HotKnot is a near-field communication technology (which is mainly used in a capacitive touch screen) used in some smart terminal devices. This near-field communication includes two processes: proximity detection process and data transmission process. The proximity detection process of the near-field communication is: a touch screen terminal of one party sends a proximity detection sequence (for example, the proximity detection sequence includes six frequencies), and after receiving the proximity detection sequence, a touch screen terminal of the other party successively scans the multiple frequencies included in the proximity detection sequence. If signal strength at each frequency is greater than a preset signal strength threshold, it is considered that a signal source exists at the frequency. After the scan is completed, if signal sources exist at all frequencies, it is determined that the sequence is valid; otherwise, it is determined that the sequence is invalid. After it is determined that the sequence is valid, the receiving party feeds back a proximity response sequence to the sending party. After receiving the proximity response sequence, the sending party successively performs scan similarly, and determines whether the response sequence is valid. The determining manner is described above. When the two parties both consider that the sequence is valid, it is considered that sequence identification succeeds once. After the sequence identification succeeds for multiple times according to an interaction rule, it is determined that a touch screen terminal approaches. After the proximity detection succeeds, an interference source is turned off, and the data transmission process is started to send or receive data. During the proximity detection, the interference source such as an LCD is not turned off, there is a relatively big difficulty to correctly determine a frequency of the sequence, and setting of a signal strength threshold plays a particularly important role in determining of a signal. Therefore, it appears to be particularly important to be capable of setting a proper signal strength threshold according to a noise situation.
During proximity detection of two HotKnot (which is a type of near-field communication and is mainly used in the capacitive touch screen) devices, a drive signal of LCD scan, or common-mode interference when a charger is connected interferes with signal detection of the capacitive touch screen, which may cause an error when the proximity detection is performed by using the touch screen, and a case in which the two parties cannot enter or one party enters by a mistake. Currently, to enable the capacitive touch screen to adapt to different LCD interference intensities, noise reduction processing is usually performed on detected data. After the noise reduction processing, a signal strength threshold determining policy is used. If signal strength is greater than the threshold, it is considered that a signal is valid; otherwise, it is considered that the signal is an invalid signal. In addition, for the foregoing interference cases, an interference frequency is detected by using an instrument, and then the interference frequency is not used as a determining basis, thereby avoiding an interference sources.
However, in a current processing manner, there are at least two problems: 1) Although some problems can be solved by using a proper signal strength threshold, when interference occurs at some frequencies, signal strength of noise is sometimes greater than strength of a signal, and the frequencies are very difficult to be identified, which finally results in failure of entire sequence identification; and in addition, interference intensity often changes, detection reliability and sensitivity are difficult to be ensured if only one fixed signal strength threshold is used. 2) Interference in an actual environment often changes; if some fixed frequencies are not identified, although a situation of interference at the fixed frequencies can be improved, when the interference at the frequencies changes, the changed interference frequencies cannot be shielded, that is, a compatibility problem exists. Therefore, in the case of weak signal or strong interference, reliability and sensitivity of proximity detection are not high.