Detection device and detection method

A detection device for communicating with an external device, comprising:

• a smart antenna, wherein the smart antenna is capable of switching between a plurality of antenna modes;
• a storage device;
• and
• a processor;
• wherein in each of the antenna modes, the smart antenna transmits a test datum and receives a feedback datum according to the test datum, the processor performs a time reversal algorithm to the feedback datum so as to obtain a time reversal datum, the processor calculates an indicator according to the feedback datum and the time reversal datum, and the storage device stores the feedback datum, the time reversal datum, and the indicator;
• wherein the processor compares all of the indicators with each other and controls the smart antenna to select a final mode of the antenna modes according to a comparison between all of the indicators;
• wherein the final mode corresponds to an average of all of the indicators or a minimum of all of the indicators.