On transient radiation from a log-periodic dipole array

An analysis of how a transient voltage is radiated from a log-periodic dipole array is presented by adopting an idealized model of the array. Due to the frequency dependent phase center location of the array and an assumed slow wave phase velocity which varies logarithmically with frequency, a time delay which decreases with increasing frequency results. This causes the envelope of the radiated pulse to have a time dependence determined by the product of the antenna's admittance and the frequency spectrum of the input pulse with time being inversely related to frequency, and to have an instantaneous frequency which varies inversely with time.