# Development of a Wideband Slotted Antenna Array with Low Profile and Low Sidelobe
## 4 Discussion  
There are several types of antennas that can provide the radiation property of low sidelobe. The radiation performance of the proposed slotted cavity antenna array is compared to several typical antenna arrays in the literature. For a reliable and scientific comparison, simulation results from the literature are mainly listed in Table 3. Especially, the designed center frequency, working bandwidth, array scale, peak gain, first SLL, aperture efficiency, and the overall size are carefully compared. Due to the simplicity of implementation, microstrip antenna arrays [32; 33; 34] are mostly designed. The radiating units are uniformly distributed, with the impedance and the power distribution being controlled by adjusting the dimensions of the units and the series-fed network. As shown in Table 3, though a first SLL as small as \(-26.3\) dB is achieved, the microstrip-based antenna array has a very limited working bandwidth. The Huygens antenna array [5] has a slightly broader bandwidth, and its bandwidth can be as large as 10% when it is designed as a 16 \(\times\) 16 large-scale array by using a smaller compact feed network with tapered amplitude [35]. Especially, since it requires only a simple feeding network, its overall size can be designed slightly smaller. The SIW slot antenna array [7] can provide further better bandwidth and has slightly lower profile height, but its aperture efficiency is very low, due to its high dielectric loss. The dielectric resonator antenna array [29] can provide a much more enhanced bandwidth, as large as 31.9% and 38.1% for simulation and measurement results, respectively, by adjusting the dimensions of the feeding ring. However, it cannot achieve a low first SLL across the entire bandwidth, as its first SLL can be only obtained from 7.22 to 7.73 GHz (6.82%). As can be seen from Table 3, slotted waveguide antenna arrays [19; 27; 36; 37; 38] can provide a relatively good balance between a wide bandwidth, a high gain, and a low sidelobe. As shown in Table 3, for a 16 \(\times\) 16 antenna array that uses a uniform feeding network, the obtained SLL is only around \(-14\) dB [19], which demonstrates that the proposed feeding network can dramatically reduce the SLL. However, as expected, using an unequal feeding network can slightly affect the aperture efficiency, especially when the array scale is large. The main part of the proposed antenna array is also based on slotted waveguide structure, but it involves a novel resonator cavity structure, which can particularly reduce the antenna size and enhance the bandwidth without affecting the gain. Therefore, as shown in Table 3, compared to most existing designs that use an unequal feeding network, the proposed antenna array can work in a sufficiently broad bandwidth, and especially, it has a comparably good first SLL and a high aperture efficiency. If the antenna arrays listed in Table 3 are all designed in the form of 16 \(\times\) 16, the proposed improved slotted structure has almost the smallest dimensions. Even compared with the substrate-based antenna arrays [5; 7; 29], the proposed array has a comparable profile while having competitive first SLLs. It should be noted that in the above discussion, only simulation results are compared. Obviously, there are usually some differences between simulated and measured results. To clarify the difference, all papers related to the proposed work in Table 3, especially some particular papers [19; 27; 28] are analyzed. A preliminary conclusion that the measured bandwidths have good agreements with (or are even better than [5; 27; 28; 29]) the corresponding simulation results can be drawn. In addition, there is little difference (\(<\)2 dB) in the first SLL between the simulation and the measurement [7; 27; 28], while the simulated gain is only about 0.5 dB lower than the measured [5; 7; 19; 28]. This means that the performance difference between simulation results and actual measurement results is very small [5; 7; 19; 28],