Browsing by Author "Thakur, Smriti"

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A fast-sensing readout circuit in 240 Hz enabled by code division multiple access (CDMA) implemented for an ultra-thin on-cell flexible capacitive touch panel
(1970-01-01)
Chang, Chia Yu
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Chao, Paul C. -P.
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Wang, Jeremy H. -S.
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Su, Ying Cheng
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Thakur, Smriti
A new fast readout circuit employing the known coding scheme of code division multiple access (CDMA) is successfully designed and applied to a 7-inch ultra-thin, flexible on-cell touch screen panel (TSP). The adopted CDMA is known originally as a coding scheme for data communication, which is applied in this study to address the sensing electrodes of the ultra-thin flexible touch panel. Due to the orthogonality between the driving signals to the touch panel coded by Walsh transform, one type of CDMA, the interference noises between sensing electrodes can be reduced effectively to render accurate touch sensing results. The electromagnetic interference from the flexible display can also be filtered out as baseline component in the output signal. And the frame time of touch reporting can be substantially shortened. Following the sensing electrode is a new readout designed of the switched-capacitor (SC) circuit, to avoid distributing sample signals from parasitic capacitance and also to enlarge the voltage changes due to the capacitance changes caused by touches. A 12-bit analog-to-digital converter (ADC) is orchestrated after the SC circuit to transform the front-end analog signal to digital codes. The digital part of the designed readout adopts a correction algorithm to eliminate the background signals from the display, and also a moving average algorithm to minimize the higher-frequency noises from the display and other electrodes. Experiments are conducted to validate the expected performance. It is evidenced that the Walsh code driving algorithm improves the quality of the readout output signal to be in 42 dB SNR, the report rate to a fast 240 Hz, and a power consumption of 0.39 mW by each sensing channel.
Design and implementation of a new high-accuracy interpolation encoder IC for magneto-resistive sensors
(1970-01-01)
Chen, Wen-Yu
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Chang, I-Feng
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Chao, Paul C-P
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Thakur, Smriti
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Tu, Tse-Yi
A new algorithm named the eight-section (ES) method for carrying out the interpolation for a magneto-resistive (MR) encoder is successfully developed and fabricated in a digital chip. It is known that a conventional magneto-resistive (MR) encoder employs the interpolation method, which converts incoming front-end analog signals in harmonics in sinusoids/co-sinusoids to moving displacement via calculating arc-tangents. This conventional interpolation requires divisions to be carried out for the displacement, which often leads to large noises while conducting digital computation, eventually undermining significantly the accuracy of the MR sensor. The proposed interpolation of eight-section (ES) is designed specially without divisions in the digital computation, leading to higher precision than the conventional interpolation conducting the computation of arc-tangents. The digital computation chip designed by this study consists of a cycle counter, two decimators for incoming analog signals of the MR sensor, a correcting circuit, and the proposal ES interpolation unit. The designed chip is successfully fabricated by TSMC 0.18-mu m CMOS process, the area of which is 1643 x 1676 mu m. The chip is than calibrated by a reference interferometer by experiments for further improving the measurement accuracy. The precision finally results in measuring displacement reaches as accurate as within 1.065 mu m, which is much favorable to the existing performance around 2 mu m by the conventional interpolation.