Lara Martin

Conformal Magnetic Composite RFID for Wearable RF and Bio-Monitoring Applications

This paper introduces for the first time a novel flexible magnetic composite material for RF identification (RFID) and wearable RF antennas. First, one conformal RFID tag working at 480 MHz is designed and fabricated as a benchmarking prototype and the miniaturization concept is verified. Then, the impact of the material is thoroughly investigated using a hybrid method involving electromagnetic and statistical tools. Two separate statistical experiments are performed, one for the analysis of the impact of the relative permittivity and permeability of the proposed material and the other for the evaluation of the impact of the dielectric and magnetic loss on the antenna performance. Finally, the effect of the bending of the antenna is investigated, both on the S-parameters and on the radiation pattern. The successful implementation of the flexible magnetic composite material enables the significant miniaturization of RF passives and antennas in UHF frequency bands, especially when conformal modules that can be easily fine-tuned are required in critical biomedical and pharmaceutical applications.

Design and optimization of 3-D compact stripline and microstrip Bluetooth/WLAN balun architectures using the design of experiments technique

In this paper, various architectures of three-dimensional compact microwave balanced to unbalanced (balun) transformers for Bluetooth/WiFi antenna applications are successfully designed and optimized using the design of experiments (DOE) approach. Two different multilayer topologies, one microstrip and one stripline, are investigated on low temperature co-fired ceramic (LTCC) substrate. The design goals for both baluns are perfectly balanced outputs from 2 to 3 GHz and a resonant frequency of exactly 2.4 GHz. It is demonstrated, using only eight simulations, that perfectly balanced outputs are not possible under the given conditions in the case of the microstrip balun. Nevertheless, the stripline balun can be optimized due to its almost symmetrical structure, and both simulations and measurement results verify the conclusions. The DOE method is very simple to implement and gives a clear understanding of the system behavior at the beginning of the design process, reducing the amount of work required for achieving the design goals by orders of magnitude compared to the widely used trial-and-error approach. The matching and unique measurement issues regarding the calibration, placement of probes and the de-embedding of the microstrip to coplanar waveguide transitions are discussed in detail for the optimized stripline balun. This technique can be easily applied to the fast and efficient optimization of complicated radiation structures, such as reconfigurable or multilayer multiband antenna arrays.

Design and development of compact conformal RFID antennas utilizing novel flexible magnetic composite materials for wearable RF and biomedical applications

This paper reports the first conformal RFID antenna printed on a flexible magnetic composite material for the UHF frequency band. The target applications are wearable RFIDs and bio-monitoring wireless probes. The successful implementation of the flexible magnetic composite material allows the tag miniaturization and provides excellent electrical performance in the 480 MHz band. First, the material is chosen for optimal electric and magnetic losses, then the antenna is designed for both the non-magnetic material and the magnetic one to prove the miniaturization. Finally, the effect of bending the antenna on the measured return loss performance is investigated.

Chemical and mechanical adhesion mechanisms of sputter-deposited metal on epoxy dielectric for high density interconnect printed circuit boards

Strong chemical reactions between metal and polymer substrates significantly enhance adhesion of the metal to the polymer. This study investigated the adhesion of three types of thin film metals, including Cu, NiCr, and Cr, to a fully epoxy-based polymer. Before depositing these thin film metals, the epoxy surface was treated with either an Ar or O/sub 2/ plasma etch. It was found that NiCr and Cr produced higher peel strengths than Cu, but NiCr and Cr did not produce different peel strengths than each other. It was also found that O/sub 2/ plasma etch produced significantly higher peel strengths than Ar plasma etch for Cu and Cr, but not for NiCr. An XPS (X-ray photoelectron spectroscopy) study was performed to investigate the reactivities and possible chemical adhesion mechanisms of the metal thin films with the epoxy. It was determined that Cr reacted more strongly than Ni in forming metal oxide at the metal-epoxy interface. Cu was not seen to react strongly in forming oxide with the epoxy. Thermodynamic information supported the relative amounts of oxides found by XPS. Thermodynamic information also suggested that O/sub 2/ plasma etch did not produce significantly higher adhesion than Ar plasma etch on the NiCr samples due to the large Ni component of the NiCr thin film. An AFM (atomic force microscopy) study was performed to investigate possible mechanical adhesion mechanisms. Implications of the AFM results were that the main adhesion mechanism for all samples was chemical and that the Cu oxide that was available on the Cu samples was beyond the detection limits of the XPS equipment.

