Planar near-field calibration of digital arrays using element plane wave spectra

• US 10,109,915 B2
• Filed: 02/13/2015
• Issued: 10/23/2018
• Est. Priority Date: 02/13/2014
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Frink, Andrew, Whitaker, George, Maas, Jeffrey, O'Haver, Kenneth W.
• Primary Examiner(s): Magloire, Vladimir
• Assistant Examiner(s): Pervin, Nuzhat
• Application Number:
  US14/622,777
• Publication Number:
  US 20150349419A1
• Time in Patent Office: 1,348 Days
• Field of Search: 342371
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices
• CPC Class Codes: H04B 17/12 of transmit antennas, e.g. of the amplitude or phase
• CPC Class Codes: H04B 17/21 for calibration; for correcting measurements
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

A calibration method, applicable to element-level digital arrays operating in the receive mode, which utilizes the individual element plane wave spectra obtained from a single planar near-field scan. The method generates highly accurate near-field measurement derived amplitude and phase calibration of both large and small digital arrays as a function of array scan. The present disclosure provides digital array calibration methods and their potential uses in satellites and directional arrays.

Claims

1. A directional digital phased finite array system including a recalibration system for recalibrating the directional digital phased finite array system when replacement array elements are installed comprising:

a directional digital phased finite array comprising a plurality of array elements comprising one or more first array elements and one or more second array elements, wherein each of the array elements comprises or is coupled with respective digital receiver;

a control system configured to control the directional digital array system;

a library of a plurality of array element configuration data for use in operating the directional digital phased finite array system, the plurality of array element configuration data comprising one or more replacement array element configuration data each associated with a respective one of said one or more second array elements that each comprises an alternative configuration calibration data for use in operation of the directional digital phased finite array system;

wherein said one or more second array elements each respectively are one of a plurality of replacement array elements each associated with a position of said array elements previously calibrated after being installed into the directional digital phased finite array during one or more calibration activities that also created or generated said alternative configuration calibration data for digital finite array configurations with one or more of said replacement array elements installed; and

a calibration system used with a moveable probe system comprising at least one processor including a plurality of modules operative to perform or enable a plurality of calibration data collection steps including;

acquiring the alternative configuration calibration data by performing one or more near-field scans of one or more alternative configurations of the directional digital phased finite array within a scan plane, wherein the one or more alternative configurations comprises one or more combinations of said first and second array elements and recording element digital in phase and quadrature (I &

Q) samples for each probe position in the one or more near-field scans, converting the element digital I &

Q samples to element near field amplitude and phase measurements for each of the one or more near-field scans, computing a unit excitation plane wave spectrum for each combination of said first and second elements for each of the one or more near-field scans by superimposing said element near-field amplitudes and phases to reconstruct a near-field response data of the directional digital phased finite array and transforming individual element near-field scan plane data to obtain individual element plane wave spectra then beam forming the element plane wave spectra to obtain an array plane wave spectrum, and then computing element amplitude and phase calibration coefficients as a function of steering angle from the array wave plane wave spectrum;

wherein, the control system being further operative to calibrate the directional digital phased array during operation of said directional digital phased array by adjusting the directional digital phased array and each array element'"'"'s operation or pattern based on said unit excitation wave spectrum data and element amplitude and phase calibration coefficients associated with each of the combinations of said first and second array elements.

2. The system of claim 1, wherein said directional digital phased array comprises a satellite communication system.

3. The system of claim 1, wherein the unit excitation plane wave spectrum is computed for each element using equations comprising

4. The system of claim 1, wherein the element amplitude and phase calibration coefficients are computed as a function of the steering angle using equations comprising

5. A method for calibrating a phased array antenna system comprising:

performing, by at least one processor of a computing system, a first plurality of processing steps comprising calibration activities for a digital phased array including;

performing a near-field scan of the digital phased array comprising a plurality array elements comprising a plurality of first array elements, the near-field scan comprising operating a near field scan probe in proximity to the plurality of first array elements and recording a first array element digital in phase and quadrature (I &

Q) samples for each probe position;

converting the first array element digital I &

Q samples to a first plurality of amplitude and phase measurements;

computing a first plurality of unit excitation plane wave spectrum for each first array element and then beam form the unit excitation plane way spectrum for each first array element to obtain an array plane wave spectrum;

computing first array element amplitude and phase calibration coefficients as a function of steering angle from the array plane wave spectrum; and

calibrating the digital phased array during operation of said digital phased array by adjusting the digital phased array and the plurality of first array elements operation or pattern based on said first plurality of unit excitation plane wave spectrum data and element amplitude and phase calibration coefficients;

performing a second plurality of calibration processing steps comprising;

providing a plurality of replacement array elements, each of said plurality of replacement array elements has a matching performance and form with one of said first array elements that is further position matched or associated with a specific position of an associated first array element;

selecting one of said plurality of replacement array elements, removing a corresponding or respective said first array element having said matching performance, fit and position, removing the corresponding or respective first array element, and installing said selected one of said replacement array elements into the digital phased array;

repeating, by the at least one processor, said first plurality of calibration activities with the selected one of said replacement array elements and generating, by the at least one processor, alternative configuration calibration data for digital array configurations with said selected one of said plurality of replacement array elements installed; and

performing, by the at least one processor, a third plurality of processing steps comprising configuration activities including;

creating a library of alternative configuration data for use in loading the alternative configuration calibration data into the digital phased array for operation thereof after said selected one of said replacement array has been installed.

6. The method of claim 5, wherein said phased array antenna system comprises a satellite communications system.

7. The method of claim 5, wherein element near-field scan plane data is equivalently transformed to obtain element plane wave spectra, and beam form the element plane wave spectra to obtain an array plane wave spectrum.