Localization of Microscale Devices In Vivo using Addressable Transmitters Operated as Magnetic Spins

The function of miniature wireless medical devices, such as capsule endoscopes, biosensors and drug-delivery systems, depends critically on their location inside the body. However, existing electromagnetic, acoustic and imaging-based methods for localizing and communicating with such devices suffer from limitations arising from physical tissue properties or from the performance of the imaging modality. Here, we embody the principles of nuclear magnetic resonance in a silicon integrated-circuit approach for microscale device localization. Analogous to the behaviour of nuclear spins, the engineered miniaturized radio frequency transmitters encode their location in space by shifting their output frequency in proportion to the local magnetic field; applied field gradients thus allow each device to be located precisely from its signal’s frequency. The devices are integrated in circuits smaller than 0.7 mm3 and manufactured through a standard complementary-metal-oxide-semiconductor process, and are capable of sub-millimetre localization in vitro and in vivo. The technology is inherently robust to tissue properties, scalable to multiple devices, and suitable for the development of microscale devices to monitor and treat disease

Monolithic low phase noise oscillators for moderate frequency applications

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (leaves 74-75).Low noise oscillators are critical building blocks in a wide range of commercial electronics. Increased levels of integration have created a strong need for integrated oscillator solutions despite generally inferior noise performance. The development of non-linear noise models that can accurately and efficiently predict noise in ring oscillators aids designers in optimizing noise performance in integrated oscillator solutions. Extending a piecewise constant model of noise in an oscillator and the resulting timing jitter reveals how the noise at the oscillator nodes changes during each portion of the cycle. The model can then be used to examine the effects of changing various process and design parameters such as threshold voltages and the effective stage gain. This analysis tool provides a means for designers to evaluate potential improvements of their oscillator design. In some cases approximate analytic solutions can be found that provide better insight into the timing jitter. A simple differential oscillator design illustrates the use of this analysis. The oscillator achieves an analog tuning range of 259MHz-314MHz (extendable with switched capacitors) with a normalized jitter of 102ppm.by Rafael A. Medina.M.Eng