# Electronic Beam Steering Metamaterial Antenna with Dual-Tuned Mode of Liquid Crystal Material
## 3 Design, Simulation and Analysis of Dual-Tuned CRLH Metamaterial Antenna Based on LC
### Simulation of CRLH Metamaterial Antenna Based on LC  
Afterward, five CRLH unit cells are cascaded to form an electronically controlled beam-steering CRLH metamaterial antenna based on the dual-tuned mode of LC, as displayed in Figure 6. In order to let the main structure of the antenna look more distinguished, the upper substrate (Substrate A), the metal cover sheet, substrate C and the ground metal layer in Figure 1 are omitted. The intermediate substrate (Substrate B) in Figure 1 is set to be semitransparent. The parallel inductor is below Substrate B, while the interdigital structure is above Substrate B. From the figure, the position relationship between the parallel inductor and the upper series interdigital capacitor can be seen more distinctly, and they are connected through the metallized via holes. Two ports are adopted to form a traveling wave antenna to avoid reflection and standing wave, which are on the left and right sides of the antenna. For the dual-tuned LC structure, the bias voltage of the first LC layer is loaded between the cover sheet and the interdigital structure, and the bias voltage of the second LC layer is loaded between the interdigital structure (loaded to the parallel inductor through the metallized via) and the ground. When Port 1 is fed and Port 2 is connected to matching load, due to the dual-tuned mode of the LC, the electronically controlled beam-steering CRLH metamaterial antenna has beam-steering characteristics at different bias voltages, as displayed in Figure 7. From Figure 7a, at the balanced frequency 14.4 GHz, the simulated realized far-field pattern shifts from \(0^{\circ}\) to \(-35^{\circ}\), including \(-8^{\circ}\) and \(-18^{\circ}\), with the side lobe below \(-10\) dB. Meanwhile, the realized gain is maintained around 6 dB. Due to the continuous scanning characteristic of the LC, the CRLH metamaterial antenna can also achieve continuous beam steering from \(0^{\circ}\) to \(-35^{\circ}\). In the case that the feed is varied to Port 2 while Port 1 is connected to the matching load, a beam scanning range from 0 to 35 degrees can be achieved. From the curve of the main lobe direction via frequency in Figure 7b, with the redshift of the balanced frequency, the broadside frequency also transforms. In addition to acquiring fixed-frequency beam steering, CRLH metamaterial antenna also has frequency scanning characteristics from negative to positive, including broadside in the range of 2 GHz (from 14 GHz to 16 GHz) in each LC state. For the CRLH structure, the zero point of the phase of the unit cell corresponds to the frequency point of the antenna broadside. Thus, under the four extreme states of the LC, the frequency point of the zero phase in the unit cell dispersion simulation results is compared with the frequency point when the antenna beam is pointing at \(0^{\circ}\), as shown in Table 2. It can be seen from the table that, in any LC state, the frequency point of phase zero is consistent with the corresponding broadside frequency of the antenna. There is no frequency offset, and the simulation results have good consistency. The radiation efficiency of the antenna under  
Figure 6: Schematic diagram of the CRLH metamaterial antenna based on LC. the four extreme states is displayed in Figure 7c. Due to the employment of multilayers and LCs, the radiation efficiency of the antenna is around 40% of 14.4 GHz. In the meantime, the magnitude of S\({}_{11}\) keeps below \(-10\) dB, which has good impedance, matching in a broad frequency band from 13.8 GHz to 17 GHz, as presented in Figure 8. Meanwhile, the S21 curves of the antenna are also described in Figure 8 to demonstrate the transmission of the electromagnetic wave. As shown in the figure, on account of the reflection of the incident port, the loss of the substrate and the LC material, and the radiation of the antenna, fewer electromagnetic waves are transmitted from Port 2.