Corrugated wall horns and smooth wall multimode horns are two comparatively ideal feeds with high efficiency. Further study on mode conversion between the two types of horns is presented. The concept of combining hybrid mode technology for corrugated wall with multimode technology for smooth wall in one horn is suggested. An engineering design method for using it to control the characteristics of different frequency zones respectively is depicted. The complex multimode horn which is of small size

good performance and easy to manufacture is successfully developed. The antenna efficiency may be increased up to 70% with the improved version of double-mirror antenna feed for the 4/6GHz band （except a few f requencres）. The possiblity to develop high efficient new feeds by making combined use of various hybrid mode and smooth wall multimode technologies is demonstrated.