# A New Low-Cost Compact Antenna for the 2.45 and 5.8 GHz ISM Bands
## 4 Experimental Results  
The proposed dual-band antenna is manufactured and experimentally characterized. Figure 13 shows a photo of the front and bottom view of the fabricated dual-band antenna. Figure 14 shows the simulated and measured reflection coefficient of the dual-band antenna as a function of frequency. The comparison results are detailed in Table 3. Measurement results show that the antenna operates at resonant frequencies of 2.44 GHz and 5.81 GHz. Relative to the modulus of the reflection coefficient, at \(-\)10 dB, a small frequency offset of 10 MHz and 40 MHz is, therefore, observed between measurements and simulation around the two ISM frequencies, respectively. In the 5.8 GHz band, the modulus of the measured reflection coefficient increases slightly, by 2.6 dB, while, in the 2.45 GHz band, it is almost constant. On the one hand, the slight frequency shift may be due to the slight modification of the characteristic impedance of the supply line after soldering of the SMA connector used during the manufacturing process. On the other hand, the slight decrease in the reflection coefficient observed at 5.8 GHz can also be explained by losses in the cables and in the SMA connector used. We also observe a 12.5% decrease and a 14.6% increase in bandwidth around the two frequency bands, respectively. These results show good agreement between simulation and measurement in terms of antenna matching at both  
Figure 12: Antenna radiation efficiency as a function of frequency. Figure 13: Dual-band antenna photography: (**a**) view from above and (**b**) bottom view. frequency bands. There is a slight difference between the measured and simulated results, but the overall results agree well, validating the design as a whole. The simulated and measured antenna's radiation patterns at the two frequencies are shown in Figure 15. At the frequency of 2.45 GHz (Figure 15a), the measured and simulated gains are 2.41 dB and 3.6 dB, respectively. In the band of 5.8 GHz, the measured gain is 5.22 dB vs. 5.09 dB simulated. Simulation and measurement show almost the same radiation pattern: quasi-omnidirectional in the E-plane (yz) and directional in the H-plane (xz). In summary, the experimental measurements show that the antenna is dual-band and has the expected performances, i.e., (i) a reflection coefficient of less than \(-10\) dB, (ii) a bandwidth of at least 100 MHz, (iii) a gain of at least 2 dBi, and (iv) an efficiency of at least 80% in both bands. Figure 14: Measured and simulated reflection coefficient influence versus frequency. Figure 15: Simulated and measured antenna radiation pattern at (**a**) 2.45 GHz and (**b**) 5.8 GHz. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Tool** & \begin{tabular}{c} **Central Frequency** \\ **(GHz)** \\ \end{tabular} & \
\begin{tabular}{c} **S11** \\ **(dB)** \\ \end{tabular} &
\begin{tabular}{c} **Bandwidth at \(-10\) dB** \\ **(MHz)** \\ \end{tabular} \\ \hline Simulation & 2.45 & \(-13.66\) & 160 \\  & 5.85 & \(-29.73\) & 445 \\  & 2.44 & \(-13.60\) & 140 \\  & 5.81 & \(-27.12\) & 510 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of measured and simulated reflection parameters and bandwidth. Several dual-band antennas operating in frequency bands of 2.45 GHz and 5.8 GHz have already been presented in the literature. Table 4 provides a comparative summary of the proposed antenna in terms of operating frequencies (Freq. ), substrate parameters, patch type, dimensions, and antenna performance in terms of bandwidth (BW), gain, and radiation efficiency (Rad. Eff.) for each of the two frequency bands. The symbol \"-\" indicates that the corresponding value is not mentioned in the reference. According to Table 4, the proposed dual-band antenna is very compact and performs well in terms of bandwidth, gain, and radiation efficiency.