應用於電容式觸控螢幕面板的增強信噪比加碼方式

An Algorithm for SNR Improvement for Capacitive Touch Screen Panel

陳政男(Cheng-Nan Chen)

指導教授 ： 李有璋

中原大學/工學院/機械工程研究所/碩士(2016年)

https://doi.org/10.6840/cycu201600085

摘要

摘要
觸控螢幕面板需要：1) 快速的反應速度，以及2) 高度的精確度。為了達到高精確度/靈敏度的目的，噪音消除的技術是ㄧ個重要的課題。而為了達成快速的反應速度，往往會使用多重訊號的驅動方法，也就是同時傳送數個加碼過後的訊號到驅動電路中，而其中最常被使用的加碼方式是 Walsh-Hadamard Code (WHC)。其與分時多感測 (time-division multiple sensing, TDMS) 相較其好處為：1) SNR較高，2) 掃描時間較短。
然而其主要存在的缺點為，其需要多重驅動信號同時經過驅動通道，並且在感測通道匯合，而在每個感測電路上產生了大電流，這是因為每個感測電路都遇上了多重驅動通道，其中感測信號的強度是 n倍於在第一個週期的 n by n WHC所產生的驅動信號，而大電流會造成需要較大的反饋電容，而其會降低系統效能以及增加面積。因此，藉由WHC搭配差分曼徹斯特物理編碼，來改善感測電路電流過大的問題，結果顯示在4行、8行、16行信號流的情況下，相對於非回歸零 WHC的SNR值分別有9.76 dB、12.21 dB以及22.42 dB的增益效果。

關鍵字

電容式觸控螢幕面板 ； 信噪比 ； 差分曼徹斯特物理編碼

並列摘要

Abstract
The demand factors of touch panel are fast response speed and high accuracy. In order to achieve the purpose of high accuracy and sensitivity, noise cancellation technology is becoming an important issue. In the past, most of people used the multiple signals driving method to achieve fast response speed that is, transmitting coded signals to the driving circuit at the same time. The most commonly coded method is Walsh-Hadamard Code (WHC) which is better than time-division multiple sensing (TDMS) because of its higher signal to noise ratio (SNR) and faster scanning time.
However, the disadvantage of WHC is it will generate bulk current in the sensing circuit since multiple driving signals pass through the driving channel simultaneously, and converge in the sensing channel. The signal strength of the sensing circuit is n times of driving signal in n by n WHC at the first cycle. The bulk current in the sensing circuit will cause an increasing feedback capacitance inducing lower system effectiveness and larger size. Therefore, this study improved the bulk current of the sensing circuit by integrating the WHC and differential Manchester encoding. The results showed that the SNR values were improved as 9.76dB, 12.21dB and 22.42dB in the case of 4 rows, 8 rows and 16 rows of signal flow by using differential Manchester encoding with WHC compared to NRZ WHC.

Keywords: Capacitive touch screen panel, SNR, differential Manchester
Coding

並列關鍵字

Capacitive touch screen panel ； SNR ； differential Manchester Coding

參考文獻

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