# Wide-Band Wide-Beam Circularly-Polarized Slot-Coupled Antenna for Wide-Angle Beam Scanning Arrays
## 4 Numerical Assessment
One can observe that the fundamental mode \(TM_{11}\) is properly excited on the circular patch [33] and there is a clock-wise rotation of the corresponding surface current distribution (Figure 9). The vector plot of the electric field distribution at a quota of \(z=10\lambda_{0}\), \(\mathbf{E}(x,\,y;\,t)\), shown in Figure 10 for the same instants, further verifies the desired _CP_ of the radiated wave, which evolves in time according to a _LHCP_. For comparison purposes, Figure 11 plots the broadside gain \(G(f,\,\theta=0,\,\varphi=0)\) [Figure 11a] and the \(AR\,AR(f,\,\theta=0,\,\varphi=0)\) [Figure 11b] within the band of interest of the proposed _WWCS_ model and of the design in [20]. It turns out that the synthesized radiator exhibits a good \(AR\) performance, especially within the band \(f\in[2.4,\,2.6]\) [GHz] where \(AR|_{WWCS}\leq 6\) [dB] [40], that results in an \(AR\) bandwidth (_ARBW_) equal to \(ARBW|_{WWCS}^{6 dB}=8\%\), while \(ARBW|_{[Pan\,2014]}^{6 dB}=0.8\%\) [i.e., an improvement by \(\frac{ARBW|_{WWCS}^{6 dB}}{ARBW|_{[Pan\,2014]}^{6 dB}}=10\) times--Figure 11b]. A similar outcome is yielded for the 3 [dB]-bandwidth, as well, since \(ARBW|_{WWCS}^{3 dB}=3.6\%\) and \(ARBW|_{[Pan\,2014]}^{3 dB}=0.3\%\) [i.e., an improvement by \(\frac{ARBW|_{WWCS}^{3 dB}}{ARBW|_{[Pan\,2014]}^{3 dB}}=12\) times--Figure 11b]. Figure 8: _Numerical Assessment_ (\(\left|f_{\min},\,f_{\max}\right|=[2.3,\,2.6]\) [GHz], \(f=f_{0}=2.45\) [GHz])—Absolute (**a**,**c**) and thresholded (**b**,**d**) 2D maps of the simulated (**a**,**b**) axial ratio, \(AR(f_{0},\,\theta,\,\varphi)\), and (**c**,**d**) cross-polar discrimination, \(XPD(f_{0},\,\theta,\,\varphi)\), in the complete upper half-space of the _WWCS_ antenna. Finally, the suitability of the _WWCS_ radiator as elementary building block of circularly-polarized wide-band _WASA_s was assessed. Towards this end, the radiation features of a large planar uniform phased array, comprising \(N=(50\times 50)\)_WWCS_ identical elementary radiators, were studied. To account for the mutual coupling in this large aperture, a periodic model was simulated in _HFSS_. Figure 12a) describes the behavior of the array gain along the angular steering direction, \((\theta_{s},\,\varphi_{s})\), when setting uniform phase shifts and isophoric excitations to scan the beam in the range \(\theta_{s}\in[-90,\,90]\) [deg] in both vertical planes (i.e., \(\varphi_{s}=0\) [deg] and \(\varphi_{s}=90\) [deg]).To avoid the insurance of grating lobes for close-to-endfire operation, an inter-element spacing of \(d=d_{x}=d_{y}=0.49\) [\(\lambda_{0}\)] was chosen by slightly shrinking the side of the _WWCS_ antenna to \(L_{a}=d\). Figure 11: _Numerical Assessment_ (\([f_{\rm min},\,f_{\rm max}]=[2.3,\,2.6]\) [GHz])—Behavior of the (**a**) broadside gain, \(G(f,\,\theta=0,\,\varphi=0)\), and (**b**) axial ratio, \(AR(f,\,\theta=0,\,\varphi=0)\), as compared to the literature result in [20]. Thanks to the wide-beam nature of the _WWCS_ elementary radiator, the array exhibits good scan loss (\(SL\)) performance [\(SL(\varphi_{s})=G(0,\,\varphi_{s})-G(90,\,\varphi_{s})\)], as illustrated by the patterns at different values of the scan angle \(\theta_{s}\) for both \(\varphi_{s}=0\) [deg] [Figure 12b] and \(\varphi_{s}=90\) [deg] [Figure 12c]. The \(SL\) on both elevation planes is always smaller than 8.5 [dB] at the central frequency [Figure 12a]. Moreover, it is worth noticing that there is a good stability of the sidelobe level (\(SLL\)) when scanning the beam on both planes [i.e., \(-13.6\leq SLL\leq-8.2\) [dB]]--Figure 13a]. Similar outcomes can be inferred for the array _HPBW_ as well, since \(2\leq HPBW\leq 6\) [deg] for \(|\theta_{s}|\leq 70\) [deg], while it rapidly increases outside such an angular interval because of the beam broadening effect [33] [i.e., \(HPBW\simeq 20\) [deg] for \(\theta_{s}=90\) [deg]--Figure 13a and [Figure 12b,c].