A Bulk Acoustic Wave (BAW) Based Transceiver for an In-Tire-Pressure Monitoring Sensor Node

Attaching a tire pressure monitoring system (TPMS) on the inner liner of a tire allows sensing of important additional technical parameters, such as vehicle load or tire wearout. The maximum weight of the sensor is limited to 5 grams including package, power supply, and antenna. Robustness is required against extreme levels of acceleration. The node size is limited to about 1 cm3 to avoid high force-gradients due to device-deformation and finally, a long power supply lifetime must be achieved. In this paper a low-power FSK transceiver is presented. Exploiting BAW resonators the use of a bulky and shock-sensitive crystal and a PLL can be avoided. This makes the system more robust and radically reduces the start-up time to 2 ?s from few ms as in state-of-the-art crystal oscillator based systems. The current consumption of the transceiver is 6 mA in transmit mode with a transmit output power of 1 dBm and 8 mA in receive mode with a sensitivity of -90 dBm at a data rate of 50 kBit/s and a bit error rate of 10^-2. The transceiver ASIC and a microcontroller ASIC, a MEMS sensor, and a BAW die are arranged in a 3-D chip stack for best compactness, lowest volume, and highest robustness. The sensor node allows sensing of pressure, acceleration, supply voltage and temperature.     

A constitutive model for fiber-reinforced polymer plies accounting for plasticity and brittle damage including softening – Implementation for implicit FEM

A constitutive ply model is developed to allow for the simulation of laminated structures made of fiber-reinforced polymers. The model accounts for stiffness degradation accompanied by strain hardening (i.e. distributed brittle damage), unrecoverable strain accumulation (i.e. multi-surface plasticity), and stiffness degradation accompanied by strain softening (i.e. localized brittle damage). Owing to the characteristics of such ply materials the model handles these effects and their evolutions in an anisotropic manner.     

Design issues of BAW employment in 3D integrated sensor nodes

In the field of wireless sensor node design a wide range of new potentials are opened by means of emerging 3D integration technologies. These technologies enable the design of highly integrated sensor nodes, but the designers face novel challenges, which specialized communications engineers are not familiar with. This work presents an advanced direct tire pressure monitoring system (TPMS) with an overall size below 1 cm³ applying through silicon vias (TSV) and points out two selected design issues arising due to this high level of integration. At first design issues caused by temperature gradients within the 3D integrated chip stack are presented. Multi physics simulations show that a systematical temperature measurement error is introduced by self heating, which would affect the communication performance if unconsidered. Furthermore the radio frequency (RF) characteristics of TSVs, focusing on their electrical efficiency, are investigated. In particular the behavior of TSVs for connecting a bulk acoustic wave resonator with an impedance of 2 kΩ at 2.1 GHz is evaluated in detail.     

Realization of a 10-µm homodyne receiver

We have realized a homodyne receiver for phase-modulated laser radiation atlambda = 10.6 mum, based on a dc-coupled optical phase-locked loop (PLL). A control loop maintains the output power of the CO2laser local oscillator at 0.7 mW. Fine frequency tuning of this laser is achieved by an acoustooptic frequency shifter whose inherent time delay has been taken into account in the design of both the PLL and the power control loop. The PLL rms phase error is some 3° for a received optical power of 4 nW. The HgCdTe photodiode serving as phase detector and as demodulator, as well as the preamplifier are operated at 80 K by means of a Stirling cooler. Clear domination of shot noise is achieved for the data rate of 140 Mbit/s. A microcomputer performs dc-offset compensation and frequency acquisition. The system is part of a breadboard of an intersatellite data link.     

Prediction of plastic strain accumulation in continuous fiber reinforced laminates by a constitutive ply model

The present paper is concerned with the prediction of plastic ply strains which accumulate in continuous fiber reinforced laminates with polymeric matrix materials. The study is based on a constitutive model which is implemented within the Finite Element Method. Plastic strains are expected to evolve when the ply is subjected to a pronounced shear load and/or to pronounced transverse compression. Two plasticity mechanisms are modeled at ply level under plane stress assumption (i.e. for thin shells and plates). They either concern the evolution of plastic shear strains or the evolution of plastic normal strains. The proposed plasticity model is combined with an existing ply level continuum damage model. The capabilities of the proposed model are assessed by comparing its predictions to experimental data from literature. Emphasis is placed on loading conditions which drive the evolution of plastic strains. Excellent correlation with experimental results is shown for proportional as well as for non-proportional ply loadings.     

Simulations and experiments of open hole tension tests – Assessment of intra-ply plasticity,damage, and localization

Laminated composites with various layups of unidirectional carbon fiber reinforced epoxy are investigated by numerical modeling and experimental testing. Open hole tension configurations are studied with special considerations of the non-linear behavior of the plies. Computational predictions are based on an anisotropic constitutive material law which includes plasticity and damage, the latter comprise hardening as well as softening. Experimental evaluations include a 3D image correlation photogrammetry system for capturing the strain fields of the sample surfaces.