Rapid Fast Fourier Transform Phase Alignment of an Electronically Scanned Antenna

Low sidelobe performance of a 1-D phased array antenna demands tight aperture phase tolerances, which require periodic retesting and phase correcting of the array elements to compensate for phase errors arising from aging, thermal deformation and component replacement. To accomplish such phase correcting without returning the antenna to a test site or calibration laboratory, a rapid self-test/phase-correcting method which can be performed on a moving vehicle has been invented. This phase alignment technique exercises the electronic phaser shifters of a 1-D antenna array, while injecting RF into the antenna through a special BITE coupler. Phase and amplitude are measured at the antenna terminals, and a Fast Fourier Transform (FFT) computation generates the required phase corrections to produce a low sidelobe radiation pattern. A detailed description of the alignment technique is presented, followed by test results obtained with an electronically phased array antenna.