Optimization of 3D multilayer RF components using the design of experiments (DOE) technique

The successful use of the design of experiments (DOE) approach in an optimization feasibility study for two microwave balanced to unbalanced transformers (baluns) is presented. The medium of interest is the multi-layer low temperature cofired ceramic (LTCC) and two different topologies, one microstrip and one stripline, are investigated. The design goals are perfectly balanced outputs from 2-3 GHz and a resonant frequency of exactly 2.4 GHz. It is demonstrated, using only eight simulations, that perfectly balanced outputs are not possible under given conditions in the case of the microstrip balun. Nevertheless, the stripline balun can be optimized due to its almost symmetrical structure, and both simulations and measurement results verify the conclusions. The DOE method is very simple to implement and gives a clear understanding of the system behavior at the beginning of the design process, reducing the amount of work required for achieving the design goals by orders of magnitude compared to the widely used trial-and-error approach.

A novel flexible magnetic composite material for RFID, wearable RF and bio-monitoring applications

This paper introduces for the first time a novel flexible magnetic composite material for RFID and wearable RF antennas. The successful implementation of the flexible magnetic composite material will enable the significant miniaturization of RF passives and antennas in UHF frequency bands, especially for applications requiring conformal modules that can be easily fine-tuned. A conformal RFID tag working at 480MHz is then fabricated and the miniaturization concept proven.

Multilayer Embedded Metamaterial Optimization for 3D Integrated Module Applications

This paper proposes a novel methodology to design and optimize a metamaterial structure for 6 GHz. Current design methods do not take into account the specific effect of each of the factors involved in the design process, the degree that these factors interact with each other, and which ones are not statistically significant and therefore can be eliminated from further analysis. The proposed methodology integrates full wave electromagnetic simulation and statistical tools and is applied for the optimization of a compact 6 GHz metamaterial structure on LTCC (low temperature cofired ceramic). The proposed methodology can be easily extended to a large number of design variables and optimized figures of merit

Design and optimization of 3D RF modules, microsystems and packages using electromagnetic, statistical and genetic tools [mm-wave interdigitated passband filter application]

The successful use of the design of experiments (DOE) and response surface modeling (RSM) approaches in an optimization study for a multilayer interdigitated passband filter is presented. The medium of interest is liquid crystal polymer (LCP) and the frequency band is in the 60 GHz range. The two figures of merit chosen are the resonating frequency and the quality factor Q with the optimization goals of f/sub o/=60 GHz and maximum Q. The electromagnetic performance of the filter is determined with a method of moments commercial simulator. The results of these simulations are incorporated into DOE and RSM techniques, statistical models are developed for the two output variables, and then applied to optimize the filter. The effectiveness of the method is compared to that of the genetic algorithm (GA) optimization.

Comprehensive Study on the Impact of Dielectric and Magnetic Loss on Performance of a Novel Flexible Magnetic Composite Material

This paper introduces a novel flexible magnetic composite material for RFID and wearable RF antennas. The critical issue of dielectric and magnetic losses combined is addressed for the first time for such a material in the UHF frequency band and is thoroughly investigated using a hybrid method including electromagnetic simulations and statistical tools. The successful implementation of the flexible magnetic composite material will enable the significant miniaturization of RF passives and antennas in UHF frequency bands, especially for applications requiring conformal modules that can be easily fine-tuned, while minimizing the decrease in performance due to losses.

Concurrent Circuit-Level/System-Level Optimization of a 24 GHz Mixer for Automotive Applications Using a Hybrid Electromagnetic/Statistical Technique

The successful use of the design of experiments (DOE) and response surface methods (RSM) approaches in the simultaneous optimization of geometrical parameters and power requirements of a 24 GHz mixer is presented. The benchmarking geometry is a low-cost mixer for a Doppler radar sensor, built in liquid crystal polymer (LCP) technology. First, the single-balanced diode mixer is designed for good RF/LO isolation and low conversion loss. The structure is then optimized using the same experiment that integrates both geometrical parameters and the LO input power levels. The optimized mixer shows a 4.5 dB conversion loss with a 23 dB isolation between RF and LO ports at the operating input power levels, the best reported so far for this frequency range and in these operating conditions.