# Chiral Dielectric Metasurfaces for Highly Integrated, Broadband Circularly Polarized Antenna
## 2 Antenna Design  
### Configuration  
Figure 1 shows a zoomed view of the antenna designed to have the center frequency at 28.5 GHz to enable high-throughput applications in 5G and satellite communications.  
Figure 1: 3D geometric view of the proposed antenna element fed by a SIW ideal connector.  
The antenna consists of five parts referred to as (i) the bottom ground plane; (ii) a substrate integrated waveguide (SIW) with a SIW-to-coax feeding; (iii) a ground plane film; (iv) a coax-fed driven patch antenna; and (v) a chiral dielectric metasurface consisting of a \(2\times 2\) array of slotted dielectric cylinders. The ground plane films were considered to be made of lossy copper. A top-view and side-view of the main building elements of the antenna design are presented in Figure 2.  
The SIW-based feeding layer is etched on a slab of Rogers RT/duroid 5880 (\(\epsilon_{r}=2.2\), \(\tan\delta=0.0009\)), with thickness \(h_{\text{SIW}}=0.5\) mm. A ground plane, \(h_{\text{sub}}=0.035\) mm thick, was used to separate the SIW-feeding and the coax-fed driven-patch antenna. A CDM is stacked at the top of the structure, consisting of four slotted cylinders made of a ceramic dielectric material with \(\epsilon_{r}=16\), layered on a low-permittivity substrate of RT/duroid 5880 (\(h_{\text{meta}}=0.5\) mm). The cylinders had a height \(h_{\text{cylinder}}=0.8\) mm and diameter \(d_{\text{cylinder}}=3.6\) mm, and were separated by a center-to-center distance of \(dy_{\text{c}}=4.8\) mm. The slots at the center of the cylinders were parallelograms whose sides were labeled as \(ls\) and \(hs\) and the tilting angle is \(\alpha\). The slots are rotated by an angle \(\theta\) with respect to the \(y\)-axis, as depicted. CDM is fed by a driven patch localized below the low-permittivity  
Figure 2: (**a**) Parametric side view of the antenna layers divided as: (**b**) SIW-to-coax feeding, (**c**) driven patch layer and (**d**) chiral dielectric metasurface layer. The design parameters are \(x_{1}=10\) mm, \(d=10\) mm, \(d_{2}=7.5\) mm, \(p_{\text{len}}=2.15\) mm, \(d_{\text{via}}=0.3\) mm, \(d_{\text{pin}}=0.4\) mm, \(dist_{\text{via}}=0.19\) mm, \(d_{1}=5.71\) mm, \(t_{\text{size}}=0.86\) mm, \(sp=3.3\) mm, \(l_{f}=0.85\) mm, \(w_{f}=0.8\) mm, \(ls=2.1\) mm, \(hs=0.8\) mm, \(\alpha=60^{\circ}\) and \(\theta=45^{\circ}\).  
layer at the center of the metasurface. The patch made of lossy copper had rectangular sides \(sp\) and corner cuts \(t_{\text{size}}\). The coax-to-patch feeding line has a width \(w_{f}=0.8\) mm and length \(l_{f}=0.85\) mm. The SIW-feeding structure is amenable to integration with planar front-end circuits. The SIW structure was designed as a rectangular waveguide input, forming a SIW-to-coax transition where the distance between the pin and the shorting wall was tuned for impedance matching [24; 25]. The dimensions of the SIW-feeding and the remaining parameters are listed in the caption of Figure 2. It is worth mentioning that with the antenna size taken as \(0.95\lambda_{0}\times 0.95\lambda_{0}\) (\(\lambda_{0}\) at the center frequency of 28.5 GHz), our concept enables the application of phase-arrayed antenna systems by designing the structure to be directly fed by a coax-wire.