Planar Printed Circuit Board Research Articles

A 10 µH Inductance Standard in PCB Technology with Enhanced Protection against Magnetic Fields

Low-frequency working standards of inductance are generally uniformly wound toroids on a ceramic core. Planar inductors made using printed circuit board (PCB) technology are simple and cheap to manufacture in comparison to inductors wound on toroid cores, but they are significantly prone to the influence of external magnetic fields. In this paper, we propose the design of a PCB inductance working standard of 10 μH, consisting of a duplex system of planar PCB coils, electrostatic shielding, and an enclosure. Alongside an electromagnetic analysis and design procedure, the measurements on the manufactured prototype included the generated magnetic field, the thermal time constant of the enclosure, temperature coefficients, and its error analysis. The measurements show negligible generated magnetic fields (<1.68 nT at 7 cm, 49 mA, 10 kHz). The minimum thermal time constant of the enclosure is 1270 s and the temperature coefficient of resistance is 0.00384 1/℃. The presented method of temperature coefficient measurement using a climate chamber allows for measurements in the temperature range of 10 °C to 40 °C. In this temperature range, the results show an inductance variation of 0.05 µH at 50 kHz, while the uncertainty of inductance measurement at this frequency was 0.03 µH (k = 2).

A high-performance sub-THz planar antenna array for THz sensing and imaging applications

Terahertz (THz) spectral region from 0.1 to 3 THz is envisaged to hold immense potential in the next generation of wireless technologies. Recently, research has focused on this terahertz gap, because of its unprecedented channel capacities. At the physical layer, the design complexities and fabrication of THz devices, especially antennas are the prime bottlenecks to realize its full potential. This article introduces a cost-effective, easy-to-fabricate, and reproducible sub-THz antenna design based on a single-layer planar printed circuit board technology. The antenna incorporates carefully designed quasi-cross slots and applied machine learning-assisted global optimization techniques to achieve the desired performance metrics. The antenna performance is elucidated through numerical simulations and verified through a rigorous in-house THz experimental framework around 100–110 GHz. The proposed antenna offers a peak gain of 13.90 dBi with less than 1 dB variation within the entire band of 100–110 GHz. The antenna holds the potential to achieve terabits per second data rates and futuristic high-resolution short-range THz imaging applications.

Ultra‐fast finite element analysis of coreless axial flux permanent magnet synchronous machines

AbstractLarge‐scale design optimisation techniques enable the design of high‐performance electric machines. Electromagnetic 3D finite element analysis (FEA) is typically employed in optimisation studies for accurate analysis of axial flux permanent magnet (AFPM) machines, which require extensive computational resources. To reduce the computational burden, a FEA‐based mathematical method relying on the geometric and magnetic symmetry of coreless AFPM machines is proposed to estimate the machine performance indicators using the least number of FEA solutions, thereby significantly lowering the running time. This method is generally applicable to AFPM machines with low saturation effects and cogging torque as exemplified for a printed circuit board (PCB) stator coreless AFPM machine. To further reduce the computation time, a systematically simplified equivalent 3D FEA model for planar PCB coils integrated with this machine is also proposed. The practical implementation of the introduced method is elaborated based on an example optimisation study, and an analytical method for fast design scaling is also discussed. The results of the proposed approach are compared with detailed transient FEA results, and a prototype 26‐pole PCB stator coreless AFPM machine was also used to validate the results experimentally.

Noise and thermal performance of a sub-attofarad capacitance sensor for precision measurements, with applications in gravitational wave detectors.

