Printed Circuit Coil Research Articles

Using Overlapped Resonators in Wireless Power Transfer for Uniform Electromagnetic Field and Removing Blank Spots in Free Moving Applications

We propose an induction link based on overlapping arrays to eliminate blank spots on the electromagnetic field for moving object applications. We use two arrays of four aligned coils that have a 50% overlap between the two plates. This mechanism compensates for the internal coil power drop at positions in the boundaries between two adjacent external coils. We showed that if these plates are excited, a uniform electromagnetic field is created in the movement direction of the moving object. This uniform electromagnetic field distribution will result in a constant receiving power at all points in the path of the moving internal coil with the same power consumption of one coil excitation. Power delivery to the moving object tolerance reaches 10% at most, while, in non-overlapped scenarios, it is approximately 50%. In addition, according to the theoretical calculations, printed circuit coils (PCB) for the array are designed for maximum efficiency. We found that the change in distance and dimensions of the receiver coil has a linear effect on power and efficiency. Moreover, a Specific Absorption Rate (SAR) simulation was performed for biocompatibility. In this paper, we investigate and record a 68% electrical power efficiency for the fabricated system. The array consists of eight transmitters coils of the same size and shape and a receiver coil at a distance of 4 cm. Furthermore, the fabricated coil has shown improved efficiency compared to similar studies in the literature and introduces a promising structure for bio-test applications.

Frequency properties of a flexible printed circuit coil and inductive measurement of conductivity

This study investigated the frequency properties of a flexible printed circuit (FPC) coil and applied it to detect conductivity change of non-ferromagnetic metal materials. Theoretical analysis and measurements showed that the coil’s resistance and inductance are almost frequency-invariant in a particular frequency range; the coil circuit resonates at its self-resonant frequency. With no concern for its thickness, the conductivity of a test object can be measured with high sensitivity and accuracy by using the coil in its frequency-invariant range, based on the “same ωσ, same impedance” principle. In the case that the influence of thickness has to be eliminated, the variation of conductivity can be sensitively detected by using the coil’s resonant properties. The proposed methods have been verified with measurement of standard test pieces whose conductivities were given in advance, and applied to detect conductivity change of deteriorated tube.

A Modified Wireless Power Transfer System for Medical Implants

Wireless Power Transfer (WPT) is a promising technique, yet still an experimental solution, to replace batteries in existing implants and overcome the related health complications. However, not all techniques are adequate to meet the safety requirements of medical implants for patients. Ensuring a compromise between a small form factor and a high Power Transfer Efficiency (PTE) for transcutaneous applications still remains a challenge. In this work, we have used a resonant inductive coupling for WPT and a coil geometry optimization approach to address constraints related to maintaining a small form factor and the efficiency of power transfer. Thus, we propose a WPT system for medical implants operating at 13.56 MHz using high-efficiency Complementary Metal Oxide-Semiconductor (CMOS) components and an optimized Printed Circuit Coil (PCC). It is divided into two main circuits, a transmitter circuit located outside the human body and a receiver circuit implanted inside the body. The transmitter circuit was designed with an oscillator, driver and a Class-E power amplifier. Experimental results acquired in the air medium show that the proposed system reaches a power transfer efficiency of 75.1% for 0.5 cm and reaches 5 cm as a maximum transfer distance for 10.67% of the efficiency, all of which holds promise for implementing WPT for medical implants that don’t require further medical intervention, and without taking up a lot of space.

Evaluation Algorithms for Linear Position Sensors Assisted by Artificial Neural Network

An artificial neural network assisted compact linear inductive position sensor is presented. The sensor operates with a long primary printed circuit coil excited with periodically alternating current, and with multiple secondary printed circuit coils possessing different induced voltages as a position of a metallic or resonant target moving along the coil system. The secondary coil signals are phase sensitively demodulated, digitized and passed to the input layer of an artificial neural network trained to estimate the position of the target, its distance from the sensor and the signal quality.

