Inductive Crosstalk Research Articles

Performance Comparison Between Current-Mode Signaling and Voltage-Mode Signaling for Single-Walled Carbon Nanotube Bundle Interconnects

Compared with the traditional copper material, carbon nanotube (CNT) has been identified as one of the most potential materials for interconnects in nanometer regime due to higher performance. However, for CNT interconnects, most of the researches focus on voltage-mode signaling (VMS) scheme, whereas current-mode signaling scheme (CMS) is meagerly investigated. The paper proposes an equivalent circuit model of two-line coupled single-walled CNT bundle interconnects, which is applicable to both CMS and VMS schemes. In addition, the model takes capacitive and inductive crosstalk into consideration. In CMS and VMS interconnects, the performance of victim line in the time domain is studied according to decoupling technique and ABCD parameter matrix approach at local, intermediate and global levels, respectively. The influence of aggressor line on victim line is discussed because of dynamic crosstalk and functional crosstalk. Furthermore, the paper comparatively analyzes the performance advantage between CMS interconnects and VMS interconnects. The results show that CMS interconnects have lower output voltage swing and propagation delay than VMS interconnects in the same condition. In terms of noise, CMS scheme has higher advantage for lesser noise peak, noise width and noise area. Moreover, it is found that the results obtained by ABCD parameter matrix approach have great consistency with Advanced Design System simulation results.

Analysis of Magnetic-Film-Type Noise Suppressor Integrated on Transmission Lines for On-Chip Crosstalk Evaluation

This paper discusses the distribution of magnetic flux density inside a magnetic film covered on a microstrip line for developing a design rule of the magnetic-film-type noise suppressor. The measured and simulation results of the magnetic field distribution and conduction loss agree with each other. The distribution of magnetic flux density B inside the magnetic film can be confirmed numerically through the theoretical calculation of the characteristic length including the complex permeability of the magnetic film. These results demonstrate that the complex permeability of the magnetic film leads to a complex characteristic length and distributed magnetic poles and results in the alternated distribution of B vectors along the distance. These results also suggest that these distributed magnetic poles are required when the inductive crosstalk and conduction loss are considered in the design of patterned magnetic-film-type noise suppressor. Based on these results, this paper could be of great use for the quantitative evaluation of crosstalk between the aggressor and victim lines.

Conducted electromagnetic interference: theoretical and experimental investigation

This paper presents theoretical and experimental study of the mechanisms of conducted couplings, generated by an electromagnetic interference such as the galvanic, capacitive and inductive crosstalk. These couplings are due to various parameters, such as the width and the length of the tracks (or drivers) for the galvanic coupling and the circulation of noise currents and voltages (between the aggressor and the victim) which are caused by the proximity of the tracks and the very high frequency interference signals for the capacitive and inductive coupling. Also, this study shows the increases of the noise level caused by the incrementing of the signal frequency for all different types of crosstalk. This work is validated with empirical formula (for the inductive effect), also by the conventional formulas such as Kirchhoff’s laws (the node law, the mesh law) and by an experimental study (represented by a work bench) on the coupling behavior.

Mitigation of Oscillator Pulling in SoCs

This paper presents a novel method to mitigate undesirable oscillator pulling effects in wireless transmitter architectures. In practice, coupling of the power amplifier (PA) signal caused by inductive or electromagnetic crosstalk, inevitably leads to injection pulling. Particularly, for nonconstant envelope modulation schemes such as Bluetooth enhanced data rate (EDR), GSM-EDGE, or WiFi, the pulling is extremely troublesome due to the amplitude-to-frequency (AM–FM) conversion effect. The difficulty to cope with this undesirable effect stems from the fact that the pulling is largely dependent on process spread and environmental factors like temperature and antenna load mismatch. This paper proposes a novel method based on stochastic-gradient algorithms to resolve the pulling effect. It can be realized inexpensively in digital design and does not rely on knowledge of the unpredictable crosstalk path which makes it extremely efficient to mitigate the pulling effect. To verify the novel idea, a prototype IC has been fabricated in 65 nm CMOS technology.

