Showing papers in "IEEE Transactions on Components, Packaging and Manufacturing Technology in 2017"

Electronics Thermal Management in Information and Communications Technologies: Challenges and Future Directions

Abstract: This paper reviews thermal management challenges encountered in a wide range of electronics cooling applications from large-scale (data center and telecommunication) to small-scale systems (personal, portable/wearable, and automotive). This paper identifies drivers for progress and immediate and future challenges based on discussions at the 3rd Workshop on Thermal Management in Telecommunication Systems and Data Centers held in Redwood City, CA, USA, on November 4–5, 2015. Participants in this workshop represented industry and academia, with backgrounds ranging from data center thermal management and energy efficiency to high-performance computing and liquid cooling, thermal management in wearable and mobile devices, and acoustic noise management. By considering a wide range of electronics cooling applications with different lengths and time scales, this paper identifies both common themes and diverging views in the thermal management community.

A Filtering Dual-Polarized Antenna Subarray Targeting for Base Stations in Millimeter-Wave 5G Wireless Communications

Abstract: A $2 \times 2$ dual-polarized antenna subarray with filtering responses is proposed in this paper. This antenna subarray is a multilayered 3-D geometry, including a dual-path $1 \times 4$ feeding network and four cavity-backed slot antennas. The isolation performance between two input ports is greatly improved by a novel method, which only needs to modify several vias in a square resonator. Cavities in the feeding network are properly arranged and coupled using different coupling structures, so that the operation modes in each cavity for different paths can always remain orthogonal, which enables the subarray to exhibit not only filtering functions (in both reflection coefficients and gain responses), but also a low cross-polarization level. A prototype is fabricated with a center frequency of 37 GHz and a bandwidth of 600 MHz for demonstration. Good agreement is achieved between simulation and measurement, for both $S$ -parameter and far-field results. The proposed filtering dual-polarized antenna array is very suitable to be employed as the subarray in millimeter-wave 5G base stations to reduce the complexity and integration loss of such beamforming systems.

Design of Compact Bandpass Filters Using Quarter-Mode and Eighth-Mode SIW Cavities

Abstract: The contribution of this paper is to propose novel balanced and dual-band bandpass filters (BPFs), using quarter-mode (QM) and eighth-mode (EM) substrate integrated waveguide (SIW) cavities, for the size reduction of the overall circuit. Two balanced BPFs, which separately demonstrate a third-order Chebyshev response and a fourth-order quasi-elliptic response, are realized by properly choosing, feeding, and coupling those QMSIW and EMSIW cavities. Not only desired differential-mode operation within the passband, but also good common-mode suppression in a certain frequency range have been achieved. Furthermore, a dual-band BPF with improved out-of-band rejection is also realized by properly constructing the coupling topology of four EMSIW cavities. An additional source-to-load coupling path is introduced in this dual-band BPF to obtain more transmission zeros (TZs). The sizes of resonant cavities utilized in the above designs are only one-fourth or one-eighth of those rectangular ones in conventional designs, which lead to a significant reduction in the overall circuit size. All proposed designs have been fabricated and measured to verify simulation predictions. Based on the author’s knowledge, it is the first time using QMSIW and EMSIW for balanced filter designs, and dual-band filter designs with TZs.

Warpage and Thermal Characterization of Fan-Out Wafer-Level Packaging

Abstract: In this paper, the warpage and thermal performances of fan-out wafer-level packaging (FOWLP) are investigated. Emphasis is placed on the characterization of the effects of FOWLP important parameters, such as chip size, chip thickness, package/chip area ratio, epoxy molding compound (EMC), chip EMC cap, reconstituted carrier material and thickness, and die-attach film, on the warpage after postmold cure and backgrinding of the EMC. The simulation results are compared to the experimental measurements. Also, the thermal performance (junction-to-ambient thermal resistance) of FOWLP with various chip thicknesses is characterized. Finally, some FOWLP important parameters affecting the warpage and thermal performances are recommended.

