## 4 Comparison with State-of-the-Art Works  
In this section, the proposed beam steering techniques are compared with the state-of-the-art works. The comparison is performed in terms of the main concept of the utilized technique, beam steering range, maximum SLL, HPBW, and the significant remarks (drawbacks and advantages) as mentioned in Table 16.  
In [19], the main beam steering is performed using a three-bit phase shifter. The steering network was formed from a uniform eight-branch power divider with each terminal feeding a microstrip line equipped with a switching mechanism that enabled three-bit periodic phase shifting for beam steering. The antenna array elements are fed by the network via coupled feeding. While the main drawbacks of the work are: (i) A complicated feeding network where the progressive phase shift of each antenna element is needed to be quantized and mapped from 0\({}^{\circ}\) to \(-360^{\circ}\) in the eight different states of the individual 3-bit phase shifter. (ii) Each three-bit phase shifter requires eight PIN diodes, DC coupling capacitors, and a DC biasing network that complicates the design and increases the feeding network cost. (iii) The realized SLL of the array is higher than the ideal case due to the phase quantization errors that reaches 22.5\({}^{\circ}\) in this quantized three-bit phase shifter. (v) In contrast to the ideal situation, when phase quantization was not used, this phase inaccuracy is the reason for the main beam direction mismatch. (iv) The array gain changes with the change in the main beam direction. In [20], a switched beam antenna array has been introduced. In order to produce four distinct main beam directions, the antenna's phase shifter made use of a 4 \(\times\) 4 planar Butler \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **Beam Steering Range (BSR)** & **Maximum SIL** & **HPBW** \\ \hline \multirow{4}{*}{[19]} & Relatively continuous beam steering from & Poor SLL performance as the realized SLL of the & \\  & \(-50^{\circ}\) to \(50^{\circ}\) by switching eight different & array is higher than the ideal case due to the phase & Whenever the main beam’s direction changes, \\  & sampling states of the switching mechanism. & quantization errors that reaches 22.5\({}^{\circ}\) in this & the HPBW correspondingly changes. \\ \hline \multirow{4}{*}{[20]} & Switched beam steering at four distinct angles : & High SLL within the range from \(-9\) dB to & Whenever the main beam’s direction changes, \\  & \((-41^{\circ},-12^{\circ},+15^{\circ},and+48^{\circ})\). & \(-4\) dB. & the HPBW correspondingly changes. \\ \hline \multirow{4}{*}{[21]} & Switched beam steering at four distinct angles : & Good SLL performance that equal & The HPBW is changed by 4.1\({}^{\circ}\) from 23.62\({}^{\circ}\) \\  & \((-13\) dB \(-8\) dB \(-8\) dB \(-13\) dB \(-6\) dB \()\) & to 27.51\({}^{\circ}\) when the main beam is stored from & to 27.51\({}^{\circ}\) \\  & \((+10^{\circ},-38^{\circ},+38^{\circ},and-10^{\circ})\). & at the directions \((+10^{\circ},-38^{\circ},+38^{\circ},and-10^{\circ})\), & \(+10^{\circ}\) to \(+38^{\circ}\) from \(-10^{\circ}\) to \(-38^{\circ}\), respectively. \\ \hline \multirow{4}{*}{[22]} & Continuous beam steering from \(-30^{\circ}\) to \(30^{\circ}\). & Maximum SLL equals \(-9\) dB & The HPBW is changed by less than 1\({}^{\circ}\). \\ \hline \multirow{4}{*}{[23]} & Continuous beam steering from \(-20^{\circ}\) to \(20^{\circ}\). & Not available & Not available \\ \cline{2-2}  & Switched beam steering from \(-19^{\circ}\) to \(19^{\circ}\). & Not available & Not available \\ \hline \multirow{4}{*}{This work} & Continuous beam steering from \(-51.36^{\circ}\)to\(51.36^{\circ}\). & High SLL \(=-2.668\) dB at the edges of the & The HPBW is decreased by 3\({}^{\circ}\) at the edges of \\  & Continuous beam steering from \(-30.73^{\circ}\) to \(30.73^{\circ}\). & Good SLL \(<-10\) dB over the entire steering & The steering range. \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Comparison with state-of-the-art works.