A New Spatially Rearranged Bundle of Mixed Carbon Nanotubes as VLSI Interconnection

Scaling of device dimensions down to nanometer range helps achieve unprecedented switching speed and multifunctional processing capabilities of nanoelectronic circuits and systems. However, interconnect constraints in the existing and emerging applications are expected to become the primary bottlenecks unless radical change is introduced in the design and technology of on-chip signal communication medium. In response to this demand, various novel and innovative interconnect solutions like carbon nanotube (CNT) are currently being explored as alternatives to metal wires. This paper proposes a unique structure of mixed CNT bundle with a specific arrangement of single-wall and multi-wall CNTs in the bundle. A comprehensive modeling and analysis of the conductance, inductance, and capacitance of the proposed mixed CNT bundle reveals that there will be no significant decrease in the overall conductance of the bundle, but the structural arrangement clearly reduces capacitive crosstalk between neighboring signal lines. Inductive crosstalk is seen to remain unchanged.

Skewing-based method for reduction of functional crosstalk and power supply noise caused by on-chip buses

In this study, the authors present an optimisation method based on analytical resistance, inductance and capacitance (RLC) models for simultaneous reduction of both functional crosstalk noise and power supply noise caused by on-chip buses. This is achieved by intentional skewing of the relative timing of adjacent wires. The method is applicable to any number of bus wires and it takes into account both capacitive and inductive coupling between wires. The authors model the effect of skewing on both functional crosstalk in a distributed RLC bus and the power noise in the surrounding RLC power distribution network. The model is verified by comparing it with HSPICE in 65 nm technology, with the average error being 1.4%. The capability of the method in reducing problematic long-range inductive crosstalk noise is demonstrated in a case study where the maximum crosstalk noise is reduced from 0.20 to 0.05 V. Implementation and the use of the method in combination with other crosstalk reduction methods and power supply noise reduction methods are presented. The influence of the number of different skewing times is analysed.

汽车线束电感性串扰动态变化预测

In order to predict the variation of inductive crosstalk in the cable bundles as the automobile was in motion,both the prediction model of the inductive crosstalk of the best/worst cases and the amended model by Monte Carlo method were established.According to the extreme positions of wires in the cable bundles,the prediction intervals of the inductive crosstalk of the best/worst cases were defined.By using the Monte Carlo method,the mathematical expectation of the inductive crosstalk was obtained,and the confidence interval for the expectation was defined under the circumstance of 80% confidence level.Here,the confidence interval was the amended prediction interval.By comparison with the results from EMC Studio electromagnetic simulation software,it is shown that the cable bundle crosstalks in all selected positions are in the best/worst case interval and most of them are in the amended interval when the frequencies are lower than 5 MHz.The length of the amended interval has decreased by 40%.Moreover,the electrical dimensions tend to electrically large and the error also increases when the frequencies are higher than 5 MHz.It concludes that the both models are simple and convenient to predict the inductive crosstalk rapidly according to different accuracy requests.

Tumor Necrosis Factor Receptors Support Murine Hematopoietic Progenitor Function in the Early Stages of Engraftment

