The letter-rack antenna - A wide-band flush-mounted antenna of log-periodic design

Some of the basic principles of log-periodic type of design of wideband antennas are outlined. A wide-band flush-mounted antenna called the Letter-rack antenna is designed on the basis of above principles. It is shown why the simple corrugated structure is not suitable for broadband design without some basic changes. A composite system consisting of a series of alternately reversed loops and the corrugated surface structure is constrcuted such that the two periodic structures couple strongly with each other. The behavior of the coupled system is studied on the basis of a coupled mode type of approach. Experimental measurements on the corrugated surface, the uniform Letter-rack antenna and the LP Letter-rack, are reported. It is indicated that the design principles may be applied to building other antennas.