Hi Nima Badizadegan,
Be careful with arbitrary increases in the electrode size. Larger electrodes easily detect the presence and absence of a finger. However, in some cases, they can be more sensitive to electrical noise or undesirable surrounding objects. Moreover, increased electrode size might also overlap with the detection areas corresponding to the surrounding electrodes, resulting in erroneous detections. It is important to keep a functional clearance between different electrodes. Functional clearance is the distance between the electrodes needed to avoid one finger touch affecting more than one electrode at a time. Functional clearance helps to avoid false touch detections caused by the physical proximity of keys.
As a recommended lecture, I would like to recommend you to take a look at the application note AN3863.
One of the things this document describes is the recommended patterns to distinguish valid touches where key size and distance between two keys are restricted.
Have a great day,
Jose Reyes
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