SYSTEM AND METHOD FOR DETERMINING ABSOLUTE POSITION USING A MULTIPLE WAVELENGTH SIGNAL

• US 20100158331A1
• Filed: 08/22/2007
• Published: 06/24/2010
• Est. Priority Date: 08/22/2006
• Status: Abandoned Application

• Current Assignee: Guohua Min, Hugh C. Lauer, James P. Jacobs
• Original Assignee: Guohua Min, Hugh C. Lauer, James P. Jacobs
• Inventors: Lauer, Hugh C., Min, Guohua, Jacobs, James P.
• Application Number:
  US12/438,052
• Publication Number:
  US 20100158331A1
• Time in Patent Office: Days
• US Class Current: 382/128
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/3975 active
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00

Abstract

Various aspects of the present invention are shown and described, each of which has stand alone utility in a navigated medical environment. A receiver position calibration system and method facilitates calibration of a reference frame prior to each navigated procedure. A concept and application of confidence weights is introduced. Confidence weights can be applied to distance calculations to mitigate the effects of interference and increase the tolerance of the navigated medical system. Multi-path interference is minimized through the transmission of a signal having a pattern of unique frequencies and filtering of the distance calculations for each frequency to identify the ‘best’ distance in the presence of multi-path interference. A position determination method and system that transmits a signal having multiple frequency components permits positions to be identified with high resolution over a large area.

Claims

1. A method for determining a position of an object with high resolution over a large area includes the steps of:

transmitting a signal between the object and an antenna, the signal having a long wavelength component and a short wavelength component;

deriving coarse distance information from the long wavelength component of the signal and deriving fine distance information from the short wavelength component of the signal; and

determining the position of the object using the coarse distance information and fine distance information.

2. The method of claim 1 further including the steps of:

receiving the signal, the received signal comprising a received long wavelength component and a received short wavelength component;

deriving the fine distance information using a first phase difference between a short wavelength component of a reference signal and the received short wavelength component; and

deriving the coarse distance information using a second phase difference between a long wavelength component of the reference signal and the received long wavelength component.

3. The method of claim 1 wherein the signal is transmitted by a transmitter coupled to the object and received by the antenna.

4. The method of claim 1 wherein the signal is transmitted by the antenna and received by the object.

5. A method for determining a position of an object with high resolution over a large area includes the steps of:

transmitting a signal between the object and an antenna, the signal comprising two components differing in frequency by a desired amount;

determining a coarse distance between the object and the antenna in response to a difference between the two components of the signal and a fine distance between the object and the antenna using at least one of the two components of the signal; and

determining a position of the object in response to the coarse distance and the fine distance.

6. The method of claim 5 further including the steps of:

determining the coarse distance between the object and the antenna by comparing a phase difference between the two components with a phase of a first reference signal; and

determining the fine distance between the object and the antenna by comparing a phase of at least one of the two components of the signal to a phase of a second reference signal.

7. The method of claim 5 wherein the two components have a fixed phase relationship with each other.

8. The method of claim 5 in which a beat signal is derived by subtracting the two components of the signal and in which the coarse difference is determined from the phase angle of the beat signal.

9. The method of claim 8 further including the steps of:

receiving the signal, the received signal comprising two received signal components;

deriving the fine distance in response to a first phase difference between at least one of the received signal components and a corresponding component of a reference signal associated with the signal;

mixing the two received components to provide a virtual beat signal;

deriving the coarse distance in response to a second phase difference between the beat signal and the virtual beat signal.

10. A system for determining a position of an object with high resolution over a large area comprising:

transmit circuitry for generating a signal for transmission between the object and an antenna, the signal having a long wavelength component and a short wavelength component;

a computer readable medium having program code stored thereon, the program code operable when executed by a processor of the system to;

derive coarse distance information from the long wavelength component of the signal and deriving fine distance information from the short wavelength component of the signal; and

determine the position of the object using the coarse distance information and fine distance information.

11. The system of claim 10 further comprising:

receiver circuitry for receiving the signal, the received signal comprising a received long wavelength component and a received short wavelength component;

a first phase discriminator for determining a first phase difference between a short wavelength component of a reference signal and the received short wavelength component;

a second phase discriminator for determining a second phase difference between a long wavelength component of the reference signal and the received long wavelength component; and

wherein the program code includes logic for deriving the fine distance information using the first phase difference and deriving the coarse distance information using the second phase difference.

