Digital delay measurement
View Patent ↗Distance between two devices is determined by sending a digital signal from a first device to a second device, and receiving a repeated signal from the second device in the first device. The repeated signal includes the digital signal sent from the first device resent by the second device. A time difference between the sent digital signal and the received repeated signal is determined by providing both the sent digital signal and the received repeated signal to a logic gate, the output of the logic gate indicating whether the digital signal and the received repeated signal are at same or different states. The output of the logic gate is evaluated to determine an approximate distance between the first device and the second device.
1. An electronic device, comprising:
a communication module operable to send a digital signal to a second device remote from the electronic device and to receive a repeated signal from the second device, the repeated signal comprising the digital signal resent by the second device;
a processing module comprising a logic gate, the logic gate coupled to the communication module to receive the digital signal as sent to the second device and the repeated digital signal, the processing module operable to determine a time difference between the sent digital signal and the received repeated signal by indicating whether the digital signal and the received repeated signal are at same or different states, the output of the logic gate indicating an approximate distance between the first device and the second device;
a lowpass filter coupled to receive the output of the logic gate, the lowpass filter operable to average the output of the logic gate over time; and
an analog-to-digital converter coupled to an output of the lowpass filter, operable to provide a digital signal representing the approximate distance between the first device and the second device.
2. The electronic device of claim 1 , wherein the communication module further comprises a wireless RF transceiver, and the digital signal and received repeated digital signal comprise wireless radio frequency signals.
3. The electronic device of claim 1 , wherein the logic gate is an XOR or XNOR logic gate.
4. The electronic device of claim 1 , wherein the digital signal is encoded to have frequent state transitions.
5. The electronic device of claim 1 , further comprising a position determination module operable to determine a position of a mobile one of the first and second devices using a known location of the other of the first and second devices and the indicated approximate distance between the first device and the second device.
6. The electronic device of claim 1 , wherein the device comprises a cellular telephone.
7. The electronic device of claim 1 , wherein the device comprises a mesh network node.