A programmable microsystem using system-on-chip for real-time biotelemetry

A telemetry microsystem, including multiple sensors, integrated instrumentation and a wireless interface has been implemented. We have employed a methodology akin to that for System-on-Chip microelectronics to design an integrated circuit instrument containing several "intellectual property" blocks that will enable convenient reuse of modules in future projects. The present system was optimized for low-power and included mixed-signal sensor circuits, a programmable digital system, a feedback clock control loop and RF circuits integrated on a 5 mm × 5 mm silicon chip using a 0.6 μm, 3.3 V CMOS process. Undesirable signal coupling between circuit components has been investigated and current injection into sensitive instrumentation nodes was minimized by careful floor-planning. The chip, the sensors, a magnetic induction-based transmitter and two silver oxide cells were packaged into a 36 mm × 12 mm capsule format. A base station was built in order to retrieve the data from the microsystem in real-time. The base station was designed to be adaptive and timing tolerant since the microsystem design was simplified to reduce power consumption and size. The telemetry system was found to have a packet error rate of 10<sup>-</sup><sup>3</sup> using an asynchronous simplex link. Trials in animal carcasses were carried out to show that the transmitter was as effective as a conventional RF device whilst consuming less power

Implanted miniaturized antenna for brain computer interface applications: Analysis and design

Implantable Brain Computer Interfaces (BCIs) are designed to provide real-time control signals for prosthetic devices, study brain function, and/or restore sensory information lost as a result of injury or disease. Using Radio Frequency (RF) to wirelessly power a BCI could widely extend the number of applications and increase chronic in-vivo viability. However, due to the limited size and the electromagnetic loss of human brain tissues, implanted miniaturized antennas suffer low radiation efficiency. This work presents simulations, analysis and designs of implanted antennas for a wireless implantable RF-powered brain computer interface application. The results show that thin (on the order of 100 micrometers thickness) biocompatible insulating layers can significantly impact the antenna performance. The proper selection of the dielectric properties of the biocompatible insulating layers and the implantation position inside human brain tissues can facilitate efficient RF power reception by the implanted antenna. While the results show that the effects of the human head shape on implanted antenna performance is somewhat negligible, the constitutive properties of the brain tissues surrounding the implanted antenna can significantly impact the electrical characteristics (input impedance, and operational frequency) of the implanted antenna. Three miniaturized antenna designs are simulated and demonstrate that maximum RF power of up to 1.8 milli-Watts can be received at 2 GHz when the antenna implanted around the dura, without violating the Specific Absorption Rate (SAR) limits. © 2014 Zhao et al

The 30-GHz monolithic receive module

The fourth year progress is described on a program to develop a 27.5 to 30 GHz GaAs monolithic receive module for spaceborne-communication antenna feed array applications, and to deliver submodules for experimental evaluation. Program goals include an overall receive module noise figure of 5 dB, a 30 dB RF to IF gain with six levels of intermediate gain control, a five bit phase shifter, and a maximum power consumption of 250 mW. Submicron gate length single and dual gate FETs are described and applied in the development of monolithic gain control amplifiers and low noise amplifiers. A two-stage monolithic gain control amplifier based on ion implanted dual gate MESFETs was designed and fabricated. The gain control amplifier has a gain of 12 dB at 29 GHz with a gain control range of over 13 dB. A two-stage monolithic low noise amplifier based on ion implanted MESFETs which provides 7 dB gain with 6.2 dB noise figure at 29 GHz was also developed. An interconnected receive module containing LNA, gain control, and phase shifter submodules was built using the LNA and gain control ICs as well as a monolithic phase shifter developed previously under this program. The design, fabrication, and evaluation of this interconnected receiver is presented. Progress in the development of an RF/IF submodule containing a unique ion implanted diode mixer diode and a broadband balanced mixer monolithic IC with on-chip IF amplifier and the initial design of circuits for the RF portion of a two submodule receiver are also discussed

