Far field monitor apparatus

• US 6,348,891 B1
• Filed: 08/01/2000
• Issued: 02/19/2002
• Est. Priority Date: 08/02/1999
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Uemura, Toshimi
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/630,275
• Time in Patent Office: 567 Days
• Field of Search: 342/407, 342/410, 342/411, 342/412, 342/413
• US Class Current: 342/413
• CPC Class Codes: G01S 1/024 of beacon transmitters
• CPC Class Codes: G01S 1/16 Azimuthal guidance systems, e.g. system for defining aircraft approach path, localiser system
• CPC Class Codes: H01Q 1/30 Means for trailing antennas
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 3/34 by electrical means active lenses or reflecting arrays H01Q3/46

Abstract

In a far field monitor apparatus, each of first and second ILS localizers includes a receiving antenna, a plurality of couplers, a combiner, a receiver, and a first detector. The receiving antenna is formed from a plurality of antenna elements symmetrically arranged in a direction perpendicular to the longitudinal direction of a runway. The receiving antennas of the first and second ILS localizers oppose each other. The couplers are arranged in units of antenna elements to pick up some of signals obtained by the antenna elements in a predetermined amplitude and phase. The combiner combines output signals from the couplers. The receiver receives a combined signal output from the combiner. The first detector detects, on the basis of a receiving signal output from the receiver, a predetermined monitor parameter representing the radiation state of a radio wave radiated from the opposing-side ILS localizer.

Claims

1. A far field monitor apparatus having first and second ILS (Instrument Landing System) localizers opposing via a runway in a longitudinal direction,

each of the first and second ILS localizers comprising:

receiving antenna means formed from a plurality of antenna elements symmetrically arranged in a direction perpendicular to the longitudinal direction of the runway, said receiving antenna means of the first and second ILS localizers opposing each other;

a plurality of coupling means, arranged in units of antenna elements, for picking up some of signals obtained by the antenna elements in a predetermined amplitude and phase;

combine means for combining output signals from said coupling means;

receiving means for receiving a combined signal output from said combine means; and

first detection means for detecting, on the basis of a receiving signal output from said receiving means, a predetermined monitor parameter representing a radiation state of a radio wave radiated from the opposing-side ILS localizer.

2. An apparatus according to claim 1, wherein said receiving antenna means comprises an array antenna.

3. An apparatus according to claim 1, further comprising

second detection means for detecting, from the combined signal output from said combine means, a predetermined monitor parameter representing a radiation state of a radio wave radiated from said receiving antenna means, and

switching means for selectively outputting the combined signal from said combine means to one of said receiving means and said second detection means.

4. An apparatus according to claim 3, wherein

when the radio wave is radiated from the first ILS localizer, said switching means selectively outputs the combined signal from said combine means to said detection means of the first ILS localizer, and

when the radio wave is radiated from the second ILS localizer, said switching means selectively outputs the combined signal from said combine means to said receiving means.

5. An apparatus according to claim 4, wherein said switching means performs a switching operation on the basis of an interlock control signal for instructing the first receiving antenna means to radiate the radio wave.

6. An apparatus according to claim 1, wherein said receiving means comprises

frequency conversion means, using a super heterodyne scheme, for converting the combined signal from said combine means into a signal having a different frequency using a predetermined local oscillation frequency, and

amplification/detection means for amplifying/detecting an output signal from said frequency conversion means and outputting the receiving signal.

7. An apparatus according to claim 6, wherein said frequency conversion means comprises a plurality of cascade-connected super heterodyne detection circuits for demodulating an input signal using different local oscillation frequencies.

8. An apparatus according to claim 1, wherein said first detection means comprises calculation means for calculating an A/D conversion output from said receiving means to detect the predetermined monitor parameter.

9. An apparatus according to claim 8, wherein said calculation means comprises a DSP processor for performing DSP (Digital Signal Processing).

10. An apparatus according to claim 8, wherein said first detection means comprises determination means for comparing the monitor parameter output from said calculation means with an upper limit value and lower limit value and, when the monitor parameter falls outside an allowable range defined by the upper limit value and lower limit value, outputting an alarm signal.

11. An apparatus according to claim 10, wherein said determination means outputs the alarm signal when the monitor parameter falls outside the allowable range for not less than a predetermined period.

