Papers by Richard Przybyla
2015 28th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), 2015
IEEE Journal of Solid-State Circuits, 2015
ABSTRACT
2014 IEEE International Solid-State Circuits Conference Digest of Technical Papers (ISSCC), 2014
Optical 3D imagers for gesture recognition suffer from large size and high power consumption. The... more Optical 3D imagers for gesture recognition suffer from large size and high power consumption. Their performance depends on ambient illumination and they generally cannot operate in sunlight. These factors have prevented widespread adoption of gesture interfaces in energy-and volume-limited environments such as tablets and smartphones. Wearable mobile devices, too small to incorporate a touchscreen more than a few fingers wide, would benefit from a small, low-power gestural interface. Gesture recognition using sound is an attractive alternative to overcome these difficulties due to the potential for chip-scale size, low power consumption, and ambient light insensitivity. Using pulse-echo time-of-flight, MEMS ultrasonic rangers work over distances of up to a meter and achieve sub-mm ranging accuracy . Using a 2-dimensional array of transducers, objects can be localized in 3 dimensions. This paper presents an ultrasonic 3D gesture-recognition system that uses a custom transducer chip and an ASIC to sense the location of targets such as hands. The system block diagram is shown in .1.1. Targets are localized using pulse-echo time-of-flight methods. Each of the 10 transceiver channels interfaces with a MEMS transducer, and each includes a transmitter and a readout circuit. Echoes from off-axis targets arrive with different phase shifts for each element in the array. The off-chip digital beamformer realigns the signal phase to maximize the SNR and determine target location.
2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS), 2014
ABSTRACT Phased array imaging with micromachined ultrasound transducer (MUT) arrays is widely use... more ABSTRACT Phased array imaging with micromachined ultrasound transducer (MUT) arrays is widely used in applications such as ranging, medical imaging, and gesture recognition. In a phased array, the maximum spacing between elements must be less than half of the wavelength to avoid large sidelobes. This places a limit on the maximum transducer size which is not attractive since the acoustic coupling drops rapidly for MUT diameters less than a wavelength. Here, we present a new approach to increase the acoustic coupling of small radius MUTs using an impedance matching resonant tube etched beneath the MUT. Impedance, laser Doppler vibrometer (LDV), and acoustic burst measurements confirm a 350% increase in SPL and 8x higher bandwidth compared to transducers without the impedance matching tube, enabling compact arrays with high fill-factor and efficiency.
2011 16th International Solid-State Sensors, Actuators and Microsystems Conference, 2011
ABSTRACT Free space ultrasonic ranging is attractive for applications such as gesture recognition... more ABSTRACT Free space ultrasonic ranging is attractive for applications such as gesture recognition and robotic navigation. Unlike optical ranging technologies, ultrasound based solutions are insensitive to ambient illumination and can therefore be used in- and outdoors. Using time-of-flight, ultrasound rangers work over distances of up to a few meters and achieve sub-mm resolution. Using arrays, objects can be localized in three dimensions. Transducers consist of 400μm aluminum-nitride membranes sandwiched between actuation electrodes batch fabricated on silicon wafers. Unlike capacitive transducers, which require actuation voltages in excess of 100 V, piezoelectric devices are compatible with low-voltage actuation. At the 200 kHz resonance frequency, the wavelength at atmospheric pressure is 2 mm, ideal for compact arrays. The transducers do not dissipate static power and are therefore ideal for battery powered applications. Energy consumption is dominated by the low-noise readout amplifier and is on the order of 1μJ per channel including analog-digital conversion and signal processing, enabling video-rate object tacking at less than 1 mW power dissipation. A prototype system consisting of seven transducers on a 1 mm grid operates up to a 750 mm range and ±35(o) angle span with ±3.5mm accuracy and ±3(o) worst case angle error.
… (IUS), 2009
AbstractPiezoelectric micromachined ultrasonic transducers for air-coupled ultrasound applicatio... more AbstractPiezoelectric micromachined ultrasonic transducers for air-coupled ultrasound applications were fabricated using aluminum nitride (AlN) as the active piezoelectric layer. The AlN is deposited via a low-temperature sputtering process that is compatible with deposition on metalized ...
In this study the characterization of an aluminum nitride (AlN) double ended tuning fork (DETF) f... more In this study the characterization of an aluminum nitride (AlN) double ended tuning fork (DETF) fabricated on a layer of silicon dioxide (SiO 2 ) is presented. The positive temperature coefficients of SiO 2 are used to achieve zero TCF for radio frequency (RF) Lamb wave resonators. This paper shows the possibility to integrate temperature compensated Lamb wave resonators with DETF-based devices on a single chip. The DETF resonates in a quasi-in-plane mode shape with a Q-factor of 578 in air and 3028 in vacuum. Through a laser Doppler velocity (LDV) measurement we also show that, due to the biomorph nature of the structure and the angle of the side walls, the motion of each tine of the DETF is a combination of in-plane bending, out-of-plane bending and torsional motion around the beam main axis.
Piezoelectric micro-machined ultrasonic transducers (pMUTs) for air-coupled ultrasound applicatio... more Piezoelectric micro-machined ultrasonic transducers (pMUTs) for air-coupled ultrasound applications were fabricated using aluminum nitride (AlN) as the active piezoelectric material. Earlier pMUTs based on a fully clamped membrane design suffer from high sensitivity to residual stress, causing large variations in the operating frequency, and have a reduced dynamic range due to nonlinearity at large drive voltages. Here we evaluate a
An ultrasonic rangefinder has a working range of 30 mm to 450 mm and operates at a 375 Hz maximum... more An ultrasonic rangefinder has a working range of 30 mm to 450 mm and operates at a 375 Hz maximum sampling rate. The random noise increases with distance and equals 1.3 mm at the maximum range. The range measurement principle is based on pulse-echo time-of-flight measurement using a single transducer for transmit and receive. The transducer consists of a piezoelectric AlN membrane with 400 µm diameter, which was fabricated using a low-temperature process compatible with processed CMOS wafers. The performance of the system exceeds the performance of other micromechanical rangefinders.
An ultrasonic rangefinder has a working range of 30 mm to 450 mm and operates at a 375 Hz maximum... more An ultrasonic rangefinder has a working range of 30 mm to 450 mm and operates at a 375 Hz maximum sampling rate. The worst-case systematic error less than 1.1mm. The rms noise is proportional to the square of the distance and equals 1.3 mm at the maximum range. The range measurement principle is based on pulse-echo time of flight measurement
Uploads
Papers by Richard Przybyla