Ultrasonic locationing system using a dual phase pulse

An ultrasonic locationing system using a dual phase pulse, comprising:

• an emitter operable to emit two consecutive frequency bursts, each having a different phase, within one ultrasonic pulse;
• a receiver with at least one microphone operable to receive the ultrasonic pulse;
• a processor operable to run an amplitude-based detection algorithm on the pulse for a band of frequencies of interest, and detect a first burst of the pulse within the proper frequency band and having an amplitude exceeding a threshold, whereupon the processor is further operable to determine a relative phase difference between the first burst and a second burst of the pulse, wherein a relative phase difference within a predetermined acceptance window indicates that the pulse is valid for use in locationing the receiver;
• and
• a position history where previously stored receiver locations are stored by the processor,
• wherein the processor is further operable to calculate a motion vector of the receiver from the position history, calculate a Doppler frequency and in turn the expected phase shift due to the motion vector, given the frequency of the frequency burst, and adjust the acceptance window by the expected phase shift, Z.