A Micro Fluxgate Magnetic Sensor Using New Printed Circuit Board Technology

This paper introduces the design of an air-filled substrate integrated waveguide (AFSIW), and a transition design from microstrip line (ML) to AFSIW at 60 GHz. The proposed structure is realized by printed circuit board (PCB) technology so that the fabrication cost is low and the whole structure is easy to be integrated with other planar components. An equivalent circuit model of the proposed ML-AFSIW transition is proposed and verified by full-wave simulation. To verify the proposed idea, a back-to-back transition is designed, fabricated and measured. The measured return loss is higher than 15 dB from 60.6 to 64.5 GHz. The minimum of measured insertion loss is 0.2 dB at 61 GHz. The measured results show that the proposed ML-AFSIW transition is suitable for millimeter-wave (mm-Wave) application.

The use of Printed Circuit Board (PCB) technology for device packaging offers new opportunities to solve these challenges. During the past decade embedding of semiconductor chips into PCB structures evolved from a research topic to volume production. The paper will briefly describe this development and categorize today's embedding technologies. First modules with embedded chips are in production in Asia and Europe, mainly for mobile applications. In Europe embedding has gained a strong interest for power modules, especially in automotive applications. Main drivers are the capability for compact and thin packaging, the high reliability and cost saving potential. The automotive industry has a strong demand for highly reliable and cost-efficient electronics. Especially the upcoming generations of hybrid cars and fully electrical vehicles need compact and efficient 400 V power modules. Within the engine compartment installation space is of major concern. Therefore small size and high integration level of the modules are needed. Embedding of power switches, and controller into compact modules using PCB (Printed Circuit Board) technologies offers the potential to reduce the thickness and size of the module. In order to replace DCB ceramics, a structure of thermal laminate material between Cu layers has been developed and the capability for thermal conduction and electrical insulation has been evaluated. For the assembly of large power IGBTs with sizes of 100 mm² and larger, new silver sintering pastes have been evaluated. They enable a pressure-less sintering at 200 °C, compatible with PCB materials. To handle the high switching current of up to 200 A, suitable copper tracks in the PCB are required. The realization of such thick copper lines with thickness up to 1 mm requires advanced processing, compared to conventional multilayer PCB production. In order to form complex power systems out of modules with embedded chips interconnections by Ag sintering are under development.

One of the beneficial methods being widely used to preserve genetic resources of imperiled animals or improved agricultural animals is cryopreservation of germplasm. During this process, the biological structure of the cells remains relatively intact by freezing and storing them at very low temperatures. Freezing condition plays an essential role in cryopreservation procedure since the exposure of the cells to low temperature can cause damage to the cells [1]. Therefore, accurate monitoring of the freezing process can improve the recovery rate of the cells after thawing. During the phase change phenomena, the dielectric and conduction properties of ice changes [2]. Herein we present, a portable platform for monitoring of the freezing and thawing processes based on the electrical impedance of the samples during cryopreservation. The system is composed of a portable temperature and impedance measurement system in conjunction with an impedance sensing probe fabricated with printed circuit board (PCB) technology. The impedance measurement circuit, temperature measurement circuit, control unit for data acquisition and wireless communication and touch screen LCD with a graphical user interface are the building blocks of the measurement system that enables users to perform impedance measurement at single or multiple frequencies with various excitation signals (Figure 1A). Utilizing impedance measurement instead of DC resistance measurement enable us to monitor both dielectric properties and resistance changes during phase change and avoids the polarization of the electrodes. In addition, an impedance sensing probe was developed by using PCB technology, which provides accurate electrodes fabrication at low cost. The probe has been designed to be used within 0.5 ml French straw which is a conventional container in cryopreservation application. Pair of parallel electrodes were fabricated on the probe at three detection zones (Figure 1B). The system was evaluated at different cryopreservation conditions including various sample solutions and cooling rates. Hank's Balanced Salt Solution (HBSS) is being widely used in cryopreservation to maintain cells in a viable state. The system was characterized by measuring the impedance in HBSS and DI water solutions solution. The 0.5 ml French straws were filled sample solution along with the probe and a T-type thermocouple. Next, the samples were placed on top of the liquid nitrogen with a 2 cm gap to freeze, and after the sample temperature reached lower than -40 oC, the samples were left at room temperature to thaw. During this process, the impedance and temperature were measured inside the samples. Figures 1C and 1D show the magnitude and phase of the measured impedance for HBSS and DI water sample respectively. When the HBSS sample starts to freeze, the impedance magnitude does not change before the latent heat removal stage. However, the impedance phase starts to increase after the sample cools down. It reaches a minimum value during nucleation and increases during latent heat removal. Therefore, the phase change phenomena can be detected with the imaginary part of the impedance. In the DI water case, the impedance starts to increase by cooling down the solution when the nucleation happens there it remains relatively constant, and it keeps increasing after that. This shows that the solution containing various ions has different impedance characteristics, which can be used as a parameter to monitor the cryopreservation phenomena. The system was also characterized by different solutions containing salts and cryoprotectants, frozen at various cooling rates, to further investigate the potential of impedimetric sensors in quality control for cell freezing protocols. Figure 1

