SI Frames Research Articles

Design, Fabrication, and Testing of a Modular Magnetic Field Microsensor on a Flexible Polymer Foil

In contrast to existing microelectromechanical systems (MEMS), this paper describes the development, fabrication, and testing of an anisotropic magnetoresistance (AMR) microsensor using a 7 μm thick polymer foil as substrate material. The modular magnetic field micro sensors are fabricated on a standard 4 in Si Wafer due to handling purposes during the sensor fabrication process. To enable a release of the micro sensors at the end of the fabrication process, initial investigations concentrated on the proof of principle applying a deep reactive-ion etching (DRIE) process to structure the Si wafer. The DRIE process was used to structure Si frames, which serve as carriers for the modular magnetic field micro sensors. For the evaluation of the fabricated modular magnetic field micro sensors, electrical resistance measurements were accomplished. The aim of these investigations was the characterization of the magnetic field dependence of the electrical resistance. The electrical output signal of the AMR sensors were subsequently compared to electrical resistance measurements of AMR sensors fabricated on a Si substrate and served as reference. The measurement results show a marginal effect of the substrate material on the characteristics of the AMR sensors.

Development, fabrication, and test of a modular eddy current micro sensor on a flexible polymer foil

This paper describes the development and fabrication of a modular eddy current micro sensor on a flexible polymer foil. Due to handling purposes during the micro sensor fabrication process the modular eddy current micro sensors are fabricated on a temporary Si substrate. To enable a release of the micro sensors at the end of the fabrication process, initial investigations concentrated on the proof of principle applying a deep reactive-ion etching (DRIE) process to structure the Si wafer. The DRIE process was used to structure Si frames, which serve as carriers for the modular micro sensors. For the evaluation of the fabricated eddy current micro sensors, electrical resistance measurements were accomplished with the integrated anisotropic magneto-resistance (AMR) sensor. The aim of these investigations was to evaluate the influence of the substrate material on the characteristics of the AMR sensor. The electrical output signal of these micro sensors were subsequently compared to electrical resistance measurements of identical AMR sensors fabricated on a Si substrate and served as reference. To prove the capability of the completed eddy current micro sensors, a defect in form of a scratch was created on the surface of a Cu probe and investigated by eddy current testing. The electrical output signal of the eddy current micro sensor was subsequently compared to an optical measurement of the surface profile of this scratch. There is a high correlation between the optical measurements and the signal of the eddy current micro sensor.

Channel adaptive video stream switching for broadband wireless links

This paper exploits an H.264/Advanced Video Coding codec's smooth stream switching to achieve robust video delivery across an IEEE 802.16 (WiMAX) broadband wireless link. As the wireless channel conditions vary over time, dynamic selection of bitrate and corresponding video quality will reduce the risk of harmful packet loss. The paper investigates choice of stream-switching with Secondary SP-frames or SI-frames relative to the selection of quantization parameter (QP) values. To control the switching points at the WiMAX server, the proposed scheme applies a feedback mechanism that monitors packet loss. As an additional suggestion, the paper considers an adaptive ARQ scheme to protect switching frames against packet loss. In summary, the broadband wireless streaming system gives more protection to higher quality video, reduces delay and packet loss, and improves received video quality. In particular, for the QP values selected, results show that increased quality primary-switching frames together with SI frames bring a significant gain in video quality compared with other switching schemes with secondary SP-frames. The other schemes in turn show an improvement to using `no switching' when streaming takes place over a typical WiMAX channel with burst errors. Link delay is also reduced.

Rate-distortion analysis and streaming of SP and SI frames

The new SP and SI picture types, introduced in the latest video coding standard H.264, allow drift-free bitstream switching and can also be used for error-resilience and random access. In this paper, we propose a model for the rate-distortion performance of SP and SI pictures and compare it to experimental results, obtained with our implementation of an SP/SI encoder, made publicly available and recently adopted by the Joint Video Team. The model predicts how the relative sizes of SP and SI slices can be traded off. We analyze, both theoretically and experimentally, how this can be used to minimize the transmitted bit rate when SP frames are used for video streaming with packet losses and derive optimal settings for our encoder. We investigate the benefits of SI and SP frames for error resilience as compared with periodic I frame insertion. Empirical rate-distortion curves predict rate-distortion gains may be obtained. Experiments carried out over a simulated throughput-limited network confirm this to be the case when the end-to-end delay is limited. We analyze the influence of loss rate and delay on the congestion-rate-distortion performance of streaming with SI and SP frames. Our results identify scenarios for which SI and SP frames provide an attractive alternative to streaming with I frames.

Effect of Ar Gas Pressure on Mechanical Properties of Sputtered Ti Thin Films

The effect of sputtering gas (Ar gas) pressure on the mechanical properties of free-standing Ti thin film membranes of 300-400 nm thickness, microfabricated by magnetron sputtering, has been studied by using a novel tensile testing machine. These free-standing thin film membranes are extremely difficult to handle because they are fragile. Therefore, the thin film test specimens were fabricated in Si frames to protect them. Sputtering gas pressure was varied from 1.5 to 15 mT. The stress and strain of the thin films was measured continuously from elastic deformation to fracture. Both the tensile strength and the strain at fracture of the thin films were affected by the sputtering gas pressure. The tensile strength of thin films increased with decreasing gas pressure. However, there was no obvious trend between the sputtering gas pressure and Young's modulus of the thin films. The experimental results confirmed that the Ti thin film membranes are more reliable with decreasing the gas pressure.