# A Novel High Gain Monopole Antenna Array for 60 GHz Millimeter-Wave Communications
## 3 Results
### The Proposed Microstrip Antenna Array Results  
To examine the actual performance and validate the simulation results, the antenna array prototype was fabricated, and its performance in terms of S-parameters was measured by Rohde and Schwarz ZVA 67 vector network analyzer using 50X port. The fabricated 5G antenna array is depicted in Figure 14. For the measurement considerations, the ground plane, as well as the microstrip feeding line of the antenna prototype, was extended long enough for placing the commercial 1.85 mm end launch connector. The spacing between the antennas and the connection method between them, as well as using an appropriate feeding network on the top plane and the addition of the two L-shaped slots as DGS on the bottom plane, enhanced the performance of the monopole antenna array. The proposed monopole antenna array had a wide bandwidth, which covered the range of 57.2-63.8 GHz, as shown in Figure 15, and the obtained bandwidth represented a 3.94% increase when compared to the bandwidth of the array reported in [28]. The measured results were consistent with the simulations since both curves cover the desired band for 5G technologies, as shown in Figure 15. However, there was a small discrepancy between them in terms of resonance frequencies and the values of the return loss at these  
Figure 14: Fabricated model of the proposed mmWave 5G array antenna system. Figure 13: The surface current distribution of the proposed mmWave antenna (**a**) Top view; (**b**) Bottom view. frequencies. This could have happened due to the fabrication tolerance and mismatch between the connector and the proposed antenna array. The radiation pattern in Figure 16a showed two main lobes and side lobes, where the side lobe level at \(-59.4\) degree had (SLL = \(-7.63\) dB), making the radiation pattern of the proposed antenna array optimal for applications that required beam steering technique as in [29]. The 2-D and 3-D radiation patterns of the proposed array were simulated and are presented in Figure 16; the radiation efficiency of the proposed antenna array was over 85% with radiation power  
Figure 16: Simulated radiation characteristics of a single antenna (a) 2-D radiation pattern; (b) 3-D radiation pattern. Figure 15: Measured and simulated S-parameters curves versus frequency of the proposed mmWave 5G antenna array. overlaps in one direction and a maximum gain of 11.6 dBi at 60.5 GHz, which was 0.93 dB higher than the gain achieved by the reported antenna array in [29]. Moreover, the size of the proposed antenna array was more compact than the presented antenna array in [30], which was utilizing the same band with a little difference in performance. Despite the importance of evaluating the current density at a variety of frequency within the operational bandwidth in the intricate characteristics of the antennas radiation characteristics, this came with added complexity. In order to compromise between the two aspects, the current distribution was only evaluated at the frequency of max gain, which was the 60.5 GHz, as shown in Figure 17.  
The current distribution was mainly localized at the edge of the slots in the ground plane. This showed the high coupling effect between the feed line and the slots, as presented in Figure 17. This was the reason for the added frequencies of resonance, which were later on merged together by the edges to achieve a wideband performance. The proposed antennas single element and array had a wideband and optimal gain, by comparing with different antennas that operate at the same band, as presented in Tables 5 and 6. The comparison was undertaken in terms of size, gain, and bandwidth, and it was worth noting that the antenna achieved a higher gain with improved bandwidth, and this was due to the modification in the radiator and the ground plane, as previously discussed in the design procedure of the suggested antenna and antenna array.