Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    Mixed-Port Scattering and Hybrid Parameters for High-Speed Differential Lines
    ( 2019)
    Engin, A.E.
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    Ndip, I.
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    Lang, K.-D.
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    Aguirre, G.
    High-speed transmission lines are commonly routed as differential lines to control sensitivity to noise on the reference planes at higher speeds. Differential lines are typically characterized in terms of mixed-mode scattering parameters, as they provide insight into the behavior of differential and common signals, as well as the mode conversion among them. These mixed-mode scattering parameters can be mathematically obtained from single-ended parameters, which can, for example, be measured with a four-port vector network analyzer. There has been recent efforts to develop extended or modified versions of mixed-mode scattering parameters, especially for tightly-coupled lines. This can be a point of confusion in interpreting the behavior of differential lines. In this paper, we introduce the mixed-port scattering and hybrid parameters, which do not suffer from any such ambiguous definitions. Mixed-port hybrid parameters are the most natural way to represent any four-port differential circuit, as they are based on intuitive differential and common-port excitations of the network. They also enable extraction of the current division factor experimentally, which is a critical parameter for electromagnetic interference analysis of differential lines. Mixed-port scattering parameters are also defined based on common and differential port excitations, allowing a simpler interpretation than their mixed-mode counterparts, without the need for defining even, odd, common, or differential-mode impedances. As such, mixed-port scattering and hybrid parameters can be used to analyze the performance of a general differential network, certainly including coupled or asymmetrical lines, without any ambiguity.
  • Publication
    Closed-form multipole debye model for time-domain modeling of lossy dielectrics
    ( 2019)
    Engin, A.E.
    ;
    Ndip, I.
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    Lang, K.-D.
    ;
    Aguirre, J.
    Lossy dielectrics in printed circuit boards and integrated circuit packages can be represented by using a Debye model. This allows accurate signal and power integrity analysis, which depends on the accuracy of material properties of the board or package. Such a Debye model needs multiple poles for accurate representation of the loss tangent over a broad frequency range. Electromagnetic and circuit simulations can then include the impact of frequency-dependent dielectric constant and loss. In this letter, we present an efficient and closed-form multipole Debye model, automating the modeling of lossy dielectrics for inclusion in time-domain electromagnetic or circuit simulators.
  • Publication
    Nonoverlapping Power/Ground Planes for Suppression of Power Plane Noise
    ( 2018)
    Engin, A.E.
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    Ndip, I.
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    Lang, K.-D.
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    Aguirre, G.
    Providing low IR-drop and inductance are two major roles of power and ground (PG) planes in chip packages and boards. However, planes can also cause switching noise coupling, especially when they resonate. This is a concern for mixed-signal boards, high-speed I/Os, and electromagnetic compatibility. Discrete decoupling capacitors are ineffective to control switching noise at gigahertz frequency regime due to their inductance. To filter such high-frequency noise, a possible approach is modifying the shape of the PG planes, such as in power islands or electromagnetic bandgap structures. In this paper, we introduce the nonoverlapping PG planes design methodology for filtering of gigahertz power plane noise. Unlike existing approaches, our approach is simple and has wide bandwidth, while avoiding narrow inductive bridges that increase IR-drop.
  • Publication
    On the Radiation Characteristics of Full-Loop, Half-Loop and Quasi Half-Loop Bond Wire Antennas
    ( 2018)
    Ndip, I.
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    Lang, K.-D.
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    Reichl, H.
    ;
    Henke, H.
    The theory, modeling, measurement and analysis of the radiation characteristics of bond wire antennas (BWAs) is presented in this work. We commence with rigorous formulations, and derivations of analytical models for calculating the vector potential, radiated electromagnetic fields and directivity of full-loop BWAs (FL-BWAs), considering non-constant current distribution along the BWAs. Based on the image theory, we derive an analytical model for calculating the directivity of half-loop BWAs (HL-BWAs) from that of FL-BWAs. Very good correlation is obtained between the directivities calculated analytically using the derived models, and numerically using commercial full-wave solvers, thus validating our analytical approach. We apply the verified models to thoroughly analyze the radiation characteristics of FL-BWAs and HL-BWAs. The radiation characteristics of a HL-BWA is based on the assumption that its reference plane is infinitely large and perfectly conducting. However , for the development of wireless systems, reference planes of finite sizes are required. Therefore, we investigate the impact of realistic dimensions of reference planes. Our results reveal that the radiation characteristics of BWAs referred to as ""HL-BWAs"" in published literature differ significantly from those of true HL-BWAs. Hence, we introduce the term ""quasi half-loop BWA (QHL-BWA)"" to describe BWAs with small reference planes. Finally, we analyze the radiation characteristics of QHL-BWAs, and compare their radiation patterns to that of HL-BWAs. For experimental verification, QHL-BWAs were fabricated and measured in the 60 GHz band. Very good correlation was obtained between measurement and simulation results.