We describe the design principles, fabrication, and characterization of a precision AC resonant capacitance bridge (RCB) sensor, based on a resonant differential planar printed circuit board transformer with a solid (ungapped) MnZn ferrite core, demonstrating a short-term sensitivity at 293K of 0.225 ± 0.005 aF/√Hz at around 120kHz resonance frequency and 1Hz Fourier measurement frequency. At 120K, the RCB short term noise sensitivity is 0.118 ± 0.005 aF/√Hz. We compare the ungapped configuration to five different RCBs: three with a core gap of 65 μm and two with a core gap of 130 μm. Their average room temperature short term noise sensitivities are 0.30 ± 0.01 and 0.45 ± 0.01 aF/√Hz, while the cryogenic operation of these transformers at 120K resulted in averaged sensitivities of 0.23 ± 0.01 and 0.36 ± 0.01 aF/√Hz, respectively. Multi-hour room temperature runs, with one core of each of the three gap types, proved the stability of their long-term sensitivities of 0.234 ± 0.005, 0.338 ± 0.009, and 0.435 ± 0.010 aF/√Hz for the ungapped (40-h duration) and the 65 and 130 μm (28-h duration) cores, respectively. At 0.1mHz, a critical frequency for space gravitational wave detectors, the respective sensitivities are 0.25 ± 0.02, 0.35 ± 0.02, and 0.53 ± 0.07 aF/√Hz. Measurements with the ungapped transformer configuration for temperatures from 325 to 349K further validate the dependence of the noise model on temperature and permeability. The performance of our RCB with an ungapped core matches the calculated performance value and shows an improvement in signal-to-noise ratio of two or more compared with capacitance bridges developed for similar applications. A further factor of about two noise reductions is achieved by cooling to 120K.

Design and simulation of a rectangular planar printed circuit board coil for nuclear magnetic resonance, radio frequency energy harvesting, and wireless power transfer devices

AbstractIn this study, a planar printed circuit board (PCB) coil with FR4 substrate was designed and simulated using the finite element method, and the results were analyzed in the frequency domain. This coil can be used in wireless power transfer (WPT) as a transmitter or receiver, eliminating wires. It can also be used as the receiver in radio frequency energy‐harvesting (RF‐EH) systems by optimizing the planar PCB coil to convert radio‐wave energy into electricity, and it can be employed as an excitation (transmitter) or receiver coil in nuclear magnetic resonance (NMR) spectroscopy. This PCB coil can replace the conventional coil, yielding a reduced occupied volume, a fine‐tuned design, reduced weight, and increased efficiency. Based on the calculated gain, power, and electromagnetic and electric field results, this planar PCB coil can be implemented in WPT, NMR spectroscopy, and RF‐EH devices with minor changes. In applications such as NMR spectroscopy, it can be used as a transceiver planar PCB coil. In this design, at frequencies of 915 MHz and 40 MHz with 5 mm between coils, we received powers of 287.3 W and 480 W, respectively, which are suitable for an NMR coil or RF‐EH system.

A multi-unit integrated electrochemical biosensor array for synergistic signal enhancing carbohydrate antigen 125 detection

Significant progress has been made in recent decades; however, the development of an accurate, portability and high-throughput electrochemical biosensor for quantifying trace biomarker in complex biological samples remains challenging. In this study, we described a novel 3 × 3 multi-unit portable integrated biosensor array, specifically designed for parallel and precise detection of trace levels of carbohydrate antigen 125 (CA-125) using multiplex synergistic signal amplification. The sensor array substrate was constructed on a planar printed circuit board (PCB) using printing technology, making them integrated, portable, affordable and disposable. The exceptional sensitivity of the biosensor is attributed to the nitrogen-doped mesoporous carbon (NMC) nanomaterial, which possesses a large surface area, superior conductivity and tunable pore size, enabling high affinity of and enzyme catalytic activity. The integrated biosensing array platform consists of individually controlled sensors, allowing for high-throughput tests of the same sample simultaneously, ensuring the reliability and accuracy of assay. The developed biosensor array system demonstrated excellent sensitivity and rapid CA-125 assay, achieving an impressive detection limit as low as 0.027 U/mL (S/N = 3). Meanwhile, the high-throughput multiplex test results (n = 9) were obtained within a short timeframe of 30 min. Ultimately, the biosensor array successfully quantified CA-125 in human serum, yielding results comparable to the enzyme–linked immunosorbent assay technique. This technology presents a highly promising strategy that can be potentially extended to detect other biomarkers for biological analysis and early disease diagnosis.