Big-Data Tensor Recovery for High-Dimensional Uncertainty Quantification of Process Variations

Abstract: Fabrication process variations are a major source of yield degradation in the nanoscale design of integrated circuits (ICs), microelectromechanical systems (MEMSs), and photonic circuits. Stochastic spectral methods are a promising technique to quantify the uncertainties caused by process variations. Despite their superior efficiency over Monte Carlo for many design cases, stochastic spectral methods suffer from the curse of dimensionality, i.e., their computational cost grows very fast as the number of random parameters increases. In order to solve this challenging problem, this paper presents a high-dimensional uncertainty quantification algorithm from a big data perspective. Specifically, we show that the huge number of (e.g., $1.5 \times 10^{27}$ ) simulation samples in standard stochastic collocation can be reduced to a very small one (e.g., 500) by exploiting some hidden structures of a high-dimensional data array. This idea is formulated as a tensor recovery problem with sparse and low-rank constraints, and it is solved with an alternating minimization approach. The numerical results show that our approach can efficiently simulate some IC, MEMS, and photonic problems with over 50 independent random parameters, whereas the traditional algorithm can only deal with a small number of random parameters.

Demonstration of RF and Microwave Passive Circuits Through 3-D Printing and Selective Metalization

Abstract: The ultimate goal of this paper is to print radio frequency (RF) and microwave structures using a 3-D platform and to pattern metal films on nonplanar structures. To overcome substrate losses, air core substrates that can readily be printed are utilized. To meet the challenge of patterning conductive layers on complex or nonplanar printed structures, two novel self-aligning patterning processes are demonstrated. One is a simple damascene-like process, and the other is a lift-off process using a 3-D printed lift-off mask layer. A range of microwave and RF circuits are designed and demonstrated between 1 and 8 GHz utilizing these processes. Designs are created and simulated using Keysight Advanced Design System and ANSYS High Frequency Structure Simulator. Circuit designs include a simple microstrip transmission line (T-line), coupled-line bandpass filter, circular ring resonator, T-line resonator, resonant cavity structure, and patch antenna. A commercially available 3-D printer and metal sputtering system are used to realize the designs. Both simulated and measured results of these structures are presented.

Improving Data Center Energy Efficiency With Advanced Thermal Management

Abstract: Experimental investigation of data center cooling and computational energy efficiency improvement through advanced thermal management was performed. A chiller-less data center liquid cooling system was developed that transfers the heat generated from computer systems to the outdoor ambient environment while eliminating the need for energy-intensive vapor-compression refrigeration. This liquid cooling system utilizes a direct-attach cold-plate approach that enables the use of warm water at temperature a few degrees above outdoor ambient to achieve lower chip junction temperatures than refrigerated air. Using this approach, we demonstrated a cooling energy reduction by over 90% and computational energy reduction of up to 14% compared to traditional refrigerated air cooled data centers. To enable future computational efficiency improvements through high-density 3-D-chip stacking, we developed a 3-D compatible chip-embedded two-phase liquid cooling technology where a dielectric coolant is pumped through microscale cavities to provide thermal management of chips within the stack. In two-phase cooling, liquid is converted to vapor, which increases the capacity to remove heat, while the dielectric fluid enables integration with chip electrical interconnects. A test vehicle simulating an eight-core microprocessor was fabricated with embedded cooling channels. Results demonstrate that this volumetrically efficient cooling solution compatible with 3-D chip stacks can manage three times the core power density of today’s high-power processor while maintaining the device temperature well within limits.

