Patent ID: 8750076

Claim:
A position detection system, comprising: a moving body including a transmission unit which sends an ultrasonic signal modulated based on a pseudo random signal whose self-correlativity is high; and a reception unit which receives said ultrasonic signal, generates a model waveform of ultrasonic modulated by the same pseudo random signal as said pseudo random signal, obtains a value of correlation with the received ultrasonic signal, and starting with the smallest one of subsidiary peaks of a correlation value appearing when the ultrasonic signal coincides in part with the model waveform, selects a plurality of pseudo random signals corresponding to said subsidiary peaks, wherein said transmission unit comprises a unit which simultaneously sends an electromagnetic wave signal and an ultrasonic signal modulated based on one of said pseudo random signals selected, and said reception unit comprises a unit which executes processing of correlation between the ultrasonic signal and a model waveform modulated by said pseudo random signal to specify an arrival time of said ultrasonic signal and calculates a propagation time of ultrasonic signal from an arrival time point of said electromagnetic wave signal and the specified arrival time, and a unit which calculates a position of said moving body based on said ultrasonic propagation time calculated and a length of interval between the ultrasonic reception units, and wherein said transmission unit uses a pseudo random signal differing in each transmission cycle, wherein said pseudo random signal is an M sequence, wherein said transmission unit sends out an ultrasonic signal modulated by M sequence data generated based on data defining an arbitrary M sequence selected from among a plurality of M sequences different from each other and an electromagnetic wave signal including data defining said M sequence.