D-Band Air-Filled Substrate Integrated Waveguide (AFSIW) and Broadband Stripline to AFSIW Launcher Embedded in Multi-Layer PCBs

We report <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$</tex-math> </inline-formula> -band air-filled substrate integrated waveguides (AFSIWs) with solid copper sidewalls fabricated inside a multi-layer printed circuit board (PCB) with broad wall width of 1.6 mm and cavity height of 300 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> m. Measurements show a loss of 0.07–0.08 dB/mm across 115–155 GHz. This result is the first demonstration of an AFSIW above 100 GHz in a low-cost mass manufacturable PCB and has the lowest loss compared to reported planar PCB lines or substrate integrated waveguides (SIWs) in PCBs and Interposers. We also introduce a broadband stripline to the AFSIW launcher using a broad wall transverse slot which offers ease of manufacturability over existing transitions having a measured insertion loss of 1.1 dB and 27% bandwidth. The combination of a low-loss AFSIW and wideband launcher allows both striplines and AFSIWs to coexist in the same multi-layer PCB.

Design of a Low-Profile Dual Linearly Polarized Antenna Array for mm-Wave 5G

This work proposes a dual linearly polarized antenna array for 5G mm-wave band, which is designed to be compatible with planar printed circuit board technology. The proposed antenna is engineered with a focus on simplifying the antenna geometry and eliminating any critical issues that may arise in antenna manufacturing. The proposed antenna has been evaluated, finding a 7% impedance bandwidth centered around 27.28 GHz. Additionally, the beam steering capability of the antenna is found to cover a ±30% angular width for both linear polarizations. These findings highlight the potential of the proposed antenna for use in 5G mm-wave band applications, where compatibility with planar printed circuit board technology and simplified antenna geometry are essential design requirements.

Dual-Band Filtering Switches Using Multimode Dielectric Resonators With Hybrid Boundaries

Miniaturized dual-band filtering switches are proposed in this article using multimode dielectric resonators (DRs). The planar printed circuit boards (PCBs) are utilized not only to construct the hybrid electromagnetic boundary for quad-mode DR, but also to offer the switchable multimode feeding structures with the p-i-n diodes. When the diodes are reversely biased, all the four modes are excited simultaneously by the mixed electric and magnetic couplings and controlled flexibly to construct the dual-band response. In this manner, extra losses from diodes are avoided, and low-loss transmission is realized. When the diodes are forward biased, all the four modes are shut off at the same time. Owing to the used mixed electric and magnetic couplings, the isolation is enhanced further by the cancellation of the electric and magnetic couplings between the feeding line and the resonant modes. For demonstration, both dual-mode and quad-mode filtering switches with dual-band operations are fabricated and tested. With only one quad-mode DR, high performance, including low-loss dual-band transmission and high-level isolation, is observed in the measurement, making the proposed switches promising in high-standard multiband time division duplex (TDD) systems.

A New Integrated Active EMI Filter Topology With Both CM Noise and DM Noise Attenuation

Integration of electromagnetic interference (EMI) filters is a good idea to further decrease the volume and weight of a power converter. However, the conventional research articles mainly focus on the integration of passive components or planar printed circuit board structures. This article proposes a new integrated active EMI filter (AEF) topology. It can attenuate both common-mode (CM) and differential-mode (DM) noise at the same time. Different from the traditional discrete CM AEFs and DM AEFs, noise sensing and cancelation of this proposed topology are performed simultaneously. The working principle and special features of this topology are analyzed in detail. Based upon the theoretical analysis, the insertion loss of this integration topology is close to the traditional separated CM AEFs or DM AEFs. Besides fewer components and dc power supply are demanded. A prototype is built and tested through experiments. Experimental results derived on standard test board and practical converter show good agreement to theoretical analysis.