  • Publication
    Development and Validation of a Chip Integration Concept for Multi-Die GaAs Front Ends for Phased Arrays up to 60 GHz
    ( 2018)
    Curran, B.
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    Reyes, J.
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    Tschoban, C.
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    Höfer, J.
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    Grams, A.
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    Wüst, F.
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    Hutter, M.
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    Leiß, J.
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    Martínez-Vázquez, M.
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    Baggen, R.
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    Ndip, I.
    ;
    Lang, K.-D.
    High-gain steerable antenna arrays in the K-, Ka-, and V-frequency bands have the potential to facilitate high-bandwidth satellite communication for a variety of applications. Copper-core printed circuit boards (PCBs) can offer a cost-effective integration platform for such systems by simultaneously addressing both the high frequency and thermal challenges. Integrating GaAs dies into test vehicles has shown that copper-core PCBs can be automatically assembled and provide high-frequency systems that show adequate reliability during thermal cycling. A single 60-GHz transmitter front end, designed to drive a single element of a phased array, with a 2-GHz bandwidth signal, composed of four GaAs dies, including a phase shifter, integrated onto a copper-core PCB produces an output power of -4 dBm and maintains an on-chip temperature under 51 °C.
  • Publication
    Power plane filter using higher order virtual ground fence
    ( 2017)
    Engin, A.E.
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    Ndip, I.
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    Lang, K.-D.
    ;
    Aguirre, G.
    The virtual ground fence (VGF) has been recently proposed to filter power plane noise in gigahertz frequency range. The VGF has distinct advantages over existing approaches, such as power islands and electromagnetic bandgap structures: The IR drop is not increased; transmission-line return-path discontinuities can be avoided; and the design procedure is simple. The basic VGF is created by using quarter-wave resonators referenced to the power or the ground plane. At the design frequency, the resonator creates an ac short circuit between the power and ground planes. An array of such resonators can be placed in electrically short intervals to create a VGF. Power plane noise will then ideally be shorted to ground at the location of the VGF. The operation principle is similar to the series resonance of a decoupling capacitor, which is usually ineffective in the gigahertz frequency range. This paper proposes a new design procedure for determining the number of quarter-wave resonators needed, their characteristic impedances, and their placement on the board. The design approach is based on the well-known insertion loss method in microwave filter theory, which allows for higher order VGF designs consisting of multiple rows of resonators.
  • Publication
    On the Modeling, Characterization, and Analysis of the Current Distribution in PCB Transmission Lines With Surface Finishes
    ( 2016)
    Curran, B.
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    Fotheringham, G.
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    Tschoban, C.
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    Ndip, I.
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    Lang, K.-D.
    Due to manufacturing requirements, surface finishes have become a necessity in printed circuit board design. These finishes have significant effects on the RF performance of the transmission lines. In this paper, a filament modeling approach is used to model skin, proximity, and surface roughness effects in transmission lines with surface finishes up to 70 GHz. The approach shows a high accuracy compared with measurements. The model also gives an insight into how the current distributes itself by showing the frequency dependent proportion of the current that flows in each surface finish layer. In the case of NiP-Au or Ni-Au surface finishes, current migrates increasingly into gold at high frequencies and reaches a maximum in the Ni or NiP at around 3.5 GHz, and then declines. The distribution of the current in different materials can also be explained as the decay of an electromagnetic wave at the surface of the conductor.
  • Publication
    A modeling approach for predicting the effects of dielectric moisture absorption on the electrical performance of passive structures
    ( 2014)
    Curran, B.
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    Ndip, I.
