Two-pass detection technique for non-echo pulsed ranging

摘要

A technique for non-echo pulsed ranging of a mobile device within an environment includes a plurality of emitters within the environment transmitting signal pulses of a predefined frequency to a mobile device that can receive a signal pulse, convert the signal pulse into a digital waveform, store the digital waveform into a buffer having a predetermined length of time, and analyze the digital waveform to detect a signal pulse at the predefined frequency. If a signal pulse is detected, the mobile device can re-analyze the digital waveform that was stored in the buffer to see if another signal pulse can be detected within the waveform, indicating the existence of a reflected signal. If another signal pulse is detected, the mobile device can select the signal pulse that was received first in time, i.e. the direct signal, for use in ranging of the mobile device.