The potential of inkjet printing technology (IjP) for the fabrication of coils for biomedical applications in inductively coupled power transfer systems is studied in terms of needed compensations, bifurcation phenomena, and power transfer efficiency. The effect of using coils manufactured with IjP in the secondary side has been analyzed by studying the effect of the increase in internal resistance. The present study makes it possible to select the best topology depending on the load impedance, the coupling coefficient, and coil design. In terms of the compensations needed at the primary side, IjP does not significantly affect the behavior of the system; however, the series¿series topology is preferable since the compensating capacitance is independent from the internal resistance. In terms of bifurcation, a more restricted condition is obtained for parallel compensated secondary circuits. There is a decrease on the power transfer efficiency due to the increase of the internal resistance introduced by IjP. However, it is important to select the best topology according to the application since the decrease could be from 63% to only 6%. It is concluded that IjP is a promising fabrication technique for coils for biomedical applications.

A simple method is presented for estimating the resonant frequency of compact slotted microstrip antennas, based on their current distribution. The method has been first tested in two basic and symmetric geometries; afterwards, through the combination of these geometries, a multi-slotted structure has been analysed. Prototypes have also been manufactured in RT/Duroid 6002 and FR4 substrates, and good agreement has been obtained between estimations, simulations and measurements. A maximum estimation error of 10% has been achieved with this method, providing a useful tool for the design of compact slotted microstrip antennas.

A broadband UHF antenna for implanted central venous catheters (CVC) is designed, implemented, and properly characterized. According to the requirements, the CVC antenna (CVCA) is low profile, surface integrated, and 3-D conformal to a 16 mm base radius, 10 mm upper radius, and 16 mm high truncated cone. It operates at the MedRadio band (401-406 MHz) for implant communication and at the ISM 2.45 GHz band for electronics wake up. A prototype implementation including a test-bed within a phantom that is representative of a body is introduced. The antenna exhibits S-11 < -10 dB at the bands of interest with broadband behavior. The measured gain is -28.95 dBi in vertical and -36.9 dBi in horizontal polarization in the MedRadio band and -25.5 dBi and -19.9 dBi at 2.45 GHz. The gain is corroborated by the link characterization between an implanted node with electronics and an external base station. Base station antenna, electronics sensitivity, transmitted power, and path loss are independently measured and introduced in a broken down link budget for read range estimate. This is 18.95 m for the MedRadio band in free space conditions. By using the power saving mode at 2.45 GHz, it is reduced to an estimate of 1.88 m.

This work presents a study of the impact of PIN diodes on the performance of reconfigurable compact microstrip antennas with high frequency-ratio. To this purpose, two frequency reconfigurable microstrip antennas with a frequency-ratio of 3 (868 MHz and 2.45 GHz ISM bands) and a different degree of compactness have been designed and measured for various PIN-diode configurations. The results show the derivative effects of using PIN diodes in the conditions mentioned, namely current cancelation, power dissipation, and frequency shift, and how to reduce their impact. The most significant repercussion is in the radiation efficiency, which can be enhanced from 46 to 74% using a less compact design, and by reducing the forward resistance of the PIN diode, what increases the radiation efficiency by a factor of 4. (C) 2014 Wiley Periodicals, Inc.

The aim of this paper is to examine the potential of inkjet printing technology for the fabrication of Near Field Communication (NFC) coil antennas. As inkjet printing technology enables deposition of a different number of layers, an accurate adjustment of the printed conductive tracks thickness is possible. As a consequence, input resistance and Q factor can be finely tuned as long as skin depth is not surpassed while keeping the same inductance levels. This allows the removal of the typical damping resistance present in current NFC inductors. A general methodology including design, simulation, fabrication, and measurement is presented for rectangular, planar-spiral inductors working at 13.56 MHz. Analytical formulas, computed numerical models, and measured results for antenna input impedance are compared. Reflection coefficient is designated as a figure of merit to analyze the correlation among them, which is found to be below -10 dB. The obtained results demonstrate the suitability of this technology in the fabrication of low cost, environmentally friendly NFC coils on flexible substrates.