Method of and apparatus for automatically calibrating a phased-array antenna
First Claim
1. Method of calibrating an array antenna comprising a plurality of radiating elements which cooperate to produce an operational transmission having an associated far field pattern and an associated aperture illumination, and an integral monitor waveguide responsive to the combined ouput of all of said radiating elements during said operational transmission, wherein:
- first signals corresponding to the far field pattern of the array antenna are derived from an output of the integral monitor waveguide during said operational transmission,second signals corresponding to the aperture illumination of the antenna are derived from the first signals using an integral transform,the second signals are compared with third signals stored in storage means,a difference signal corresponding to the deviation of the second signals from the third signals is produced which is fed to a controller whose output acts on phase shifters connected to the array antenna, andthe foregoing steps are repeated until the difference signal lies within a predetermined tolerance band.
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Accused Products
Abstract
Landing aids using phased-array antennas must be very carefully calibrated. Conventional methods use probes which are inserted into each individual radiating element of the array antenna. For 6-bit phase shifters, this method is not suficiently accurate. A method and an apparatus are disclosed wherein the aperture illumination of the array antenna is determined from the output of an integral waveguide and compared with a desired aperture illumination. The difference between actual value and desired value is compensated for iteratively with the aid of an adaptive control system.
36 Citations
16 Claims
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1. Method of calibrating an array antenna comprising a plurality of radiating elements which cooperate to produce an operational transmission having an associated far field pattern and an associated aperture illumination, and an integral monitor waveguide responsive to the combined ouput of all of said radiating elements during said operational transmission, wherein:
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first signals corresponding to the far field pattern of the array antenna are derived from an output of the integral monitor waveguide during said operational transmission, second signals corresponding to the aperture illumination of the antenna are derived from the first signals using an integral transform, the second signals are compared with third signals stored in storage means, a difference signal corresponding to the deviation of the second signals from the third signals is produced which is fed to a controller whose output acts on phase shifters connected to the array antenna, and the foregoing steps are repeated until the difference signal lies within a predetermined tolerance band. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Apparatus for calibrating a phased-array antenna having a plurality of radiating elements supplied with radio-frequency energy via electronically controlled phase shifters, the apparatus comprising
an integral monitor waveguide responsive to the outputs of said radiating elements for producing a combined output signal corresponding to the far field pattern of the antenna, first means for using a Fourier transform to convert the combined output signal of the integral monitor waveguide into an aperture illumination of the array antenna, storage means for storing a desired aperture illumination, comparing means for determining the deviation between the desired aperture illumination stored by the storage means and the aperture illumination of the array antenna determined by the first means, and control means for controlling each of the electronic phase shifters as a function of the deviation determined by the comparing means.
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11. Method of determining a complex aperture illumination of a phased-array antenna having a plurality of radiating elements, said method comprising the steps:
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a) using a Fourier transform to derive a time-varying complex signal from an output from an integral monitor waveguide responsive to the combined output of said radiating elements, b) using homodyne detection apparatus to detect the real part of the complex signal, and c) using a Hilbert transform to compute the imaginary part of the complex signal. - View Dependent Claims (12, 13)
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14. Apparatus for determining a complex aperture illumination of a phased-array antenna having a plurality of radiating elements for producing a radiation pattern, said apparatus comprising
an integral monitor waveguide whose output provides a complex, time-varying first signal having real and imaginary parts each corresponding to said radiation pattern, a source of radio-frequency energy having a carrier frequency f0, a network for distributing the radio-frequency energy to the radiating elements to produce said radiation pattern, a single mixer directly coupled to the output of the integral monitor waveguide for multiplying the first signal by a time-invariant second signal having a frequency equal to said carrier frequency f0 to thereby produce a time-varying third signal corresponding to the real part of said first signal, and a low-pass filter coupled to an output of said single mixer for passing only a low frequency component of said third signal.
Specification