Two-layer Printed Circuit Board Research Articles

Detection of defects in printed circuit boards by the acoustic emission method

Objectives. Defects in the form of layering may occur during lamination in the production of multilayer printed circuit boards (MPCB). These defects cannot be detected by optical and electrical methods of output control. However, they can lead to breaches of the mechanical mode of operation and failures while running radioelectronic devices. In order to detect such defects, the acoustic emission (AE) method is proposed. This is based on the occurrence and propagation of acoustic waves in MPCBs caused by the presence of defects. The aim of this study is to investigate the possibility of using the AE method to detect defects in multilayer printed circuit boards. These defects can occur, in particular, in the lamination process.Methods. A mechanical processes modeling program (for research on the MPCB model) and various samples of two-layer printed circuit boards with pre-introduced defects (for experimental studies) were used to study the propagation of acoustic signals in the MPCB in the presence of defects. A solenoid mounted on the MPCB was used as a source of acoustic signals, while a piezoelectric sensor was used to receive signals. Data processing was carried out by comparing AE signals obtained for a serviceable MPCB sample and for MPCB samples with defects.Results. Simulation of the acoustic signal propagation in MPCBs in serviceable and faulty (with a rectangular defect in the form of delamination) states was carried out to show the difference in the received signals at the sensor installation point. Experimental studies were also conducted to examine the AE method applicability for detecting defects of various sizes and quantities.Conclusions. The studies demonstrated that the AE method allows the presence of defects in MPCB occurring during the lamination process to be detected effectively and reliably. This study proposes a new approach to non-destructive testing of MPCB using the AE method. This method significantly increases the reliability of MPCBs and the efficiency of their production processes.

A Novel Patterned Ground Structure With Shunt and Series Lumped Elements for Synthesizing Absorption Common-Mode Filters

To synthesize an absorption common-mode filter (A-CMF) in a two-layer printed circuit board, patterned ground structures (PGSs) have been studied in the past few years. A conventional PGS consists of slotlines and shunt lumped elements across slots. On the contrary, the proposed new PGS uses both shunt and series lumped elements (SSLEs) in a ground plane with a closed-loop asymmetrical coplanar strip. To validate the proposed SSLE PGS, two circuits of bidirectional A-CMFs are developed to absorb common-mode (CM) noise in the 2.4 GHz industrial scientific medical (ISM) band. The one with higher CM noise absorption bandwidth is finally implemented and demonstrated in this article. Besides, nonideal CM return current paths are considered to modify the ideal circuit and reduce the discrepancies between the full-wave and circuit simulations. The measurement results show that the proposed bidirectional A-CMF attains CM noise absorption from 2.29–2.57 GHz for electromagnetic interference suppression in the 2.4 GHz ISM band. Most of all, the proposed work reveals a notable differential-mode −3 dB bandwidth up to 16.3 GHz with an ultracompact size of 0.0143 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _g^2$</tex-math></inline-formula> .

A circuit level analysis of power distribution network on a PCB layout exposed to intentional/unintentional electromagnetic threats

In this article a circuit level analytic approach is proposed for radiated susceptibility analysis of a system power distribution network (PDN). For this purpose, electromagnetic wave impacts a two-layer printed circuit board (PCB). This external wave can be radiated from the antenna of a wireless communication device or an intentional electromagnetic interference source. The radiated susceptibility of the PDN is studied by decomposing the stochastic voltage sources for vertical and horizontal transmission lines. The effect of distribution network on the individual induced signal are considered using ABCD matrix for handling the disturbance propagation entire system. The PDN self voltage fluctuation is considered using a simple mathematic model. A measurement procedure is proposed for evaluating the performance degradation without loading effect. Analytic conclusion and simulation results disclose that the induced voltage from external electromagnetic threat on the PDN is comparable with the operating PDN self fluctuation. The results show that the PDN is a susceptible section of the PCB and is an accessible target for interferer systems. This can be a potential susceptibility concern and should be considered in design procedure.

