Log-Periodic Transmission Line Circuits--Part I: One-Port Circuits

Suppresion of Log‐Periodic Dipole Antenna Spurious Radiation by Lumped Element Loading for Radioastronomical Application

“…For an LPDA, this region "moves" when focusing on a different frequency. As has been shown in Carrel (1961) and DuHamel and Armstrong (1966), these dipoles load in parallel the boom transmission line, in this case capacitively. If a log-periodic cell n has an equivalent transmission line inductance L 0,n , capacitance C 0,n and thus characteristic impedance 𝐴𝐴 𝐴𝐴0,𝑛𝑛 = √ 𝐿𝐿0,𝑛𝑛∕𝐶𝐶0,𝑛𝑛 , then the reactance added to the boom is:…”

“…In the early years of log‐periodic antenna design, where computational resources were limited, theoretical work was the basis of understanding the log‐periodic parameters, and a number of standard tools guided their choice (among which the optimum σ − τ curve, the bandwidth vs. opening angle α (Carrel, 1961) etc.). Of special interest for the resonant behavior of LPDAs, as examined in this work, are also the early theoretical derivations of the log‐periodic cell, that constitute a near‐field model of the antenna for evaluation of its reflection, a parameter expected to be log‐periodically repeatable (DuHamel & Armstrong, 1966; Jones & Mayes, 1969). More recent work (McLean et al., 2014) has used these results to describe the stop‐region of an LPDA, comparing it to modern accurate simulations.…”

Log periodic bandstop filter

“…The difference between simulated and measured frequency range is probably due to that there is an air gap between the DRA and the substrate, which slightly lowers the equivalent permittivity of the DRA, thus lead to an increasing of frequency and expand the bandwidth [5]. The tolerance in the dielectric constant of DRA and dimensions would also contribute to the shift in the measured frequency.…”