An integrated micro fluxgate magnetic sensor

Since the 1960s, interconnection technology has been dominated by implementations of printed circuit board (PCB) technology. However, in response to the ever increasing demand for higher routing densities and improved electrical performance, this technology has been increasingly challenged by multichip module (MCM) technology and in particular the MCM‐L type. MCM‐L technology is a laminate construction and is basically a further development of PCB technology with two or more bare chips and fine line interconnects. Consequently, it is perceived that the current PCB fabricators are ideally positioned to take the initiative with MCM‐L technology. Reviews the current state of PCB industry and MCM‐L technological (process and material) requirements, within the UK, such that a comparison can be made between the two technologies. Planning, training and investment requirements for new technology implementation are then identified and compared with PCB fabricators’ technological, training, planning and investment capabilities. The shortfalls between MCM‐L fabrication requirements and PCB fabricators capability are identified and discussed.

This paper presents the design and implementation of a high density 150 V-200 V to 28 V, 200 W-400 W resonant dc-dc converter with embedded inductors. The converter has a switching frequency of 13.56 MHz and uses air-core toroidal inductors fabricated with printed circuit board (PCB) technology. Implementing the inductors with the PCB eliminates inductance variation, minimizes unwanted stray magnetic fields and parasitics, and reduces undesired coupling to the rest of the circuit. Hence, the tuning and implementation of the converter are simplified while achieving high levels of performance and power density. By not using magnetic cores, the inductors also maintain stable values over a wide temperature range. Moreover, the paper discusses the trade-offs between simplicity and performance of implementing a hard-switched gate drive at MHz switching frequencies. We describe the advantages of resonant power converter topologies in applications requiring high density and high performance in demanding environmental conditions.

This paper presents a micro fluxgate sensor fabricated by Si-based Micro Electro Mechanical Systems (MEMS). To measure X- and Y-axis magnetic fields, two fluxgate sensing elements were perpendicularly aligned. The fluxgate sensor was composed of rectangular-ring shaped magnetic core, solenoid excitation and pick-up coils. The 2 /spl mu/m thick Ni/sub 0.8/Fe/sub 0.2/ (permalloy) magnetic core layer was electroplated with photoresist frame using sputtered Ni/sub 0.8/Fe/sub 0.2/ seed layer. The fabricated fluxgate chip size was 4.5/spl times/2.7 mm/sup 2/. Excellent linear response over the range of -100 /spl mu/T to +100 /spl mu/T was obtained with 210 V/T sensitivity at excitation square wave of 2.8 V/sub p-p/ and 1.2 MHz. When two-axis fluxgate sensing element was rotated in terrestrial field, induced second harmonic voltages from X-and Y-axis were sine and cosine wave without distortion, respectively. It is very useful to commercialize the portable navigation system including north-up and map matching, military research, medical research, and space research.

Fluxgate sensor has high sensitivity and temperature stability, small size and low power consumption. Fluxgate sensors can often provide very useful alternative in determining the location or position of a magnetic object, where other technologies cannot be used. For example, the GPR only, does not provide maximum results when used to characterize the magnetic material in the conductive subsurface or has a high reflectivity zone, but fluxgate sensors are capable. Characterization of magnetic materials in the soil subsurface is required. It is used as a proxy to determine the content of heavy metals and pollutants in the soil. In this work, we have carried out the development of fluxgate sensors for detection of magnetic material in soil subsurface. The fluxgate element consists of two pick-up coils, four excitation coils, and the ferromagnetic core. The highest sensitivity of fluxgate sensors that have been developed is 877 mV/µT and a maximum absolute error of 0.066 mV/µT. This paper will discuss the influence of the frequency of the primary magnetic field of the solenoid on the sensor response, the influence of soil magnetic susceptibility, and the effect of the presence of magnetic material in the soil subsurface to the sensor response.

