Phased-array antennas have become almost essential parts of modern aerospace and defense radar systems. The multiple elements combine for high-speed and effective beamforming and beam diversity, allowing a radar system to receive and transmit advanced waveforms under a variety of operating conditions. Unfortunately, those antenna array elements can fail, resulting in some amount of degradation in the antenna pattern and the radar system performance.
Researchers at KIIT University (BhuBaneswar, India) and the Indian Institute of Technology (Roorkee, India) explored the use of two algorithms—the particle swarm optimization (PSO) and the bacteria foraging optimization (BSO) algorithms—to analyze the effects of failed antenna array elements on the overall performance of the antenna. The simplest form of analysis is an assumption in the loss of amplitude from the failed element, but without affecting the amplitude contributions of the other antenna elements. As the researchers explain, the argument for replacing the failed or partially radiating antenna element is not valid in all cases.
In some cases, the original beam pattern can be resynthesized by recalculating the excitations of the remaining working antenna elements. Newer active phased-array antennas include remote control of antenna element excitations, allowing for retuning of the remaining elements for desirable antenna beamforming. By applying the BSO and PSO algorithms and amplitude-only method, the experimenters developed a relatively simple technique for reconstructing a desired antenna pattern when one or more antenna elements failed partially or fully.
They examined the sidelobe levels (SLLs) of different phased-array antenna designs, using three different experimental cases: restoration of the single null in a failed array, restoration of a double null in a failed array, and restoration of the broad/sector null in a failed array. The researchers found the PSO approach to perform considerably better than the BSP technique when correcting for the failure of antenna elements in phased arrays.
See “Antenna Array Failure Correction,” IEEE Antennas & Propagation Magazine, December 2017, p. 106.