US4390949A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic system and method for self-calibration of instrument landing systems
Assignee: Boeing North American Inc
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Filing: 1981-05-26
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Granted: 1983-06-28
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Expires: 2001-05-26
Abstract
Abstract A method for calibrating and correcting circuit errors induced in an aircraft ILS receiving system is disclosed herein. The spectral components of the input signal are processed through bandpass filters and then rectified and integrated in order to produce an output signal representative of the deviation from the desired centerline course. First and second test signals are generated corresponding to first and second known positions. These test signals are sequentially processed in the same manner as the operational input signals in order to develop first and second position errors which represent distortion and circuit induced errors within the processing system. A corrective function is then derived for a range of operational input signals by interpolating from the first and second position errors. All subsequently processed signals are adjusted by applying the corrective function. In this manner, the various distortions that are introduced through the processing system will be measured and then subtracted from the output signals in order to define a corrected representation of deviation from the desired centerline course. Sampling periods are utilized which contain an integer multiple of cycles of each of the major frequencies present in the operational input signal.
Inventors
- 👤 Harley W. Beningfield
- 👤 Donna F. Wilt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:04
CPC Classifications
G; G05; G05D; G05D1/00; G05D1/04; G05D1/06; G05D1/0607; G05D1/0653; G05D1/0676; G01; G01S; G01S1/00; G01S1/02; G01S1/022; G01S1/026
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
225 words
A method for correcting circuit induced errors in a navigation system of the type in which an operational input signal, having discrete spectral components each of known frequency and varying amplitude, is processed through frequency selective circuits in order to produce an output signal representative of deviation from a desired position, said method comprising the steps of: A. generating a first test signal representative of a known first position, said first test signal including a plurality of spectral components having frequencies generally corresponding to those of the operational input signal and having known amplitudes; B. processing said first test signal through the frequency selective circuits in order to derive a first position error corresponding to said known first position; C. changing the amplitude of said spectral components of said first test signal so as to produce a second test signal representative of a second known position; D. processing said second test signal through the frequency selective circuits in order to derive a second position error corresponding to said known second position; E. deriving an error corrective function, effective over a range of operational input signals, from said first and second position errors; and F. modifying the output signal from the frequency selective circuits with said error correction function for all subsequently processed operational input signals so as to correct for position errors introduced by processing.
Claim 2
Independent Claim
225 words
A method for correcting circuit induced errors in a navigation system of the type in which an operational input signal, having discrete spectral components each of known frequency and varying amplitude, is processed through frequency selective circuits in order to produce an output signal representative of deviation from a desired position, said method comprising the steps of: A. generating a first test signal representative of a known first position, said first test signal including a plurality of spectral components having frequencies generally corresponding to those of the operational input signal and having known amplitudes; B. processing said first test signal through the frequency selective circuits in order to derive a first position error corresponding to said known first position; C. changing the amplitude of said spectral components of said first test signal so as to produce a second test signal representative of a second known position; D. processing said second test signal through the frequency selective circuits in order to derive a second position error corresponding to said known second position; E. deriving an error corrective function, effective over a range of operational input signals, from said first and second position errors; and F. modifying the output signal from the frequency selective circuits with said error correction function for all subsequently processed operational input signals so as to correct for position errors introduced by processing.
Claim 3
Dependent Claim
49 words
The method as described in claim 1 wherein step A includes the substep (A1) of generating said first test signal as having a periodic rectangular waveform with a repetition frequency which is a submultiple of the frequency of each of the discrete spectral components of the operational input signal.
Claim 4
Dependent Claim
46 words
The method as described in claim 2 wherein step C includes the substep (C1) of changing the duty cycle of said periodic retangular waveform signal, whereby the Fourier transform of said first and second test signals will yield known amplitude relationships between said spectral components therein.
Claim 5
Dependent Claim
40 words
The method as described in claim 3 wherein step E includes the substep (E1) of linearly extrapolating said corrective function as a straight line through said first and second position errors for all expected values of the operational input signal.
Claim 6
Dependent Claim
63 words
The method as described in claim 4 further comprising step G of alternately processing, as the operational input signal, the output signals from a localizer receiver and then from a glide slope receiver for deriving output signals representative of lateral and vertical deviations from the desired position, whereby said corrective function may be utilized for deriving both vertical and horizontal error output signals.