PCB Reverse Engineering Using Nondestructive X-ray Tomography and Advanced Image Processing

Abstract: Reverse engineering (RE) of electronic systems is performed for many different reasons, including, but not limited to, failure analysis and fault isolation, obsolescence management, proof of IP rights infringement, security assessment, development of attacks, and counterfeiting. Regardless of the goal, it is imperative that the community understands the requirements, complexities, and limitations of RE. Traditional RE is based on a destructive process of serial sectioning followed by imaging, which is time-consuming, expensive, and error-prone. However, with the advent of advanced characterization tools and imaging software, this is starting to change. In this paper, we introduce a nondestructive approach for printed circuit board (PCB) RE based on X-ray tomography. The imaging parameters for a successful tomography are explained in detail and combined with advanced 3-D image processing and analysis to automate RE, thereby lowering the associated time and cost. We demonstrate our proposed process on two PCBs, a four-layer custom designed board, and a more complex commercial board. Lessons learned from this effort can be used to both develop advanced countermeasures and establish a more efficient workflow for instances where RE is unavoidable.

Through Silicon Via (TSV) Defect Modeling, Measurement, and Analysis

Abstract: Through silicon via (TSV)-based 3-D integrated circuit has introduced the solution to limitlessly growing demand on high system bandwidth, low power consumption, and small form factor of electronic devices. As the system design aims for higher performance, the physical dimensions of the channels are continuously decreasing. With TSV diameter of less than 10 $\mu \text{m}$ and pitch of several tens of micrometers, the I/O count has increased up to the order of tens of thousands for wide bandwidth data transmission. However, without highly precise fabrication process, such small structures are susceptible to a variety of defects. For the first time, in this paper, we propose a noninvasive defect analysis method for high-speed TSV channel. With designed and fabricated test vehicles, the proposed method is demonstrated with ${S}$ -parameter and time-domain reflectometry measurement results. In addition, we present equivalent circuit models of TSV daisy-chain structures, including the circuit components for open defect and short defect. With characterized dominant factors in each frequency range, $S_{11}$ is analyzed to distinguish and locate the defects by the amount of capacitance, resistance, and inductance that the signal experiences. ${S}$ -parameter measurement sufficiently allows high-frequency defect analysis of TSV channel without destroying the test sample. We experimentally verified the accuracy of the suggested model by comparing the ${S}$ -parameter results from circuit simulations and measurements. Finally, the model is modified to discuss the effects of open defect and short defect on the electrical characteristics of TSV channel.

Self-Packaged, Low-Loss, Planar Bandpass Filters for Millimeter-Wave Application Based on Printed Gap Waveguide Technology

Abstract: A new concept of printed planar technology is introduced for the realization of low-loss bandpass filters in millimeter band. The new technology is self-packaged, and the insertion loss shows meaningful improvement compared to microstrip (MS) filters. The designs are based on the ridge gap waveguide (RGW), which is composed of printed parallel-plate waveguide surrounded by beds of mushrooms that suppress the signal around the waveguide. Several examples are designed, optimized, and measured. All-pole bandpass filters and filters with finite transmission zeros are proposed and studied. The performance of the proposed designs is compared to MS filters with different packaging options. In addition, an efficient transition from MS to printed RGW is designed and used in the circuits. The proposed circuits are low-cost and realizable using conventional printed circuit board technology. Measured results show good agreement with the analyses.

PCB Embedded Semiconductors for Low-Voltage Power Electronic Applications

Abstract: Power conversion applications in the low voltage (LV) range (≤ 1.2 kV)—such as three-phase inverters—are required to operate at higher efficiencies, higher ambient temperatures, increasingly smaller form factor, and higher power density. Up to now, most research has focused on voltages up to 650 V for printed circuit board (PCB) embedded power electronics. This research evaluates a novel three-phase invertor module based on six insulated gate bipolar transistors and six diodes rated to 1.2 kV and 25 A each. This unique module is compared to the Semikron MiniSKiiP 23AC126V1. This paper considers some key details of the PCB embedding assembly process, a comparative switching performance assessment, measurement of thermal resistance, comparative lifetime, and electric insulation. First, a detailed outline of the package is presented including the top- and bottom-side metallization and the copper interconnect technology. The switching performances of both modules are compared for turn-ON and turn-OFF currents for a waveform at 600 V and 25 A at 150 °C. A finite-element-method thermal simulation demonstrates up to 44% lower thermal resistance for the PCB embedded package than that of the traditional wire-bonded direct bonded copper (DBC) package for an identical applied current and cooling condition. Furthermore, both packages are active power cycled to failure with the PCB embedded package demonstrating superior lifetime to the traditional DBC module. Finally, the maximum breakdown limit and the onset of partial discharge with the embedded PCB module are reported for both aged and non-aged conditions. The overall findings identify the promising application of PCB embedded power electronics for LV power conversion.

