Mehdi Azadmehr

A foveated AER imager chip [address event representation]

We have developed a foveated imager chip with high resolution photo-cells (referred to as static pixels) in the center that are surrounded by more space consuming adaptive change detection pixels (referred to as dynamic pixels). Inspired by the neurons of biological nervous systems, they emit short voltage pulses, the static pixels with a frequency proportional to light intensity, the dynamic pixels whenever they detect a relative change in irradiance. The pulses are transmitted off-chip by the address event representation (AER) protocol, i.e. via a digital bus as the identifying address of the sending pixel. For the motion pixels, this read-out strategy has the advantage of low latency in the order of 100 ns after a change is encountered. (Whereas a scanning read-out strategy would on average suffer a delay of half of the frame scanning period.) Mounted on a pan-tilt system, the peripheral motion detectors could, for instance, be used to steer the imager such that the image of a moving object falls onto the central pixel array where it can then be examined in detail at a higher resolution. Or, if the imager is mounted statically, they can detect an intruder and cause the central pixels to be turned on for more detailed observation

Band Pass Pseudo Floating-Gate Amplifier

In this paper we present a current starved pseudo-floating- gate (PFG) amplifier. The PFG amplifier will suppress low frequency components due to a local feedback. PFG circuits can be utilized for low voltage (LV) binary-, multiple valued logic and analog circuits. Typical applications are detection of high frequency components in sensor signals, i.e. airbag sensors. A differential LV amplifier is presented. Simulated data is valid for a 90 nm CMOS process with at threshold voltage equal to 0.25 V. The simulated data presented are obtained using Spectres in the Cadence simulator environment.

A bidirectional circuit for actuation and read-out of resonating sensors

In this paper we have demonstrated a novel approach for actuation and read-out of resonating sensors. In this approach, instead of reading the amplitude of the resonating beam in resonance, we use the frequency of the beam as a measure of the sensors response. By using a bidirectional amplifier a pulse is sent to a resonating sensor in one direction and the frequency response of the sensor is measured using the opposite direction of the amplifier. This approach results in more compact and more power conservative systems. This approach mimics the way radars operate where a pulse is sent out and the reflection is measured. The circuit is very compact with low component spread and consumes an average power of 22μW and a maximum power of 100μW when actuating the sensor.

An ultra-low voltage tunable dual-Band Pass Filter

In this paper we present an ultra-low voltage dual Band Pass Filter with tunable pass bands. The dual band pass filter has two pass bands which can be tuned individually and can operate at supply voltages down to 300mV. The filter is based on Pseudo Floating-Gate and in addition to frequency band adjustment, it offers gain. Both the center frequencies are controlled electronically using bias voltages through the bulk of transistors. The filter benefits from low component spread and compactness, containing only small size transistors and capacitors suited for integration. The simulations presented in this paper are valid for the 90nm CMOS transistor models from STM having a VDD equal to 1.2V and threshold voltage of 250mV.

A discrete implementation of a bidirectional circuit for actuation and read-out of resonating sensors

In this paper we propose a simple and compact way to realize a bi-directional interface to drive resonant sensors. The bi-directional interface can be set to both activate the resonating sensor (activation mode) and to read its response (read-out mode). During the normal operation of the system these two modes are activated alternatively, depend on the state of the control signals. The directionality of this device is decided by swapping the power supply rails. The system has been tested using a RLC load, considered as the model for a resonant sensor. Experimental results of a discrete board prototype show the applicability of the interface for resonant load.

Low power integrated electronics system for the operation of a miniaturized hydration sensor

The application of MEMS devices with integrated electronics are paving the way for a new generation of miniaturized biomedical sensors with the potential of monitoring physiological parameters in the body. This article presents an application-specific integrated circuit (ASIC) that has been designed for integration in a biomedical sensor capable of detecting events associated with the dehydration and overhydration in the body and presents measurement results from a sensor prototype. The sensor converts the hydration level into an osmotic pressure which in turn is translated into a frequency modulated asynchronous digital signal with a 5.71 bit resolution (ENOB). The ASIC was designed and fabricated using the TSMC90nm CMOS processing technology and is based on a low power architecture with a simulated power consumption of 39.4 μW. The circuit layout has a footprint of 565×265 μm2 and the linear temperature dependent node of the voltage bandgap reference is used to monitor the temperature.

Design and Characterization of an Osmotic Sensor for the Detection of Events Associated With Dehydration and Overhydration

The level of hydration in the human body is carefully adjusted to control the electrolyte balance that governs the biochemical processes that sustain life. An electrolyte deficiency caused by de- or overhydration will not only limit human performance, but can also lead to serious health problems and death if left untreated. Because humans can withstand a change in hydration of only ±20%, frequent monitoring should be performed in risk groups. This paper presents an osmotic hydration sensor that can record the level of hydration as a function of osmotic pressure in phosphate buffered saline or sodium-chloride solutions that simulate the interstitial fluid in the body. The osmotic pressure is recorded with the aid of an ion-exchange membrane that facilitates the migration of water and cations, in favor of reverse osmosis or gas separation membranes. The hydration sensor is designed to be coupled to an inductively powered readout circuit designed for integration in a micro-implant that has previously been shown to consume only 76 μW of power. The dynamic range spans a state of serious overhydration (220 mOsm L-1) to a serious state of dehydration (340 mOsm L-1) with a response time of ~ 7 h (for a variation of hydration of 20%).

Bi-directional Band pass / Band stop filter based on Current-Starved Pseudo Floating-Gate inverters

In this paper a bi-directional band pass/band stop filter is presented. The circuit takes advantage of capacitive coupling and uses Current-Starved Pseudo Floating-Gate (CSPFG) inverters to perform the bi-directional frequency selection. Simply by Changing a bias voltage from vdd to gnd or vice versa the circuit changes directionality and operation mode. Typical applications are detection of high frequency components sensory signals, where a 2 way communication is needed. AC simulation of the circuits are presented to show that these circuits are suited for high performance filter design.

Bi-directional Current-Starved Pseudo Floating-Gate differentiator / integrator

In this paper we show how a simple Current-Starved Pseudo Floating-Gate (CSPFG) inverter can be used to realize bi-directional Circuits. The direction of the signal through the inverter is reversed (the input becomes output and vise versa) by swapping vdd and gnd, without adding any extra amplifier or circuitry. This is possible because of the symmetry of the CSPFG inverters. We use the bi-directionality property of the inverter to realize a bi-directional CSPFG Differentiator/integrator. Typical applications are in filter design and IO ports in ICs. Linearity and AC simulations are presented to show the good properties and versatility suited for Bi-directional analog circuit design.

Bidirectional front-end for piezoelectric resonator

This paper presents a bidirectional circuit as front-end for piezoelectric ceramic resonators. The front-end both actives and reads the response of the resonator in different directions and the directionality of the front-end is controlled by swapping the supply rails. Experimental results are obtained by measuring on a semi-discrete board prototype. The resonant frequency of the sensor is 110kHz, the bandwidth of the bidirectional front-end is 1kHz - 500kHz which was implemented by using a CD4007UBE IC. Results show that the system provides an easy and effective way to send an activation signal and to read the response of a piezoelectric resonator.