Claim 7
Independent Claim
258 words
A method for correcting circuit induced errors in an ILS receiving system of the type which processes an operational input signal, having discrete spectral components of known frequency and varying amplitudes, in order to develop an output signal representative of deviation from a desired centerline course, said method comprising the steps of: A. filtering each of the discrete spectral components through bandpass filters for removing noise and distortion products; B. rectifying said filtered discrete components and filtering a recombined signal, comprising DC components resulting from rectification, for deriving the output signal; C. generating a first test signal representative of a known first position, said first test signal having spectral components of known amplitude and frequencies generally corresponding to the spectral components of the operational input signals; C. processing said first test signal through steps A and B in order to derive a first processing error corresponding to said first known position; E. generating a second test signal, representative of a second known position, by changing the amplitude of the spectral components of said first test signal; F. processing said second test signal through steps A and B in order to derive a second processing error corresponding to said second known position; G. deriving an error corrective function representative of said processing errors for a range of operational input signals by interpolating from said first and second processing errors; and H. processing the operational input signals through steps A and B and then applying said corrective function to the output signal so as to eliminate said processing errors therefrom.
Claim 8
Independent Claim
258 words
A method for correcting circuit induced errors in an ILS receiving system of the type which processes an operational input signal, having discrete spectral components of known frequency and varying amplitudes, in order to develop an output signal representative of deviation from a desired centerline course, said method comprising the steps of: A. filtering each of the discrete spectral components through bandpass filters for removing noise and distortion products; B. rectifying said filtered discrete components and filtering a recombined signal, comprising DC components resulting from rectification, for deriving the output signal; C. generating a first test signal representative of a known first position, said first test signal having spectral components of known amplitude and frequencies generally corresponding to the spectral components of the operational input signals; C. processing said first test signal through steps A and B in order to derive a first processing error corresponding to said first known position; E. generating a second test signal, representative of a second known position, by changing the amplitude of the spectral components of said first test signal; F. processing said second test signal through steps A and B in order to derive a second processing error corresponding to said second known position; G. deriving an error corrective function representative of said processing errors for a range of operational input signals by interpolating from said first and second processing errors; and H. processing the operational input signals through steps A and B and then applying said corrective function to the output signal so as to eliminate said processing errors therefrom.
Claim 9
Dependent Claim
80 words
The method as described in claim 6 wherein step (B) further includes the substep of: (B1) sampling said recombined signal after said rectifying and filtering processes in order to obtain a generally steady state sampling level representative of the output signal, with said sampling occurring for a first sampling period which includes an integer number of cycles of each of the spectral components of the operational input signal, whereby any residual ripple components will be cancelled over the sampling period.
Claim 10
Dependent Claim
67 words
The method as described in claim 7 wherein step B further includes the substeps of: (B2) generating a periodic output signal having a frequency determined by said sampling level obtained during said first sampling period; and (B3) counting the frequency of said periodic output signal for a second sampling period, thereby defining a digital value for the output signal representative of deviation from the desired centerline course.
Claim 11
Dependent Claim
45 words
The method as described in claim 8 further including the substep of regulating said second sampling period to include an integer number of cycles of each of the spectral components of the operational input signal, thereby further reducing the effects of any residual ripple components.
Claim 12
Dependent Claim
29 words
The method as described in claim 9 further including the substep of regulating said first sampling period of step (B1) to equal said second sampling period of step (B3).
Claim 13
Dependent Claim
45 words
The method as described in claim 9 wherein step (C) includes the substep (C1) of generating a periodic rectangular waveform signal having a repetition frequency which is a submultiple of the frequencies of each of the multiple discrete spectral components of the operational input signal.
Claim 14
Dependent Claim
47 words
The method as described in claim 11 wherein step (E) includes the substep (E1) of changing the duty cycle of said periodic rectangular waveform signal, whereby the Fourier transform of said first and said second test signals will yield known amplitude relationships between said spectral components therein.
Claim 15
Dependent Claim
42 words
The method as described in claim 12 further including the step of generating a master timebase signal for controlling; (a) the repetition frequency of said first and second test signals; and (b) the duty cycles of said first and second test signals.
Claim 16
Dependent Claim
29 words
The method as described in claim 13 wherein step (B1) further includes the substep of determining said first and second sampling periods through reference to said master timebase signal.
