Deterministic subarray feed line adjustment method for array antennas

The authors propose a deterministic subarray feed line adjustment method for array antennas. In a typical base-station antenna with subarray feed cables, lengths of fine-tuning cables are adjusted to obtain the designed radiation characteristics after the antenna is provided. However, determination of the lengths is normally a time-consuming effort because the array excitation deviates from the designed value by the multi-reflection etc. between the components. The Rotating Element electric field Vector (REV) method is known as a phased array calibration method, however it cannot be used for such structures. In this paper, we describe the optimization theory of subarray feed line and the optimization procedure of the proposed method that determines the lengths of the fine-tuning cables with the least-square method by using S-parameters of array antenna components. We confirm the validity of this theory by simulation results. In this way, we can determine the optimal lengths at once and can realize desired array excitation with the multi-reflections of subarray feed circuits taken into consideration.