SOME THEORETICAL ASPECTS OF LOG PERIODIC AND CONTINUOUSLY SCALED ANTENNA DESIGNS.
Antenna Lab. technical rept. no. 76,
ILLINOIS UNIV URBANA ENGINEERING EXPERIMENT STATION
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Consideration is given to certain theoretical aspects of LP and CS antenna designs. It is shown that the problem of designing a truly frequency independent antenna with an ideal transient response remains unsolved to date and it is doubtful that one such practical antenna could ever be designed. Floquets theorem for periodic structures is generalized to structures containing additional symmetries and the notion of effective period for such structures is intruduced. The K-Beta diagrams for several periodic structures are discussed and it is indicated how one could predict the potentially successful type of structures on the basis of their K-Beta diagram. A non-uniform transmission line with CS properties, whose characteristics are close to those of the LPDA is studied and several general conclusions are drawn on the basis of the results of the study. It is pointed out that for analysis and design purposes, the log-periodic variations in a LP device should be viewed as perturbations and that the emphasis should be laid on the CS portion of the behavior.