A Low Power Wide Dynamic Range Envelope Detector

We report a 75dB, 2.8mW, 100Hz-10kHz envelope detector in a 1.5mm 2.8V CMOS technology. The envelope detector performs input-dc-insensitive voltage-to-currentconverting rectification followed by novel nanopower current-mode peak detection. The use of a subthreshold wide- linear-range transconductor (WLR OTA) allows greater than 1.7Vpp input voltage swings. We show theoretically that this optimal performance is technology-independent for the given topology and may be improved only by spending more power. A novel circuit topology is used to perform 140nW peak detection with controllable attack and release time constants. The lower limits of envelope detection are determined by the more dominant of two effects: The first effect is caused by the inability of amplified high-frequency signals to exceed the deadzone created by exponential nonlinearities in the rectifier. The second effect is due to an output current caused by thermal noise rectification. We demonstrate good agreement of experimentally measured results with theory. The envelope detector is useful in low power bionic implants for the deaf, hearing aids, and speech-recognition front ends. Extension of the envelope detector to higher- frequency applications is straightforward if power consumption is inc

Proceedings of the Second PHANToM User's Group Workshop

On October 19-22, 1997 the Second PHANToM Users Group Workshop was held at the MIT Endicott House in Dedham, Massachusetts. Designed as a forum for sharing results and insights, the workshop was attended by more than 60 participants from 7 countries. These proceedings report on workshop presentations in diverse areas including rigid and compliant rendering, tool kits, development environments, techniques for scientific data visualization, multi-modal issues and a programming tutorial.

The Proceedings of the First PHANToM User's Group Workshop

These proceedings summarize the results of the First PHANToM User's Group Workshop held September 27-30, 1996 MIT. The goal of the workshop was to bring together a group of active users of the PHANToM Haptic Interface to discuss the scientific and engineering challenges involved in bringing haptics into widespread use, and to explore the future possibilities of this exciting technology. With over 50 attendees and 25 presentations the workshop provided the first large forum for users of a common haptic interface to share results and engage in collaborative discussions. Short papers from the presenters are contained herein and address the following topics: Research Effort Overviews, Displays and Effects, Applications in Teleoperation and Training, Tools for Simulated Worlds and, Data Visualization.

Presentation Based User Interface

A prototype presentation system base is described. It offers mechanisms, tools, and ready-made parts for building user interfaces. A general user interface model underlies the base, organized around the concept of a presentation: a visible text or graphic for conveying information. Te base and model emphasize domain independence and style independence, to apply to the widest possible range of interfaces. The primitive presentation system model treats the interface as a system of processes maintaining a semantic relation between an application data base and a presentation data base, the symbolic screen description containing presentations. A presenter continually updates the presentation data base from the application data base. The user manipulates presentations with a presentation editor. A recognizer translates the user's presentation manipulation into application data base commands. The primitive presentation system can be extended to model more complex systems by attaching additional presentation systems. In order to illustrate the model's generality and descriptive capabilities, extended model structures for several existing user interfaces are discussed. The base provides support for building the application and presentation data bases, linked together into a single, uniform network, including descriptions of classes of objects as we as the objects themselves. The base provides an initial presentation data base network graphics to continually display it, and editing functions. A variety of tools and mechanisms help create and control presenters and recognizers. To demonstrate the base's utility, three interfaces to an operating system were constructed, embodying different styles: icons, menu, and graphical annotation.