# A Compact, Low-Profile, Broadband Quasi-Isotropic Antenna for Non-Line-of-Sight Communications
## 5 Antenna Performance Verification under an NLOS Environment  
The quasi-isotropic antenna can be strategically used to provide reliable and robust communications under the NLOS environment [2; 17; 22]. In this section, we verify the performance of the proposed broadband quasi-isotropic antenna by comparing the received power under line-of-sight (LOS) and NLOS measurement scenarios at the university building corridor. The overall Rx power measurement setup is shown in Figure 16. Two different pairs were set for the measurement. One pair consisted of commercial broadband omni-directional monopole antennas being placed as both Tx and Rx antennas [43]. The monopole antenna was vertically polarized with a length and width of 275 and 45 mm, respectively. The received power values from this setup were used as references. The other consisted of the Rx antenna being replaced with the proposed antenna as a means of verifying the broadband quasi-isotropic performance. The Tx signal was fed from a signal generator, Anritsu MG3692C (Anritsu, Kanagawa, Japan), and amplified by a ZX345 power amplifier (Doggett, Houston, TX, USA) from mini circuits [44]. The Rx antenna was connected to the signal analyzer, Anritsu MS2830A, to measure the amount of received power. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & \multirow{2}{*}{**Design Method**} & \multirow{2}{*}{\begin{tabular}{c} **Dimension** \\ **[mm]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **\(ka\)** \\ **Frequency** \\ **[GHz]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Fractional** \\ **Bandwidth** \\ **[\%]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Pattern** \\ **Bandwidth** \\ **[GHz]** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Gain** \\ **Deviation** \\ **[dB]** \\ \end{tabular} } & \multirow{2}{*}{**CP**} & \multirow{2}{*}{
\begin{tabular}{c} **Eff.** \\ **[\%]** \\ \end{tabular} } \\ \hline
[16] &
\begin{tabular}{c} Electric dipole and \\ loop antenna \\ \end{tabular} & 25 (Radius) \(\times\) 2.2 (H) & 0.48 & 0.95 & 2.4 & N/A & 4.5 & No & 81 \\ \hline
[23] &
\begin{tabular}{c} Meandered dipole \\ with matching \\ network \\ \end{tabular} & 98.7 (L) \(\times\) 14.2 (W) \(\times\) 0.05 (H) & 0.9 & 0.84–0.95 & 20 & N/A & N/A & No & N/A \\ \hline
[24] &
\begin{tabular}{c} Twisted dipole \\ with matching \\ network \\ \end{tabular} & 79.2 (L) \(\times\) 53.1 (W) \(\times\) 0.05 (H) & 1.6 & 0.84–0.92 & 8.5 & 0.88–0.96 & 6 & No & N/A \\ \hline
[25] &
\begin{tabular}{c} L-shaped monopole \\ with feeding \\ network \\ \end{tabular} & 45 (L) \(\times\) 45 (W) \(\times\) 0.8 (H) & 1.46 & 2.2–2.7 & 20.8 & 2.36–2.53 & 6 & No & 80 \\ \hline
[26] &
\begin{tabular}{c} Electric dipole along \\ x, y, and z-axes \\ \end{tabular} & 95 (L) \(\times\) 95 (W) \(\times\) 95 (H) & 1.2 & 1.31–1.81 & 32 & 1.5 & 12.52 & Yes & N/A \\ \hline
[27] &
\begin{tabular}{c} Inverted-F antenna \\ \end{tabular} & 52 (L) \(\times\) 37 (W) \(\times\) 1.6 (H) & 7.01 & 10.5 & 15 & N/A & 10.5 & No & N/A \\ \hline
[30] &
\begin{tabular}{c} Inverted-F antenna \\ \end{tabular} & 25 (L) \(\times\) 25 (W) \(\times\) 3.1 (H) & 0.88 & 2.4 & 4.1 & N/A & 3.6 & Yes & 65 \\ \hline
[42] & \
\begin{tabular}{c} Elliptical loop \\ with \(\mathrm{L}\) \\ with \(\mathrm{L}\) \\ with \(\mathrm{L}\) \\ network \\ \end{tabular} & 100 (L) \(\times\) 90 (W) \(\times\) 1.59 (H) & 1.15 & 0.82–3.5 & 124 & N/A & N/A & No & N/A \\ \hline This work &
\begin{tabular}{c} Crossed dipole \\ \end{tabular} & 25 (Radius) \(\times\) 0.254 (H) & 0.94 & 1.8–4.2 & 80 & 1.9–3.3 & 8.4–9.8 & Yes & 90 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Performance comparison of the proposed broadband quasi-isotropic antenna with other reported quasi-isotropic antennas. The measurement was performed by moving the position of the Rx antenna from position 0 to position 7, as illustrated in Figure 16. As shown in Figure 17, a concrete wall was used as a block to create the NLOS circumstance between the Tx and Rx antennas.