Microwave measurements of minute dielectric property variations have many advantages such as noninvasive test, rapid sensing capability, and being label-free. Several researches including concentration detection are promoted by measuring the minute dielectric property variations of samples. Highly sensitive and accurate device is required for measurement of electrolyte concentration in biological fluids, especially when measuring samples in nanoliter or less scale. In this paper, a miniaturized broadband coplanar waveguide (CPW) transmission-line (TL) sensor with enhanced sensitivity is proposed. The sensitive device is realized by introducing interdigital capacitance (IDC) at the central conduction band of the CPW TL. The sensor is fabricated using print circuit board (PCB) technology with a microfluidic channel designed on it. A calibration based on microwave network theory is used to obtain the characteristic impedance and propagation constant of the sensing part. And accordingly, variations in magnitude and phase of S-parameters are employed to express the changes in concentration of the sample. Furthermore, an extracted equation between S-parameters and electrolyte concentration of the sample is first proposed. Experiments show the proposed sensor can detect the minimum concentration of 0.05 g/l for the three electrolytes (NaCl, KCl, and GaCl2 in deionized (DI) water)). Compared with a corrugator coplanar transmission line and a split ring resonator senor, the proposed sensor has a much higher sensitivity. Moreover, the device is robust in front of cross sensitivity caused by external factors (such as temperature variations, moisture, etc.). Thus, the proposed sensor is well suited for low-cost, real-tine, and CMOS compatibles sensing technologies.

Rotational electret energy harvester (EH) is prototyped for powering low-power electronics from human motion. Stator with electrodes and rotor with electret are fabricated using flexible print circuit board (PCB) technology, which makes it easier to combine with metal ball bearing for rotational support. The maximum thickness for the rotational part including the eccentric mass is as thin as 3.3 mm. Output power up to 80 μW has been obtained from arm swing during walking at 1.45 m/s in our initial test.

CMOS magnetic sensors with integrated ferromagnetic parts

A novel 2-D single-layer reflective phase gradient metasurface (RPGM) with polarization-independent property is proposed based on the generalized Snell's law of reflection. The well optimized RPGM consists of 24×24 suitably selected elements with paraboloidal phase distribution along x direction and −45° phase gradient along y direction, respectively. Pure focusing effect and anomalous reflection are unambiguously observed by illuminating with different polarizations to afford physical insight into the principle of the RPGM. For demonstration and potential applications, a polarization-controlled wideband reflective device with radiation pattern selectivity is proposed based on the specially designed RPGM for the first time. Numerical and experimental results coincide well, indicating that the designed reflective device can work as a reflectarray antenna under excitation of horizontal polarization, and operate as a beam reflector under vertical polarization. More importantly, the reflective device advances in many aspects such as bifunctional radiation patterns, quite broad bandwidth of more than 5GHz (10–15GHz), and also a simple fabrication process based on the convenient print circuit board (PCB) technology. The finding opens up a new avenue to design bifunctional devices in a wide spectrum ranging from microwave to optical.

This paper presents the design and implementation of a high density 150–200 V to 28 V, 200–400 W resonant dc–dc converter with embedded inductors. The converter has a switching frequency of 13.56 MHz and uses air-core toroidal inductors fabricated with printed circuit board (PCB) technology. Implementing toroidal inductors with the PCB reduces inductance variation. Hence, the tuning and implementation of the converter are simplified while achieving high levels of performance and power density. By not using magnetic cores, the inductors also maintain stable values over a wide temperature range. Moreover, the paper discusses the tradeoffs between simplicity and performance of implementing a hard-switched gate drive at megahertz switching frequencies. We describe the advantages of resonant power converter topologies in applications requiring high density and high performance in demanding environmental conditions.

Generally, in the modern field of nanodosimetry, the Printed Circuit Board (PCB) technology based 3D positive ion detector has been identified as a device to detect cancers in lungs and breast region. In the nano environment, these cancer cells have been diagnosed by the exhalation of specific volatile organic compounds (VOCs) which serves as eminent source biomarkers for cancer diagnosis. Earlier studies reported that lungs emit various VOCs include Benzene, Ethylbenzene, Cyclohexane, methanol, ethanol, dodecane and tridecane, and the breast emit alkanes, alkenes, ketones, halogenated hydrocarbons, aldehydes, alcohols, esters, unsaturated hydrocarbons, terpenes, siloxanes, and aromates. By employing VOCs exhalation, the field of nanodosimetry aids as a direct evidence that the diagnosis of critical organs like lungs and breast cancer cells without harming the patients is possible. In our present out, we carried out in diagnosing and to distinguishing the cancer tissues of breast and lung using PCB technology based nanodosimeter.

Feasibility study of a flux-gate magnetic field sensor suitable for ITER neutral beam injectors