# A Low-Cost Printed Log-Periodic Dipole Array for DVB-T2 Digital TV Applications
## 3 Results  
The final layout of the designed LPDA antenna is shown in Figure 1. Since the typical installation of receiving television antennas is outdoors, such antennas are subjected to extremely variable weather conditions. In particular, they could be exposed to moderate or even strong wind during normal working conditions. Hence, we have designed holes in the dielectric substrate at each inter-space between the radiating dipoles to increase the wind resistance of the LPDA (as indicated in Figure 1). The presence of the holes creates a passage for the wind through the antenna, preventing oscillations and folds, which in the long run could move the antenna from its optimal position, or deform or even break the structure, thus creating significant reception problems until service interruption. Moreover, since we positioned these holes in a strategic region, where the electric field is very low (i.e., the inter-space between the dipoles), they have only a negligible effect on the antenna performance. The frequency response of the input reflection coefficient of the designed printed LPDA antenna for DVB-T2 Digital TV applications is shown in Figure 5. The broadband input matching specification between 470 and 860 MHz (percentage bandwidth of 60%) is completely fulfilled, with the matching extending well beyond the requested range. The 10 dB antenna bandwidth approximately extends from 450 to 940 MHz (\(\approx\)74%), covering the whole DVB-T2 UHF band from Channel 21 to Channel 69. The satisfying frequency behavior of the proposed compact low-cost LPDA antenna is confirmed by the antenna input impedance reported in Figure 6, where both real and imaginary parts are relatively flat within the specified frequency band, ensuring a good matching with the requested reference impedance for Digital TV Applications, equal to 75 \(\Omega\). \begin{table}
\begin{tabular}{c c c c} \hline
**Dipole** & \(L_{n}\) **(mm)** & \(W_{n}\) **(mm)** & \(S_{n}\) **(mm)** \\ \hline
1 & 97.5 & 44.6 & - \\ \hline
2 & 82.9 & 37.9 & 60 \\ \hline
3 & 70.4 & 32.2 & 51 \\ \hline
4 & 59.9 & 27.4 & 43.3 \\ \hline
5 & 50.9 & 23.3 & 36.8 \\ \hline
6 & 43.3 & 19.8 & 31.3 \\ \hline
7 & 36.8 & 16.8 & 26.6 \\ \hline \end{tabular}
\end{table} 
Table 2: Geometrical parameters of the proposed LPDA shown in Figure 1.  
In Figure 7, the LPDA antenna directivity, gain, and radiation efficiency are reported as a function of the frequency. The LPDA gain and directivity are quite stable over the required frequency range, and their average values are equal to 6.56 dB and 6.75 dB, respectively. The predicted reduction in the directivity and gain in comparison with a standard wire LPDA with the same values of \(\tau=0.85\) and \(\sigma=0.11\) is confirmed by these results. Moreover, we used meandered dipoles as radiating elements instead of standard printed dipoles, and this resulted in a further small decrease in the value of D, as already discussed when comparing the far fields of the isolated dipoles reported in Figure 4. Finally, the radiation efficiency of the proposed antenna is excellent within the operating frequency band, with a flat behavior and an average value above 97%. Finally, Figure 8 reports the E-plane and H-plane radiation patterns at 470 MHz, 860 MHz, and 665 MHz, i.e., at the center frequency and at the extremes of the requested frequency band. The cross-polar component is more than 30 dB below the co-polar one in the E-plane, and more than 40 dB lower in the H-plane. Comparing the radiation performance of the wired LPDAs and printed LPDAs of Table 1 that are implemented using traditional dipoles with our printed LPDA with meandered dipoles, we can conclude that the printed LPDA proposed here shows substantially the same radiation pattern and  
Figure 5: Reflection coefficient of the designed LPDA antenna. Figure 6: Input impedance of the designed LPDA antenna. similar levels of cross-polar components.