Exploiting Near Field and Surface Wave Propagation for Implanted Devices

<p>This thesis examines the bandwidth shortcomings of conventional inductive coupling biotelemetry systems for implantable devices, and presents two approaches toward an end-to-end biotelemetry system for reducing the power consumption of implanted devices at increased levels of bandwidth. By leveraging the transition zone between the near and far field, scattering in the near field at UHF frequencies for increased bandwidth at low power budgets can be employed. Additionally, taking advantage of surface wave propagation permits the use of single-wire RF transmission lines in biological tissue, offering more efficient signal routing over near field coupling resulting in controlled implant depth at low power budgets.</p><p>Due to the dielectric properties of biological tissue, and the necessity to operate in the radiating near field to communicate via scattered fields, the implant depth drives the carrier frequency. The information bandwidth supplied by each sensing electrode in conventional implants also drives the operating frequency and regime. At typical implant depths, frequencies in the UHF range permit operation in the radiating near field as well as sufficient bandwidth.</p><p>Backscatter modulation provides a low-power, high-bandwidth alternative to conventional low frequency inductive coupling. A prototype active implantable device presented in this thesis is capable of transmitting data at 30 Mbps over a 915 MHz link while immersed in saline, at a communication efficiency of 16.4 pJ/bit. A prototype passive device presented in this thesis is capable of operating battery-free, fully immersed in saline, while transmitting data at 5 Mbps and consuming 1.23 mW. This prototype accurately demodulates neural data while immersed in saline at a distance of 2 cm. This communication distance is extended at similar power budgets by exploiting surface wave propagation along a single-wire transmission line. Theoretical models of single-wire RF transmission lines embedded in high permittivity and conductivity dielectrics are validated by measurements. A single-wire transmission line of radius 152.4 um exhibits a loss of 1 dB/cm at 915 MHz in saline, and extends the implant depth to 6 cm while staying within SAR limits.</p><p>This work opens the door for implantable biotelemetry systems to handle the vast amount of data generated by modern sensing devices, potentially offering new insight into neurological diseases, and may aid in the development of BMI's.</p>Dissertatio

Ka-band Ga-As FET noise receiver/device development

The development of technology for a 30 GHz low noise receiver utilizing GaAs FET devices exclusively is discussed. This program required single and dual-gate FET devices, low noise FET amplifiers, dual-gate FET mixers, and FET oscillators operating at Ka-band frequencies. A 0.25 micrometer gate FET device, developed with a minimum noise figure of 3.3 dB at 29 GHz and an associated gain of 7.4 dB, was used to fabricate a 3-stage amplifier with a minimum noise figure and associated gain of 4.4 dB and 17 dB, respectively. The 1-dB gain bandwidth of this amplifier extended from below 26.5 GHz to 30.5 GHz. A dual-gate mixer with a 2 dB conversion loss and a minimum noise figure of 10 dB at 29 GHz as well as a dielectric resonator stabilized FET oscillator at 25 GHz for the receiver L0. From these components, a hybrid microwave integrated circuit receiver was constructed which demonstrates a minimum single-side band noise figure of 4.6 dB at 29 GHz with a conversion gain of 17 dB. The output power at the 1-dB gain compression point was -5 dBm

Remote power delivery and signal amplification for MEMS applications

Device such as remotely located sensors and bio-implanted devices such as gastric pacer require power for operation. The most commonly used energy source for such devices is a battery cell included in the receiver capsule. Wires can also be used with an external power source but in some applications have serious limitations. This work examines a wireless power transmitter and receiver system to provide power to a remotely located microsystem. Inductive power coupling is the method of choice. For gastric pacer application, external transmitter coil can be worn around the waist as a belt and the receiver coil can be a part of a remotely located bio-implanted system. The coupling between transmitter and receiver coils when the diameters are markedly different is analyzed. A conventional rectifier circuit converts ac voltage to required dc voltage. This dc voltage supplies power to the charging chip, which is used to recharge lithium batteries in the implanted system. For an input supply voltage of 0.35 Vrms, the induced voltage in the receiver coil across the load resistor was 0.37 Vrms, when the receiver coil was placed at the center of the transmitter coil. When the receiver coil was placed close to the rim of the transmitter, the induced voltage across the load resistor for the same input supply voltage was 0.67 Vrms. Corresponding transmitted power to the load resistor of the receiver coil were 4 and 13.2 mW, respectively. Means are suggested to improve the power transfer to the receiver coil. The second objective of this thesis is to design an op-amp for on-chip amplification of sensor signals. On-chip detection and amplification are crucial for obtaining high sensitivity and improved signal to noise ratio. Designed op-amp is simulated using PSPICE with Level-3 MOS model parameters. The simulation results show a gain of 40.7 dB and a 3-dB bandwidth of 580 kHz. Experimental measurements made on the fabricated chip observed a gain of 3 and a 3-dB bandwidth of 1 MHz, which was attributed to differences in the values of simulated model parameters and the values appropriate for the fabrication process used by the foundry

NASA Tech Briefs Index, 1977, volume 2, numbers 1-4

Announcements of new technology derived from the research and development activities of NASA are presented. Abstracts, and indexes for subject, personal author, originating center, and Tech Brief number are presented for 1977

Nanometric constrictions in superconducting coplanar waveguide resonators

We report on the design, fabrication and characterization of superconducting coplanar waveguide resonators with nanoscopic constrictions. By reducing the size of the center line down to 50 nm, the radio frequency currents are concentrated and the magnetic field in its vicinity is increased. The device characteristics are only slightly modified by the constrictions, with changes in resonance frequency lower than 1% and internal quality factors of the same order of magnitude as the original ones. These devices could enable the achievement of higher couplings to small magnetic samples or even to single molecular spins and have applications in circuit quantum electrodynamics, quantum computing and electron paramagnetic resonance.Comment: 4 pages, 4 figure