Patent ID: 7752010

Claim:
A distance measuring apparatus measuring a distance between a first wireless communication device and a second wireless communication device communicating with each other, the apparatus comprising: a reference pulse generator including a first programmable clock generation unit generating a clock of a first frequency and a first duty ratio control unit generating a reference pulse by adjusting a duty ratio of the clock of the first frequency, and outputting the reference pulse at a point in time that the first wireless communication device transmits a distance measuring signal to the second wireless communication device; a delay pulse generator including a second programmable clock generation unit generating a clock of a second frequency different from the first frequency and a second duty ratio control unit generating a delay pulse by adjusting a duty ratio of the clock of the second frequency, and generating the delay pulse at a point in time that the first wireless communication device receives a response signal transmitted from the second wireless communication device in response to the distance measuring signal; an overlap detector detecting a point in time that the reference pulse overlaps the delay pulse; a counter counting one of the reference pulse and the delay pulse to the overlap point in time; and a distance calculator calculating an amount of time from a point in time of receiving the distance measuring signal to a point in time of receiving the response signal by applying the first frequency, the second frequency, and a count value of the counter, and calculating the distance between the first wireless communication device and the second wireless communication device by using the amount of time.