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This brief presents a readout IC with a 20 V high-voltage (HV) transmitter (Tx) and On-Chip Differentially Modulated Time-Interleaved Sensing Method (DM-TISM) in a BCD process for a mutual-capacitive Transparent Fingerprint Sensor (TFPS) in order to achieve high SNR, AC & DC offset reduction, high noise immunity, and compensate for the signal loss under thick cover glass. A proposed readout IC with on-chip DM-TISM is composed of 42 identical HV Tx channels, 32 identical Rx channels, and a diamond-patterned TFPS. The performance results including those for transient noise show that the DM-TISM achieves greater SNR than conventional TISM. The measured raw data show that the proposed readout IC achieves SNR of 32 dB with current consumption of 25 mA for the Tx and 13 mA for the Rx. It can be applied to any type of mobile device that needs fingerprint recognition. The ICs for the Tx and Rx are fabricated using 0.25- $\mu \text{m}$ BCD process and 0.18- $\mu \text{m}$ CMOS process with $1.6\,\,\mathrm {mm} \times 3.5$ mm and $2.5\,\,\mathrm {mm} \times 2.5$ mm areas, respectively.

This paper presents a fingerprint mutual capacitive touchscreen panel (TSP) readout IC, which uses a differential coded multiple signaling (DCMS) method. A readout IC with high SNR and fast frame rate is required for fingerprint recognition. However, achieving high SNR is challenging owing to the limited capacitance difference originating from the small depth variations between the ridges and valleys of the fingerprint. In addition, scanning the entire fingerprint TSP with multiple electrodes is time-consuming. A fully differential receiver with DCMS is proposed to detect the low capacitance difference in a fingerprint TSP. The internal noise is minimized by the low-noise amplifier, and external noise is eliminated by a lock-in sensing architecture. In addition, DCMS reduces the offset and enhances the SNR while achieving faster frame rate in multiple channels. The proposed architecture can detect capacitance of 50 aF, which is the capacitance difference resulting from the ridges and valleys of a finger under a 0.3-mm-thick (T) cover glass. The readout IC achieves 15.1-dB peak-to-peak SNR and 23-Hz frame rate with a transparent mutual capacitive fingerprint TSP under 0.3T glass. The power consumption is below 21 mW at 3.3-V supply voltage. The IC was fabricated using a 0.18- $ {\mu }\text{m}$ standard CMOS process.

Displays represent information visually, so they have become the fundamental building block to visualize the data of current electronics including smartphones. Recently, electronics have been advanced toward flexible and wearable electronics that can be bent, folded, or stretched while maintaining their performance under various deformations. Here, recent advances in research to demonstrate flexible and wearable displays are reviewed. We introduce these results by dividing them into several categories according to the components of the display: active-matrix backplane, touch screen panel, light sources, integrated circuit for fingerprint touch screen panel, and characterization tests; and we also present mechanical tests in nano-meter scale and visual ergonomics research.

The need for personal security in portable devices has increased. Among several biometric sensing technologies, fingerprint sensing is the most highlighted method. However, a fingerprint sensor in electronics is stifling the demands for a larger interactive display. In this paper, the bottlenecks of placing the sensor on display is discussed, and an on-display mutual capacitive high-resolution transparent fingerprint sensor with a half-diamond pattern is proposed for adapting to the needs of personal security on a larger screen. To overcome various performance limitations on the on-display fingerprint sensor, a metal mesh is used as an electrode material, and the half-diamond pattern is applied. The proposed pattern is compatible with the diamond-patterned active matrix organic light emitter diode display. The proposed sensor has $72\times72$ channels in a 6 mm $\times6$ mm area. The sensor satisfies the criteria set by the Federal Bureau of Investigation for fingerprint sensing with 322 capacitors per inch, and the measured transmittance in the visible light region is 79.7%. The proposed sensor achieved a capacitance variation 2.3 times larger than that achieved by the conventional sensor. The five-channel fingerprint sensing circuit to examine the feasibility of fingerprint detection is fabricated with the TSMC 0.18- $\mu \text{m}$ process.

This paper presents a mutual capacitive touch screen panel (TSP) readout IC (ROIC) with a differential continuous-mode parallel operation architecture (DCPA). 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. This architecture is implemented using a continuous-type transmitter for parallel signaling and a differential-architecture receiver. 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- $\mu$ m CMOS process and occupied an active area of 1.25 $\text{mm}^{2}$ . 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.

A current subtraction technique with parallel operation system is proposed to remove excessive current in touch screen application. The proposed current subtraction remove the current which go into the input node of charge amplifier. The value of subtraction current is same with current when touch screen is not touched. As a result, charge amplifier output is only proportional to variation of mutual capacitor, which make dynamic rage is increased. Also, Transmitter (Tx) driving signal and subtraction driving signal are out of phase each other. Thus, noise generated in Tx is cancelled. The proposed IC is implemented in a mixed-mode 0.18-um CMOS process. Overall system is designed for touch screen panel (TSP) with 16 driving lines and 8 sensing lines. 5-V supply voltages are used in the proposed circuits. For multiple Tx driving signal, Walsh codes are used and signal frequency is 300 khz. By using proposed technique, dynamic rage is improved 36 dB.

