Ahmad Hassan

Spatial carrier position modulation based multichannel capacitive link for bioelectronic implants

We present in this paper a multichannel capacitive-link intended for data transmission to biomedical electronic implants using spatial carrier position modulation (SCPM) communication scheme. This SCPM-based system is composed of a transmitter, an array of fabricated capacitor plates, and data and clock recovery receiver. Crosstalk between channels is investigated and solution is proposed. Characterization of capacitor plates and system modeling including skin are reported. 20Mbps data rate is achieved. The functionality of the system is validated using sheeps skin placed between 4-capacitor plates which are coated with Parylene. Simulation and experimental results are presented.

Wireless power transfer through metallic barriers enclosing a harsh environment; feasibility and preliminary results

Modern sensor networks are evolving toward wireless interfaces for both power and data transmission. Design of these devices is challenging, especially when both power and data transmission must reach a harsh environment subject to high temperature, high pressure and through thick metallic layers. This paper reports the design and simulation of an inductive power transfer (IPT) system, which characterizes achievable link efficiency. The problem formulation comes from a family of aerospace applications in which electronic must operate at high temperature (500°C) and high pressure (100 bar) and in which a metal casing (15mm thick) isolates the harsh environment from the environment. Specifically, the requirements of booster rockets in aerospace industry are considered. The proposed IPT system was modeled and simulate d using COMSOL. Reported results demonstrate the feasibility of wirelessly transferring power to a high temperature and high pressure zone through various metallic layers using custom electromagnetic link configurations. Power transfer efficiencies of 38% and 15.5% are reported with Titanium and Steel metal booster interfaces at resonance frequencies of 450Hz and 220Hz respectively.

Stability of GaN150-based HEMT in high temperature up to 400°C

The first high-temperature characterization of GaN150 HEMT devices is presented from ambient temperature to 400°C. With a 2-gate length of 150nm, three configurations of GaN150 are investigated. They have gate widths of 40µm (T<inf>1</inf>), 100µm (T<inf>2</inf>) and 200µm (T<inf>3</inf>) respectively. The stability with temperature of the electrical characteristics of the AlGaN/GaN devices are measured with tungsten probes while the tested die is heated by a hot plate. The packaging is a standard tungsten based metallization, with Ni and Au plating, supporting a 92% alumina ceramic substrate. The drain saturation current decreases from 50mA, 150mA and 290mA at room temperature (RT) to 35mA, 110mA and 175mA at 400°C for T<inf>1</inf>, T<inf>2</inf> and T<inf>3</inf> respectively. The peak transconductance value of T<inf>1</inf> is dropped from 22mS at ambient temperature to 8mS at 250°C. The pinch-off voltage is stable at VGS = −5V during the whole temperature change.

Wireless monitoring of collagen progression around implantable prostheses

Bıocompatıbılıty remains a critical issue due to the foreign body response following device implantation. “Collagen” is the main bio-material composed around the implanted devices. This paper reports the possibility to measure the thickness of the “Collagen layers” using impedance measurement. An implanted passive circuit sensitive to the collagen thickness is wirelessly connected to the external reading circuit through inductive coupling. The resonance frequency of the system is directly proportional to the Collagen layer thickness variation. A modeling and simulation study of the Collagen material is presented by “COMSOL” to verify the functionality and obtain the optimal design parameters. Reported results demonstrate the increment of collagen capacitance from 30fF to 120fF when the collagen thickness rises from 1mm to 6mm. The experimental validation is reported using Impedance Analyzer. The measured resonance frequency drops from 55.78MHz to 54.98MHz when the collagen thickness increases from 0 to 10mm.

Ultra-low power CMOS voltage reference for high temperature applications up to 300°C

A voltage reference circuit dedicated for high temperature applications is presented. A high-temperature operation range up to 300°C and an ultra-low-power consumption of 6 μA @ 25°C and 18 μA @ 300°C are achieved by the presented new circuit which is implemented in 0.18 μm CMOS standard technology occupying layout area of 0.00063 mm2. The proposed voltage reference is based on the weighted difference of the gate-sources of NMOS and PMOS transistors operating in weak-inversion region. A reference voltage of 1.375 V is obtained with a temperature coefficient of 25 ppm/°C in a wide temperature range from 0°C to 280°C and 89 ppm/°C @ 300°C. The measured noise densities with a 100nF filtering capacitor are 80 nV/sqrt Hz and 1 nV/sqrt Hz at 100 Hz and 100 kHz respectively, and with a power-supply rejection ration (PSRR) better than -33 dB at 10 MHz.