Printed Circuit Technology Research Articles

Low-cost flexible printed circuit technology based microelectrode array for extracellular stimulation of the invertebrate locomotory system

The biobotic control of invertebrates through functional electrical stimulation of neural and neuromuscular tissue is under active exploration. Implantable microelectrodes are often designed to be used in chronic long term applications in vertebrates and subjected to strict endurance and resolution requirements. However, these constraints can be relaxed in invertebrate-related applications to allow low cost production for high-volume markets. In this study, we propose flexible printed circuit board (flex-PCB) based electrodes for implantable neuromuscular stimulation, address related shortcomings, and suggest modifications in the fabrication process. We were able to obtain a charge storage capacity of 3.18 mC/cm 2 and 1 kHz impedance of 52 kΩ with gold electroplated 100 μm × 100 μm electrode sites on the flex-PCB electrodes. The electrodeposition of iridium oxide and electrochemical polymerization of PEDOT with dopant PSS on microelectrodes enhanced the charge storage capacity to 38.9 and 124.3 mC/cm 2 where the 1 kHz impedance magnitude was 16 kΩ and 3 kΩ, respectively. This improvement in electrochemical performance was also corroborated by current pulsed voltage excursion studies. The long term dip test in saline solution supports the potential of flex-PCB electrodes for neural electrostimulation of insects, while revealing potential instability in PEDOT-PSS coatings with continuous high current density pulsing.

Simple analytical calculation approach for input impedance of printed monopole and dipole antennas on thin substrate

AbstractPrinted antennas are very popular for commercial and military RF (radio frequency)/microwave communication systems because there is an enormous evolution in printed circuit technology. In this study, printed monopole and filamentary excited dipole, which are basic models and easily applicable antennas within printed antennas, are analyzed, and analytical closed‐form relations have been obtained. The expressions obtained in this article have been verified by CST Microwave Studio simulation numerically, and experimentally measured and published results are available in the open literature. The compared results are close to each other. Therefore, these relations could be used as an initial design step just before detailed numerical analyses. Moreover, the given closed‐form formulations can be realized in CAD platforms easily for fast calculations. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:827–830, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25880

Frequency Steerable Two Dimensional Focusing Using Rectilinear Leaky-Wave Lenses

The concept of frequency steerable two-dimensional electromagnetic focusing by using a tapered leaky-wave line source embedded in a parallel-plate medium is presented. Accurate expressions for analyzing the focusing pattern of a rectilinear leaky-wave lens (LWL) from its constituent leaky-mode tapered propagation constant are described. The influence of the main LWL structural parameters on the synthesis of the focusing pattern is discussed. The ability to generate frequency steerable focusing patterns has been demonstrated by means of an example involving a LWL in hybrid waveguide printed-circuit technology and the results are validated by a commercial full-wave solver.

Evolutionary Generation of Subwavelength Planar Element Loaded Monopole Antenna

A very compact monopole antenna with an evolutionarily generated subwavelength planar element is proposed for the antenna miniaturization without using any lumped capacitors and inductors. The monopole antenna is composed of a coaxial-fed short line etched on one side of dielectric substrate and a subwavelength element on the other side, enabling an easy fabrication using a printed circuit technology. To design the arbitrarily shaped subwavelength element, an efficient genetic algorithm (GA) design technique is employed. As a design example, a monopole antenna with 1/23-wavelength height and 1/17-wavelength width at 430 MHz is demonstrated. The predicted results of the radiation pattern and the reflection characteristic are compared to measured data, and good agreement between the two results is achieved.

Special Reviews of Trends in Recent Printed Circuit Technology

Special Reviews of Trends in Recent Printed Circuit Technology

Special Reviews of Trends in Recent Printed Circuit Technology

Special Reviews of Trends in Recent Printed Circuit Technology

Instrumentation and Quench Protection for LARP ${\rm Nb}_{3}{\rm Sn}$ Magnets

The US LHC Accelerator Research Program (LARP) is developing Nb3Sn prototype quadrupoles for the LHC interaction region upgrades. Several magnets have been tested within this program and understanding of their behavior and performance is a primary goal. The instrumentation is consequently a key consideration, as is protection of the magnet during quenches. In all LARP magnets, the flexible circuits traces combine the instrumentation and the protection heaters. Their fabrication relies on printed circuit technology based on a laminate made of a 45-micron thick kapton sheet and a 25-micron thick foil of stainless steel. This paper reviews the protection heaters designs used in the TQ (Technology Quadrupole) and LR (Long Racetrack) series as well as the one used in LBNL HD2a high field dipole and presents the design of the traces for the Long Quadrupole (LQ), addressing challenges associated with the stored energy and the length of the magnet.

