Object tracker

• US 20080071495A1
• Filed: 07/02/2007
• Published: 03/20/2008
• Est. Priority Date: 09/15/2006
• Status: Active Grant

• Current Assignee: VLSI Solution Oy
• Original Assignee: VLSI Solution Oy
• Inventors: Kiiskila, Sami, Ritoniemi, Tapani, Liitola, Toni
• Granted Patent: US 7,672,809 B2
• Time in Patent Office: Days
• US Class Current: 702/150
• CPC Class Codes: G01S 3/808 using transducers spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 5/186 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

Object tracking using ultrasonic signals. A receiver receives a signal transmitted from a transmitter. The receiver uses at least two receiving elements for forming at least two analysis signals on the basis of the received signal. The receiver includes a detector, such as a phase detector, which examines the analysis signals and forms an indication on a difference between the analysis signals. The indication is, for example, indicative of a phase difference between the analysis signals. The transmitted signal is a modulated ultrasonic signal, wherein the receiver demodulates the signal to recover the modulating signal. The indication can be used to determine a heading angle information of the object to be tracked. The heading angle information may be a direction of the object with respect to the transmitter. The heading angle information can be used to make e.g. a corrective action to audio signals to be formed for listening.

Claims

1. A receiver for receiving a modulated signal from a transmitter to form an analysis signal on the basis of the received signal;

the receiver comprising;

a first receiving element for receiving the modulated signal from a transmitter to form a first analysis signal on the basis of the received signal;

a second receiving element for receiving the modulated signal from the transmitter to form a second analysis signal on the basis of the received signal;

a detector for providing an indication on the basis of a difference between said first and second analysis signals; and

an analysing element for analysing said indication to determine the heading angle of an object.

2. The receiver according to claim 1, wherein said analysing element comprises

a first scaling element,

a second scaling element,

an input for inputting said indication, and

a control element to adjust scaling parameters of the first scaling element and a second scaling element.

3. The receiver according to claim 2, wherein said analysing element further comprises

a memory for storing one or more estimates of the heading angle of the object, wherein said analysing element is adapted to use said indication and at least one of said one or more estimates in determining a reliability of the indication.

4. The receiver according to claim 1, wherein

said first receiving element comprises a first detector for demodulating the received signal to form said first analysis signal;

and

said second receiving element comprises a second detector for demodulating the received signal to form said second analysis signal.

5. The receiver according to claim 1, further comprising

a phase detector adapted to produce a signal indicative of phase differences between the first analysis signal and the second analysis signal.

6. An object tracking device comprising:

a first receiving element for receiving a modulated signal from a transmitter to form a first analysis signal on the basis of the received signal;

a second receiving element for receiving the modulated signal from the transmitter to form a second analysis signal on the basis of the received signal;

a detector for providing an indication on the basis of a difference between said first and second analysis signals; and

an analysing element for analysing said indication to determine the heading angle of the object.

7. A system comprising:

a transmitter for transmitting a modulated signal;

a receiver for receiving the modulated signal transmitted from the transmitter to form an analysis signal on the basis of the received signal; and

an analysing element for analysing said first and second analysis signals to determine the heading angle of an object,

wherein said receiver comprises;

a first receiving element for receiving the modulated signal from a transmitter to form a first analysis signal on the basis of the received signal;

a second receiving element for receiving the modulated signal from the transmitter to form a second analysis signal on the basis of the received signal; and

a detector for providing an indication on the basis of a difference between said first and second analysis signals;

and wherein said analysing element is configured to use said indication in the analysis to determine the heading angle of the object.

8. The system according to claim 7, wherein said analysing element comprises

a first scaling element,

a second scaling element,

an input for inputting said indication, and

a control element to adjust scaling parameters of the first scaling element and a second scaling element.

9. The system according to claim 8, wherein said analysing element further comprises

a memory for storing one or more estimates of the heading angle of the object, wherein said analysing element is adapted to use said indication and at least one of said one or more estimates in determining a reliability of the indication.

10. The system according to claim 7, wherein

said first receiving element comprises a first detector for demodulating the received signal to form said first analysis signal;

and

said second receiving element comprises a second detector for demodulating the received signal to form said second analysis signal.

11. The system according to claim 7, further comprising

a phase detector adapted to produce a signal indicative of phase differences between the first analysis signal and the second analysis signal.

12. The system according to claim 7, wherein said modulated signal comprises a carrier wave having a first frequency, said carrier wave having been modulated by a modulating signal having a second frequency.

13. The system according to claim 12, wherein said second frequency is more than one decade lower that said first frequency.

14. The system according to claim 13, wherein said first frequency is within a range of 30-50 kHz, and said second frequency is within the a range of 800-1000 Hz.

15. The system according to claim 7, further comprising

a second transmitter for transmitting a second modulated signal, wherein said receiver is further configured to receive said second modulated signal.

16. The system according to claim 7, further comprising a second receiver configured to receive said modulated signal and to determine a heading angle of another object.

17. A method for tracking an object comprising:

transmitting a modulated signal from a transmitter;

receiving said modulated signal;

forming a first analysis signal on the basis of the received signal;

forming a second analysis signal on the basis of the received signal;

examining said first and second analysis signals to provide an indication on the basis of a difference between said first and second analysis signals; and

analysing said indication to determine the heading angle of the object.

18. The method according to claim 17, wherein said analysing comprises

forming a first scaling parameter;

forming a second scaling parameter;

forming a rough estimate on the basis of said indication on the phase difference;

comparing said rough estimate to one or more previous estimates to determine the reliability of said indication; and

adjusting said first scaling parameter and said second scaling parameter on the basis of the first scaling element and a second scaling element, if said comparing indicates that said indication is reliable.

19. The method according to claim 18 further comprising

storing said indication as a current indication of the heading angle, if said indication was determined reliable.

20. The method according to claim 17, wherein said examining comprises

forming a signal indicative of a phase difference between the first analysis signal and the second analysis signal;

and using said signal as said indication.

21. The method according to claim 17, wherein said transmitting comprises

modulating a carrier wave having a first frequency by a modulating signal having a second frequency.