigated for biomedical applications. Both linearly polarized (LP) and circularly polarized (CP) reader antennas are investigated with mathematical modeling and analysis. The radiation characteristics are evaluated along with the full-wave analysis and physical measurement. The first LP antenna design presented in this thesis can be used as an RFID reader having a wide bandwidth of 64.86% for vital sign monitoring applications. The planar monopole antenna comprises of a primary radiating element having one half of a Koch snowflake fractal geometry, and a partial ground plane. The analytical model provides a comprehensive understanding of the antenna operation. Measurement of the fabricated prototype confirms that the design possesses an operational bandwidth from 4􀀀7.84 GHz with a peak realized gain of 3.4 dBi at 7.2 GHz with omnidirectional radiation characteristics. The proposed antenna has a dimension of 0.33__0.49__0.03_, at 5.8 GHz and is found compact compared to some recently reported designs. Similarly, a Pythagorean-tree fractal monopole RFID reader antenna is analyzed for sleep apnoea applications. The antenna is fed by the coplanar waveguide (CPW) feeding method with the filleted ground plane. The lumped element circuit of proposed design is validated with full-wave simulation model to understand the operation of the structure. The measurement results show a wide bandwidth in the frequency range of 4.22􀀀7.52 GHz and a peak realized gain of 2.9 dBi at 5.8 GHz. The use of fractal geometry is mainly to reduce the metallic footprint size, along with to obtain a wider bandwidth. The LP antenna is having an overall dimension of 0.36__0.43__0.015_ at 5.8 GHz covering the industrial scientific and medical (ISM) band. In this thesis, a planar monopole antenna having a slotted ground plane is also presented. The antenna is energized by a 50-Ω feedline having a sigma-shaped radiator. The proposed design resonates at 5.8 GHz with an operational bandwidth from 5.71􀀀5.9 GHz. The radiation characteristics of the structure show the realized gain value greater than 3.6 dBi in the entire operating frequency range. The antenna has an overall dimension of 0.55__0.55__0.03_ at 5.8 GHz and can be a suitable RFID reader in the ISM band. In another LP antenna design, the analysis of a meandered line monopole antenna with a defected ground structure (DGS) for RFID applications is investigated. In the proposed antenna, the linearly polarized meandered line acts as the main radiator whereas the inverted C-shaped patch acts as a parasitic element. The defects on the ground plane are responsible for providing low pass filter performance. From the measurement, it is found that the antenna operates over the 5.74–6 GHz with a resonance at 5.82 GHz. The designed antenna structure shows omnidirectional radiation characteristics with the realized gain value greater than 4 dBi in the entire operating frequency range. It has an overall dimension of 0.55_ _ 0.55_ _ 0.03_ at resonating frequency which is effectively fit for use in RFID readers operating at 5.82 GHz ISM band. In this thesis, a single-feed, miniaturized, CP microstrip patch antenna (MPA) using Koch fractal geometry for RFID applications is presented. The design consists of a probe-fed slotted square-shaped patch with the fractal edge and two pairs of capacitively coupled grounded metal strips. The proposed design methodology is validated by designing two prototypes (Antenna 1 and Antenna 2), which are operating at 2.435 GHz and 5.78 GHz respectively. Both antennas show right-hand circular polarization (RHCP) characteristics with 3 dB axial ratio bandwidth (ARBW) covering 2.433–2.439 GHz and 5.75–5.8 GHz respectively. This design offers a compact antenna to meet the demands of portable wireless devices. The thesis also describes the design, modeling, and analysis of a two-bit retransmission-based chipless RFID tag operating in the microwave ISM band. The chipless RFID tag has cross-polarized transmitting and receiving antennas along with open-stub resonators. The fabricated prototype confirms 2-bit data encoding in which the simulation results are strongly related to the experimental outcomes. The proposed tag occupy an overall size of 0:53__0:53__0:012_ (at f = 2:4 GHz) and can be suitable for biomedical applications. At the end of this research work, the broad idea of a chipless RFID system is provided in the Appendix section. It includes the overview of a complete reader system to read the encoded data from a chipless RFID tag. This investigates each of the elements of the reader system and the functionality.