Experimental Verification and Optimization Analysis of Warpage for Panel-Level Fan-Out Package

Abstract: Nowadays, fan-out package is regarded as one of the latest and most potential technologies because it possesses lower cost, thinner profile, and better electrical performance and thermal performance. However, thermally induced warpage in the molding process is a critical issue due to the larger wafer or panel size, the shrinkage of epoxy mold compound (EMC) during the curing stage, and the mismatch of coefficient of thermal expansion (CTE) among the constituent materials during the cooling stage, which needs to be controlled effectively for successful subsequent process of the fan-out package. In this paper, a novel $320 \times 320$ -mm2 panel-level fan-out package based on “Die Last” process is developed. A coreless substrate with redistribution layer is fabricated and bonded onto a low-CTE and high-glass-transition-temperature (Tg) FR4 carrier through thermal release film. The thermally induced warpage issue in the molding process is investigated. A warpage simulation method is presented and verified by Shadow Moire experiment. The error between the simulation and experimental results is about 4.8%. For the warpage optimization analysis, the effect of geometry structure on the warpage is first investigated by the design of simulation approach. Full factor experiment is conducted, and Minitab statistical software is utilized to analyze the effect of the geometry structure on warpage. It is found that decreasing die thickness and molding thicker EMC can effectively decrease the warpage. Then, the effects of molding temperature and in-plane CTE of FR4 on warpage are studied, respectively. When molding temperature is 120 °C and in-plane CTE of FR4 decreases to 10.5 ppm/°C, the thermally induced warpage in the molding process is only about 0.31 mm, thus subsequent process of fan-out package can be conducted successfully.

A Universal Approach for Designing an Unequal Branch-Line Coupler With Arbitrary Phase Differences and Input/Output Impedances

Abstract: For the first time, this paper presents a novel approach for designing a coupler with arbitrary division, optional phase difference, and alternative input/output impedances. In the section of theoretical analysis, rigorous closed-form design equations are derived, and explicit methodology for computer-aided design is given based on the equations. To validate the idea, several numerical examples extracted from the design procedure are constructed and demonstrated. Eventually, three prototypes of the coupler are fabricated, and experiments are carried out. The excellent agreement between the theoretical and experimental results sufficiently verifies the theoretical methodology. This proposed coupler is well applicable to the applications that require high flexibility in couplers’ performances.

Peridynamic Modeling of Diffusion by Using Finite-Element Analysis

Abstract: Diffusion modeling is essential in understanding many physical phenomena such as heat transfer, moisture concentration, and electrical conductivity. In the presence of material and geometric discontinuities and nonlocal effects, a nonlocal continuum approach, named peridynamics (PD), can be advantageous over the traditional local approaches. PD is based on integro-differential equations without including any spatial derivatives. In general, these equations are solved numerically by employing meshless discretization techniques. Although fundamentally different, commercial finite-element software can be a suitable platform for PD simulations that may result in several computational benefits. Hence, this paper presents the PD diffusion modeling and implementation procedure in a widely used commercial finite-element analysis software, ANSYS. The accuracy and capability of this approach is demonstrated by considering several benchmark problems.