Tumor necrosis factor (TNF) family receptors/ligands are important participants in hematopoietic homeostasis, in particular as essential negative expansion regulators of differentiated clones. As a prominent injury cytokine, TNF-alpha has been traditionally considered to suppress donor hematopoietic stem and progenitor cell function after transplantation. We monitored the involvement of TNF receptors (TNF-R) 1 and 2 in murine hematopoietic cell engraftment and their inter-relationship with Fas. Transplantation of lineage-negative (lin(-)) bone marrow cells (BMC) from TNF receptor-deficient mice into wild-type recipients showed defective early engraftment and loss of durable hematopoietic contribution upon recovery of host hematopoiesis. Consistently, cells deficient in TNF receptors had reduced competitive capacity as compared to wild-type progenitors. The TNF receptors were acutely upregulated in bone marrow (BM)-homed donor cells (wild-type) early after transplantation, being expressed in 60%-75% of the donor cells after 6 days. Both TNF receptors were detected in fast cycling, early differentiating progenitors, and were ubiquitously expressed in the most primitive progenitors with long-term reconstituting potential (lin(-)c-kit(+) stem cell antigen (SCA)-1(+)). BM-homed donor cells were insensitive to apoptosis induced by TNF-alpha and Fas-ligand and their combination, despite reciprocal inductive cross talk between the TNF and Fas receptors. The engraftment supporting effect of TNF-alpha is attributed to stimulation of progenitors through TNF-R1, which involves activation of the caspase cascade. This stimulatory effect was not observed for TNF-R2, and this receptor did not assume redundant stimulatory function in TNFR1-deficient cells. It is concluded that TNF-alpha plays a tropic role early after transplantation, which is essential to successful progenitor engraftment.

Analysis of the Impacts of Signal Slew and Skew on the Behavior of Coupled RLC Interconnects for Different Switching Patterns

This paper presents an in-depth analysis of signal slew and skew variations in coupled inductive lines for different switching patterns. It is revealed that variations of rise/fall time and skew alter the behavior of coupled inductive lines under different switching patterns. We observe that crosstalk noise reduces with increasing signal skew, and the impact of skew variation on crosstalk noise is more prominent for lines with strong capacitive coupling. A performance comparison is done between power supply and ground line as inductive shield, and it is found that ground lines work better than power lines in inductive crosstalk minimization. The 100%-delay measurement technique has been proposed as opposed to the conventional 50%-delay method, and we notice that the 50%-delay technique underestimates the propagation delay for an inductive dominant line with varying signal slew times. Closed-form equations for propagation delay in terms of signal slew time have been derived, which are within 9% of HSPICE-simulated results for a set of interconnect structures. These expressions are simple, and accuracy increases with growing number of interconnect lines.

Robust On-Chip Signaling by Staggered and Twisted Bundle

Existing shield insertion for multiple signal nets can lead to a nonuniformly distributed, capacitive-coupling length and inductive return paths, introducing large delays and delay variation by crosstalk. This article discusses a twisted, staggered interconnect structure that reduces both inductive and capacitive crosstalk. The proposed design reduces delay by 25% and reduces delay variation by 25times compared to designs employing coplanar shields.

Reduction of Inductive Crosstalk Using Quadrupole Inductors

Interference due to inductor crosstalk is a growing concern in modern RFICs where inductors are placed in close proximity. A quadrupole inductor is explored as a method to reduce inductive crosstalk. A quadrupole inductor and standard inductor are compared with respect to inductance, quality factor, and area. Then, physics-based calculations are corroborated with simulation and measurement to predict crosstalk reduction as a function of position. Measurements verify up to a 31 dB reduction in crosstalk. Finally, phase noise measurements of voltage-controlled oscillators show that the quadrupole inductor can be used in circuits without negatively impacting performance.

Tinkering with the inductive mesenchyme: Sostdc1 uncovers the role of dental mesenchyme in limiting tooth induction

Like epithelial organs in general, tooth development involves inductive crosstalk between the epithelium and the mesenchyme. Classically, the inductive potential for tooth formation is considered to reside in the mesenchyme during the visible morphogenesis of teeth, and dental mesenchyme can induce tooth formation even when combined with non-dental epithelium. Here, we have investigated induction of mouse incisors using Sostdc1 (ectodin), a putative antagonist of BMP signaling in the mesenchymal induction of teeth. Deletion of Sostdc1 leads to the full development of single extra incisors adjacent to the main incisors. We show that initially, Sostdc1 expression is limited to the mesenchyme, suggesting that dental mesenchyme may limit supernumerary tooth induction. We test this in wild-type incisors by minimizing the amount of mesenchymal tissue surrounding the incisor tooth germs prior to culture in vitro. The cultured teeth phenocopy the extra incisors phenotype of the Sostdc1-deficient mice. Furthermore, we show that minimizing the amount of dental mesenchyme in cultured Sostdc1-deficient incisors causes the formation of additional de novo incisors that resemble the successional incisor development that results from activated Wnt signaling. Finally, Noggin and Dkk1 prevent individually the formation of extra incisors, and we therefore suggest that inhibition of both BMP and Wnt signaling contributes to the inhibitory role of the dental mesenchyme. Considering the role of mesenchyme in tooth induction and the design of tissue engineering protocols, our work may have uncovered how delicate control of tissue quantities alone influences the outcome between induction and inhibition.

