InP DHBT Single-Stage and Multiplicative Distributed Amplifiers for Ultra-Wideband Amplification

This paper highlights the gain-bandwidth merit of the single stage distributed amplifier (SSDA) and its derivative multiplicative amplifier topologies (i.e. the cascaded SSDA (C-SSDA) and the matrix SSDA (M-SSDA)), for ultra-wideband amplification. Two new monolithic microwave integrated circuit (MMIC) amplifiers are presented: an SSDA MMIC with 7.1dB average gain and 200GHz bandwidth; and the world's first M-SSDA, which has a 12dB average gain and 170GHz bandwidth. Both amplifiers are based on an Indium Phosphide DHBT process with 250nm emitter width. To the authors best knowledge, the SSDA has the widest bandwidth for any single stage amplifier reported to date. Furthermore, the three tier M-SSDA has the highest bandwidth and gain-bandwidth product for any matrix amplifier reported to date

Constraining tropospheric mixing timescales using airborne observations and numerical models

International audienceA technique is demonstrated for estimating atmospheric mixing time-scales from in-situ data, using a Lagrangian model initialised from an Eulerian chemical transport model (CTM). This method is applied to airborne tropospheric CO observations taken during seven flights of the Mediterranean Intensive Oxidant Study (MINOS) campaign, of August 2001. The time-scales derived, correspond to mixing applied at the spatial scale of the CTM grid. Specifically, they are upper bound estimates of the mix-down lifetime that should be imposed for a Lagrangian model to reproduce the observed small-scale tracer structure. They are relevant to the family of hybrid Lagrangian-Eulerian models, which impose Eulerian grid mixing to an underlying Lagrangian model. The method uses the fact that in Lagrangian tracer transport modelling, the mixing spatial and temporal scales are decoupled: the spatial scale is determined by the resolution of the initial tracer field, and the time scale by the trajectory length. The chaotic nature of lower-atmospheric advection results in the continuous generation of smaller spatial scales, a process terminated in the real atmosphere by mixing. Thus, a mix-down lifetime can be estimated by varying trajectory length so that the model reproduces the observed amount of small-scale tracer structure. Selecting a trajectory length is equivalent to choosing a mixing timescale. For the cases studied, the results are very insensitive to CO photochemical change calculated along the trajectories. The method is most appropriate for relatively homogeneous regions, i.e. it is not too important to account for changes in aircraft altitude or the positioning of stratospheric intrusions, so that small scale structure is easily distinguished. The chosen flights showed a range of mix-down time upper limits: 1 and 3 days for 8 August and 3 August, due to recent convective and boundary layer mixing respectively, and 7?9 days for 16, 17, 22a, 22c and 24 August. For the flight of 3 August, the observed concentrations result from a complex set of transport histories, and the models are used to interpret the observed structure, while illustrating where more caution is required with this method of estimating mix-down lifetimes

Development of a fretting-fatigue mapping concept: The effect of material properties and surface treatments

Fretting-fatigue induced by combined localized cyclic contact motion and external bulk fatigue loadings may result in premature and dramatic failure of the contacting components. Depending on fretting and fatigue loading conditions, crack nucleation and possibly crack propagation can be activated. This paper proposes a procedure for estimating these two damage thresholds. The crack nucleation boundary is formalized by applying the Crossland high cycle fatigue criterion, taking into account the stress gradient and the ensuing #size##effect#. The prediction of the crack propagation condition is formalized using a short crack arrest description. Applied to an AISI 1034 steel, this methodology allows the development of an original material response fretting-fatigue map (FFM). The impact of material properties and surface treatments is investigated

Robotic Extrusion of Algae-Laden Hydrogels for Large-Scale Applications

A bioprinting technique for large‐scale, custom‐printed immobilization of microalgae is developed for potential applications within architecture and the built environment. Alginate‐based hydrogels with various rheology modifying polymers and varying water percentages are characterized to establish a window of operation suitable for layer‐by‐layer deposition on a large scale. Hydrogels formulated with methylcellulose and carrageenan, with water percentages ranging from 80% to 92.5%, demonstrate a dominant viscoelastic solid–like property with G′ > G″ and a low phase angle, making them the most suitable for extrusion‐based printing. A custom multimaterial pneumatic extrusion system is developed to be attached on the end effector of an industrial multiaxis robot arm, allowing precision‐based numerically controlled layered deposition of the viscous hydrogel. The relationship between the various printing parameters, namely air pressure, material viscosity, viscoelasticity, feed rate, printing distance, nozzle diameter, and the speed of printing, are characterized to achieve the desired resolution of the component. Printed prototypes are postcured in CaCl2 via crosslinking. Biocompatibility tests show that cells can survive for 21 days after printing the constructs. To demonstrate the methodology for scale‐up, a 1000 × 500 mm fibrous hydrogel panel is additively deposited with 3 different hydrogels with varying water percentages

Transimpedance amplifiers with 133 GHz bandwidth on 130 nm indium phosphide double heterojunction bipolar transistors

In this work, the authors present two transimpedance amplifier (TIA) circuits designed for fibre optical interconnect systems. They compare a common base (CB) topology with a common emitter (CE) shunt-shunt feedback topology in terms of frequency response, power consumption, noise, and input impedance. The two TIAs are designed on a 130 nm indium phosphide double heterojunction bipolar transistor technology from Teledyne Scientific Company (TSC) with an ft/fmax of 520 GHz/1.15 THz and are measured in the frequency and time domains. They exhibit a transimpedance gain of 42 dBΩ with a 133 GHz bandwidth, the highest bandwidth reported in the literature and power consumption of 32.3 mW for the CB and 25.5 mW for the CE. Eye diagram measurements were conducted up to 64 Gbps and input referred noise density was measured at 30.2 pA/√Hz for the CB and 13.9 pA/√Hz for the CE