Electrically Controllable Composite Right/Left-Handed Leaky-Wave Antenna Using Liquid Crystals in PCB Technology

Abstract: A design method for electrically controllable composite right/left-handed (CRLH) leaky-wave antennas (LWAs) with large beam-steering range employing liquid crystal (LC) in printed circuit board technology is proposed. It is demonstrated with detailed mathematical derivation that the design principle enables the LC-CRLH-LWA to keep the balanced condition with all bias states applied to the LC, yielding LC-CRLH-LWAs that feature a steady balanced condition and a broadband property. Based on this principle, an LC-CRLH-LWA prototype is designed, simulated, optimized, and experimentally validated. According to the simulation results, the designed LC-CRLH-LWA operates in the band from 11.14 to 12.77 GHz with a frequency-agile radiation direction. By tuning the permittivity of LC, the radiation direction of the designed antenna scans from −21° to +23° at the fixed operating frequency of 12.4 GHz. The experimental results agree well with the simulated data. Furthermore, sidelobe level suppression of the designed antenna is achieved through decreasing the reflection between the unit cells of the antenna.

3-D Printed Air Substrates for the Design and Fabrication of RF Components

Abstract: This paper presents the fabrication and characterization of radio frequency (RF) and microwave passive structures on an air substrate using additive manufacturing (3-D printing). The air substrate is realized by 3-D printing RF structures in two separate pieces and snapped together face to face using a LEGO-like process. Spacers printed on the periphery provide the desired air substrate thickness. Metal patterning on nonplanar printed plastic structures is carried out using a damascene-like process. Various RF structures such as low dispersion transmission line, T-line resonator, high-gain patch antenna, slot antenna, and cavity resonator are demonstrated using this process. Good performance is achieved; for example, measured 50- $\Omega $ transmission line shows low loss of 0.17 dB/cm at 4 GHz, and a patch antenna (center frequency of 4.5 GHz) shows gain and bandwidth of 7.6 dB and 0.2 GHz, respectively. Details of both measured and simulation results are presented.

A Fully 3-D Printed Waveguide and Its Application as Microfluidically Controlled Waveguide Switch

Abstract: This paper reports the design, fabrication, and characterization of a fully 3-D printed waveguide (WG) and a microfluidically controlled WG switch, operating at K-band. The WG body is printed using a benchtop 3-D printer with thermoplastic substrate acrylonitrile butadiene styrene, and the conductive layer is incorporated using the same printer by automated deposition of conductive silver ink. The measured total insertion loss of the 3-D printed WG is in good match with the simulations showing better than 0.11 dB/cm for the entire K-band. The 3-D printed WG is characterized, and its attenuation and propagation constants are computed for the K-band using a multiline technique. In addition, microfluidically controlled eutectic gallium–indium and galistan liquid metals are integrated with the 3-D printed WG, and a novel reflective WG switch is implemented. The insertion loss and isolation of the switch are measured to be better than 0.5 dB and better than 15 dB for the entire K-band, respectively. Furthermore, the switch’s performance with respect to changes in ambient temperature has been studied. To the best of our knowledge, this is the first time that fused deposition modeling printing and automated ink dispensing is used to fabricate fully 3-D printed WGs, and a 3-D printed WG switch is developed, exhibiting the potential of such technology for rapid prototyping of RF devices.

IC Solder Joint Inspection via Robust Principle Component Analysis

Abstract: Defect inspection of integrated circuits (ICs) solder joints is a long-standing task. This paper proposes a novel IC solder joint inspection method based on the idea of robust principle component analysis (RPCA), which is a celebrated optimization technique. To the best of our knowledge, this is the first time IC solder joint inspection is formulated as an optimization problem. In particular, we model an IC solder joint image as observed data corrupted by gross errors. According to the RPCA theory, the observed data can be approximately decomposed into a low-rank component and an error component. In this paper, an appearance model of qualified IC solder joints is defined for IC solder joint inspection based on RPCA. Then, a defect score is defined based on the appearance model and is used to evaluate the quality of IC solder joints. Meanwhile, location prior knowledge related to human perception is incorporated in the defect score to further evaluate the defects of IC solder joints. Finally, a simple discrimination scheme is proposed to inspect IC solder joints. Experimental results indicate that the proposed method is superior to the existing methods in inspection performance.