Learning on the Rings

This paper presents ssLOTR (self-supervised learning on the rings), a system that shows the feasibility of designing self-supervised learning based techniques for 3D finger motion tracking using a custom-designed wearable inertial measurement unit (IMU) sensor with a minimal overhead of labeled training data. Ubiquitous finger motion tracking enables a number of applications in augmented and virtual reality, sign language recognition, rehabilitation healthcare, sports analytics, etc. However, unlike vision, there are no large-scale training datasets for developing robust machine learning (ML) models on wearable devices. ssLOTR designs ML models based on data augmentation and self-supervised learning to first extract efficient representations from raw IMU data without the need for any training labels. The extracted representations are further trained with small-scale labeled training data. In comparison to fully supervised learning, we show that only 15% of labeled training data is sufficient with self-supervised learning to achieve similar accuracy. Our sensor device is designed using a two-layer printed circuit board (PCB) to minimize the footprint and uses a combination of Polylactic acid (PLA) and Thermoplastic polyurethane (TPU) as housing materials for sturdiness and flexibility. It incorporates a system-on-chip (SoC) microcontroller with integrated WiFi/Bluetooth Low Energy (BLE) modules for real-time wireless communication, portability, and ubiquity. In contrast to gloves, our device is worn like rings on fingers, and therefore, does not impede dexterous finger motion. Extensive evaluation with 12 users depicts a 3D joint angle tracking accuracy of 9.07° (joint position accuracy of 6.55mm) with robustness to natural variation in sensor positions, wrist motion, etc, with low overhead in latency and power consumption on embedded platforms.

Design of Miniaturized Incident Angle-Insensitive 2.45 GHz RF-Based Energy Harvesting System for IoT Applications

Using a license-free industrial, scientific, and medical (ISM) frequency band as 2.45 GHz, a miniaturized incident angle-insensitive radio frequency (RF) energy harvester design for the Internet-of-Things (IoT) applications is proposed. For incident angle insensitivity of ambient RF energy and a low-profile compact design, the proposed harvester is used to a two-layer printed circuit board (PCB) substrate, which consists of orthogonally deployed antennas with an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LC$ </tex-math></inline-formula> balun, impedance matching, and Dickson charge pump circuits at each layer. The dual-polarized antenna for miniaturized design uses a bowtie-shaped meander dipole antenna having orthogonal arrangement. By measuring the efficiency of each diode stage of the rectifier circuit, a two-stage Dickson charge pump circuit with optimal efficiency was selected, and the dc outputs of the two rectifier circuits are connected in parallel. This rectifier circuit has a conversion efficiency of up to 71.4% and harvests approximately 1.6 times more power than a single-polarized circuit from any incident ambient RF signal. Due to its compact size and improved harvesting power at various incident angles, the proposed energy harvester can act as a power source, such as many kinds of ultralow power consumption systems, such as IoT sensors and medical applications.

A Compact Symmetrical Single-Cell Bidirectional Absorption Common-Mode Filter

A novel circuit with two mirror symmetry planes is proposed to synthesize bidirectional absorption common-mode filters (A-CMFs). In contrast to the literature, this proposed circuit first realizes bidirectional A-CMFs in only one stage (also called a single cell) featuring a compact size. Based on the symmetry property, bidirectional common-mode (CM) noise absorption can be achieved in the proposed single-cell circuit. Analytical design formulas have been found; thus, all circuit parameters can be straightforwardly determined. To validate the proposed circuit, two configurations are developed for CM noise absorption in the 2.4-GHz industrial, scientific, and medical (ISM) band. One uses a meander differential pair with a slotline, and the other applies a straight differential pair with a meander asymmetrical coplanar strip (MACPS). To obtain a better differential-mode (DM) signal integrity and 43&#x0025; size reduction, the latter one, MACPS-type A-CMF, is fabricated and measured. The measurement results show that <inline-formula> <tex-math notation="LaTeX">$\vert S_{\text {cc21}}\vert $ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$\vert S_{\text {cc12}}\vert $ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$\vert S_{\text {cc11}}\vert $ </tex-math></inline-formula>, and <inline-formula> <tex-math notation="LaTeX">$\vert S_{\text {cc22}}\vert $ </tex-math></inline-formula> are less than &#x2212;10 dB from 2.37 to 2.76 GHz to have the bidirectional CM absorption efficiency of more than 80&#x0025;, and the &#x2212;3-dB bandwidth of DM insertion loss reaches 7.83 GHz. In the time domain, the measured eye diagram of the proposed A-CMF is identical to that of a reference board for data rates up to 20 Gb/s. Above all, having a cost advantage, a compact size of <inline-formula> <tex-math notation="LaTeX">$0.0317\lambda _{\text {g}}^{{2}}$ </tex-math></inline-formula> in a two-layer printed circuit board (PCB) is presented.

