Projected Capacitive screen mutual capacitance touch screen technology analysis

Mutual capacitance screen is a type of projected capacitive screen, the Projected Capacitive screen there is a type of self capacitance screen. Mutual capacitance technology has direct, efficient, accurate, smooth, stylish and so, to a great extent, improve the efficiency and convenience of the human and computer dialogue, the future will become the future mainstream consumer.
Mutual capacitance screen ITO glass surface produced a lateral electrode and a longitudinal electrode, self capacitance screen difference is that the two electrode groups will cross to form a capacitor, i.e., these two sets of electrodes respectively constitute a capacitor poles. Affected when the finger touch capacitive screen, near the touch point of the coupling between the two electrodes, thereby changing the capacitance between the two electrodes. The mutual capacitance size is detected, the lateral electrode sequentially issued by the excitation signal, the longitudinal direction of all the electrodes at the same time the received signal, so that all horizontal and vertical electrode capacitance value of the size of the junctions can be obtained, i.e. the capacitance of the two-dimensional plane size of the entire touch screen. 2D capacitance change amount data based on the touch screen, it can calculate the coordinates of each touch point. Accordingly, the screen even if there is a plurality of touch points, the real coordinates of each touch point can be calculated.4.3 TFT display module
1) immunity to electromagnetic interference
Anti-electromagnetic interference is the most crucial factor of the capacitive touch screen system performance. Since 2007, that company began offering the program of self-capacitance capacitive touch screen technology, but poorly designed anti-electromagnetic interference often occurs when a call can not answer the phone, or the end of the call can not hang. Plus touch screen on the environmental changes frequent failure, resulting in a plurality of capacitive touch screen mobile phone project failure, even indirectly caused the collapse of the company of some programs. Learn from the modern field of wireless communications frequency hopping technology, while increasing the the TX transmit power, improve the signal-to-noise ratio of the system while effectively suppress electromagnetic interference.
2) The signal-to-noise ratio (SNR)
SNR is defined as the means of the received signal power and noise power ratio. SNR is a touch screen system performance is another key factor, which directly determines the level of touch precision, linearity and resolution performance is good or bad. Mainly through three ways to improve the SNR. The first is to improve the signal transmission power. Improves the signal transmission signal power corresponding to enhance the power of the received signal, thus increasing the SNR. Secondly, reducing the noise is also an effective method. Touch screen design, these programs have done a very good shielding design, to increase ground plane for example, rely on the LCD side of the bottom of the touch screen, the screen around the body to increase ground isolation. These measures can effectively reduce the noise power. There is a way to improve the amount of the change in capacitance caused by touch. Touch capacitive variation is proportional to the signal power. I.e., the the touch change amount is larger, the greater the power of the signal detected. Unique touchscreen patented technology, can greatly enhance the rate of change in capacitance caused by the touch, and usually more than 30%.16x4 lcd