Position Tracking for Passive UHF RFID Tags with the Aid of a Scanned Array

Thanks to the proliferation of radio frequency identification systems (RFID), applications have emerged concerning positioning techniques for inexpensive passive RFID tags. The most accurate approaches for tracking the tag's position, deliver precision in the order of 20 cm over a range of a few meters and require moving parts in a predefined pattern (mechanical antenna steering), which limits their application. Herein, we introduce an RFID tag positioning system that utilizes an active electronically-steered array, based on the principles of modern radar systems. We thoroughly examine and present the main attributes of the system with the aid of an finite element method simulation model and investigate the system performance with far-field tests. The demonstrated positioning precision of 1.5, which translates to under 1 cm laterally for a range of a few meters can be helpful in applications like mobile robot localization and the automated handling of packaged goods.DF

Hybrid antenna design for an optically powered SHF RFID transponder applicable in metals

This paper presents a hybrid antenna design for an optically powered super high frequency (SHF) radio frequency identification transponder applicable for the integration into metal. The key feature of the antenna is its ability to receive microwave signals at SHF for data communication and optical signals for the power supply of the transponder. The antenna design is based on a circular waveguide which is filled with a bundle of polymer optical fibers to guide light to the photodiodes. In addition, a transition is placed within the circular waveguide to transfer the waveguide mode of the SHF signal into a microstrip mode which is a more suitable structure for the integration of electronic transponder components. This paper discusses the constraints and solutions for the aforementioned combination of SHF microwave and light. The figures of merit of the optical power supply are presented, including considerations of the light distribution and the obtained power as a function of the incident angle and the used polymer optical fiber diameter. Furthermore, the measured gain and return loss of the SHF antenna structure is compared to the simulated results. © Cambridge University Press and the European Microwave Association, 2013

Printing polymer optical waveguides on conditioned transparent flexible foils by using the aerosol jet technology

The optical data transfer is considered as the future of signal transfer due to its various advantages compared to conventional copper-based technologies. The Aerosol Jet Printing (AJP) technology offers the opportunity to print materials with high viscosities, such as liquid transparent polymer adhesives (epoxy resins), on almost any possible substrate material and even in third dimension. This paper introduces a new flexible and comparatively cost-effective way of generating polymer optical waveguides through AJP. Furthermore, the conditioning of the substrate material and the printing process of planar waveguides are presented. In the first step, two lines with hydrophobic behavior are applied on foil material (PMMA, PVC, PI) by using a flexographic printing machine. These silicone based patterns containing functional polymer form barriers for the core material due to their low surface energy after curing. In the second step, the core material (liquid polymer, varnish) is printed between the barrier lines. Because of the hydrophobic behavior of the lines, the contact angle between the substrate surface and the liquid core material is increased which yields to higher aspect ratio. The distance between the barrier lines is at least 100 μm, which defines the width of the waveguide. The minimum height of the core shall be 50 μm. After UV-curing of the core polymer, the cladding material is printed on the top. This is also applied by using the AJP technology. Various tests were performed to achieve the optimal surface properties for adequate adhesion and machine process parameters. © 2016 SPIE.DF

Laser sintering of copper conductive traces on primer pre-treated additive manufactured 3D surfaces

This paper introduces a novel process for creating conductive copper traces on 3D surfaces from different additive manufacturing technologies by employing printed electronics techniques. An essential step in this process was the dip-coating pre-treatment with a primer to reduce the surface roughness below 100 nm, seal pores if present, and increase the thermal stability. This was followed by a dip-coating with copper nanoparticle ink, drying using a heat gun and thermal curing by laser sintering. The experiments determined the optimal laser peak intensity for achieving conductors with the lowest electrical resistance possible. The laser parameters' processing window provided conductive traces on 3D surfaces with properties comparable to photonic sintering on planar substrates. Thereby, the conductive traces reached electrical specific resistances lower than 18 µΩ cm (elemental copper: ρ = 1.8 µΩ cm) and a copper material percentage higher than 90 atom %. Shear tests validated the assembly with surfacemount device (SMD) resistors. Electrical tests resulted in maximum current densities higher than 100 A mm-2 and lateral breakdown voltages higher than 2kV mm-1. Thus, this paper presents essential prerequisites for a future application of the technology

Functionalization of UV-curing adhesives for surface-integrated micro-polymer optical fibers

Polymer optical waveguides, especially single-mode waveguides are increasingly used for short distance communication, as well as for sensing applications. The realization of a working communication route requires different and sequentially realized steps. Generally, these steps are the packaging of semiconductor beam senders and receivers, the fabrication of an optical waveguide, the preparation of its end-facets, the alignment of different elements along their optical axis and the integration into a desired communication route. The development of a process, which integrates all these steps for planar surfaces, offers a reduction in time and an increase in flexibility. A sub-step toward such a highly automated system is the integration of optical waveguides into the planar surface. In this context, we are investigating the use of the micro-dispensing process to realize this integration step. We functionalize UV-curing adhesives as cladding for micro-optical cores as well as for inherent bonding to the substrate surface. For this purpose an optical characterization of the adhesives is necessary for an adequate core and cladding material combination. A ow behavior characterization is also relevant in order to analyze the used dispensing process with the selected adhesive. Finally, a mechanical characterization is done to test the adhesion of the core to the adhesive, as well as the adhesive to the substrate surface. In this paper we present a summary of the realized characterization of the selected polymer. Based on experiment results we infer limits and opportunities of this method. © 2016 SPIE

Evaluation of polymer-based eccentric FBG bending sensor for humidity, strain, temperature and torsion

We analyse and evaluate the sensitivity and robustness of an eccentric fiber Bragg grating sensor micro-structured into a polymer optical fiber under different relative humidity, temperature, strain and torsion conditions. Relative humidity and temperature conditions are established with a climate test chamber and prepared salt solutions. Though made of polymer, the cross-sensitivity of the sensor to relative humidity is low, enabling usage in rapidly changing environment applications, e.g., for movement detecting gloves or in vehicles, but also in high moisture situations. We find a linear dependence on temperature, so that either bending or temperature can be measured separately from each other. After rotation of one end, the sensor measures torsion by observing the light intensity and the change of the full width at half maximum. Strain measurement shows multiple elastic strain regions before final plastic deformations occur. In the next step, the flexible sensor system will be implemented in a sensor glove to monitor finger movement and detect different hand gestures