A Novel Compact Single-Stage Absorption Common-Mode Filter

In this article, a novel circuit is proposed to synthesize absorption common-mode filters (A-CMFs) in only one stage, which can be implemented with different kinds of transmission lines. This proposed one-stage absorption circuit has been derived with analytical equations, and design formulas are found to determine circuit parameters. To validate the proposed circuit and derived formulas, an intuitional structure composed of a meander slotline (MSL), a straight differential pair, and one resistor is proposed. Moreover, a technique named meander asymmetrical coplanar strip (MACPS) has also been developed to reduce the size of MSL-type A-CMF by up to 26%. Finally, the proposed test sample of MACPS-type A-CMF is fabricated in a two-layer printed circuit board (PCB) and measured. The common-mode (CM) noise absorption efficiency of above 80% can be obtained from 2.33 to 2.67 GHz to eliminate CM noises in the Wi-Fi 2.4 GHz band. Besides, the MACPS-type A-CMF provides an excellent differential-mode (DM) signal integrity. The −3 dB bandwidth of DM insertion loss can reach 7.5 GHz, and the measured eye diagram of the proposed work is identical to that of the reference board even the transmitted data rate is up to 16 Gb/s. To our best knowledge, the smallest A-CMF implemented in a two-layer PCB is achieved in this article with the electrical dimension being only 0.0358 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_g</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Construction of a Wireless-Enabled Endoscopically Implantable Sensor for pH Monitoring with Zero-Bias Schottky Diode-based Receiver.

Ambulatory pH monitoring of pathological reflux is an opportunity to observe the relationship between symptoms and exposure of the esophagus to acidic or non-acidic refluxate. This paper describes a method for the development, manufacturing, and implantation of a miniature wireless-enabled pH sensor. The sensor is designed to be implanted endoscopically with a single hemostatic clip. A fully passive rectenna-based receiver based on a zero-bias Schottky diode is also constructed and tested. To construct the device, a two-layer printed circuit board and off-the-shelf components were used. A miniature microcontroller with integrated analog peripherals is used as an analog front end for the ion-sensitive field-effect transistor (ISFET) sensor and to generate a digital signal which is transmitted with an amplitude shift keying transmitter chip. The device is powered by two primary alkaline cells. The implantable device has a total volume of 0.6 cm3 and a weight of 1.2 grams, and its performance was verified in an ex vivo model (porcine esophagus and stomach). Next, a small footprint passive rectenna-based receiver which can be easily integrated either into an external receiver or the implantable neurostimulator, was constructed and proven to receive the RF signal from the implant when in proximity (20 cm) to it. The small size of the sensor provides continuous pH monitoring with minimal obstruction of the esophagus. The sensor could be used in routine clinical practice for 24/96 h esophageal pH monitoring without the need to insert a nasal catheter. The "zero-power" nature of the receiver also enables the use of the sensor for automatic in-vivo calibration of miniature lower esophageal sphincter neurostimulation devices. An active sensor-based control enables the development of advanced algorithms to minimize the used energy to achieve a desirable clinical outcome. One of the examples of such an algorithm would be a closed-loop system for on-demand neurostimulation therapy of gastroesophageal reflux disease (GERD).