Chiral Media Based on Printed-Circuit Board Technology: A Numerical Time-Domain Approach

The common design of artificial chiral media for microwave frequencies is based on the inclusion of particles with chiral symmetry (i.e., specular symmetry or handedness) into a host medium. Recently, we have considered new fabrication techniques based on printed-circuit board technology, because the use of via holes gives us great additional flexibility to select the type of chiral inclusions from helix to cranks. In this paper, a numerical study in the time domain of the electromagnetic-wave propagation through these types of structures is achieved by using the commercial software MEFiSTo, a time-domain electromagnetic simulator based on the transmission-line matrix method.

A DUAL-BAND MULTIFUNCTION CARBORNE HYBRID ANTENNA FOR SATELLITE COMMUNICATION RELAY SYSTEM

A dual-band multifunction hybrid antenna for carborne satellite communication relay system is presented in this paper. As a consequence of the radiation requirements, the proposed antenna consists of a left-hand circularly polarized (LHCP) microstrip patch and an omnidirectional biconical antenna with a conductor tube holding and radome. The LHCP microstrip antenna is used for satellite signal reception, and biconical antenna is used for relay communication transmission. A novel overmoded coaxial waveguide feed structure eliminates the interference between two feed ports. The proposed antenna has the advantages of robustness, low cost, and easy fabrication with conventional materials and printed circuit technology. An antenna prototype is fabricated to validate the design. Both the simulated and measured results are obtained with reasonable agreement.

A Broadband Printed Helix-Type Antenna for Wireless Communications at High Frequencies

A broadband printed helix-type antenna element is presented in this paper for its operation at high frequencies. This helix-type antenna is first equivalently modeled by a series of horizontal arcs which are then connected by vertical wires. This antenna element can be realized by printed circuit technologies by printing its arcs on the interfaces of a multi-layer substrate and connecting the arcs' terminals by using conducting via. Thus the manufacture cost may be significantly reduced for mass production. Numerical and experimental studies indicate that this antenna may retain the characteristics of broadband operational frequencies as exhibited in the regular helix antenna with reasonably well gains.

A Frequency Selective Surface With Miniaturized Elements

We demonstrate a new class of bandpass frequency selective surface (FSS), the building block of which, unlike the traditional FSSs, makes use of resonant dipole and slot structures that have dimensions much smaller than the operating wavelength. This design allows localization of bandpass characteristics to within a small area on the surface which in turn facilitates flexible spatial filtering for an arbitrary wave phasefront. The proposed FSS is made up of periodic array of metallic patches separated by thin air-gaps backed by a wire mesh having the same periodicity (Ltlambda). The array of metallic patches constitute a capacitive surface and the wire mesh a coupled inductive surface, which together act as a resonant structure in the path of an incident plane wave. Like traditional FSSs, the capacitive and inductive surfaces of the proposed FSS can easily be fabricated using printed circuit technology on both sides of microwave substrates. It is shown that by cascading such bandpass surfaces in a proper fashion, any arbitrary multipole filter or non-commensurate multiband response can be obtained. The frequency response of the proposed miniaturized-element frequency selective surface (MEFSS) is demonstrated for various incident angles and it is shown that one-pole designs are less sensitive than two-pole designs to the angle of incidence. Dual band designs are also possible based on two-pole designs, but are more sensitive to incident angle than single band designs because of their larger (in terms of wavelengths) spacing. Prototypes of single-pole and dual-pole MEFSSs are fabricated and tested in a waveguide environment at X-band frequencies and excellent agreements between the measured and simulated results are demonstrated

Circularly polarized omnidirectional millimeter wave monopole with parasitic strip elements

AbstractA circularly polarized omnidirectional millimeter wave monopole with parasitic strip elements for a system of arrival signal direction detection in millimeter band is presented. As a consequence of the radiation pattern requirements, the proposed antenna consists of a conical skirt monopole with a polarizer radome. The polarizer converts a wave from linear to circular polarization. The proposed antenna has the advantage to be robust, low cost, and easy to fabricate with conventional materials and printed circuit technology. The study presents simulation and experimental results obtained with an antenna prototype that validate the design. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 664–668, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22237

Correction of Dielectric Losses in Practical Leaky-wave Antenna Designs

In this paper, the leaky-mode theory is applied to take into account for the dielectric losses in millimetre waveband inhomogeneous leaky-wave antennas. A practical dielectric-filled cosine-tapered periodic leaky-wave antenna working in the 45 GHz band is studied, showing how the desired sidelobes level and directivity are spoilt due to the effect of the losses. An iterative procedure is used to correct the negative effects of the losses in the radiation patterns of the leaky-wave structure. It is also shown the practical limits of the proposed correction approach. The leaky-mode theory is applied for the first time to compensate the losses in a practical leaky-wave antenna in hybrid waveguide printed circuit technology. This leaky-mode theory is validated with full-wave three-dimensional finite element method simulations of the designed antenna.

