Question

Which of the following expression is correct?

(a) \(\frac{L_N}{L_{N+1}} = \frac{S_N}{S_{N+1}} = τ\)

(b) \(\frac{L_N}{L_{N+1}} = \frac{S_{N+1}}{S_N} = τ\)

(c) \(\frac{L_N}{L_{N+1}} = \frac{S_{N+1}}{S_N} = \frac{1}{τ} \)

(d) \(\frac{L_N}{L_{N+1}} = \frac{S_N}{S_{N+1}} = \frac{1}{τ} \)

The question was asked in a job interview.

This interesting question is from Frequency Independent Antenna in division Frequency Independent Antenna of Antennas

Answer 1

Correct option is (a) \(\frac{L_N}{L_{N+1}} = \frac{S_N}{S_{N+1}} = τ\)

To elaborate: The ratio of adjacent spacing of dipoles and its lengths in the LPDA are equal. The electrical properties of the log periodic antenna are repeated periodically in terms of logarithmic frequency. The relation between the antenna dipole adjacent lengths, spacing and the scaling factor is given as \(\frac{L_N}{L_{N+1}} = \frac{S_N}{S_{N+1}} = τ.\)