Quasi-Static Modeling and Optimization of Two-Layer PCB Resonators in Wireless Power Transfer Systems for 110-kV Power Grid Online Monitoring Equipment

The expanding functions of the emerging smart grid have posed new technical challenges on the power supplies for online monitoring systems in the transmission and distribution networks. A recent study has suggested that magnetic energy around the transmission line can be harvested and delivered wirelessly to the monitoring equipment through printed circuit board (PCB) resonators embedded inside an insulation rod. This article presents a rigorous analysis, modeling, and optimization of such PCB resonators. A new closed-form quasi-static model of the PCB resonators is derived. A fully automated simulation-driven optimization framework is constructed to enhance the quality factor of the resonator. Practical measurements show that the optimal design improves the quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> factor) from 52 to 132 as compared to the existing trial-and-error design. The corresponding wireless power transfer efficiency in a 20-W prototype across a 1.14-m distance improves significantly from 11 to 46%.

First self‐resonant frequency of power inductors based on approximated corrected stray capacitances

Inductive devices are extensively employed in power electronic systems due to their magnetic energy storage and power transfer capabilities. The current trend is towards increasing the frequency of operation in order to reduce the size of the magnetic components, but the main drawback is that the parasitic capacitance effect can become significant, and degrade the performance of the system. This work analyses the influence of this stray capacitance, and considers how to improve the performance of the device. In general, the impact of the stray capacitance on a magnetic component can be reduced by two methods: reducing the parasitic capacitance between turns of the winding or, alternatively, modifying the arrangement of the connection between turns. To evaluate the last option, an approximated expression of the first self-resonant frequency of the magnetic device is proposed. This gives a rapid assessment of the performance of different devices maintaining the overall equivalent inductance. The proposed expression accounts for the influence of the connection between turns in the bandwidth of the component. Finally, some numerical results are verified with planar coils manufactured on two-layer printed circuit boards.

High Directivity Fabry–Perot Antenna With a Nonuniform Partially Reflective Surface and a Phase Correcting Structure

In this communication, a superstrate for the high radiation performance of a Fabry-Perot antenna (FPA) is proposed that consists of a nonuniform partially reflective surface (NPRS) and a phase correcting structure (PCS). The NPRS and the PCS function to uniformize the amplitude and phase distributions, successively, of the FPA's aperture field, thereby achieving a high directivity and a high aperture efficiency. Due to the independent amplitude and phase manipulations, the antenna design procedure is relatively rapid and effective. As a proof of concept, an FPA sample at an operating frequency of 5.8 GHz with a diameter of 200 mm is designed. The NPRS, comprising metallic square rings with dissimilar dimensions printed on a printed circuit board (PCB), is designed according to the leaky-wave method. A two-layer PCB structure is adopted as the PCS, which is designed by the transmission line model integrated with full-wave simulations. The FPA with the NPRS and the PCS is fabricated and measured for verification. The simulated and measured results are in good agreement. The directivity of the FPA with the proposed superstrate is 21.49 dB and the corresponding aperture efficiency is as high as 95.49% at 5.8 GHz.

Probe-antenna and multifunctional switch for biomedical neural implants.

A probe-antenna and a multifunctional single-pole-four-throw switch are proposed for biomedical neural implants. The multifunctional switch is fabricated in TSMC 90-nm CMOS process and occupies the core area of 297 × 248μm2. Operating in transmitter/receiver mode, the switch achieves the insertion loss of 4.5/4.8dB, return loss of 16.7/15.4dB, isolation of 19.2/20.3dB and P1dB of 4/5dBm at 60GHz. Based on the dipole antenna, the antenna with probe function is designed and fabricated on the Roger 4003C two-layer printed circuit board. This probe-antenna achieves the input matching over 59.35-65GHz. According to the simulation, it achieves the radiation efficiency of 69.8/34.4% and gain of 3.88/5.47 dBi without/with a drop of deionized water on the feed. The probe/electrode function is verified by performing impedance measurement on the deionized water, phosphate buffered saline (PBS) solution, and solution with conductivity of 1413μS/cm.