Minimum Shield Insertion on Full-Chip RLC Crosstalk Budgeting Routing

This work presents a full-chip RLC crosstalk budgeting routing flow to generate a high-quality routing design under stringent crosstalk constraints. Based on the cost function addressing the sensitive nets in visited global cells for each net, global routing can lower routing congestion as well as coupling effect. Crosstalk-driven track routing minimizes capacitive coupling effects and decreases inductive coupling effects by avoiding placing sensitive nets on adjacent tracks. To achieve inductive crosstalk budgeting optimization, the shield insertion problem can be solved with a minimum column covering algorithm which is undertaken following track routing to process nets with an excess of inductive crosstalk. The proposed routing flow method can identify the required number of shields more accurately, and process more complex routing problems than the linear programming (LP) methods. Results of this study demonstrate that the proposed approach can effectively and quickly lower inductive crosstalk by up to one-third.

Behavior of Short Pulses on Tightly Coupled Microstrip Lines and Reduction of Crosstalk by Using Overlying Dielectric

Forward crosstalk can be a problem in the design of printed circuit boards. We explore two aspects of forward crosstalk in tightly coupled microstrip lines. First, we demonstrate, as far as we are aware, the first direct experimental verification of different velocities of propagation in tightly coupled microstrip lines. (These are the even and odd modes for symmetric lines.) Second, we verify by modeling and by experiments the reduction in forward crosstalk when microstrip lines are covered by the proper overlying thickness of dielectric and the simultaneous reduction in differences in modal velocities. In 1981, Anderson introduced a clever means to reduce forward crosstalk in microstrip lines to zero by burying the lines under a relatively thin dielectric layer of an appropriate thickness. At this critical overlayer thickness, the capacitive and inductive crosstalk components are equal even for inhomogeneous media. Anderson's work is not well known to most packaging engineers because it appeared only in the patent literature and in the review of scientific instruments, an excellent journal, but not one usually read by the packaging community. We extend Anderson's results by demonstrating that at the critical thickness of the overlying dielectric the velocities of the two modes become equal. We verify that Anderson's argument extends to the case where the lines are so tightly coupled that the modal velocities differ by more than 10%. We also generalize his results to the case where the lines are asymmetric. Experimental results on microstrip lines approximately 61 cm in length confirm the modeling predictions.

Quantitative Prediction of On-Chip Capacitive and Inductive Crosstalk Noise and Tradeoff between Wire Cross-Sectional Area and Inductive Crosstalk Effect

Capacitive and inductive crosstalk noises are expected to be more serious in advanced technologies. However, capacitive and inductive crosstalk noises in the future have not been concurrently and sufficiently discussed quantitatively, though capacitive crosstalk noise has been intensively studied solely as a primary factor of interconnect delay variation. This paper quantitatively predicts the impact of capacitive and inductive crosstalk in prospective processes, and reveals that interconnect scaling strategies strongly affect relative dominance between capacitive and inductive coupling. Our prediction also makes the point that the interconnect resistance significantly influences both inductive coupling noise and propagation delay. We then evaluate a tradeoff between wire cross-sectional area and worst-case propagation delay focusing on inductive coupling noise, and show that an appropriate selection of wire cross-section can reduce delay uncertainty at the small sacrifice of propagation delay.

