V. A. Yatskevich, V. P. Kudzin, A. S. Smirnov

It is known that characteristics of the log-periodic dipole antenna (LPDA) become worse at presence of some asymmetry in its design or in its environment. This phenomenon is accounted for the excitation of in-phase wave in the two-wire line connected with dipoles. It leads to resonant rise of side radiation and variations of an input impedance and an antenna gain across the antenna operating band. This phenomenon hinder with application LPDA in phased arrays scanning in a E-plane. In this case there are some resonant frequencies at which the antenna performances become unacceptable. We have proposed the easily realizable method of suppression of the specified resonances. The method is based on insertion of the additional steel wire into the antenna to absorb the power of in-phase wave, originating at a resonance. This wire does not influence on basic, an anti-phase wave. Earlier this method has been justified experimentally and applied successfully to improve the performances of LPDA formed of vertically oriented dipoles above an earth surface. In the present paper the method is applied to the linear and planar phased antenna arrays. Computer simulation has shown, that it is possible to reduce parasitic resonances originating in the log-periodic antenna and, thus, to expand sector of scanning up to 50 .