A study on broadening beamwidth of E-plane radiation pattern of a dipole antenna with reactance loaded monopole antennas

摘要

This report investigates broadening beamwidth of E-plane radiation pattern of a dipole antenna. Two parasitic monopole antennas with loaded reactance are placed adjacent to the dipole and their reactances are appropriately chosen to form a beam. First of all, current coefficients at driving points of the dipole and monopole antennas are obtained by circuit equations. Then a radiation pattern is derived. Next, we obtain a condition of broadening the beamwidth. By introducing a complex plane with a variable as a ratio of current coefficients at the driving points of the antennas, the condition allows remarkable geometrical interpretation, e.g. the optimum value of loaded reactance is easily obtained by using a locus on the complex plane. Finally, numerical simulations by using the method of moment are presented for verification of the theory.