Accurate distance measurement using RF techniques

A wireless communication device, comprising:

• a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency ft0;
• 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, wherein the frequencies of the sequence of carriers of the second RF signal are different from ft0;
• a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the frequencies of the corresponding 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 carriers of the third RF signal to generate a corresponding 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 phase offsets relative to the frequencies of the sequence of carriers of the second RF signal.

A half-duplex wireless communication device, comprising:

• a synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers fn, where n is a plurality of integers;
• a transmitter for transmitting the first RF signal during a first time slot An;
• a receiver for receiving a second RF signal, during a second time slot Bn, from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers fn corresponding to the carriers of the first RF signal, wherein the sequence of carriers of the first RF signal are the same as the sequence of carriers of the second RF signal, and wherein the first and second time slots altenatingly repeat as n changes;
• a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the first RF signal to generate a corresponding 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 phase offsets relative to the frequencies of the sequence of carriers of the second RF signal.

A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:

• generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;
• transmitting the first RF signal;
• receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;
• 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 first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;
• 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 to generate a sequence of phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.

A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:

• generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency ft0;
• transmitting the first RF signal;
• receiving a second RF signal from a remote wireless device phase locked with the remote wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the corresponding sequence of carriers of the second RF signal are different from ft0;
• generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the corresponding sequence of carriers of the third RF signal;
• 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 to generate a sequence of phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal. wherein the distance between the wireless communication device and the remote wireless device is proportional to the slope.

The computer readable medium of clam 41, further comprising instructions for:

• mixing the received second RF signal with the third RF signal to produce In-phase (I) and Quadrature (Q) signals,
• solving for phase angle Θ by applying the following relationship:
• Θ=Arctan(Q/I)/2, and
• generating the phase offsets based on the phase angle Θ.

A computer readable medium containing program instructions for controlling a half-duplex wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:

• generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers fn, where n is a plurality of integers;
• transmitting the first RF signal during a first time slot An;
• receiving a second RF signal, during a second time slot Bn, from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers fn corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are the same as the frequencies of the sequence of carriers of the second RF signal, and wherein the first and second time slots alternatingly repeat as n changes;
• comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the first RF signal to generate a corresponding sequence of phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal to determine the distance between the wireless communication device and the remote wireless device.

A method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of:

• generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;
• transmitting the first RF signal;
• receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;
• 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 first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;
• 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 to generate a sequence of phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.

A method of determining distance between a wireless communication device and a remote wireless device, comprising the steps of:

• generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency ft0;
• transmitting the first RF signal;
• receiving a second RF signal from a remote wireless device phase locked with the remote wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the corresponding sequence of carriers of the second RF signal are different from ft0;
• generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the corresponding sequence of carriers of the third RF signal;
• 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 to generate a sequence of phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal. wherein the distance between the wireless communication device and the remote wireless device is proportional to the slope.

A method of determining the distance between a wireless communication device and a remote wireless device using half-duplex communication, the method comprising the steps of:

• generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers fn, where n is a plurality of integers;
• transmitting the first RF signal during a first time slot An;
• receiving a second RF signal, during a second time slot Bn, from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers fn corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are the same as the frequencies of the sequence of carriers of the second RF signal, and wherein the first and second time slots alternatingly repeat as n changes;
• comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the first RF signal to generate a corresponding sequence of phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal to determine the distance between the wireless communication device and the remote wireless device.

A method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of:

• generating a first signal;
• transmitting the first signal;
• receiving a second signal from the remote wireless device, the second signal including multiple carriers at different frequencies, wherein each of the multiple carriers are phase coherent with the first signal;
• performing a phase comparison using phase information of the first signal and the received second signal to generate multiple phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the multiple carriers of the second signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.

A wireless communication device, comprising:

• a synthesizer for generating a first signal;
• a transmitter for transmitting the first signal;
• a receiver for receiving a second signal from a remote wireless device, the second signal including multiple carriers having different frequencies;
• a phase comparator for performing a phase comparison using phase information of the first signal and the received second signal to generate multiple phase offsets;
• and
• a processor for calculating an estimated slope of the phase offsets relative to the frequencies of the multiple carriers of the second signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.

A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:

• controlling a first synthesizer that generates a first signal;
• controlling a transmitter that transmits the first signal;
• controlling a receiver that receives a second signal from the remote wireless device, the second signal including multiple carriers at different frequencies, wherein each of the multiple carriers of the second signal are phase coherent with the first signal;
• controlling a phase comparator that performs a phase comparison using phase information of the first signal and the received second signal to generate multiple phase offsets;
• and
• calculating an estimated slope of the phase offsets relative to the frequencies of the multiple carriers of the second signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device.