A system in package based on a piezoelectric micromachined ultrasonic transducer matrix for ranging applications

This paper proposes a system in package (SiP) for ultrasonic ranging composed of a 4 × 8 matrix of piezoelectric micromachined ultrasonic transducers (PMUT) and an interface integrated circuit (IC). The PMUT matrix is fabricated using the PiezoMUMPS process and the IC is implemented in the AMS 0.35 µm technology. Simulation results for the PMUT are compared to the measurement results, and an equivalent circuit has been derived to allow a better approximation of the load of the PMUT on the IC. The control circuit is composed of a high-voltage pulser to drive the PMUT for transmission and of a transimpedance amplifier to amplify the received echo. The working frequency of the system is 1.5 MHz

RF Sensor-based Liveness Detection Scheme with Loop Stability Compensation Circuit for a Capacitive Fingerprint System

A capacitive fingerprint system is the most widely used biometric identification method for smartphones. In this paper, we propose a RF sensor-based liveness detection scheme. This method solves the problem of spoofing attacks, which is a primary disadvantage to capacitive fingerprint sensors. The proposed scheme measures the inherent impedance characteristic difference of the target fingerprint caused by the eddy-current effect with an auto-balancing bridge method. The magnetic field is generated by a small form-factor inductor coil of ?? = 1.5mm. This detection scheme can be easily integrated with an existing capacitive fingerprint sensor by using the same CMOS process. The measured results demonstrate the liveness detection capability of the Si-graphite (silicone-graphite) and polyvinyl fake fingerprints that cannot be distinguished by conventional capacitive fingerprint sensors

Transparent Fingerprint Sensor System for Large Flat Panel Display

In this paper, we introduce a transparent fingerprint sensing system using a thin film transistor (TFT) sensor panel, based on a self-capacitive sensing scheme. An armorphousindium gallium zinc oxide (a-IGZO) TFT sensor array and associated custom Read-Out IC (ROIC) are implemented for the system. The sensor panel has a 200 ?? 200 pixel array and each pixel size is as small as 50 ??m ?? 50 ??m. The ROIC uses only eight analog front-end (AFE) amplifier stages along with a successive approximation analog-to-digital converter (SAR ADC). To get the fingerprint image data from the sensor array, the ROIC senses a capacitance, which is formed by a cover glass material between a human finger and an electrode of each pixel of the sensor array. Three methods are reviewed for estimating the self-capacitance. The measurement result demonstrates that the transparent fingerprint sensor system has an ability to differentiate a human finger???s ridges and valleys through the fingerprint sensor array

Design of Touch Screen Controller IC for Transparent Fingerprint Sensor

Department of Electrical EngineeringA design of system architecture and analog-front-end (AFE) with high SNR and high frame rate for mutual capacitive touch screen with multiple electrodes is presented. Firstly, a differential continuous-mode parallel operation architecture (DCPA) is proposed for large-sized TSP. The proposed architecture achieves a high product of signal-to-noise ratio (SNR) and frame rate, which is a requirement of ROIC for large-sized TSP. DCPA is accomplished by using the proposed differential sensing method with a parallel architecture in a continuous-mode. A continuous-type differential charge amplifier removes the common-mode noise component, and reduces the self-noise by the band-pass filtering effect of the continuous-mode charge amplifier. In addition, the differential parallel architecture cancels the timing skew problem caused by the continuous-mode parallel operation and effectively enhances the power spectrum density of the signal. The proposed ROIC was fabricated using a 0.18-um CMOS process and occupied an active area of 1.25 mm2. The proposed system achieved a 72 dB SNR and 240 Hz frame rate with a 32 channel TX by 10 channel RX mutual capacitive TSP. Moreover, the proposed differential-parallel architecture demonstrated higher immunity to lamp noise and display noise. The proposed system consumed 42.5 mW with a 3.3-V supply. Secondly, readout IC (ROIC) with a differential coded multiple signaling method (DCMS) is proposed to detect an atto-farad capacitance difference for fingerprint recognition in fingerprint TSP. A readout IC with high SNR and fast frame rate are required in the fingerprint recognition. However, the capacitance difference by the ridge and valley of the fingerprint is very small, so that the signal-to-noise ratio is very low. In addition, it takes long time to scan whole fingerprint TSP with multiple electrodes. A fully differential architecture with differential signaling is proposed to detect the low capacitance difference in fingerprint TSP. The internal noise generated is minimized by 2nd fully differential operational amplifier and external noise is eliminated by a lock-in sensing structure. In addition, DCMS reduces an AC offset and enhances a higher product of SNR and frame rate in multiple channels. The proposed architectures can distinguish a 50-atto-farad which is a capacitance difference resulted from the ridges and valley of the finger under the 0.3T glass. The total scan time for 42 ?? 42 fingerprint TSP is less than 21 ms and the power consumption is below 20 mW at 3.3 V supply voltage. IC has been fabricated using a 0.18 ??m standard CMOS process.ope