Liquid Crystal Leaky-Wave Antennas With Dispersion Sensitivity Enhancement

Abstract: A novel design, fabrication, and packaging technology is proposed for liquid crystal (LC)-based beam-scanning leaky-wave antennas (LWAs). Different from conventional ones, extra dispersion sensitivity enhancement (DSE) components are introduced to increase the slope of effective phase constant versus frequency of LWAs and, hence, the beam scanning range. CST MW Studio software package is used to validate the design method. It is shown that, by adding the DSE components, the electrical beam scanning range is extended by more than 56% in the Ku satellite communication band, where good impedance matching and balanced condition are kept for both extreme tuning states of LCs. Prototypes of the designed LC-composite right/left-handed LWAs with and without the DSE components are fabricated and measured. The fabrication methodology incorporating printed circuit board and precision metal processing technology ensures the mechanical stability, flexible design, perfect packaging, and low cost. Finally, the feature-selective validation technique validates that the measured and simulated results are in good agreement.

Development of a Wideband and High-Efficiency Waveguide-Based Compact Antenna Radiator With Binder-Jetting Technique

Abstract: A multilayer waveguide-based antenna radiator is proposed to achieve a wide operational bandwidth of high gain and high efficiency in a compact size. It is a $2\times 2$ array, consisting of a feeding waveguide, a matching cavity, and a radiating aperture. The proposed design provides sufficient freedom for the radiator to achieve broadband impedance matching. In order to improve radiation efficiency and avoid drawbacks from the traditional machining techniques, a binder-jetting process using metallic particles is adopted to realize the relatively complicated structure. This 3-D metal-direct-printing technique is competent to fabricate waveguide-based structures with high precision. Experimental results are favorably compared to the results of the fabrication by the machining technique. The measured relative bandwidth with VSWR $\leq1.5$ is 23.7% (13.0–16.5 GHz). A high efficiency of 90% is obtained at the center frequency, and more than 80% efficiency can be maintained over a 2.3-GHz bandwidth. This paper shows that the binder-jetting printing technique is a promising manufacturing approach to realizing high-performance waveguide-based antennas and microwave components.

High-Selectivity and Miniaturized Filtering Wilkinson Power Dividers Integrated With Multimode Resonators

Abstract: This paper presents two filtering Wilkinson power dividers (FWPDs) with high selectivity and miniature size. A multimode resonator is used to replace a quarter-wavelength transmission line in a conventional Wilkinson power divider, and then the resonator-based FWPD is capable of splitting power and selecting frequency simultaneously. Two tri-mode resonators and two quad-mode resonators are applied to design a single- and a dual-band FWPD, respectively. Characteristics of the tri- and quad-mode resonators are analyzed, and the equivalent circuits of the proposed single- and dual-band FWPDs are presented. The input port matching and filtering response are explained by the even-mode equivalent circuit, while the output port matching and isolation characteristics can be investigated by the odd-mode equivalent circuit. Moreover, the magnetic source-load coupling introduces multiple transmission zeros to improve the frequency selectivity. All measured results are in good agreement with the full-wave simulation results.

Hybrid DC Circuit Breaker Feasibility Study

Abstract: Recently, a growing number of dc systems exist based on the development of electrical energy consumption. For low-voltage dc grids, switching devices are needed that have to meet technically sophisticated requirements. These devices have to handle fault currents of several hundred amperes and system voltages up to 1000 V. A typical dc circuit breaker has to provide low on-state losses, light weight, and small volume. On the way toward fulfilling these requirements, hybrid circuit breakers can represent the optimal solution. A hybrid dc circuit breaker combines the advantages of mechanical contacts and semiconductors. In this paper, such a device has been designed and constructed using a commercial switch and electronic components in the laboratory. The breaking performance of this experimental prototype has been investigated, and thus the interruption of the nominal and failure currents in the case of different time constants can be identified. The investigated hybrid switching device has been optimized in order to maximize the switching capacity and the protection of the semiconductors.

