On The Dual Log-periodic Airborne Antenna With High-Gain And Wideband In Small Size

The design theory and implementation method of the directional airborne antenna on very high frequency (VHF) band are discussed. Two types of the log-periodic antennas, the traditional log-periodic antenna (LPA) and the printed planar version, are designed for the specified electrical and mechanical specifications. The size and electric parameters of printed planar and traditional log-periodic antennas are respectively simulated and optimized as well as dual LPA by the commercial software IE3D based on the method of moment (MOM), and the corresponding dimensions are obtained. Then their radiation characteristics are compared, and the results indicate that the dual LPA is a probable candidate which can meet the requirements of airborne antenna. Due to rigorous limitations of the weight and size, the antenna is redesigned using the same software, and the dipoles should be folded to shorten the width of the antenna. Compared with the traditional log-periodic antenna, the printed planar one has the advantages of light weight and small size. But the feed line of the printed planar LPA is too narrow, some troublesome problems appear during the engineering realization such as the coaxial cable jointing. Moreover, the antenna has no a good impedance match on some frequency points. However, dual traditional LPA with linear and tubular dipoles has good electrical characteristics. Based on the aforementioned, the two types of dual LPAs are manufactured and measured. The measured results show that dual log-periodic antenna with linear and tubular dipoles is of wide band (2:1 bandwidth ),high gain (9dBi),small size (580×580×1000mm~3), and fully satisfies the requirements of airborne antenna, and that this research method is valid and the work is valuable practically.