Method for locating and positioning using broadcast fm signals and phase difference computation technique

An indoor and/or outdoor locating or positioning system utilizing three frequency modulation (FM) broadcast stations or locally installed FM stations, wherein three received FM 19 KHz sinusoidal pilot tones are used for TDOA (time difference of arrival) hyperbolic positioning, and wherein three receiver reference stations designated as a first reference station (Rc), a second reference station (Rd) and a reference base station (BS) are used to assist in locating a mobile unit (MU);

• wherein said BS is used as base station performing two-way communications with said Rc, Rd and MU to transmit and receive data in order to compute the position of said MU;
• and wherein said BS, Rc, Rd and MU are equipped with FM receivers and digital processors to perform three phase measurements of said three FM pilot tones, said three phase measurements are subtracted in specified identical order to obtain phase differences pair of said three pilot tones at said Rc, Rd, MU and BS, and wherein said phase differences pairs at said Rc, Rd and MU are transmitted to said BS for locating said MU.