Gyrator-Based Synthesis of Active On-Chip Inductances

A detailed analysis of a gyrator-based inductance using operational transconductance amplifiers is presented. The advantages of such integrated inductances over passive spirals include higher quality factors and the ability to tune inductance values. Design equations are derived using a practical high-frequency model of each transconductor, and operating constraints are provided to mitigate the effects of parasitics and to ensure optimal performance and stability.     

Ni-Cu-Zn ferrites with high Curie temperature for multilayer inductors with increased operating temperatures

We studied the sintering behavior and magnetic properties of Ni_0.60-yCu_yZn_0.42Fe_1.98O_3.99 ferrites. The shrinkage is shifted toward lower temperature with increasing Cu content y. The addition of Bi₂O₃ sintering aid induces enhanced shrinkage at T < 900°C and dense ceramics are obtained after sintering at 900°C. Such ferrites exhibit a permeability of µ = 135-250 depending on the composition, sintering temperature and concentration of sintering additive. Ferrites with y = 0.20 show a high Curie temperature of T_c = 307°C. Multilayer inductors were fabricated and cofired at 900°C using ferrite tapes without and with 0.75 wt% Bi₂O₃. The compatibility of ferrite tapes with different metal pastes (Ag, AgPd, and Au) was evaluated. Ferrite tapes were also integrated between layers of low-k dielectric CT708 tapes and successfully cofired at 900°C. Preliminary tests indicate that the multilayer inductors can be operated up to temperatures of 250°C. This demonstrates that high-T_c Ni-Cu-Zn ferrites are promising magnetic materials for inductive components for high operating temperatures.     

宽带硅衬底RF片上螺旋电感物理模型

针对高损耗硅衬底,源自部分元等效电路方法考虑了趋肤效应和邻近效应对螺旋电感中串联电感L_s、串联电阻R_s频率特性的制约,并基于全耦合变压器模型计入了复杂的衬底涡流损耗,从而建立了一种新的片上螺旋电感物理模型.通过与全波分析方法对比,验证了在20GHz范围内由该模型导出的等效电感L_eff、等效电阻R_eff和Q值误差仅在7%以内.该模型可望用于硅基射频集成电路中电感进一步的理论探讨和优化设计.     

Synthesis of active inductors using SFG stamps

This paper proposes a new approach for the systematic synthesis of active inductors via signal-flow graphs (SFGs). The basic idea consists of proposing and using SFG stamps of active basic building blocks (ABBs) to construct the equivalent SFG of a classical inductor. We show that a large number of active inductors can be thus synthesized; twelve are proposed, most of them are novel. Known ABBs, as well as newly proposed ones are used, namely current conveyors (CC), operational transconductance amplifiers (OTA), current conveyor transconductance amplifiers (CCII-TA), current feedback operational amplifiers (CFOA), operational transresistance amplifiers (OTRA), current backward transconductance amplifiers (CBTA), current feedback transconductance amplifiers (CFTA) and voltage differencing inverting buffered amplifiers (VDIBA). SPICE simulations are given to show the viability of the proposed technique.     

On-chip growth of patterned ZnO nanorod sensors with PdO decoration for enhancement of hydrogen-sensing performance

In this study, we used a low-temperature hydrothermal technique to fabricate arrays of sensors with ZnO nanorods grown on-chip. The sensors on the glass substrate then were sputter decorated with Pd at thicknesses of 2, 4, and 8 nm and annealed at 650 °C in air for an hour. Scanning electron microscopy, high resolution transmission microscopy, X-ray diffraction, and surface analysis by X-ray photoelectron spectroscopy characterization demonstrated that decoration of homogenous PdO nanoparticles on the surface of ZnO nanorods had been achieved. The sensors were tested against three reducing gases, namely hydrogen, ethanol, and ammonia, at 350, 400, and 450 °C. The ZnO nanorods decorated with PdO particles from the 2 and 4 nm layers showed the highest responses to H₂ at 450 and 350 °C, respectively. These samples also generally exhibited better selectivity for hydrogen than for ethanol and ammonia at the same concentrations and at all tested temperatures. However, the ZnO nanorods decorated with PdO particles from the 8 nm layer showed a reverse sensing behaviour compared with the first two. The sensing mechanism behind these phenomena is discussed in the light of the spillover effect of hydrogen in contact with the PdO particles as well as the negative competition of the PdO thin film formed between the sensor electrodes during sputter decoration, Pd–Zn heterojunction that forms at high temperature and thus influences the conductivity of the ZnO nanorods.     