12. An apparatus according to claim 8, wherein said calculation means comprises

an A/D conversion section for converting an analog input signal into digital data,

an averaging section for averaging the digital data output from said A/D conversion section and outputting an RF level representing a DC component of the input signal,

a 90-Hz bandpass filter for outputting a 90-Hz AC component in a 90-Hz band from the digital data output from said A/D conversion section,

a 150-Hz bandpass filter for outputting a 150-Hz AC component in a 150-Hz band from the digital data output from said A/D conversion section,

a first adder for adding the RF level from said averaging section and the 90-Hz AC component from said 90-Hz bandpass filter,

a second adder for adding the RF level from said averaging section and the 150-Hz AC component from said 150-Hz bandpass filter,

a first modulation depth calculation section for calculating a depth of modulation on the basis of a maximum and minimum values output from said first adder,

a second modulation depth calculation section for calculating a depth of modulation on the basis of a maximum and minimum values output from said second adder,

a subtractor for subtracting outputs from said first and second modulation depth calculation sections to output a DDM (Difference of Depth of Modulation) signal, and

an adder for adding the outputs from said first and second modulation depth calculation sections to output an SDM (Sum of Depth of Modulation) signal.

13. An apparatus according to claim 12, wherein said averaging section accumulates and adds the digital data from said A/D conversion section a predetermined number of times and divides a sum result by the predetermined number to calculate the RF level.

14. An apparatus according to claim 12, wherein

said first modulation depth calculation section calculates the depth of modulation on the basis of an RF level representing a DC component of an output from said first adder and a maximum amplitude value for the RF level, and

said second modulation depth calculation section calculates the depth of modulation on the basis of an RF level representing a DC component of an output from said second adder and a maximum amplitude value for the RF level.

15. An apparatus according to claim 14, wherein

said first modulation depth calculation section uses, for calculation of the depth of modulation, an average value of a predetermined number of maximum amplitude values for the RF level representing the DC component of the output from said first adder, and

said second modulation depth calculation section uses, for calculation of the depth of modulation, an average value of a predetermined number of maximum amplitude values for the RF level representing the DC component of the output from said second adder.

16. An apparatus according to claim 3, wherein said second detection means comprises

amplification/detection means for amplifying/detecting the receiving signal from said receiving means, and

calculation means for calculating an A/D conversion output from said amplification/detection means to detect the predetermined monitor parameter.

17. An apparatus according to claim 16, wherein said calculation means comprises a DSP processor for performing DSP (Digital Signal Processing).

18. An apparatus according to claim 16, wherein said first detection means comprises determination means for comparing the monitor parameter output from said calculation means with an upper limit value and lower limit value and, when the monitor parameter falls outside an allowable range defined by the upper limit value and lower limit value, outputting an alarm signal.

19. An apparatus according to claim 18, wherein said determination means outputs the alarm signal when the monitor parameter falls outside the allowable range for not less than a predetermined period.

20. An apparatus according to claim 16, wherein said calculation means comprises an A/D conversion section for converting an analog input signal into digital data,

an averaging section for averaging the digital data output from said A/D conversion section and outputting an RF level representing a DC component of the input signal,

a 90-Hz bandpass filter for outputting a 90-Hz AC component in a 90-Hz band from the digital data output from said A/D conversion section, a 150-Hz bandpass filter for outputting a 150-Hz AC component in a 150-Hz band from the digital data output from said A/D conversion section,

a first adder for adding the RF level from said averaging section and the 90-Hz AC component from said 90-Hz bandpass filter,

a second adder for adding the RF level from said averaging section and the 150-Hz AC component from said 150-Hz bandpass filter,

a first modulation depth calculation section for calculating a depth of modulation on the basis of a maximum and minimum values output from said first adder,

a second modulation depth calculation section for calculating a depth of modulation on the basis of a maximum and minimum values output from said second adder,

a subtractor for subtracting outputs from said first and second modulation depth calculation sections to output a DDM (Difference of Depth of Modulation) signal, and

an adder for adding the outputs from said first and second modulation depth calculation sections to output an SDM (Sum of Depth of Modulation) signal.

21. An apparatus according to claim 20, wherein said averaging section accumulates and adds the digital data from said A/D conversion section a predetermined number of times and divides a sum result by the predetermined number to calculate the RF level.

22. An apparatus according to claim 20, wherein

said first modulation depth calculation section calculates the depth of modulation on the basis of an RF level representing a DC component of an output from said first adder and a maximum amplitude value for the RF level, and

said second modulation depth calculation section calculates the depth of modulation on the basis of an RF level representing a DC component of an output from said second adder and a maximum amplitude value for the RF level.

23. An apparatus according to claim 22, wherein

said first modulation depth calculation section uses, for calculation of the depth of modulation, an average value of a predetermined number of maximum amplitude values for the RF level representing the DC component of the output from said first adder, and

said second modulation depth calculation section uses, for calculation of the depth of modulation, an average value of a predetermined number of maximum amplitude values for the RF level representing the DC component of the output from said second adder.