Jaeyul Choo

UHF RFID Tag Applicable to Various Objects

This communication proposes a label tag and a radiator for both dielectric and metallic target objects in UHF radio frequency identification (UHF RFID). Good impedance matching is achieved by the use of a cross-shaped loop when it is placed on dielectric objects and the inserted radiator. The radiator is printed on plastic substrate with a finite ground plane. After optimization and fabrication based on a geometrical study, the manufactured tag shows the half-power bandwidth of 65 MHz (7.1%) and 17 MHz (1.9%), in free space and on the underlying radiator, respectively. A reading range over 6.2 m with a deviation of 5.1 m (6.2 m-11.3 m) is confirmed on various target objects under the condition of 36 dBm EIRP at 912 MHz in UHF RFID band.

Full Wave Simulation of Flip-Chip Packaging Effects on RFID Transponder

In this paper, we firstly present the full wave simulation model for flip-chip bonding onto a PET(Polyethylene) substrate. We considered the chip, bumps, electrically conductive adhesive, substrate, and short conductive trace for antenna. These five elements are interdependent, and hence it is important to see the full picture in order to design a low cost transponder and to efficiently produce the transponder. The S-parameter of HFSS simulated model for physical location of chip onto conductive trace and equivalent RC-circuits for chip impedance are used to study the influence of flip-chip bonding on conductive trace, and we calculate the target impedance for transponder design. The results indicate that the bump height and the pattern inside the tag chip significantly effect on the impedance of strap, short conductive trace with flip-chip bonded transponder chip. That means the two parameters must be treated more carefully in RFID transponder production. Focusing on the manufacturing reliable, low-cost RFID transponder, this paper offers an idea in determine the matching impedance for antenna design.

Novel UHF RFID Tag Antenna for Metallic Foil Packages

A low-cost wideband antenna for radio-frequency identification (RFID) tags for use with metallic foil packages is designed in this communication. An proximity inductively coupled feed structure is employed to perform wideband impedance matching between a slot on a metallic foil package and a small rectangular feeding loop connected to a microchip. The results show a measured half-power bandwidth of 32.2% (799 MHz-1,093 MHz) and a reading distance of over 10 m.

Characteristic Impedance of Pyramidal Transmission Line

The characteristic impedance of a pyramidal transmission line is investigated. The eigenfunction expansions in spherical coordinates are used to represent the potentials in pyramidal regions. The mode-matching method is applied to obtain a set of simultaneous equations for modal coefficients. Computations are performed to examine the behavior of the characteristic impedance of a pyramidal transmission line.

Design of a Flexible Planar RFID Tag Antenna with Low Performance Degradation from Nearby Target Objects

In this letter, we propose a novel tag antenna that has low performance degradation with nearby dielectric material. We obtained a stable reading performance and a broad matching bandwidth on nearby dielectric materials by employing a T-matching network with thick line width and capacitively slot-loaded arms. We then built the proposed antenna and measured the tag sensitivity to examine the reading characteristics with nearby dielectric materials. The measured results clearly demonstrate stable tag sensitivity with various nearby dielectric materials, such as foam, acrylic-plastic, glass, and ceramic plates. To more closely observe the antenna characteristics with nearby dielectric materials, we also examined the impedance variation and surface current distribution with respect to the dielectric constant of nearby target objects, which ranged from 1×e? to 16×e?.

Analysis of Flip Chip Bonding for Performance Stability of UHF RFID Tags

Thermocompression bonding is one of the most important procedures in radio frequency identification tag fabrication because the electrical and mechanical properties of the joint greatly influence the overall tag performances. The characteristics of the joint are determined by the alignment between the microchip and antenna pads, the adhesives used, and various bonding parameters (temperature, pressure, and time). This paper uses an electrical equivalent circuit analysis, electromagnetic full-wave simulations, and environmental tests to investigate the factors that influence the reading performance of the flip chip bonding process. First, based on an equivalent circuit analysis of the bonded tag, the effect of the parasitic impedance on impedance matching and power transfer is analyzed. The parasitic impedance is then estimated by comparison with the measured impedance of the bonded chips. Second, we investigate the variation in the reading performance of the tag when various geometrical errors are generated at the joint between the microchip and the antenna. Finally, the bonding parameters for stable reading performance are studied by completing environmental tests. The results provide useful information for achieving stable reading performance of tags in flip chip bonding.

Transverse Electric Scattering of Open Cabinet in Nuclear Power Plants

This letter investigates the strength of an electric field that penetrates a cabinet containing digital equipment for a nuclear power plant. Based on Helmholtzs equation in conjunction with both the separation of variables and the Fourier transform, we utilize the mode-matching method to obtain a set of simultaneous equations for modal coefficients. We computationally examine the strength behavior of an electric field near the digital equipment in a cabinet when a plane wave with transverse electric polarization is applied to an open cabinet.

Simple quasi-static analysis for coplanar stripline within multilayer dielectrics

We apply the mode-matching method to the analysis of coplanar striplines surrounded by multilayer dielectrics and lateral conductive shields. Then the characteristic impedances and the effective dielectric constants of various coplanar striplines are calculated based on assumption that the electromagnetic coupling between the lateral shield and striplines could be neglected with a proper condition. Also we verify the accuracy of the modematching method compared with the conformal mapping technique.

Quasi-static analysis of slotted coaxial cable

This paper represents quasi-static analysis of a slotted coaxial cable used in a nuclear power plant. We assume that a coaxial cable is ruptured in the shape of an infinite axial slot. We employ mode-matching method to interpret a slotted coaxial with high efficiency in computation. After performing potential formulation and enforcing boundary conditions, we extract the distributions of potential and electric field to check how much adjacent objects are electromagnetically interfered through the axial slot.

Shielding Effectiveness of Open Cabinet Containing Digital Modules Using Ferrite Sheet

This paper presents an enhancement in the shielding effectiveness (SE) of an open cabinet containing digital modules using a ferrite sheet when an external electromagnetic source impinges on the gate of the cabinet. We perform an electromagnetic analysis on the inner space of an open cabinet using a mode-matching method, which proceeds in the following order: the separation of the analyzed region, the representation of fields, and the enforcement of the boundary conditions on the tangential field continuities between the separated regions. To be specific, it is efficiently utilized in the representation of electric and magnetic fields by Helmholtz’s equation in conjunction with both the separation of the variable and the Fourier transform. After confirming the convergence of the solutions to the set of simultaneous equations, we investigate the SE in the open cabinet in terms of a frequency, an incident angle, and the number and the size of slits. The computed results provide us with useful information for avoiding electromagnetic interference. We then examine the improvement of shielding performance by inserting a ferrite sheet at the gate of a cabinet. We verify that the usage of the ferrite sheet with high permeability can be a preferable solution for removing the undesirable problems caused by an external electromagnetic source.