Patent ID: 8073465

Claim:
A positioning system, comprising: a node which transmits a first transmission signal; a reference station which transmits a second transmission signal after receiving the first transmission signal transmitted by the node; a plurality of access points each of which includes; a reception unit which receives the first transmission signal and the second transmission signal; an A/D conversion unit which includes an A/D converter for converting the first transmission signal and the second transmission signal from an analog form to a digital form and a sampling clock generator unit for generating sampling clocks determining timings at which the A/D converter performs analog-to-digital conversion; a sampling timing control unit which outputs control signals for shifting a phase of the sampling clocks; a synchronization trap unit which matches phases of the first transmission signal and the second transmission signal with the phase of the sampling clocks by using the control signals; a synchronization tracking unit which adjusts the phase of the sampling clocks to maintain synchronization of the first transmission signal and the second transmission signal; a time difference measurement unit which counts respective numbers of the sampling clocks and the control signals, and measures a reception time difference between the first transmission signal and the second transmission signal using the counted numbers of the sampling clocks and the control signals; and a frequency deviation measuring unit which counts respective numbers of the sampling clocks and the control signals, and measures a frequency deviation of a clock between a transmitter and the access point using the counted numbers of the sampling clocks and the control signals; a server which calculates the position of the node using the reception time difference corrected based on the frequency deviation.