Fast techniques for sensor array calibration

Antennas arrays have long been used on airborne reconnaissance platforms for direction finding (DF) applications. The antenna arrays used for communications signals (20-500 MHz) are usually calibrated during special calibration flights. In a calibration flight, the airborne platform flies a known flight path where the angle-of-arrival (AOA) to the calibration source varies over 360 deg. Calibration flights are extremely expensive, time consuming and often experience co-channel interference. As calibration requirements become more demanding, the duration of the calibration flights can grow dramatically. For example, if azimuth and elevation calibration is required, the calibration flight time may increase by five to ten times. The authors propose a new calibration technique based on the constant-modulus, blind-adaptive beamforming methods where one can calibrate an antenna array using multiple co-channel signal sources, thereby significantly reducing the calibration time. The effectiveness of this technique with real data collected from an airborne platform is shown