Powering an Implantable Minipump with a Multi-layered Printed Circuit Coil for Drug Infusion Applications in Rodents

We report the use of a multi-layer printed coil circuit for powering (36-94 mW) an implantable microbolus infusion pump (MIP) that can be activated remotely for use in drug infusion in nontethered, freely moving small animals. This implantable device provides a unique experimental tool with applications in the fields of animal behavior, pharmacology, physiology, and functional brain imaging. Two different designs are described: a battery-less pump usable when the animal is inside a home-cage surrounded by a primary inductive coil and a pump powered by a rechargeable battery that can be used for studies outside the home-cage. The use of printed coils for powering of small devices by inductive power transfer presents significant advantages over similar approaches using hand-wound coils in terms of ease of manufacturing and uniformity of design. The high efficiency of a class-E oscillator allowed powering of the minipumps without the need for close physical contact of the primary and secondary coils, as is currently the case for most devices powered by inductive power transfer.

Designing printed circuit stators for brushless permanent magnet motors

Progress in a number of areas of technology has made printed circuit motors a serious contender for many applications. Modern cost effective neodymium magnets have allowed compact motor designs. Multi-layer circuit board production techniques have made the production of printed circuit coils cheaper and easier. However, in spite of the growing importance of printed circuit brushless motors, there is a lack of analytical tools to assist with their design. Geometrical analysis has been used to allow the plotting of printed circuit tracks to be carried out more systematically. The track plotting procedures have been linked with the finite element method to predict rotational electromotive force (EMF) waveforms. Six prototype motors were built and they were used to experimentally validate the method of predicting EMF waveforms. A general design algorithm is presented based on the suggested track plotting procedure and the EMF prediction technique.

Rotating coil measurement system for the APT/LEDA CCDTL quadrupole magnets

A rotating coil measurement system has been developed to characterize the magnetic properties of the Coupled Cavity Drift Tube Linac (CCDTL) quadrupole magnets for the Accelerator Production of Tritium-Low Energy Demonstration Accelerator (APT/LEDA) at the Los Alamos Neutron Science Center (LANSCE). The setup is designed to measure the quadrupole gradient-length product with an absolute error of less than 0.25%, and to determine the relative multipole content of the quadrupole at a radius of 80% of the aperture. The bench for the system consists of a granite surface plate with a pair of rails attached on which the magnet and rotating coil supports rest. The signal is routed through a slipring to a digital voltage integrator triggered by an incremental encoder attached to one end of the coil. Two different rotating coils were designed and fabricated for the system. The first coil is a conventional radially-wound harmonic coil that provides a good measure of the relative quadrupole strength and harmonic content, while the second coil is a specially designed printed circuit coil that can accurately measure the quadrupole gradient-length product.

A method to measure poloidal field coil irregularities in toroidal plasma devices

A ring of accurately placed and matched printed circuit coils is placed at the center of the DIII-D tokamak vacuum vessel, aligned magnetically with the toroidal field and used to measure the nonaxisymmetric magnetic field of each of the 18 poloidal field coils. [Toroidal and poloidal variations can be of mode n and m, respectively, with helical variations of form cos(nφ−mθ).] From the error fields, it is computed that the most irregular poloidal field coil is one of the outer vertical field coils having a shift of 1.9 ±0.2 cm (compared to a diameter of 482 cm), and having an ellipticity 1.0027. All the 18 poloidal field coils together make a resonant, helical, radial error field for m=2, n=1 of about 1.4 × 10−4 of the toroidal field.

A method to measure magnetic field perturbations in plasma devices

Magnetic field perturbations with specific spatial geometry can be detected in the presence of a large magnetic field ‘‘background’’ using printed circuit pickup coils which have the advantages of large effective area, near dc frequency response, precise geometry, thin profile, and low cost. The design and construction techniques to produce these coils are presented. A printed circuit coil has been used to detect the magnetic field from the perturbed plasma current distribution in the TEXT tokamak due to current in an external helical (m=7,n=3) winding. The measured sensitivity of this coil, ΔBcoil/Btotal, is ∼3×10−6.

Magnitude and Phase Measurements of Flux Density Profiles in AC Machine Airgaps

The development and testing of a technique capable of measuring and displaying the instantaneous flux density profile in the airgaps of ac electromagnetic machines is described. An over-layed system of flexible printed-circuit coils is used, which permits measurements to be made under rotating conditions in airgaps as small as 0.3 mm, giving good profile definition over the whole of the airgap. The signals are processed on line by a digital computer. The ability to cover large areas and small airgaps with on-line signal processing gives the technique considerable advantage over existing methods.