Compact K-Band Phased Array Antenna with Orthogonal Calibration and Error Assessment

This paper presents a 24-channel K-band beamforming phased array antenna incorporating orthogonal coding for calibration and calibration error assessment. The phased array antenna integrates a 1 : 24Wilkinson power divider, 24 elements of a modified antipodal Vivaldi antenna, and T/R modules onto a multi-layer PCB, achieving a compact size of 23.5 × 9 cm² and enhanced portability, making it suitable for space-constrained platforms such as drones, vehicles, and satellite terminals. The array offers a high gain of 21.82 dBi and a wide bandwidth covering the entire 18–20 GHz band. Furthermore, it supports beam steering from −40° to +40° while maintaining low sidelobe levels and minimal gain degradation during beamforming. An orthogonal coding-based calibration method is implemented to mitigate performance degradation due to mismatched line impedance and fabrication errors. By applying a set of orthogonal codes through onboard phase control circuitry, phase errors of each element are simultaneously measured. Furthermore, a new approach for assessing calibration error is introduced, which uses RMS amplitude and phase error metrics to evaluate post-calibration performance. This information can subsequently be used to correct residual amplitude and phase errors in the calibrated data. The paper covers the design specifications, theoretical framework, and measured results of the phased array antenna, including the calibration technique, its performance assessment, and several key findings from the experiments conducted in this work.