Storage medium location detection system and program

A storage medium location detection system comprising:

• an antenna;
• a storage medium-compatible communications unit that communicates through the antenna with a storage medium by wireless using electromagnetic waves at a predetermined frequency;
• a phase detection unit that detects phases of signals received from the storage medium;
• and
• a controller that is configured to function as a parameter acquisition part and a location detection part, wherein
• the parameter acquisition part configured to acquire a distance detection parameter, the distance detection parameter being a predetermined value set in accordance with a positional relationship between a first position of the antenna and a second position of the antenna that is different from the first position, each of the first position and the second position being a position of the antenna in a range of positions of the antenna, and a distance from the first position to the storage medium being shortest;
• and
• the location detection part configured to detect a storage medium distance from the first position to the storage medium, the location detection part using a first phase detected by the phase detection unit at the first position, a second phase detected by the phase detection unit at the second position, and the distance detection parameter acquired by the parameter acquisition part,
• wherein the location detection part identifies the first position at a time at which a trend of changes of phase detected by the phase detection unit in association with movement of the antenna reverses.