Abstract: In order to meet the requirement of the broadband communication system, a novel broadband 90° corrugated-horn antenna is proposed. The corrugations of the horn expand outward in the shape of Archimedes spiral.Simulated and measured results indicate that the optimal bandwidth of the new corrugated horn can reach 2∶1. Over the frequencies from 10 GHz to 20 GHz, the proposed antenna can produce the relatively-the-same phase center with low cross-polarization levels in 45° plane below −25 dB. In the wide frequency band, the beamwidth is relative constant and the −10 dB beamwidth of E-plane and H-plane is very close. The proposed design of corrugated slots can make the radiation pattern of the horn more symmetrical in a wide frequency band, which is a new idea to improve the performance of corrugated horn.