A Planar Distributed Multicoil Antenna to Generate 3-D Ellipsoidally Polarized H-Field for Angular Misalignment Tolerant WPT System

This article presents 3-D polarized magnetic-field forming using a planar multicoil transmitter antenna for wireless power transfer (WPT) applications. Three orthogonal <inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula>-field components resulting in optimized 3-D ellipsoidal polarization are generated to mitigate the angular misalignment problem by the proposed antenna. The analytical optimization of the 3-D polarized <inline-formula> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula>-field is presented, and its effect on induced voltage in the receiver coil is investigated. To achieve unconstrained induced voltage in the receiver independent of its angular movement, an optimized planar multicoil design is proposed for a maximum S21 between the transmitter and the receiver coil antennas. Unlike the 3-D transmitter designs available in the literature, the proposed antenna is a 2-D planar printed circuit board (PCB) design, therefore, represents a cost-effective solution and is suitable for various practical WPT applications. The analytical results of the design are verified experimentally. The result proves that the proposed antenna is able to completely mitigate the angular misalignment problem, which represents a potential planar antenna solution for orientation-insensitive WPT applications.

Direct cooling of a planar magnetic converter using dielectric liquid forced convection enabled by additive manufacturing

Power densification of magnetic converters has encountered a fundamental challenge due to the inability to effectively remove heat produced by power losses. State-of-the-art thermal management technologies for planar printed circuit board (PCB) transformers are limited by the inability to substantially improve the overall thermal conductance from the transformer to the cold plate. Furthermore, a lack of thermal management technologies capable of reducing temperature gradients in these devices exists. Direct liquid cooling reduces the number of thermal resistances from hot spot to coolant, resulting in lower maximum temperatures and reduced thermal gradients. Here, we study the thermal-hydraulic performance of a PCB planar transformer cooled using a polymer additively manufactured (AM) housing and single-phase internal flow with Novec 7300 and pure ethylene glycol. Computational fluid dynamics simulations were used to identify hot spots, quantify temperature gradients, and characterize pressure drop. Experiments in a custom-made setup quantified the maximum temperature and pressure drop with different flow rates (0.4–4 LPM) of Novec 7300 and ethylene glycol. Both working fluids showed better thermal-hydraulic performance when compared to results found in literature which implements cold-plates. Analysis reveals that selection between both fluids is guided by flow rate, pressure drop and pumping power, such that if low pressure drop is a priority, Novec 7300 is a better choice, and if low pumping power and flow rate are a priority, ethylene glycol is better. Our results show that direct liquid cooling can reduce thermal resistance by up to 80% using an 80% lower pressure drop when compared to a cold-plate benchmark. As a result, the developed AM-enabled thermal management technology can potentially improve the reliability of the converter, provide an alternative for high temperature heat recovery, and facilitate further converter power densification.

A Review of Flexible Multilayer Foil Integration Technology for Passive Components

Passive integration technology is widely used in power electric converters since it can significantly reduce the volume of the passive components and improve the power density. This article highlights the flexible multilayer foil (FMLF) integration technology since it can meet the future requirements than other integration technologies. The realization, structures, and applications of the FMLF integration technology are summarized. The magnetic materials, dielectric materials, and conductive materials used in FMLF are investigated. Then, the approaches of the analysis and design for FMLF integrated units are introduced. Finally, it is compared with the planar printed circuit board integration technology to highlight the advantages of its characteristics and expounds its future research fields. Eventually, the power electronics engineers and researchers can comprehend the intrinsic properties of the FMLF integration technology.

Mutual inductance of two coaxial rectangular PCB coils incorporating magnetic layer

Abstract The wireless connection distance between the transmission and reception coils of printed circuit boards (PCB) influences the mutual inductance and affects circuit performance. In this study, the mutual inductance M of PCB coils was investigated, and two analytical methods were presented for calculating the mutual inductance between two coaxial rectangular planar PCB coils incorporating magnetic layer. The results were acquired through calculations by using the Neumann integral and Biot-Savart methods. The complete integral calculations and detailed demonstrations of the two methods are presented. The obtained formulas were introduced in some examples of coils with different number of turns. The analytical and experimental results were compared, and a strong agreement between them was observed.

A 28-GHz Switched-Beam Antenna with Integrated Butler Matrix and Switch for 5G Applications.

