Equivalent Circuits for Electric Dipoles

A 3-element equivalent circuit proposed by Chu [1] is used to simulate regions of the time-harmonic impedance spectrum of an electric dipole (monopole) antenna near 1st and 3rd (short-circuit) resonant frequencies. As an intermediate step toward the creation of an accurate broadband equivalent circuit, a 6-element circuit is created by combining the two 3-element sub-circuits in parallel; the final step is to insert a capacitance at the input to simulate the spectral region near 2nd (open-circuit) resonance. This completes a broadband equivalent circuit. This method of circuit development is illustrated by applying it to a thin, center-driven, electric dipole. Extension of this technique to more practical antennas having significant ohmic loss and near-base capacitance is suggested for future work.