Power waves formulation of oscillation conditions: avoidance of bifurcation modes in cross-coupled VCO architectures

This paper discusses necessity of power-waves formulation to extend voltage-current oriented approaches based on linear concepts such as admittance/impedance operators and transfer-function representations. Importance of multi-physics methodologies, throughout power-waves formulation, for the analysis and design of crystal oscillators is discussed. Interpretation of bifurcation modes in differential cross-coupled VCO architectures in terms of gyrator-like behavior, is proposed. Impact of amplitude level control (ALC) on large-signal phase noise performances is underlined showing necessity of robust control analysis approach relative to power-energy considerations

Broadband equivalent circuit derivation for multi-port circuits based on eigen-state formulation

In this paper a passive guaranteed wide-band equivalent circuit derivation methodology, attempting to bridge physical geometry considerations with equivalent circuits model extractions, is proposed. Electromagnetic (EM) eigen-states formulation is introduced to bridge between physical topology (geometry) and equivalent network architectures. Instead of casting global Z or Y parameters in pole-residue expansions following or T-networks, the proposed methodology considers eigen-states input impedances/admittances as primary goal functions to derive in canonical equivalent circuit models. While classical or T representations are based on global ground assumptions, the proposed methodology refers to local ground references. The validity of the broadband extraction methodology is demonstrated through correlations with RF measurement carried out on CPW transmission lines and coupled RF inductors up to very high frequencies

Characterisation and macro-modeling of patterned micronic and nano-scale dummy metal-fills in integrated circuits

In this paper, a wideband characterization and macro-modeling of patterned micronic and nano-scale dummy metal-fills is presented. Impacts of patterned dummy metal-fill topologies including square, cross, vertical and horizontal shaped arrays on electrical performances (isolation/coupling, attenuation, guiding properties, etc…) are investigated. The validity of the proposed macro-modeling methodology is demonstrated by comparison with high frequency measurements of dedicated carrier structures including on-chip interconnects and RF inductive loops. An original extraction approach, based on local ground concept, is proposed to capture high frequency behaviour of dummy metal-fill in physics-based compact broadband SPICE model. The RLC parameters are accurately derived using fully scalable closed-form semi-analytical expressions

Modeling and characterization of VCSEL-based avionics full-duplex ethernet (AFDX) gigabit links

Low cost and intrinsic performances of 850 nm Vertical Cavity Surface Emitting Lasers (VCSELs) compared to Light Emitting Diodes make them very attractive for high speed and short distances data communication links through optical fibers. Weight saving and Electromagnetic Interference withstanding requirements have led to the need of a reliable solution to improve existing avionics high speed buses (e.g. AFDX) up to 1Gbps over 100m. To predict and optimize the performance of the link, the physical behavior of the VCSEL must be well understood. First, a theoretical study is performed through the rate equations adapted to VCSEL in large signal modulation. Averaged turn-on delays and oscillation effects are analytically computed and analyzed for different values of the on - and off state currents. This will affect the eye pattern, timing jitter and Bit Error Rate (BER) of the signal that must remain within IEEE 802.3 standard limits. In particular, the off-state current is minimized below the threshold to allow the highest possible Extinction Ratio. At this level, the spontaneous emission is dominating and leads to significant turn-on delay, turn-on jitter and bit pattern effects. Also, the transverse multimode behavior of VCSELs, caused by Spatial Hole Burning leads to some dispersion in the fiber and degradation of BER. VCSEL to Multimode Fiber coupling model is provided for prediction and optimization of modal dispersion. Lastly, turn-on delay measurements are performed on a real mock-up and results are compared with calculations

Integrated static and dynamic modeling of an ionic polymer–metal composite actuator

Ionic polymer–metal composites have been widely used as actuators for robotic systems. In this article, we investigate and verify the characteristics of ionic polymer–metal composite actuators experimentally and theoretically. Two analytical models are utilized to analyze the performance of ionic polymer–metal composites: a linear irreversible electrodynamical model and a dynamic model. We find that the first model accurately predicts the static characteristics of the ionic polymer–metal composite according to the Onsager equations, while the second model is able to reveal the back relaxation characteristics of the ionic polymer–metal composite. We combine the static and dynamic models of the ionic polymer–metal composite and derive the transfer function for the ionic polymer–metal composite’s mechanical response to an electrical signal. A driving signal with a smooth slope and a low frequency is beneficial for the power efficiency

Caractérisation et modélisation du champ émis par des VCSELs à différents diaphragme d'oxyde

Cet article présente la modélisation et simulation du profil d'intensité d'un VCSEL à diaphragme d'oxyde émettant à 850nm. Le modèle est validé par la confrontation des simulation et des mesures de profil d'intensité de VCSELs à différents diamètre de diaphragme d'oxyde

Terahertz Time-Domain Spectroscopy of Thermoresponsive Polymers in Aqueous Solution

The behavior of highly concentrated aqueous solutions of two thermoresponsive polymers poly(N-isopropylacrylamide) (PNIPAm) and poly(N-vinylcaprolactam) (PVCL) have been investigated by terahertz time-domain spectroscopy (THz-TDS). Measurements have been performed for concentrations up to 20 wt %, over a frequency range from 0.3 to 1.5 THz and for temperatures from 20 to 45 °C including the zone for lower critical solution temperature (LCST). THz-TDS enables the study of the behavior of water present in the solution (i.e., free or bound to the polymer). From these measurements, in addition to phase transition temperature, thermodynamic data such as variation of enthalpy and entropy can be inferred. Thanks to these data, further insights upon the mechanism involved during the dehydration phenomenon were obtained. These results were compared to the ones issued from dynamic light scattering, spectroscopy, or microscopy techniques to underline the interest to use THz-TDS as a powerful tool to characterize the behavior of thermoresponsive polymers in highly concentrated solutions

Concept of marco-pixel formulation using non-uniform fourier transform

A multi-grid formulation of Green’s functions in the spatial domain based on the idea of partitioning overall electromagnetic simulation domain into macro-pixels is proposed. The concept of macro-pixel is introduced, based on physical considerations, as extension of the notion of pixel with possible spatial variations within its sub-domain, to capture both lower and higher order variations. Interactions between macro-pixels are derived to evaluate higher order and lower order modal couplings as function of normalized separation distances. The interactions between macro-pixels are efficiently computed using an original NUFFT (Non-Uniform Fast Fourier Transform) which renders possible systematic use of multi-grid space stepping. Attributes of observed coupling ranges and potential control of truncation orders at macro-pixel levels are very attractive for hybridization with time domain formulations

Reconfigurable sensors for extraction of dielectric material and liquid properties

International audienc

DC-40 GHz SPDTs in 22 nm FD-SOI and Back-Gate Impact Study

In this paper, ultra-wideband SPDTs fabricated in the 22 nm FD-SOI process from GLOBALFOUNDRIES are presented. Three SPDT modules were implemented, each using a different type of millimeter-wave NFET, namely a conventional-well regular-V t (RVT) device, a flipped-well super-low-V t (SLVT) device and a specially treated device without back-gate well contact for decreased substrate parasitics (BFMOAT device). It is shown that using the back-gate achieves lower losses, higher isolation and better linearity for the RVT and SLVT based switches, while the reduced parasitic BFMOAT switch shows better performance at the high-end of the mm-wave spectrum