This work presents a 28-GHz Butler matrix based switched-beam antenna for fifth-generation (5G) wireless applications. It integrates a 1 × 4 microstrip antenna, a 4 × 4 Butler matrix, and a single-pole four-throw (SP4T) absorptive switch in a single planar printed circuit board and is housed in a metal enclosure. Co-integration of a packaged switch chip with the Butler matrix based switched-beam antenna greatly enhances the form factor and integration level of the entire system. A wideband two-section branch line coupler is employed to minimize the phase and magnitude errors and variations of the Butler matrix. The aluminum metal enclosure stabilizes the electrical performances, reduces the sidelobes, and improves the structural stability. The fabricated antenna with the metal enclosure assembled has a dimension of 37 × 50 × 6.2 mm3. With an RF input signal fed to the antenna’s input port through a single Ka-band connector, and the switching states chosen by 2-bit dc control voltages, the antenna successfully demonstrates four directional switched beams. The beam switching operations are verified through the over-the-air far-field measurements. The measured results show that the four beam steering directions are −43°, −17°, +10°, +34° with side lobe levels < −5.3 dB at 28 GHz. The antenna also shows reasonably wideband radiation patterns over 27–29 GHz band. The 10-dB impedance bandwidth is 25.4–27.6 GHz, while a slightly relaxed 8-dB bandwidth is 25.2–29.6 GHz. Compared to previous works, this four-directional switched-beam antenna successfully exhibits the advantages of high integration level and satisfactory performances for the 28-GHz 5G wireless applications.

High-Voltage Insulation Design of Coreless, Planar PCB Transformers for Multi-MHz Power Supplies

This article investigates the insulation design for printed, planar, coreless, and high-frequency transformers with high isolation-voltage. By using finite element analysis on 2-D axial-symmetry, the transformer circuit parameters and electric field distribution are modeled and estimated. Several transformers are designed for an operating frequency of 6.78 MHz. The high frequency, coreless design allows for using thicker insulation material while ensuring a high transformer efficiency. The inclusion of the coupling capacitance in the design optimization results in several design solutions with the same figure of merit, but with different footprint and isolation voltages. Moreover, high electric fields are identified around the sharp edges of the printed circuit board (PCB) windings. Finally, the electrical and isolation performance is verified experimentally. The measured electrical properties are close to the simulated values, validating the chosen model. Breakdown tests demonstrate the feasibility of isolation voltage levels up to several tens of kilovolts. The majority of breakdowns occurs at the outer edge of the PCB winding that was identified as a high-field area. Additionally, a concept for grading the electric field of PCB windings is also proposed. Based on the results, the design aspects are discussed in detail for planar, high-frequency isolation transformers with medium-voltage isolation level.

Analysis and Suppression of Common-Mode EMI Noise in 1 MHz 380 V-12 V DCX Converter With Low NFoM Devices

For the thriving information technology industrial applications, the series resonant converter (SRC) dc transformer (DCX) using integrated printed circuit board (PCB) windings is a preferred candidate because of its high efficiency and high power density characteristics by pushing the frequency to megahertz. However, the planar PCB transformer possesses large interwinding capacitance, which leads to severe common-mode (CM) noise and a large electromagnetic interference filter. Hence, the total volume of the conversion system is still high. In this article, a series inputs and parallel outputs (ISOP) structure for DCX is analyzed and discussed to demonstrate the CM noise reduction with the static point construction method, in which several dv/dt static points are constructed. Unlike most of the present suppressing methods, it can maintain high efficiency as well. Additionally, the ISOP structure provides more opportunities for optimizing control strategies to achieve the cancelation effect and further reducing the CM noise by the interleaving within a cell and the interleaving among cells. The excellence of the aforementioned methods is verified by experiments on 1-MHz 380 V–12 V 1.8-kW SRC DCX prototypes with a peak efficiency of 98.3%. The proposed methods ultimately reduce the CM noise by 50 dB.