This paper presents a new kind of touch sensor that utilizes the concept of wireless energy transfer (WET). A near-field sheet like a waveguide-based WET system was used for this purpose based on its geometric suitability. The approaching target object (human finger bioimpedance) disturbs the overall sheet reactance based on a complex power conservation equation at the resonant frequency. Thus, the drop in the efficiency of the power transfer can be utilized to carry out the task of sensing. The WET sensor was designed to operate at 29 MHZ, with a power transfer efficiency of −3.18 dB. An experimental demonstration was performed by feeding a 10 V peak-to-peak sine wave at the transmitter end and reading a dc output using a full-wave rectifier and multimeter at the receiver end. The system was designed to achieve a drop of 2.1 V when a touch was registered. The sensor was also designed to operate in the proximity mode. For operation in the proximity mode, the receiver had to be a wave trap cavity. This was achieved by designing the receiver to have a cylindrical wave cavity arrangement. The WET sensor had to be unaffected by the presence of an electric field, and this was demonstrated by carrying out sensing while the sensor was located under an LCD, which has a considerable electric field. It was experimentally demonstrated that the sensor had a linear output in proximity mode. Proposed sensor could be ideal candidate for: 1) touch screen panels; 2) human-robotics interactions; and 3) security applications.

This paper presents a fingerprint mutual capacitive touch-screen panel (TSP) readout IC (ROIC) with a differential signaling method for fast fingerprint recognition. 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. Proposed IC has been fabricated using a 0.18 μm standard CMOS process.

We introduce a new type of multi-functional capacitive sensor that can sense several different external stimuli. It is fabricated only with polydimethylsiloxane (PDMS) films and silver nanowire electrodes by using selective oxygen plasma treatment method without photolithography and etching processes. Differently from the conventional single-capacitor multi-functional sensors, our new multi-functional sensor is composed of two vertically-stacked capacitors (dual-capacitor). The unique dual-capacitor structure can detect the type and strength of external stimuli including curvature, pressure, strain, and touch with clear distinction, and it can also detect the surface-normal directionality of curvature, pressure, and touch. Meanwhile, the conventional single-capacitor sensor has ambiguity in distinguishing curvature and pressure and it can detect only the strength of external stimulus. The type, directionality, and strength of external stimulus can be determined based on the relative capacitance changes of the two stacked capacitors. Additionally, the logical flow reflected on a tree structure with its branches reaching the direction and strength of the corresponding external stimulus unambiguously is devised. This logical flow can be readily implemented in the sensor driving circuit if the dual-capacitor sensor is commercialized actually in the future.

This paper describes an atto farad capacitive sensing system for a finger-print sensor. The architecture of mutual capacitive finger-print sensor is obtained by investigating the capacitance change by the finger-print based on the Q3D Extractor model. An electrostatic simulation shows that the 200aF difference caused by the valley and the ridge in the sensor. In order to sense the atto farad capacitance in finger-print sensor, a continuous-type fully differential architecture with a differential transmitted signals is proposed to amplify a capacitance difference only with a reduced the parasitic effect caused by a large number of electrodes. The prototype IC with 0.18um CMOS achieves 300mV/200aF.

An algorithm for a capacitive touch screen panel that can make the sum of the signal into `0' for the use of high voltage is presented. The differential Manchester code is combined with the Walsh-Hadamard code to generate an input coded signal. Owing to the property of the differential Manchester code, the Moore-Penrose pseudoinverse matrix is employed to decode-mutual capacitance from the received signal. As only the variation between the un-touch and touch condition is detected at the receiver, a high-voltage input coded signal is used. Unlike a normal touch system, the decoded sensing capacitance in the proposed algorithm does not have an absolute value. Positive decoded capacitance is the un-touch condition and negative decoded capacitance is the touch condition. The simulated signal-to-noise ratio (SNR) of the proposed algorithm is 27.9 dB, which is 8.26 dB higher than SNR in not return to zero (NRZ).

The potential use of sheet-like waveguide-based wireless energy transfer systems for a two-way power and/or high-data rate transmission–reception through thick metal walls is investigated. The proposed system utilises the near-field evanescent wave concept to transmit energy and/or data. Compared with wireless energy transfer devices based on magnetic resonance coupling, the transmission efficiency of the investigated method is not affected by the shielding offered by metal sheets. For the investigation, a 150 × 150 mm2 sheet-like waveguide transmitter and a cylindrical wave-cavity receiver were designed. The receiver achieved a transfer efficiency of −3.76 dB, while transmitting power through galvanised iron sheets. The prime objective of this investigation was to sustain the power and/or data transfer efficiency despite the variation of the obstructing metal wall thicknesses from 1.5 to 22.5 mm. The proposed system was designed to operate at 25 MHz, enabling 50 Mbit/s data transfer using a function generator.

In this paper, a continuous-time differential type multi-signal parallel driving architecture touch screen sensing circuit for projective capacitive type panel is presented. In order to further enhance the Signal-to-Noise Ratio (SNR), a new transmitter (TX) architecture is proposed with parallel signal processing algorithm. In this work, charge amplifiers with built-in band-pass filter are designed that filter out low frequency noise and common-mode noise simultaneously. Conventional approaches in continuous-time operation with band-pass filter suffer from a synchronization problem in the case of multi-signal parallel driving. In this work, a built-in delay calibration circuit is proposed that can align signal timing for TX signal and adjacent receiver (RX) sensing line. This proposed architecture enables multi-signal parallel driving in continuous-time operation for projective capacitive sensing circuits. The proposed work supports 16 × 8 mutual capacitive touch screen panel (TSP). TSP load is 12.5 kΩ and 40 pF with frame rate of 200 Hz and 58 dB SNR. Power dissipation is 46 mW.