Direct distributed memory access for CMPs

On-chip distributed memory has emerged as a promising memory organization for future many-core systems, since it efficiently exploits memory level parallelism and can lighten off the load on each memory module by providing a comparable number of memory interfaces with on-chip cores. The packet-based memory access model (PDMA) has provided a scalable and flexible solution for distributed memory management, but suffers from complicated and costly on-chip network protocol translation and massive interferences among packets, which leads to unpredictable performance. In this paper we propose a direct distributed memory access (DDMA) model, in which remote memory can be directly accessed by local cores via remote-to-local virtualization, without network protocol translation. From the perspective of local cores, remote memory controllers (MC) can be directly manipulated through accessing the local agent MC, which is responsible for accessing remote memory through high-performance inter-tile communication. We further discuss some detailed architecture supports for the DDMA model, including the memory interface design, work flow and the protocols involved. Simulation results of executing PARSEC benchmarks show that our DDMA architecture outperforms PDMA in terms of both average memory access latency and IPC by 17.8% and 16.6% respectively on average. Besides, DDMA can better manage congested memory traffic, since a reduction of bandwidth in running memory-intensive SPEC2006 workloads only incurs 18.9% performance penalty, compared with 38.3% for PDMA.     

一种用于PCRAM的嵌入式片内电容电荷泵

针对相变存储器小片内电容和低功耗的应用要求,在分析传统升压式电容电荷泵局限性的基础上,提出了一种应用于相变存储单元的嵌入式片内电容电荷泵。该电容电荷泵无需电感器件,存储单元不会受到高电磁干扰,采用了特殊的互补型电荷泵升压方法,具有电源效率高、瞬态响应速度快、面积小、电容可片内集成等优点。在SMIC 40 nm标准CMOS工艺条件下,对设计的嵌入式片内电容电荷泵进行仿真。结果表明,负载电流变化为250 mA/μs时,输出瞬态响应时间为374.2 ns,电源转换效率可达81.65%,静态电流为7.22 μA,输出能力为4 V/2.5 mA。     

Modeling and performance improvement of folded coupled lines in miniaturized Quasi‐lumped directional couplers

An efficient modeling method for folded coupled inductors for application in quasi‐lumped directional couplers designed in both symmetric and asymmetric structures has been proposed. The presented model takes into account the deteriorative effects which occur when coupled inductors realized as electrically short coupled‐lines matched to the high impedance standard are folded into, for example, meander or spiral pattern. The deteriorative influence of coupled‐lines' folding on the performance of the resulting directional coupler has been modeled as additional lumped inductors and capacitors on the schematic diagram of a quasi‐lumped directional coupler's subsection. Moreover, it has been shown that this deteriorative influence can be substantially minimized when values of lumped elements constituting the directional coupler are appropriately changed. The proposed design procedure has been experimentally verified by measurements of two 3‐dB single‐section directional couplers designed in symmetric and asymmetric structures as quasi‐lumped couplers with folded coupled inductors. The measurement results show a good agreement with both circuit and electromagnetic analysis which proves the correctness and usefulness of the presented methods. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:1–9, 2015.     

Analysis of scalable two‐π equivalent‐circuit model for on‐chip spiral inductors

High‐accuracy inductor model is vital for the success of RF/mm‐wave circuit design. In this article, the development of two‐π scalable model with four ladder skin effect structure has been described in detail. For the scalable compact circuit modeling, a set of formulas by which all of the compact circuit elements can be calculated according to the components geometric dimensions and process parameters will be given. The proposed modeling method is regarded as full scalable as all the component parameters are calculated by physical equations or revise equations. A series of spiral inductors with various geometries have been fabricated with 0.13 μm SiGe BiCMOS aluminum process to verify the model. Excellent agreements are obtained between the measured data and calculation form the proposed model up to frequencies above self‐resonant. This scalable 28‐element two‐π model enables to accurately characterize RF behaviors of on‐chip spiral inductors and optimize the inductor performance. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:93–100, 2015.