Claim 17
Dependent Claim
243 words
An improved system for correcting circuit induced errors in an ILS receiving system of the type wherein an operational input signal, of the type having discrete major spectral components of known frequency and varying amplitudes representative of position errors, is processed through processing circuits in order to develop an output signal representative of deviation from a desired centerline course, wherein the improvement comprises; signal generator means for generating a first test signal, representative of a first known position, having major spectral components of known amplitude and frequencies generally corresponding to the major spectral components of the operational input signal, and for generating a second test signal, representative of a second known position, by changing the amplitude of the major spectral components of said first test signal; switching means for inserting said first test signal into the signal processing circuits in order to derive a first processing error corresponding to said first known position, and for inserting said second test signal into the signal processing circuits in order to derive a second processing error corresponding to said second known position; and computer means for receiving said first and second processing errors and responsive thereto deriving an error corrective function representative of a range of said processing errors corresponding to a range of the operational input signals, with said computer means further including error correcting means for receiving and then modifying the output signal with said error corrective function for eliminating the processing errors therefrom.
Claim 18
Dependent Claim
243 words
An improved system for correcting circuit induced errors in an ILS receiving system of the type wherein an operational input signal, of the type having discrete major spectral components of known frequency and varying amplitudes representative of position errors, is processed through processing circuits in order to develop an output signal representative of deviation from a desired centerline course, wherein the improvement comprises; signal generator means for generating a first test signal, representative of a first known position, having major spectral components of known amplitude and frequencies generally corresponding to the major spectral components of the operational input signal, and for generating a second test signal, representative of a second known position, by changing the amplitude of the major spectral components of said first test signal; switching means for inserting said first test signal into the signal processing circuits in order to derive a first processing error corresponding to said first known position, and for inserting said second test signal into the signal processing circuits in order to derive a second processing error corresponding to said second known position; and computer means for receiving said first and second processing errors and responsive thereto deriving an error corrective function representative of a range of said processing errors corresponding to a range of the operational input signals, with said computer means further including error correcting means for receiving and then modifying the output signal with said error corrective function for eliminating the processing errors therefrom.
Claim 19
Dependent Claim
40 words
The improvement as described in claim 15 wherein said first and second test signals have periodic and generally rectangular waveforms with a repetition frequency which is a submultiple of each of the discrete spectral components of the operational input signal.
Claim 20
Dependent Claim
56 words
The improvement as described in claim 16 wherein said signal generator means includes means for changing the duty cycle of said first test signal in order to form said second test signal, whereby the Fourier transform of said first and second test signals will yield known amplitude relationships between corresponding ones of said spectral components therein.
Claim 21
Dependent Claim
28 words
The improvement as described in claim 17 wherein said repetition frequency is 30 Hz when the operational input signal includes 90 Hz and 150 Hz major spectral components.
Claim 22
Dependent Claim
69 words
The improvement as described in claim 17 wherein said error correcting means further includes means for sampling the output signal in order to obtain a generally steady state representation thereof, with said sampling occurring for a first period which includes an integer number of cycles of each of the major spectral components of the operational input signal, whereby any residual ripple components should be cancelled over the sampling period.
Claim 23
Dependent Claim
70 words
The improvement as described in claim 19 wherein said error correcting means further includes: means for generating a periodic output signal having a variable frequency representative of the level of the output signal during said first sampling period; means for counting the frequency of said periodic output signal for a second sampling period, thereby defining a digital value for the output signal representative of deviation from the desired centerline course.
Claim 24
Dependent Claim
40 words
The improvement as described in claim 20 wherein said second sampling period includes an integer number of cycles of each of the major spectral components of the operational input signal, thereby further reducing the effects of any residual ripple components.
Claim 25
Dependent Claim
45 words
The improvement as described in claim 21 wherein said error correcting means further includes a master timebase generator for generating a master timebase signal coupled to said signal generator means for controlling the repetition frequency and duty cycle of said first and second test signals.
Claim 26
Dependent Claim
33 words
The improvement as described in claim 22 wherein said master timebase generator is coupled to said error correcting means for controlling said first and second sampling periods responsive to said master timebase signal.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-06-27 | 1986-12-27 | 1987-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-06-27 | 1990-12-27 | 1991-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-06-27 | 1994-12-27 | 1995-06-28 | $7700.00 | Window Closed / Lapsed |