A Novel Ultrawideband Absorptive Common-Mode Filter Design Using a Miniaturized and Resistive Defected Ground Structure

An ultrawideband absorptive common-mode filter (A-CMF) with a newly developed defected ground structure (DGS) is proposed in this article. The DGS miniaturized to a subwavelength size is able to totally suppress the common-mode noise while maintaining the signal integrity of the differential mode. In addition, the reflection and radiation of the common-mode noise are negligible in the stopband. For quick design, a simplified equivalent circuit model is also proposed. This model can be employed to estimate the resistances of the lumped resistors embedded in the DGS to obtain a very wide absorption band. In the demonstrated example, the fractional bandwidth determined by a 90% absorption efficiency can achieve as large as 104% around 3.55 GHz for an A-CMF realized on a simple two-layer printed circuit board. Such a widely absorptive bandwidth is never achieved before to our knowledge. The design methodology is validated by full-wave simulation. Finally, real measurement of the design is also carried out to confirm the design and analysis.

A compact, dual-polarized patch antenna with improved Tx–Rx isolation for 2.4 GHz single frequency full-duplex applications

AbstractA compact dual-polarized monostatic antenna (single radiator for transmit and receive modes) is presented with differential receive mode operation to achieve excellent interport isolation for 2.4 GHz single frequency full-duplex or in-band full-duplex applications. The presented antenna comprises three ports radiating element (patch) and a simple 3 dB/180o ring hybrid coupler has been utilized for differentially excited receive mode operation. The 3 dB/180o ring hybrid coupler acts as a self-interference cancellation (SIC) circuit for effective suppression of RF leakage from the transmit port to provide very high interport decoupling between transmit and receive ports. A compact antenna structure has been realized by using two-layered printed circuit board through vias interconnections of both receive ports of the antenna with inputs of SIC circuit. The validation model of proposed antenna offers more than 95 dB peak interport isolation. Moreover, the experimentally measured interport isolation is better than 70 dB throughout the antenna's 10 dB return-loss impedance bandwidth (BW) of 50 MHz (2.38–2.43 GHz). Furthermore, the recorded isolation is more than 80 dB in 20 MHz BW. The implemented antenna has good radiation characteristics including nice gain and low cross-polarization levels as endorsed by measurements. Same antenna structure with microstrip-T feeds can provide DC isolated ports with same interport RF isolation performance for active antenna applications. Such antenna with DC interport isolation will avoid the requirements of additional series capacitors on transmit and receive ports of antenna.

A Bidirectional Absorptive Common-Mode Filter Based on Interdigitated Microstrip Coupled Lines for 5G “Green” Communications

This paper proposes a bidirectional absorptive common-mode filter (A-CMF) for 5G “green” communication systems. The A-CMF is a balanced-to-balanced structure using interdigitated coupled lines to replace normal double parallel-coupled lines for enhanced coupling and easy manufacturing. The resistors are introduced to dissipate the common-mode (CM) noises into heat and thus to avoid the noises being reflected and still existing in the communication system. This novel A-CMF features an intrinsic CM noises absorption while maintaining its differential-mode (DM) filtering characteristics. As a proof-of-concept demonstration, one microstrip prototype is fabricated in a two-layer printed circuit board (PCB) and the measurements are consistent with the simulations. The DM signals can pass through this A-CMF without being attenuated from 1.38 GHz to 5.19 GHz but the CM noises are suppressed throughout the broad frequency range between 0.72 GHz and 8 GHz. It is worth noting that this A-CMF realizes a wide band with 90% absorption efficiency of CM noises from 2.18 GHz to 4.97 GHz.

Nonperiodic Flipped EBG for Dual-Band SSN Mitigation in Two-Layer PCB

Several electromagnetic bandgap (EBG) structures have been designed to mitigate simultaneous switching noise (SSN) problems in dual bands in wireless local area networks (WLANs). In order to be applicable to two-layer printed circuit boards (PCBs), a novel flipped structure is introduced, which also creates slots for a wide stopband. This article proposes a $2 \times 2$ nonperiodic flipped-EBG (FEBG) for dual-band SSN mitigation in the WLAN, exhibiting noise suppression of 21 and 26 dB in 2.4–2.6 and 5–6 GHz bands, respectively. The simulation results are in good agreement with the experimental data. In addition, a method of positioning optimization is introduced as well to demonstrate the application of the FEBG on a two-layer PCB.

