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.     

Experimental investigation of solid bed depth at the discharge end of rotary kilns

The solid bed depth at the discharge end of rotary kilns was experimentally investigated for different mass flow rates, rotational speeds, inclination angles and materials using two lab kilns with sizes of 0.4 m (ID) ? 5 m (L) and 0.25 m (ID) ? 6.7 m (L), respectively. The solid depth at the discharge was found to be several more times higher than the particle diameter. All parameters according to Saeman's model were combined in a newly developed dimensionless ‘Bed depth number’ designated as ‘Bd’. The filling degree of a solid bed at the discharge can be correlated with F₀ = 1.75 ? Bd^0.5 (for an inclination angle between 1° and 4°). The range of the researched Bed depth number (Bd) is suitable for all industrial kilns. These values should be used as the initial condition, which was still unknown before, to solve the differential equation for the profile of the solid bed depth through the cylinder.     

Video-realistic image-based eye animation via statistically driven state machines

In this work we elaborate on a novel image-based system for creating video-realistic eye animations to arbitrary spoken output. These animations are useful to give a face to multimedia applications such as virtual operators in dialog systems. Our eye animation system consists of two parts: eye control unit and rendering engine, which synthesizes eye animations by combining 3D and image-based models. The designed eye control unit is based on eye movement physiology and the statistical analysis of recorded human subjects. As already analyzed in previous publications, eye movements vary while listening and talking. We focus on the latter and are the first to design a new model which fully automatically couples eye blinks and movements with phonetic and prosodic information extracted from spoken language. We extended the already known simple gaze model by refining mutual gaze to better model human eye movements. Furthermore, we improved the eye movement models by considering head tilts, torsion, and eyelid movements. Mainly due to our integrated blink and gaze model and to the control of eye movements based on spoken language, subjective tests indicate that participants are not able to distinguish between real eye motions and our animations, which has not been achieved before.     

Automatic library migration for the generation of hardware-in-the-loop models

Embedded systems are widely used in several applications nowadays. As they integrate hard- and software elements, their functionality and reliability are often tested by hardware-in-the-loop methods, in which the system under test runs in a simulated environment. Due to the rising complexity of the embedded functions, performance limitations and practicability reasons, the simulations are often specialized to test specific aspects of the embedded system and develop a high diversity by themselves. This diversity is difficult to manage for a user and results in erroneously selected test components and compatibility problems in the test configuration. This paper presents a generative programming approach that handles the diversity of test libraries. Compatibility issues are explicitly evaluated by a new interface concept. Furthermore, a novel model analyzer facilitates the efficient application in practice by migrating existing libraries. The approach is evaluated for an example from the automotive domain using MATLAB/Simulink.     

Polarization-Controlled Surface Grating VCSELs Under Unpolarized and Polarized Optical Feedback

The polarization control of a surface grating vertical-cavity surface-emitting laser (VCSEL) and of a nominally identical standard VCSEL without a surface grating are compared for unpolarized and polarized optical feedback with different feedback levels in the long external cavity regime. While the polarization of the standard VCSEL is strongly influenced by isotropic feedback with a feedback level of just 1% and can even be controlled by polarized feedback, the surface grating VCSEL remains polarization-stable under isotropic feedback. Its polarization can only be disturbed by optical feedback polarized orthogonal to the polarization of the solitary surface grating VCSEL for feedback levels exceeding 18%.     

Investigation of polarization properties of VCSELs subject to optical feedback from an extremely short external cavity-part II: experiments

The effect of isotropic optical feedback from an extremely short external cavity on the emission properties of vertical-cavity surface-emitting lasers (VCSELs) is experimentally investigated. When changing the external cavity length a modulation of the total power and the wavelength emitted by the VCSEL is observed with a period of half the wavelength of operation of the device. When biasing the VCSEL around its solitary (without optical feedback) polarization switching (PS) current, PS between the two linearly polarized modes is observed by changing the external cavity length. This PS is found to occur through a hysteresis region. Our experimental results show a modulation of the PS currents and the hysteresis width when changing the external cavity length with a period of half the wavelength of operation. The experimental results are well explained by a two mode rate equation model.     

Investigation of polarization properties of VCSELs subject to optical feedback from an extremely short external cavity-part I: theoretical analysis

A two modes rate equation model for vertical-cavity surface-emitting lasers (VCSELs) subject to optical feedback from an extremely short external cavity (ESEC) is presented. By making use of it we develop a map of bistability to investigate the parametric dependence of polarization properties of VCSELs in such configuration, finding out a periodic dependence of the polarization switching (PS) currents on the ESEC length. By increasing the external mirror reflectivity we can make this periodic dependence stronger and strongly asymmetric providing the possibility to prevent PS for any injection current achieving polarization stabilization in VCSELs. Further numerical simulations with isotropic and non isotropic feedback show how parameters as the compression coefficients, the frequency splitting between the linearly polarized (LP) modes, the differential gain and the top mirror reflection coefficient, affect the map of bistability.