Systems and methods for removing undesired signals in instrument landing systems

• US 7,409,272 B2
• Filed: 09/27/2005
• Issued: 08/05/2008
• Est. Priority Date: 09/27/2005
• Status: Expired due to Fees

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Hanneman, Charles K.
• Primary Examiner(s): Black; Thomas G.
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US11/235,199
• Publication Number:
  US 20070069942A1
• Time in Patent Office: 1,043 Days
• Field of Search: None
• US Class Current: 701/17
• 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, comprising:

receiving a localizer signal having a first phase;

receiving a glide slope signal having the first phase;

receiving an undesired signal having a second phase non-phase synchronous with the first phase of the localizer and glide slope signals;

comparing a phase relationship between the localizer and glide slope signals, and the undesired signal to identify the undesired signal; and

removing the undesired signal.

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

3. The method of claim 2, wherein said signal processing comprises using at least one of an analog filter, a digital signal processor, and a Fast Fourier Transform.

4. The method of claim 1, wherein the localizer and glide slope signals each include navigation tones having a first frequency of about 90 Hz and a second frequency of about 150 Hz.

5. 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.

6. The method of claim 1, wherein the undesired signal includes at least one of propeller modulation, rotor modulation, and multipath.

7. 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.

8. The method of claim 1, further including:

determining whether an aircraft receiver is continuing to be tuned to an instrument landing system (ILS) frequency.

9. An aviation guidance system, comprising:

a receiver configured to receive a localizer signal having a first phase, a glide slope signal having the first phase, and an undesired signal having a second phase non-synchronous with the first phase of the localizer and glide slope signals; and

a controller configured to compare a phase relationship between the localizer and glide slope signals, and the undesired signal to identify the undesired signal, and remove the undesired signal.

10. The system of claim 9, wherein the controller comprises a signal processor, and the receiver comprises a first receiver configured to receive the localizer signal and a second receiver configured to receive the glide slope signal.

11. The system of claim 10, wherein said signal processer comprises at least one of an analog filter, a digital signal processor, and a Fast Fourier Transform.

12. The system of claim 9, wherein the localizer and glide slope signals each include navigation tones having a first frequency of about 90 Hz and a second frequency of about 150 Hz.

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

14. The system of claim 9, wherein the undesired signal includes at least one of propeller modulation, rotor modulation, and multipath.

15. The system of claim 9, wherein the controller determines whether an aircraft receiver is continuing to be tuned to an instrument landing system (ILS) frequency.

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

receiving a localizer signal representative of localizer information for an aircraft, the localizer signal having a first phase;

receiving a glide slope signal representative of glide slope information for an aircraft, the glide slope signal having the first phase;

receiving an undesired signal having a second phase non-phase synchronous with the first phase of the localizer and glide slope signals, the undesired signal including propeller modulation, rotor modulation, or multipath;

comparing a phase relationship between the localizer and glide slope signals, and the undesired signal for a referenced glide path angle to identify the undesired signal; and

removing the undesired signal.

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 localizer and glide slope signals each include navigation tones having a first frequency of about 90 Hz and a second frequency of 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.