Sharp-Rejection Wideband Bandstop Filter Using Stepped Impedance Resonators

Abstract: A novel wideband bandstop filter is proposed in this paper. Using one uniform impedance resonator and two stepped impedance resonators, five transmission zeros are introduced in the stopband. Appropriate positioning of these zeros ensures the high selectivity and flat rejection level of the stopband. The bandwidth of the filter can be conveniently controlled by the characteristic impedances of the connecting lines and resonators. A complete analytic analysis is proposed to fully control the positions of transmission zeros, and the design equations and design rules for the bandstop filter are given in detail by using the lossless transmission line model. To illustrate the concept, a wideband bandstop filter with center frequency at 2 GHz and rejection level below 20 dB is fabricated. Theoretical, simulated, and measured results are found in good agreement with each other, and the measured 20-dB rejection bandwidth is as wide as 150%.

Integrated Circuit Cooling Using Heterogeneous Micropin-Fin Arrays for Nonuniform Power Maps

Abstract: As microelectronic system density continues to increase, cooling with conventional technologies continues to become more challenging and is often a limiter of performance and efficiency. The challenge arises due to both large heat fluxes generated across entire chips and packages, and localized hotspots with even higher heat flux. In this paper, nonuniform micropin-fin heat sinks are investigated for the cooling of integrated circuits with nonuniform power maps. Four heterogeneous micropin-fin samples were fabricated and tested in single-phase experiments with deionized water to investigate the effectiveness of local micropin-fin clustering for the cooling of hotspots. Cylindrical and hydrofoil micropin-fins were tested, as well as two types of heterogeneous arrays: those with pin-fins clustered directly over the hotspot and those with the high density cluster spanning the entire width of the channel to prevent flow bypass around the cluster. Samples were tested with a uniform nominal heat flux of 250 W/cm2 as well as a hotspot heat flux of 500 W/cm2. Local micropin-fin clustering was found to be an effective method of reducing local thermal resistance with a modest pressure drop penalty.

Manufacturing Considerations in the 3-D Printing of Fractal Antennas

Abstract: The use of additive manufacturing (AM) techniques for the fabrication of 3-D fractal monopole antennas is presented. The 3-D printing (3-D P) of 3-D designs based on the Sierpinski fractal concept is studied, and the performance discussed. The AM allows the fabrication of the complex features of these antennas. The specific structures, on the other hand, provide a reduction of the material used in AM compared with the equivalent nonfractal designs, in which two cases can be described by over 75%. This is the first time that 3-D fractals have been studied in terms of volume reduction and their potential benefits to AM of antennas. The first investigated antenna derives from the Sierspinki tetrahedron fractal shape. From this initial design, two new structures have been developed: the dual Sierpinksi fractal and the dual inverse Sierpinski fractal. The new designs offer improved matching and radiation pattern. All the antennas operate at 2.4 GHz used in Bluetooth and wireless LAN band. Furthermore, the final inverse fractal shape is able to cover both the 2.4- and 5.5-GHz WLAN frequencies with a reflection coefficient ( $S_{11}$ ) better than −10 dB, together with coverage at bands around 8 GHz. This ratio of resonant frequencies is achieved after a series of described design stages. The radiation patterns of the antennas are monopole-like at both bands. The AM technique employed is metal powder embinder printing where a binding material is jetted on a powder bed containing metal particles. Metal 3-D P is ideal for maintaining the mechanical strength of the structures. The envisaged applications are in the defense and aerospace sectors where high-value, lightweight, and mechanically robust antennas can be integrated with other 3-D printed parts. Transient simulations based on the finite integration technique compare well with measurements.