Optimizing AC Resistance of Solid PCB Winding

At high frequency, power losses of a winding due to eddy currents becomes significant. Moreover, the skin and proximity AC resistances are influenced by the width of printed circuit board (PCB) conductors and distance between the adjacent tracks which causes many difficulties to design windings with lowest AC resistances. To clarify this phenomenon, this paper focuses on modeling the influence of skin and proximity effects on AC resistance of planar PCB winding, thereby providing guidelines to reduce the winding AC resistance. An approximate electromagnetic calculation method is proposed and it shows that when the winding proximity AC to DC ratio ( F p r o x i m i t y ) is equal to 1 3 the AC on DC ratio caused by skin effect ( F s k i n ) , the winding is optimized and it has lowest AC resistance. 3-D finite element simulations of 3, 7 and 10-Turn windings, which are divided into 3 groups with the same footprint, are presented to investigate the lowest AC resistance when the track width varies from 3 mm to 5 mm and the frequency range is up to 700 kHz. In order to verify the theoretical analysis and simulation results, an experiment with 3 simulated groups, (9 prototypes in total) is built and has a very good fit with simulation results. Experimental results show that at the optimal width, the AC resistance of the windings can be reduced up to 16.5 % in the frequency range from 200 kHz to 700 kHz.

Wideband Waveguide-to-Microstrip Transition for mm-Wave Applications

Introduction. Increased data rate in modern communication systems can be achieved by raising the operational frequency to millimeter wave range where wide transmission bands are available. In millimeter wave communication systems, the passive components of the antenna feeding system, which are based on hollow metal waveguides, and active elements of the radiofrequency circuit, which have an interface constructed on planar printed circuit boards (PCB) are interconnected using waveguide-to-microstrip transition.Aim. To design and investigate a high-performance wideband and low loss waveguide-to-microstrip transition dedicated to the 60 GHz frequency range applications that can provide effective transmission of signals between the active components of the radiofrequency circuit and the passive components of the antenna feeding systemMaterials and methods. Full-wave electromagnetic simulations in the CST Microwave Studio software were used to estimate the impact of the substrate material and metal foil on the characteristics of printed structures and to calculate the waveguide-to-microstrip transition characteristics. The results were confirmed via experimental investigation of fabricated wideband transition samples using a vector network analyzer Results. The probe-type transition consist of a PCB fixed between a standard WR-15 waveguide and a back-short with a simple structure and the same cross-section. The proposed transition also includes two through-holes on the PCB in the center of the transition area on either side of the probe. A significant part of the lossy PCB dielectric is removed from that area, thus providing wideband and low-loss performance of the transition without any additional matching elements. The design of the transition was adapted for implementation on the PCBs made of two popular dielectric materials RO4350B and RT/Duroid 5880. The results of full-wave simulation and experimental investigation of the designed waveguide to microstrip transition are presented. The transmission bandwidth for reflection coefficient S11 &lt; –10 dB is in excess of 50…70 GHz. The measured insertion loss for a single transition is 0.4 and 0.7 dB relatively for transitions based on RO4350B and RT/Duroid 5880.Conclusion. The proposed method of insertion loss reduction in the waveguide-to-microstrip transition provides effective operation due to reduction of the dielectric substrate portion in the transition region for various high-frequency PCB materials. The designed waveguide-to -microstrip transition can be considered as an effective solution for interconnection between the waveguide and microstrip elements of the various millimeter-wave devices dedicated for the 60 GHz frequency range applications.

Chaotic Oscillators as Inductive Sensors: Theory and Practice.

Engineering solutions based on dynamical chaos may improve the characteristics of various sensors such as metal detectors, salinometers, optical and magnetic field sensors, and so on. In this study, we investigated the possibility of creating inductive sensors based on Sprott chaotic oscillators with a planar printed circuit board inductive coil. The electric circuit of each sensor was obtained by merging two parts, namely, a harmonic oscillator and a nonlinear filter. A novel method for real-time oscillation analysis using a bandpass filter is presented. The suggested design technique was experimentally validated, and the sensor prototype showed characteristics making it practically applicable. In addition, the proposed technique can be used for the development of other types of sensors based on chaotic oscillators.