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    Engin, E.
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    Bauer, J.
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    Pötter, H.
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    Lang, K.-D.
    ;
    Reichl, H.
    In this paper a modeling approach for predicting the electrical behavior of nonresonant and resonant structures under the influence of the absorption of moisture into the dielectric is presented. The paper focuses on the encapsulation materials used for printed circuit boards (PCBs) as a case study. For the investigated cases, analytical modeling shows that the loss of electrical insulation resulting from moisture absorption has minimal effects on the losses in transmission lines (TMLs), which would only cause system failure when combined with other aging effects. However, potential cases are discussed where the loss of electrical insulation could be significantly increased. Full-wave modeling shows that moisture absorption can cause the detuning of passive components, specifically antennas and impedance-controlled TMLs, that can have significant effects on system performance. Antenna resonance frequencies shift by up to 3-5%.
  • Publication
    Impact of process tolerances on the performance of bond wire antennas at RF/microwave frequencies
    ( 2012)
    Ndip, I.
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    Öz, A.
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    Tschoban, C.
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    Schmitz, S.
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    Schneider-Ramelow, M.
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    Guttowski, S.
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    Reichl, H.
    ;
    Lang, K.-D.
    Due to the multitude of advantages bond wire antennas have over conventional planar antennas (especially on-chip planar antennas), they have received much research attention within the last Jour years. The Jocus oj the contributions made so Jar has been on exploiting different configurations oj single- element and array bond wire antennas Jor short-range applications at RF/microwave jrequencies. However, the effects of process tolerances of bond wires on the radiation characteristics of bond wire antennas have not been studied in published literature. Therefore in this paper; we investigate the impact of up to 20% fluctuations in the parameters of bond wires on the performance of 42 GHz and 60 GHz bond wire antennas. Our results reveal that the length and radius of bond wires are the most and least sensitive parameters, respectively. Furthermore, the severity of the impact of process tolerances depends on the impedance bandwidth of the original antenna, before consideri ng the tolerances. For example, a 10% change in the length of a bond wire causes the resonance frequency of a 42 GHz antenna to be shifted out of the specified 3GHz bandwidth (40.5 GHz-43.5 GHz) required for point-to-point communication. However, although a 10% change in length of a bond wire yields a 2.5 GHz shift in the resonance frequency of a 60 GHz bond wire antenna, it doesn't completely detune the antenna because of the original 6 GHz bandwidth available, prior to the fluctuation. Therefore, to prevent the impact of process tolerances from severely degrading the performance bond wire antennas, these antennas should be designed to have larger bandwidths than specified. For experimental verification, a bond wire antenna was designed, jabricated and measured. Very good correlation was obtained between measurement and simulation.
  • Publication
    Modeling, quantification, and reduction of the impact of uncontrolled return currents of vias transiting multilayered packages and boards
    ( 2010)
    Ndip, I.
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    Ohnimus, F.
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    Löbbicke, K.
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    Bierwirth, M.
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    Tschoban, C.
    ;
    Guttowski, S.
    ;
    Reichl, H.
    ;
    Lang, K.-D.
    ;
    Henke, H.
    The returning displacement currents of vias transiting multilayered stack-ups in electronic packages and boards excite parasitic transverse electromagnetic modes in power-ground plane pairs, causing them to behave as parallel-plate waveguides. These waves may cause significant coupling in the power-ground cavity, leading to electromagnetic reliability (EMR) issues such as simultaneous switching noise coupling, high insertion loss degradation of signal vias, and stray radiation from the periphery/edges of the package/board. In this contribution, we model and quantify EMR problems caused by uncontrolled return currents of signal vias in conventional multilayer stack-ups. Traditional methods used to minimize these problems, and their limitations are discussed. We propose a low-cost layer stack-up, which overcomes most of the limitations of conventional stack-ups by providing well-defined return-current paths formicrostrip-to-microstrip via transitions. Test samples of the proposed configuration are designed, fabricated, and measured. Very good correlation is obtained between measurement and simulation. Finally, a circuit model for the microstrip-to-microstrip via transition, considering the return-current paths, is developed and the circuit parameters are analytically calculated. Conventional closed-form expressions used for the extraction of these parameters, particularly the via capacitance, are extended and modified.