Analysis and Design Method of a Novel Absorptive Common-Mode Filter

In this paper, a bidirectional absorptive common-mode filter (A-CMF) is proposed to suppress the common-mode (CM) noise which would induce unwanted electromagnetic interference (EMI) and radio-frequency interference (RFI) problems. Different from the conventional CM filters (CMFs) which reflect the CM noise, the proposed A-CMF will absorb the CM wave, and thus suppress the radiation caused by reflected wave. An analysis and design method by using Smith chart with more physical insight is also proposed in this paper. To validate the proposed concept, the A-CMFs are implemented in the two-layer printed circuit boards. The absorbing frequency is selected at 2.4 GHz band where CM insertion loss is larger than 30 dB and the CM reflection loss is larger than 20 dB. With the proposed A-CMFs, more than 98% of the CM power can be eliminated. The proposed A-CMFs also provide a broadband CM suppression with fractional bandwidth lager than 126%, and a high bandwidth of differential-mode (DM) signal from dc to 7.4 GHz, which is about three times of the CM absorbing frequency. Eye diagrams are also measured to check the signal integrity, and the results show that the proposed A-CMF can still keep a good eye even under a high throughput of 7.5 Gb/s.

Novel Absorptive Balanced Bandpass Filters Using Resistive Loaded Transmission Lines

This paper reports on design of novel balanced bandpass filters (BPFs) using quarter-wavelength stub resonators. For the design purposes, differential-mode (DM) and common-mode (CM) half-equivalent circuits are established and analyzed carefully. In this paper, CM noise is introduced into the filter and dissipated on the resistors on periodic bands. First, a balanced BPF topology based on conventional quarter-wavelength stub filter is presented. By symmetrically introducing series matching resistors to the ground at the center of the stub, CM noise can be rejected either reflectively or reflectionlessly without affecting DM performance. The harmonic property of stubs provides periodic CM suppressing response as long as the resistor has no serious parasitic reactance. By doing so, CM noise can be suppressed under a certain level at all frequencies. However, the harmonic property also leads to some spurious passbands. This defect can be avoided by an improved filter topology with two additional capacitors. To reserve the CM feature, the corresponding DM and CM half equivalent circuits are developed as well. The proposed layouts are fabricated on a two-layer printed circuit board. The resulting experimental circuits exhibit the expected electrical performance, forming balanced BPFs with CM noise suppression level over 12 dB at all frequencies, and show an agreement with the simulated results.

A 200-Mb/s Energy Efficient Transcranial Transmitter Using Inductive Coupling.

This paper presents an energy efficient wireless transmitter (TX) for neural implants. It utilizes inductive coupling with de-Q'ed TX inductor to achieve 200Mb/s throughput. An ultra-low power injection-locked phase lock loop with background frequency calibration generates a clean 200-MHz TX clock from a 10-MHz reference. The TX chip is fabricated in TSMC 65-nm CMOS process, and the [Formula: see text] coupled inductors are implemented on two-layer printed circuit boards. A custom receiver is fabricated in the same CMOS process to facilitate measurements. The prototype transceiver achieves 5e-11 bit error rate (BER) over the 11.8-mm-thick skull of an eight-week primordial piglet carcass and <1e-12 BER over 11-mm air gap. The entire TX chip consumes 300 μW from a single 0.5V supply. The energy efficiency of the TX is 1.5pJ/b.

Codesign of Electrostatic Discharge Protection Device and Common Mode Suppression Circuit on Printed Circuit Board

A codesign of an electrostatic discharge (ESD) protection device and a common-mode suppression circuit on printed circuit board (PCB) for high-speed input/output interfaces is introduced in this paper. The characteristic and the circuit model of the ESD protection device are investigated and applied into the design of the common-mode suppression circuit. The proposed one-stage design of two-layered PCB structure performs –10-dB common-mode noise suppression from 2.22 to 2.76 GHz; the proposed two-stage design with additional common-mode suppression unit performs wideband suppression from 2.25 GHz to over 8 GHz, covering IEEE 802.11ac WiFi band with –20-dB suppression level. The mode conversion for both designs is lower than –30 dB. The signal integrity and the ESD protection function of proposed design are investigated by eye diagram measurement and system-level ESD simulation. The proposed PCB design provides a low-cost solution for the integration on the high-speed input/output interface of next generation.