Further comments on the design of log-periodic dipole antennas

Abstract

The design procedure for the log-periodic dipole (LPD) antenna is discussed, by extending the results presented in a previous paper by the authors. The results of gain calculations, already published, are summarized and extended to cases of very thick dipoles. The gain analysis is completed with a discussion of the optimum antenna input feed lineZ_{0}'the achievable VSWR, the voltage gradient, and the effects of the presence of the ground. All the results of calculations given here are presented as a function ofZ_{0}(the characteristic impedance of the transmission line feeder),h/a(the ratio between the half-length and the radius of the dipoles), au(the logarithmic decrement of the geometrical configuration), andsigma(the spacing ratio of dipoles), i.e., the parameters, which usually describe the geometry of an LPD array. The results of calculations are presented in many diagrams, for different values of au,sigma, Z_{0}andh/a, which can be useful for accurate design of LPD antennas including those for high-power applications. Measurements of VSWR performed on antenna models have confirmed the computed results.