Space Charge Observation in Aramid/Epoxy Insulations Under DC Electric Fields

With the progress of printed circuit technology, the reliability of bulk insulation has become important, as well as that of surface insulation, particularly in multilayer boards and embedded boards. We observed the space charge behavior of various insulating materials used in printed circuit boards, and found that internal charges move in aramid/epoxy specimens under dc electric fields. The electric field near the surface of the specimen, therefore, was increased to have more than twice the strength of the average applied field. The space charge profile was influenced by the internal structure, and its formation was accelerated by the increase of temperature. Since the space charge profile affects the internal electric field distribution, the internal charge behavior should be examined with respect to the design of the insulation of a printed circuit board

Simple Analysis and Design of a New Leaky-Wave Directional Coupler in Hybrid Dielectric-Waveguide Printed-Circuit Technology

This paper presents a new theory to analyze and design a novel leaky-wave coupler based on a hybrid dielectric-waveguide printed-circuit technology. The analysis theory is based on a combined method of moments (MoM) geometrical optics (GO) technique, which makes use of the leaky mode complex propagation constant. This MoM-GO approach allows to easily obtain the response of the coupler, and to illustratively understand the working mechanism of the proposed structure. A coupler is designed to work at 5.5 GHz. Leaky mode results are compared with three-dimensional finite-element method simulations, showing the validity and accuracy of the new theory developed. This novel directional coupler presents interesting advantages when compared to previous wave couplers

A novel full-wave CAD for the design of tapered leaky-wave antennas in hybrid waveguide printed-circuit technology

This work presents a novel computer-aided design (CAD) tool for the design of tapered leaky-wave antennas (LWAs) in hybrid waveguide printed-circuit technology. The software package is composed of several tools, which are connected together to provide a semi-automated step-by-step design procedure. The design procedure is presented and the different tools are described, together with the involved theory, leading to the design of tapered LWAs. A practical taper design is performed, and comparisons with simulations using commercial software (HFSS) are presented for validation purposes. Due to the full-wave nature of the technique used in the analysis engine, excellent agreement is shown between the proposed 2D-based approach, and 3D HFSS results. Also, the analysis procedure is fast, thus leading to semi-automated designs that are not affordable with common 3D optimization techniques. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.

Microheater-integrated single gas sensor array chip fabricated on flexible polyimide substrate

A microheater-integrated sensor substrate for the single 16-channel sensor array chip was prepared from a polyimide film by modifying the fabrication processes used in the flexible printed circuit technology. Conductive copper layers were patterned to form interdigitated detection electrodes and a resistive heating line at front and backsides, respectively. The microheater was found to have the power consumption of 1.35 mW mm −2 at an operation temperature of 40 °C and was possible to act as a thermometer, simultaneously, possessing the temperature coefficient of resistance of 37 × 10 −4 °C −1. Vapor-sensing materials were deposited on the detection electrodes by casting of carbon black–polymer composite solutions. Their ethanol-sensing characteristics have been investigated carefully as a function of the analyte concentration and the operation temperature. The response magnitude linearly intensified with increasing the ethanol concentration in the wide range of 60–8000 ppm in air and generally decreased as the operation temperature goes from 22 to 60 °C. This temperature dependence could be explained with the variation in analyte solubility induced by the thermodynamic enthalpy change during the sensing process. By using the sensor array chip and the principal component analysis, classification was successfully made among the three different volatile organic compounds of ethanol, toluene and benzene.

Low-cost microelectrode array with integrated heater for extracellular recording of cardiomyocyte cultures using commercial flexible printed circuit technology

This article reports the use of commercial, flexible printed circuit technology for the fabrication of low-cost microelectrode arrays (MEAs) for recording extracellular electrical signals from cardiomyocyte cultures. A 36-electrode array has been designed and manufactured using standard, two-layer, polyimide-based flexible circuit technology, with electrode diameters of 75 and 100 μm. Copper structures defined on the backside of the array have been used for low-power thermal regulation of the culture. Electrical characterization of the gold-plated electrodes showed impedances below 250 kΩ at 1 kHz. Functional testing was conducted using HL-1 cardiac myocytes. The arrays proved biocompatible, and supported the formation of functional syncytia, as demonstrated by electrical recordings of depolarization waves across the array. A comparison with conventional, glass-based MEAs is presented, which reveals differences in signal strength (smaller for larger electrode) and variability (less for larger electrodes), but no effect of the substrate types on culture parameters such as beat rate or conduction velocity. The performance of the on-chip heating was evaluated, with typical temperature settling times (to ±0.1 °C) below 10 s, for a power consumption around 1 W (at 37 °C). Accuracy and stability are discussed. HL-1 cell responses to various temperature profiles enabled by the on-chip heating are presented, showing a remarkable correlation between temperature and beat rate.

A microchip-based PCR device using flexible printed circuit technology

A microchip-based PCR device using flexible printed circuit technology

Electromagnetic crystal technology for waveguides and bends at microwave frequencies

The design, breadboarding and measurements of a waveguide and a 90° bend in electromagnetic crystal technology at Ku band are presented. These devices were fabricated in printed circuit technology fed by two microstrip lines. A good match between simulation and measurement has been achieved. Their promising properties make them potentially suitable for microwave and more stringent millimetre-wave applications.