Patent ID: 6859761

Claim:
A wireless communication device, comprising: a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers; a transmitter for transmitting the first RF signal; a receiver for receiving a second RF signal from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the corresponding sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal; a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase of the first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signals are the same as the frequencies of the sequence of carriers of the third RF signal; a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal and generating a sequence of phase offsets; and a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the sequence of phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the phase detector generates the phase offsets by producing In-phase (I) and Quadrature (Q) signals by mixing the received second RF signal with the third RF signal, and wherein the processor solves for phase angle Θ by applying the following relationship: Θ=Arctan(Q/I)/2.