Design of sensor electronics for electrical capacitance tomography

The design of the sensor electronics for a tomographic imaging system based on electrical capacitance sensors is described. The performance of the sensor electronics is crucial to the performance of the imaging system. The problems associated with such a measurement process are discussed and solutions to these are described. Test results show that the present design has a resolution of 0.3 femtofarad. (For a 12-electrode system imaging an oil/gas flow, this represents a 2% gas void fraction change at the centre of the pipe) with a low noise level of 0.08 fF (RMS value), a large dynamic range of 76 dB and a data acquisition speed of 6600 measurements per second. This enables sensors with up to 12 electrodes to be used in a system with a maximum imaging rate of 100 frames per second, and thus provides an improved image resolution over the earlier 8-electrode system and an adequate electrode area to give sufficient measurement sensitivit

Integrated Electronics for Wireless Imaging Microsystems with CMUT Arrays

Integration of transducer arrays with interface electronics in the form of single-chip CMUT-on-CMOS has emerged into the field of medical ultrasound imaging and is transforming this field. It has already been used in several commercial products such as handheld full-body imagers and it is being implemented by commercial and academic groups for Intravascular Ultrasound and Intracardiac Echocardiography. However, large attenuation of ultrasonic waves transmitted through the skull has prevented ultrasound imaging of the brain. This research is a prime step toward implantable wireless microsystems that use ultrasound to image the brain by bypassing the skull. These microsystems offer autonomous scanning (beam steering and focusing) of the brain and transferring data out of the brain for further processing and image reconstruction. The objective of the presented research is to develop building blocks of an integrated electronics architecture for CMUT based wireless ultrasound imaging systems while providing a fundamental study on interfacing CMUT arrays with their associated integrated electronics in terms of electrical power transfer and acoustic reflection which would potentially lead to more efficient and high-performance systems. A fully wireless architecture for ultrasound imaging is demonstrated for the first time. An on-chip programmable transmit (TX) beamformer enables phased array focusing and steering of ultrasound waves in the transmit mode while its on-chip bandpass noise shaping digitizer followed by an ultra-wideband (UWB) uplink transmitter minimizes the effect of path loss on the transmitted image data out of the brain. A single-chip application-specific integrated circuit (ASIC) is de- signed to realize the wireless architecture and interface with array elements, each of which includes a transceiver (TRX) front-end with a high-voltage (HV) pulser, a high-voltage T/R switch, and a low-noise amplifier (LNA). Novel design techniques are implemented in the system to enhance the performance of its building blocks. Apart from imaging capability, the implantable wireless microsystems can include a pressure sensing readout to measure intracranial pressure. To do so, a power-efficient readout for pressure sensing is presented. It uses pseudo-pseudo differential readout topology to cut down the static power consumption of the sensor for further power savings in wireless microsystems. In addition, the effect of matching and electrical termination on CMUT array elements is explored leading to new interface structures to improve bandwidth and sensitivity of CMUT arrays in different operation regions. Comprehensive analysis, modeling, and simulation methodologies are presented for further investigation.Ph.D

SPRZĘT I OPROGRAMOWANIE DO BADAŃ ELEMENTÓW ELEKTRONICZNYCH I CZUJNIKÓW

The main results of RETwix development are presented in the paper. RETwix is an universal hardware and software means for laboratory research, which can be used for investigation both electronic components and arbitrary electrical, thermal, chemical or biochemical processes. Sensors, actuators and signal transducers of the Analog Front-End are used for this purpose. The RETwix means includes two CV-LAB devices (Capacitance & Voltage LABoratory) and UA-LAB (Universal Analog LABoratory). The peculiarities of construction and examples of RETwix using are described.Główne wyniki opracowania RETwix zostały przedstawione w artykule. RETwix jest uniwersalnym sprzętem i oprogramowaniem do badań laboratoryjnych, które można wykorzystać do badania zarówno komponentów elektronicznych, jak i dowolnych procesów elektrycznych, termicznych, chemicznych lub biochemicznych. W tym celu zostały wykorzystane czujniki, aktuatory i przetworniki sygnału Analog Front-End. RETwix zawiera dwa urządzenia CV-LAB (Capacitance & Voltage LABoratory) oraz UA-LAB (Universal Analog LABoratory). Zostały opisane osobliwości budowy oraz przykłady zastosowania RETwix

Investigation of a piezo-polymer array transducer for pulse-echo ultrasonic material examinations

The aim of this investigation was to make a flexible array of pulse-echo ultrasound transducers by etching two orthogonal linear arrays of conducting elements into the metallisation of either side of a sheet of PVdF. These would then be multiplexed under computer control in an X-Y raster, thereby forming an image of subsurface defects in a material specimen. A potential source model was used to predict the sensitivity of a single element air-backed transducer far from resonance. Initial investigations confirmed the predictions, and reaffirmed the results of previous workers. In making a prototype array, it was found necessary to use a bi-laminar arrangement with a central ground plane, due to difficulties with crosstalk and charge leakage into the specimen materials. The radiation pattern of this array was tested and found to agree with the predictions for Fraunhofer (Far-Field) radiation. A 10 MHz analogue to digital converter was constructed to interface with the IBM-PC clone as a transient recorder, through a data capture program written in 'C'. However, the electrical noise generated by the PC was found to interfere strongly with the signal from the array transducer. A wide-band amplifier and full-wave rectifier was then added to the multiplexer and A/D converter, and the system enclosed in an electrically isolated environment, which made it possible to obtain clear signal data from the transducer. Non-linear regression was implemented in the software, to smooth the data and locate echo peaks, and the most frequently occurring peak separation was used to indicate sample thickness at that location in a false-colour mapping on the screen of the PC

Index to NASA Tech Briefs, January - June 1966

Index to NASA technological innovations for January-June 196