A Novel Absorptive Common-Mode Filter for Cable Radiation Reduction

Abstract: An absorptive common-mode filter (A-CMF) embedded in a four-layer printed circuit board is proposed. Unlike traditional CMFs, for the A-CMF, common-mode (CM) noise is absorbed through the surface mount resistor, so the transmitted and reflected CM noises can be suppressed simultaneously. The proposed A-CMF is synthesized and implemented based on the corresponding equivalent circuit model. To achieve a high-efficiency CM absorption at the desired frequency, through the analytical design equations, the values of the model elements are calculated and are all realizable. In this paper, at the operating frequency of 2.4 GHz, the 15-dB suppression level and 96% absorption efficiency are measured, while the size of the A-CMF is merely $8.65 \times 2.5$ mm2. Lastly, we designed two in situ experiments for fully demonstrating the suppression performances of CM-induced radiated noise. The measured results, within the operating frequency band of the A-CMF, show the receiving noise of an antenna nearby can be effectively reduced.

LTCC Wideband Bandpass Filters With High Performance Using Coupled Lines With Open/Shorted Stubs

Abstract: Two compact low-temperature co-fired ceramic (LTCC) wideband bandpass filters using coupled lines with open/shorted stubs are proposed in this paper. Two conventional coupled lines with open/shorted stubs are used to increase the passband order for the wideband filters. Two independent transmission zeros realized by the open/shorted coupled lines are used to further improve the passband selectivity and harmonic suppression. Due to the 3-D LTCC circuit, the coupled lines and stubs can be located at different layers to overcome the large circuit size. Two fifth-order wideband LTCC bandpass filters centered at 3.1 GHz with multiple transmission zeros are designed and fabricated for verification. The theoretical and measured results are in good agreement and show good in-band performances.

Efficient Modeling of Power Supply Induced Jitter in Voltage-Mode Drivers (EMPSIJ)

Abstract: An efficient methodology for estimation of power supply induced jitter (PSIJ) in high-speed designs is presented. Semianalytical expressions for jitter are derived based on separating the large signal response and the small signal noise response and subsequently combining the results. Proposed simplified relations enable the designers to estimate the PSIJ based on a single bit simulation. Proposed methods are validated on several examples of voltage-mode driver circuits, designed in different technologies and in the presence of different types of noise sources.

LTCC Out-of-Phase Filtering Power Divider Based on Multiple Broadside Coupled Lines

Abstract: This paper presents a compact microwave out-of-phase filtering power divider in low-temperature co-fired ceramic (LTCC) technology. The proposed device is composed of three resonators and an isolation resistor. One resonator is symmetrically coupled with the other two by employing multiple broadside coupled lines. Utilizing the transmission line theory, the magnitude and phase characteristics are addressed. Theoretical analysis indicates the proposed circuit provides two signal paths with bandpass responses and 180° phase difference. Also, the realization of the isolation between two output ports is analyzed. For validation, a filtering power divider with out-of-phase outputs is designed, fabricated, and measured. It occupies a compact area of $3.1 \times 3.2 \times 1.6$ mm3. Comparisons of the measured and simulated results are presented to verify the theoretical method.

Modeling, Fabrication, and Characterization of Large Carbon Nanotube Interconnects With Negative Temperature Coefficient of the Resistance

Abstract: One of the most appealing properties of carbon nanotube (CNT) interconnects is the possibility of exhibiting, under certain circumstances, a negative temperature coefficient of the electrical resistance, i.e., a resistance that decreases as temperature increases. In the past, this behavior has been theoretically predicted and experimentally observed, but only for a certain class of CNTs, with short lengths (up to some micrometers) and in a limited range of temperature. This paper demonstrates the possibility of obtaining such a desirable behavior in a larger scale (up to fractions of millimeters). An accurate electrothermal model is used to define the conditions under which a negative derivative of the resistance may be observed. Then, a novel bottom–up technique is proposed to realize the interconnect, by self-assembly of short CNTs. The experimental results of an electrothermal characterization demonstrate the possibility of obtaining a negative temperature coefficient of the resistance and confirm the validity of the theoretical model.