MINIMIZING CROSSTALKS IN UNSHIELDED TWISTED-PAIR CABLES BY USING ELECTROMAGNETIC TOPOLOGY TECHNIQUES

Crosstalk reduction is analyzed for a reconfigured category-five cable network using electromagnetic topology-based simulation. The reconfigured network results in a marked reduction in inductive near-end crosstalk for the unshielded twisted-pair cable network. Analyses show that half-loop shifting of the generator-pair wires placed next to the receptor is the most effective way to control the near-end crosstalk level. This is primarily due to additional coupling sources induced on receptor wires that effectively deactivate the original cross coupling effect. The analysis also reveals the usefulness of electromagnetic topology-based simulations. The technique applied in this paper is applicable for any large network systems. A sub-network compaction scheme is critical in creating the equivalent junctions that provide a significant reduction in total computational time and total computer memory requirement for analyzing large network systems. For a 5.28-m long cable we have considered in this paper, the results are valid up to 10 MHz.

Moment Computations of Distributed Coupled RLC Interconnects with Applications to Estimating Crosstalk Noise

A method is proposed to compute moments of distributed coupled RLC interconnects. Both uniform line models and non-uniform line models will be developed. Considering both self inductances and mutual inductances in multi-conductors, recursive moment computations formulae of lumped coupled RLC interconnects are extended to those of distributed coupled RLC interconnects. By using the moment computation technique in conjunction with the projection-based order reduction method, the inductive crosstalk noise waveform can be accurately and efficiently estimated. Fundamental developments of the proposed approach will be described. Simulation results demonstrate the improved accuracy of the proposed method over the traditional lumped methods.

Traces in Proximity to Gaps in Return Planes

Coupling between circuitry on printed circuit boards can be mitigated by a variety of well-known techniques. One such technique is to isolate circuitry in different areas of the printed circuit board by strategically placing a gap in the signal return plane. However, this technique is only effective at reducing common-impedance coupling, which is generally not a significant coupling mechanism at frequencies above 1 MHz. This paper investigates the effect of a gap located between and parallel to adjacent microstrip traces. The effect of the gap on the mutual inductance and mutual capacitance is evaluated. Laboratory measurements and numerical simulations show that gaps in the return plane are ineffective at reducing inductive and capacitive crosstalk in most configurations, and in some cases they increase the mutual coupling between printed circuit board traces.

Woven Fabric-Based Electrical Circuits

One important problem in electronic textiles is crosstalk and lack of signal integrity between conductive lines. Two significant advantages of electronic textiles over tradi tional circuit boards are flexibility and the ability to scale to large areas. Capacitive and inductive crosstalk is aggravated by long parallel conductors, and varies as the electronic textile is flexed into different configurations. This paper evaluates crosstalk between woven parallel conductors. Two new thread structures—coaxial and twisted pair copper threads—to minimize cross talk are developed and evaluated. Significant reductions in crosstalk are obtained with the coaxial and twisted pair thread structures when compared with bare copper threads or insulated conductive threads.

Full-Chip Routing Optimization With RLC Crosstalk Budgeting

Existing layout-optimization methods for both capacitive and inductive (RLC) crosstalk reduction assume a set of interconnects with a priori given crosstalk bounds in a routing region. RLC crosstalk budgeting is critical for effectively applying these methods at the full-chip level. In this paper, we formulate a full-chip routing optimization problem with RLC crosstalk budgeting, and solve this problem with a multiphase algorithm. In phase I, we solve an optimal RLC crosstalk budgeting based on linear programming to partition crosstalk bounds at sinks into bounds for net segments in routing regions. In phase II, we perform simultaneous shield insertion and net ordering to meet the partitioned crosstalk bounds in each region. In phase III, we carry out a local refinement procedure to reduce the total number of shields. Compared with the best alternative approach in experiments, the proposed algorithm reduces the total routing area by up to 5.71% and uses less runtime. To the best of our knowledge, this work is the first in-depth study on full-chip routing optimization with RLC crosstalk budgeting.