## 3 The 16 \(\times\) 24 Antenna Array  
With the use of the 4 \(\times\) 4 subarrays, a 16 \(\times\) 24 antenna is designed and fabricated. The configurations of the 16 \(\times\) 24 non-uniform phased array are presented in Figure 8. For the purpose of elements feeding under the equal power division radios without phase difference, the one-three powder dividers and one-two power dividers shown in Figure 8c,d are introduced. In detail, the metal Via walls of the Rx-band one-three power divider embedded in Substrate 4 are proposed to reduce the coupling between the adjacent MS lines aligned in parallel. Furthermore, Ground 2 on the upper layer of Substrate 4 is placed between the PP layer and the Rx-band feed network, which can effectively suppress the surface wave and transmission loss. Meanwhile, the metallic Vias of the Tx-band SICL feed line are embedded in Substrates 2 and 3. The feeding structures with a wide-narrow-wide-narrow-wide SICL for the Tx-band one-three power divider contribute to achieving the wide impedance bandwidth, and the shared metallic Vias between the adjacent narrow-SICL structures are responsible for the suppression of the coupling with a miniaturized feed network design. In addition, compared with the one-three power divider, only the T-junction for feeding the additional port is replaced with a U-shaped line for the one-two powder divider, ensuring in-phase excitation. The simulated S-parameters of the one-three corporate feed networks are shown in Figure 9. The input port of the one-three parallel feed network with \(\,\mathrm{1S_{11}}\,\mathrm{|<}\mathrm{-}\mathrm{20\,dB}\) is obtained at the Rx band, and the transmission coefficients of output ports 2, 3, and 4 (i.e., \(\,\mathrm{1S_{12}}\,\mathrm{|,\,}\mathrm{1S_{13}}\,\mathrm{|,\,}\mathrm{and} \,\mathrm{|\,}\mathrm{S_{14}}\,\mathrm{|\,}\mathrm{)}\) approximately equal \(-\)5.9 dB, with an amplitude difference less than 0.5 dB. Meanwhile, the simulated magnitude and phase differences between the output port are less than 0.1 dB and 6\({}^{\circ}\) at the Tx band. It should be noted that the SICL-to-microstrip transition eliminates the 180\({}^{\circ}\) phase difference and then keeps the in-phase excitation for the proposed antenna array. Figure 7: Simulated S-parameters of Rx-band feed network: (**a**) Miniaturized ring coupler. (**b**) Four-way corporate feed network. The fabricated 16 \(\times\) 24 antenna is illustrated in Figure 10. The proposed antenna arrays are fabricated by printed circuit board (PCB) and computer numerical control (CNC) machining technology. A metal Reflector cavity consisting of rectangular and cross-shaped supporting metal blocks is introduced as the container for the antenna array, machined by aluminum plate and treated by conductive oxidation. As shown in Figure 10d, these metal blocks can serve as a supporting structure between the antenna array surface and the metal Reflector. Four Tx SMA ports and four Rx SMA ports on the metal Reflector are used to connect with the T/R RF modules. Furthermore, the S-parameters are obtained by Keysight N5247B. The radiation patterns and gains are measured by the planar near-field anechoic chamber technology, and the photograph of the measurement setup is shown in Figure 11.  
Figure 8: Configurations of the proposed 16 \(\times\) 24 antenna array. (**a**) Top view. (**b**) Bottom view. (**c**) Rx-band feed network. (**d**) Tx-band feed network. Figure 9: Simulated S-parameters of the one–three corporate feed network: (**a**) Rx-band feed network. (**b**) Tx-band feed network. The measured S-parameter results of the 16 \(\times\) 24 antenna array are given in Figure 12a. The results show that the measured impedance bandwidths of the Rx and Tx ports are 22.1 % (10.57-13.33 GHz) and 21.1 % (12.31-15.32 GHz), respectively. The isolation is better than 47.5 dB in the Tx and Rx bands.