Patent ID: 8659477

Claim:
A base station apparatus in a radio distance measuring system that uses a reader ID and a tag ID, the base station apparatus comprising: a pulse generation section configured to generate a unique word containing P pulses, each of which is on/off modulated according to whether each of P bits representing the reader ID is 1 or 0, generates a frame containing 2×M unique words, configured to generate a burst containing Q frames, and configured to output a transmission signal containing a plurality of bursts; and a receiving section configured to perform sampling reception of a signal resulting from modulation of the transmission signal by the radio terminal based on whether each of Q bits representing the tag ID is 1 or 0 at timings with a phase difference of 1/M (where M is an integer not smaller than 1) of a transmission clock period, the transmission clock period being a time period of a length which is the same as a width of each one of the pulses, wherein: the reader ID is represented by a code string composed of P bits (where P is a natural number) for identifying a base station apparatus, and the tag ID is represented by a code string composed of Q bits (where Q is a natural number) for identifying a radio terminal and detecting a first traveling wave from a tag by means of correlation calculation.