1. Field of the Invention
The invention generally relates to an electrical circuit and a signal processing method, in particular, to a touch sensing circuit and a signal demodulating method.
2. Description of Related Art
As the technology of touch panel develops, touch panels become widely used as the screens of electronic devices, such as mobile phones, laptop computers, and tablet computers. Touch panels allow the user to input or operate the electronic devices more conveniently and make the interface more user-friendly and convenient.
Generally speaking, the electrode structure of a capacitive touch panel includes multiple scanning electrodes and multiple sensing electrodes. In terms of actual application, the scanning electrodes are used to receive the driving signals inputted by a panel controller/driver, so as to drive the touch panel to sense the touch of the user. The sensing electrodes are used to generate touch sensing signals corresponding to the user's touch. In the conventional technology, AFE (analog front-end) hardware modules are used as interface sensors of many kinds to digital systems, providing hardware modularity. For touch sensing circuits, AFE circuits are also configured to compensate the touch sensing signals by using a compensation capacitor. However, the compensation capacitor may occupy large circuit area, so as to increase manufacturing costs. In addition, the touch sensing circuit demodulates the touch sensing signals with a sine wave signal. Accordingly, a high-bit multiplier for signal demodulation is necessary, thereby increasing the complexity of the touch sensing circuit, and reducing circuit performance.
Hence, how to design a touch sensing circuit that has simplified circuit structure and satisfactory circuit performance without increasing the manufacturing costs is one of the most important topics in the pertinent field.