The comparison between simulated and measured results shows that the proposed LPDA can be used as an Ultra Wideband Antenna in the range 4.
The wideband matching of the printed LPDA is obtained with an infinite balun, realized with a coaxial cable.
Since the printed LPDA lies on a dielectric substrate, the geometric parameters of this antenna cannot be computed as in the case of a standard wire-LPDA , which radiates in free space.
The LPDA antenna, designed in Section 2, has been fed by a coaxial cable in order to implement the infinite balun providing the required wideband matching.
Nevertheless, the fractal dipoles extend to two sides of the dipoles in vertical direction, leading to that the spacing factor of Euclidean LPDA is not suitable for design requirements.
The impedance bandwidth of LPDA (VSWR < 2) is from 0.
Compared with Euclidean LPDA, the widths (in co-polarization direction) of LPTDA and [LPT.
The electric field amplitudes in the aperture are those fields produced in the slotted aperture by a nominal "free" electric field of 20V/m existing at the position of the slotted aperture produced by the LPDA when the cylinder is absent (while the aluminum ground plane is present).
Figures 6 and 7 present the "spatial average" of the electric fields (actually the square root of the averaged power densities) measured inside the hollow cylinder (at the 13 interior points as indicated in Figure 8) when the applied "free" field radiated by the LPDA is 20V/m.
The previous plots of fields represent values measured with a calibrated electric field probe positioned in the aperture and at specific points inside the cylinder when the LPDA is radiating the prescribed "free" electric field of 20 V/m for each polarization (vertical--TE case and horizontal--TM case) in the presence of a finite aluminum ground plane.
This is probably due to an imperfect symmetry of the LPDA on the ground plane.
An antenna array of 4x LPDA has been built and measured.