Systems and methods for removing undesired signals in instrument landing systems

• US 20070069942A1
• Filed: 09/27/2005
• Published: 03/29/2007
• Est. Priority Date: 09/27/2005
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Hanneman, Charles
• Granted Patent: US 7,409,272 B2
• Time in Patent Office: Days
• US Class Current: 342/33
• CPC Class Codes: G01S 1/045 Receivers
• CPC Class Codes: G01S 1/14 using amplitude comparison of signals transmitted simultaneously from antennas or antenna systems having differently oriented overlapping directivity-characteristics

Abstract

A method of removing undesired signals in an aviation guidance system may include receiving at least one first desired signal having a first frequency of amplitude modulation, receiving at least one second desired signal having a second frequency of amplitude modulation, and receiving at least one undesired signal having any frequency including a frequency that is substantially the same as or a subharmonic of at least one of the first and second desired signals. The first and second frequencies of amplitude modulation are phase synchronous, and the undesired signals are non-synchronous with at least one of the first and second desired signals. The method may also include identifying the undesired signals and removing the undesired signals.

Claims

1. A method of removing undesired signals in an aviation guidance system, the method comprising:

receiving at least one first desired signal having a first frequency of amplitude modulation;

receiving at least one second desired signal having a second frequency of amplitude modulation, the first and second frequencies of amplitude modulation being phase synchronous;

receiving at least one undesired signal having any frequency including a frequency that is substantially the same as or a subharmonic of at least one of the first and second desired signals, the undesired signals being non-synchronous with at least one of the first and second desired signals;

identifying the undesired signals; and

removing the undesired signals.

2. The method of claim 1, wherein said identifying comprises:

comparing amplitude and phase of the first and second desired signals and the at least one undesired signal;

determining which of the desired and undesired signals are non-synchronous.

3. The method of claim 1, wherein said removing comprises signal processing.

4. The method of claim 3, wherein said signal processing comprises using at least one of an analog filter, a digital signal processor, and a Fast Fourier Transform.

5. The method of claim 1, wherein the first frequency of amplitude modulation is about 90 Hz and the second frequency of amplitude modulation is about 150 Hz.

6. The method of claim 1, wherein the first and second desired signals represent at least one of localizer information and glide slope information for an aircraft.

7. The method of claim 1, wherein the undesired signals include at least one of propeller modulation, rotor modulation, and multipath.

8. A recording medium having computer executable program code for performing the method of removing undesired signals in an aviation guidance system as claimed in claim 1.

9. An aviation guidance system, comprising:

at least one receiver configured to receive at least one first desired signal having a first frequency of amplitude modulation and at least one second desired signal having a second frequency modulation, the first and second frequencies of amplitude modulation being phase synchronous; and

a controller configured to identify and remove undesired signals received by the receiver, the undesired signals having any frequency including frequencies that are substantially the same as or subharmonics of at least one of the first and second desired signals, the undesired signals being non-synchronous with at least one of the first and second desired signals.

10. The system of claim 9, wherein the controller is configured to compare amplitude and phase of the first and second desired signals and the at least one undesired signal and determine which of the desired and undesired signals are non-synchronous.

11. The system of claim 9;

wherein the controller comprises a signal processor, and the receiver comprises a first receiver configured to receive signals representing localizer information for an aircraft and a second receiver configured to receive signals representing glide slope information for an aircraft.

12. The system of claim 11, wherein said signal processer comprises at least one of an analog filter, a digital signal processor, and a Fast Fourier Transform.

13. The system of claim 9, wherein the first desired frequency of amplitude modulation is about 90 Hz and the second desired frequency of amplitude modulation is about 150 Hz.

14. The system of claim 9, wherein the first and second desired signals represent at least one of localizer information and glide slope information for an aircraft.

15. The system of claim 9, wherein the undesired signals include at least one of propeller modulation, rotor modulation, and multipath.

16. A method of minimizing localizer and glideslope errors in an aviation guidance system, the method comprising:

receiving at least one first desired signal having a first frequency of amplitude modulation;

receiving at least one second desired signal having a second frequency of amplitude modulation, the first and second desired signals representing at least one of localizer information and glide slope information for an aircraft, the first and second frequencies of amplitude modulation being phase synchronous;

receiving undesired signals having any frequency including frequencies that are substantially the same as or subharmonics of at least one of the first and second desired signals, the undesired signals being non-synchronous with at least one of the first and second desired signals, the undesired signals including one of propeller modulation, rotor modulation, and multipath;

comparing amplitude and phase of the first and second desired signals and the at least one undesired signal;

determining which of the desired and undesired signals are non-synchronous; and

removing the undesired signals.

17. The method of claim 16, wherein said removing comprises signal processing.

18. The method of claim 17, wherein said signal processing comprises using at least one of an analog filter, a digital signal processor, and a Fast Fourier Transform.

19. The method of claim 16, wherein the first frequency of amplitude modulation is about 90 Hz and the second frequency of amplitude modulation is about 150 Hz.

20. A recording medium having computer executable program code for performing the method of removing undesired signals in an aviation guidance system as claimed in claim 16.