Antenna calibration method and system
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsEung Gi Paek, Mark Parent, Joon Y Choe
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Abstract
A phased array antenna system includes an RF front end, a radome, and an optical calibrator embedded in the radome for enabling in-situ calibration of the RF front end. The optical calibrator employs an optical timing signal generator (OTSG), a Variable Optical Amplitude and Delay Generator array (VOADGA) for receiving the modulated optical output signal and generating a plurality of VOADGA timing signals, and an optical timing signal distributor (OTSD). The in-situ optical calibrator allows for reduced calibration time and makes it feasible to perform calibration whenever necessary.
Claims8
A method of calibrating a phased array antenna housed within a radome, comprising:
- a) providing an optical timing signal generator (OTSG) having a DFB laser source for generating an optical calibration signal, a modulator for modulating the light calibration signal and generating a modulated optical output signal, and a Variable Optical Amplitude and Delay Generator array (VOADGA) for receiving the modulated optical output signal and generating a plurality of VOADGA timing signals, and an optical timing signal distributor (OTSD) housed within the radome for receiving the plurality of VOADGA timing signals, the OTSD having a matrix-addressable PLC having N horizontal waveguides and N vertical waveguides for receiving the VOADGA timing signals, said wave guides having a plurality of intersections, each intersection having a photodiode positioned thereon for receiving a portion of the VOADGA timing signals and for generating a proportional electrical output signal for subsequent processing and calibrating of the phased array antenna;
- b) optimizing RF delays to compensate for PLC delays, line-by-line;
- c) aligning VOADGA delays so that incoming input signals have the same phase at the entrance of the matrix;
- d) adding linear chirp delays to VOADGA to steer beam directions;
- e) optimizing RF delays to match the additional VOADGA delays and record the RF delay values to form a look-up-table (LUT);
- f) repeating steps d)-e) for all the beam positions along the azimuth and elevation directions;
- g) adding additional linear chirp delays to the VOADGA to scan through the beam pattern and to estimate sidelobes;
- and
- h) then tapering RF amplitudes in the RF front-end of the phased array antenna to minimize the sidelobe level.
Dependencies are inferred from the claim text.