Corrugated horn with stable phase center for Ka-band compact antenna test range measurement systems

In this article, a corrugated horn feed antenna with a stable phase center is designed for the millimeter wave compact antenna test range (CATR). The calculation method of the phase center of a horn is analyzed in this article. The 45°-plane phase center is used as the combined phase center of the horn in order to perform the phase center calculation only once, thus faster, and to optimize the phase performance more conveniently. By adding an absorbing material surrounding the edge of the outer surface of the horn, the irregular currents on the outer surface of the horn are suppressed, thus achieving a more stable phase center. The absorbing material can also reduce the radar cross section of the antenna. The designed corrugated horn works in the 24–40 GHz wide band with the following performances: the deviation of the phase center in the working frequency band is less than ±0.25 mm, the phase variation within a ±30° beam width is less than ±2.5°. Moreover, the measured return loss is lower than −10 dB, the measured gain is 8–12 dBi, and the measured cross-polarization level is less than −30 dB. The beamwidth is about 56°–70° in the whole band, and the beamwidth difference between different planes is less than 5°. The achieved targets listed above makes the proposed corrugated horn suitable for very precise antenna measurements in CATR systems.