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Ultrasound is widely used for nondestructive evaluation (NDE), structural health monitoring (SHM), acoustic emission, sound navigation ranging, and in sensors for automobiles, medicine, and many other applications. Ultrasound fingerprint sensors[1,2] [...]

In this work, we propose a novel procedure to generate and select threshold inverter quantized (TIQ) comparators for TIQ Flash ADCs. The new procedure generates more TIQ comparators than the procedure designed by Lee , Yoo, and Choi (LYC) (Proceedings of International Symposium on Quality Electronic Design, 2002). Two 6-bit TIQ Flash ADCs were designed, the LYC flash ADC, which selects its TIQ comparators using the current threshold selection algorithm, and the AC TIQ Flash ADC, which selects its TIQ comparators using the threshold selection algorithm proposed herein. Both ADCs were designed in $$0.5\,{\upmu }\hbox {m}$$ CMOS technology and compared against the process, voltage source, and temperature (PVT) variations. Proposed TIQ selection procedure allows the designer to select the optimum TIQ set for desired ADC. AC ADC has a DNL values ±0.015 LSB and INL values between $$\pm 0.0225$$ compared to ±0.1 LSB and 0.3 to −0.1 LSB for DNL and INL values of the LYC ADC. ENOB and SNDR for the AC were improved by at least $$31.3\%$$ compared to LYC ADC, at typical process settings. For process, voltage source, and temperature (PVT) variations, in overall the AC ADC has at least better the DNL values by at least $$22.5\%$$ and reduced INL values by at least $$35\%$$ . Over PVT variation, AC ADC has maintained ENOB value greater than 5.3 bits for all 16 variation corners. ENOB was improved by at least 1.5 bits over all corners. SNDR and SFDR were increased by at least 4 dB over the PVT corners. Proposed AC procedure shows scalability feature by generating extra threshold points for the $$65\hbox {-nm}$$ TIQ comparators. [ABSTRACT FROM AUTHOR]

This letter reports a low-power full-wave active rectifier using double-gate ZnO thin-film transistors (TFTs). The active rectifier is designed to operate at low voltage and low power to allow integration with mechanical energy harvesters. Double-gate TFTs allow the TFT threshold voltage to be tuned and enable enhancement/depletion-mode circuits with high gain and low power consumption. The active rectifier is designed to work with input voltage as small as 200-mV peak-to-peak and frequencies up to 4 Hz. The active rectifier circuit includes 12 TFTs and operates with a power consumption <150 nW. The low fabrication temperature for the active rectifier circuit allows direct and distributed integration with micro-electromechanical energy harvesters. [ABSTRACT FROM AUTHOR]

High-frequency ultrasound array transducers using piezoelectric thin films on larger structures are being developed for high-resolution imaging systems. The increase in resolution is achieved by a simultaneous increase in operating frequency (30 MHz to about 1 GHz) and close coupling of the electronic circuitry. Two different processing methods were explored to fabricate array transducers. In one implementation, a xylophone bar transducer was prototyped, using thin film PbZr0.52Ti0.48O3 (PZT) as the active piezoelectric layer. In the other, the piezoelectric transducer was prepared by mist deposition of PZT films over electroplated Ni posts. Because the PZT films are excited through the film thickness, the drive voltages of these transducers are low, and close coupling of the electronic circuitry is possible. A complementary metal-oxide- semiconductor (CMOS) transceiver chip for a 16-element array was fabricated in 0.35-μm process technology. The ultrasound front-end chip contains beam-forming electronics, receiver circuitry, and analog-to-digital converters with 3-Kbyte on-chip buffer memory. [ABSTRACT FROM AUTHOR]

We report flexible thin-film lead zirconate titanate (PZT)-based ultrasonic transducers on polyimide substrates. The transducers are bar resonators designed to operate in the width extension mode. The active elements are 1 µm thick PZT films that were crystallized on Si substrates at 700 °C and transferred to 5 µm thick solution-cast polyimide via dissolution of an underlying release layer. Underwater pitch–catch testing between two neighboring 100 µm × 1000 µm elements showed a 0.2 mV signal at a 1.5 cm distance for a driving voltage of 5 V peak at 9.5 MHz. With the same excitation, a 33 kPa sound pressure output at a 6 mm distance and a 32% bandwidth at −6 dB were measured by hydrophone. [ABSTRACT FROM AUTHOR]

Piezoelectric micromachined ultrasound transducers (PMUT) incorporating lead zirconate titanate PbZr0.52Ti0.48O3 (PZT) thin films were investigated for miniaturized high-frequency ultrasound systems. A recently developed process to remove a PMUT from an underlying silicon (Si) substrate has enabled curved arrays to be readily formed. This research aimed to improve the design of flexible PMUT arrays using PZFlex, a finite element method software package. A 10 MHz PMUT 2D array working in 3-1 mode was designed. A circular unit-cell was structured from the top, with concentric layers of platinum (Pt)/PZT/Pt/titanium (Ti) on a polyimide (PI) substrate. Pulse-echo and spectral response analyses predicted a center frequency of 10 MHz and bandwidth of 87% under water load and air backing. A 2D array, consisting of the 256 (16 × 16) unit-cells, was created and characterized in terms of pulse-echo and spectral responses, surface displacement profiles, crosstalk, and beam profiles. The 2D array showed: decreased bandwidth due to protracted oscillation decay and guided wave effects; mechanical focal length at 2.9 mm; 3.7 mm depth of field for -6 dB; and -55.6 dB crosstalk. Finite element-based virtual prototyping identified figures of merit—center frequency, bandwidth, depth of field, and crosstalk—that could be optimized to design robust, flexible PMUT arrays. [ABSTRACT FROM AUTHOR]

A novel design for a chip-scale miniature ovencontrolled crystal oscillator (OCXO) is presented. In this design, all the main components of an OCXO-consisting of an oscillator, a temperature sensor, a heater, and temperaturecontrol circuitry-are integrated on a single CMOS chip. The OCXO package size can be reduced significantly with this design, because the resonator does not require a separate package and most of the circuitry is integrated on a single CMOS chip. Other characteristics such as power consumption and warm-up time are also improved. Two different types of quartz resonators, an AT-cut tab mesa-type quartz crystal and a frame enclosed resonator, allow miniaturization of the OCXO structure. Neither of these quartz resonator types requires a separate package inside the oven structure; therefore, they can each be directly integrated with the custom-designed CMOS chip. The miniature OCXO achieves a frequency stability of + 0.35 ppm with an AT-cut tab mesa-type quartz crystal in the temperature range of 0°C to 60°C. The maximum power consumption of this miniature OCXO is 1.2 W at start-up and 303 mW at steady state. The warm-up time to reach the steady state is 190 s. These results using the proposed design are better than or the same as high-frequency commercial OCXOs. [ABSTRACT FROM PUBLISHER]