Wideband Beam-Steering Emulation and Measurement for Digital Active Phased-Array Antennas

In recent years, wideband systems in radar, satellite, and electronic warfare have been increasingly in demand for high-resolution and simultaneous acquisition of massive amounts of information.In active phased-array antennas for wideband systems, beam steering using phase shifters (PSs) suffers from "beam squint," wherein the steering angle shifts with frequency, which is a major cause of system performance degradation.Therefore, a beam-steering technique based on true time delay (TTD), which can maintain a constant steering angle regardless of frequency, is essential.However, conventional near-field measurement methods are inadequate for verifying wideband beam steering.This paper proposes a near-field test method that applies the transmit-receive frequency offset and demonstrates its validity theoretically.Furthermore, an 8×8 active phased-array antenna was fabricated, and its wideband beam-steering characteristics were measured using the proposed method.The beam-steering error was significantly improved using the TTD method compared with the PS method.Both the wideband beam-steering capability of the fabricated antenna and effectiveness of the proposed test method were verified experimentally.