23. The system of claim 10, 12 or 17 wherein the system is a navigated medical system.

12. A system for determining a position of an object with high resolution over a large area comprising:

a transmitter for transmitting a signal between the object and an antenna, the signal comprising two components differing in frequency by a desired amount;

program code stored on a computer readable medium of the system and operable when executed by a processor of the system to;

determine a coarse distance between the object and the antenna in response to a difference between the two components of the signal and a fine distance between the object and the antenna using at least one of the two components of the signal; and

determine a position of the object in response to the coarse distance and the fine distance.

13. The system of claim 12 wherein the two components have a fixed phase relationship with each other.

14. The system of claim 12 including:

a first phase discriminator for determining a first phase angle of a first of the two signal components;

a second phase discriminator for determining a second phase angle of a second of the two signal components; and

wherein the program code is further operable to determine the coarse distance as the difference between the first phase angle and the second phase angle.

15. The system of claim 12 including:

a mixer for generating a beat signal is derived by subtracting the two components of the signal;

a phase discriminator for determining a phase angle of the beat signal; and

wherein the program code is further operable to determine the coarse distance from the phase angle of the beat signal.

16. The system of claim 15 further comprising:

a receiver comprising at least two filters for receiving the signal and extracting two received signal components;

a first phase discriminator for detecting a first phase difference between at least one of the received signal components and a corresponding component of a reference signal associated with the signal;

a mixer for mixing the two received components to provide a virtual beat signal;

a second phase discriminator for detecting a second phase difference between the beat signal and the virtual beat signal; and

wherein the program code is further operable when executed to determine the fine distance information in response to the first phase difference and the coarse distance information in response to the second phase difference.

17. A system for determining a position of an object with high resolution over a large area comprising:

a first signal generator for generating a first signal;

a second signal generator for generating a second signal, the second signal having a frequency relatively higher than the first frequency;

means for determining a position of the object relative to an antenna including means for deriving coarse distance information associated with the antenna and the object and fine distance information associated with the antenna and the object using the first and second signals.

18. The system of claim 17, further comprising:

means, coupled to the first signal generator and the second signal generator, for generating a signal having two signal components that differ in frequency by a desired amount; and

wherein the coarse distance information is determined by subtracting phases of the two signal components.

19. The system of claim 17 wherein the first signal has a long wavelength component and the second signal has a short wavelength component wherein the means for determining a position further includes:

a mixer for mixing the first signal and the second signal to provide a mixed signal;

a transmitter for transmitting the mixed signal between the object and the antenna;

a filter for filtering the mixed signal to extract a received long wavelength component and a received short length component;

a first phase discriminator for determining a first phase offset between a long wavelength component of a first reference signal associated with the first signal and the received long wavelength;

a second phase discriminator for determining a second phase offset between a short wavelength component of a second reference signal associated with the second signal and the received short wavelength component; and

wherein the first phase offset provides coarse distance information and the second phase offset provides fine distance information.

20. The system of claim 17 wherein the means for determining the position further includes:

a first mixer for mixing the first and second signals to provide a mixed signal;

a filter for filtering the mixed signal to extract a transmission signal comprising two transmission signal components, wherein the two transmission signal components are in fixed phase relationship with each other;

a transmitter for transmitting the transmission signal between the object and the antenna;

a filter for filtering the transmission signal to extract a received signal comprising two received signal components; and

a first phase discriminator for determining a first phase difference between a reference signal associated with at least one transmission signal component and a corresponding received signal component to provide a first phase difference, wherein the fine distance information is related to the first phase difference.

21. The system of claim 20 further comprising:

a second mixer for mixing the two transmission signal components to provide a reference beat signal;

a third mixer for mixing the two received signal components to derive a virtual beat signal; and

a second phase discriminator for determining a second phase difference between the reference beat signal and the virtual beat signal, wherein the coarse distance information is related to the second phase difference.

22. The system of claim 20 further comprising:

a second phase discriminator for subtracting the phases of the received signal components to determine the coarse distance information.