• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.133-138
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• 2019

The a-InGaZnO (a-IGZO) thin film transistor (TFT) has the advantages of larger mobility than that of amorphous silicon TFTs, acceptable reliability and uniformity over a large area, and low process cost. A capacitive-type touch sensor was studied with an a-IGZO TFT that can be used on the front side of a display due to its transparency. A capacitive sensor detects changes of capacitance between the surface of the finger and the sensor electrode. The capacitance varies according to the distance between the sensor plate and the touching or non-touching of the sensing electrode. A capacitive touch sensor using only one a-IGZO TFT was developed with the reduction of two bus lines, which made it easy to reduce the pixel pitch. The proposed sensor circuit maintained the amplification performance, which was investigated for various drive conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.799-805
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• 2015

In this paper, an inkjet-printed capacitive touch pad is proposed. This touch pad detects contacts of human finger by detecting changes in effective capacitance due to electrical impedance of human finger. A flexible, low-cost and disposable paper is used as a substrate. Inkjet printing technology makes the fabrication fast, simple and environmentally friendly. Measured capacitances of the touched and untouched states are in the range of 163 to 182pF and 218 to 272pF, respectively. The differences in the measured capacitance of each state are sufficiently large to recognize that a finger has made contact with touch pad.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.6
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• pp.25-30
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• 2009

In this paper, a full-digital capacitive sensor for touch key applications is proposed. The proposed circuit consists of two capacitive loads to measure and a resistor between the capacitive loads. As the method measures the delays of the resistor and two capacitive loads respectively, and obtains difference between the capacitive loads by subtracting the two delays, it can reduce the effects of changing of operating environment variables such as supplying voltage, temperature and humidity. Experimental results show the method has l.02pF resolution and can be applied to touch key applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.317-322
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• 2010

This paper reports the fabrication and characterization of surface micromachined poly 3C-SiC capacitive pressure sensors on silicon wafer operable in touch mode and normal mode for high temperature applications. FEM(finite elements method) simulation has been performed to verify the analytical mode. The sensing capacitor of the capacitive pressure sensor is composed of the upper metal and the poly 3C-SiC layer. Measurements have been performed in a temperature range from $25^{\circ}C$ to $500^{\circ}C$. Fabrication process of designed poly 3C-SiC touch mode capacitive pressure sensor was optimized and would be applicable to capacitive pressure sensors that are required high precision and sensitivity at high pressure and temperature.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.4
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• pp.26-33
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• 2010

This paper presents a multi-channel capacitive touch sensing unit for SoC applications. This unit includes a simple common processing unit and switch array to detect the touch sensing input by capacitive-time(C-T) conversion method. This touch sensor ASIC is designed based on the Capacitive-Time(C-T) conversion method to have advantages of small current and chip area, and the minimum resolution of the unit is 41 fF per count with the built-in sensing oscillator, LDO regulator and $I^2C$ for no additional external components. This unit is implemented in 0.18 um CMOS process with dual supply voltage of 1.8 V and 3.3 V. The total power consumption of the unit is 60 uA and the area is 0.26 $mm^2$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.88-94
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• 2013

This paper proposes a capacitive touch switch using a switched-capacitor. The proposed method charges capacitance for measurement using the switched-capacitor until the voltage across the capacitance reaches a threshold voltage. As the proposed method uses the number of times being charged to measure the capacitance, the method has no relation with the operating frequency of the switched-capacitor. This paper also shows the quantization resolution of the proposed method is related to the capacitance in the switched-capacitor and the threshold voltage, i.e., the resolution is improved when the capacitance in the switched-capacitor is decreased and the threshold voltage is increased. Simulation result shows the method gives 31fF quantization resolution when the capacitance in the switched-capacitor is 50fF and threshold voltage is 80% of the supply voltage.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.140-145
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• 2016

In this paper, we fabricate arrayed-type flexible capacitive touch sensor using liquid metal (LM) droplets (4 mm spatial resolution). Poly-4-vinylphenol (PVP) layer is used as a dielectric layer on the electrode patterned Polyethylene naphthalate (PEN) film. Bonding tests between hydroxyl group (-OH) on the PVP film and polydimethylsiloxane (PDMS) are conducted in a various $O_2$ plasma treatment conditions. Through the tests, we can confirm that non-$O_2$ plasma treated PVP layer and $O_2$ plasma treated PDMS can make a chemical bond. To measure dynamic range of the device, one-cell experiments are conducted and we confirmed that the fabricated device has a large dynamic range (~60 pF).

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.3
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• pp.406-412
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• 1998

This paper describes a contact position detection method of a capacitive touch screen panel. The proposed method is composed of a circuited compensating algorithm generating an output signal having phase difference to an input signal associated with contact position, converts both input and output signals into digital waveform (5V logic), and calculates the phase difference. Finally, position information with the phase difference is obtained by using a low-cost microprocessor, which is convenient to compensate non-linearity error. The proposed method, that computes phase difference directly, has advantages in feasibility and cost because it minimizes the use of analog devices; rather, it utilizes, cost effective digital circuit. Analytical results are also given.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.964-967
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• 2009

A new hybrid-type touch screen panel (TSP) has been developed based on a-Si:H TFT which can detect the change of both $C_{LC}$ and photo-current. This TSP can detect the difference of $C_{LC}$ between touch and no-touch states in unfavorable conditions such as dark ambient light and shadows. The hybrid TSP sensor consists of a detection area which includes one TFT for photo sensing and two TFTs for amplification. Compared to a single internal capacitive TSP or an optical sensing TSP, this new proposed hybrid-type TSP enables larger sensing margin due to embedding of both optical and capacitive sensors.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.875-877
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• 2011

This paper introduces a touch screen panel driver using modified charge pump circuit. The touch screen panel driver is composed of an analog circuit part which senses a touch and a digital circuit which analyse the sensed signal. To verify the functions the touch screen panel driver, a mixed-mode circuit was built and simulated using Cadence Spectre. The digital circuits were modeled with Verilog-A in order to interface with the analog circuits and verify the functionalities of the driver with less simulation time. From the simulation results, we can verify the reliable operations of the simple structured touch screen panel driver which does not include an ADC.