| The requirement on the performance of phased array antenna is increasing rapidly in the development of modern communication technology. Electrical scanning antenna system operating at a fixed-frequency is the trend of future development. As a core component, phase shifters are crucial to the performance of phased array antenna.In chapter 3, based on the new sealing method, the mini aturization of tunable meandered-line phase shifter based on liquid crystal is discussed. Two miniaturized broadband meandered-line tunable phase shifters are developed as the thickness of liquid crystal is 0.1mm and 0.25 mm, respectively. Without the diele ctric loss, the insertion loss is less than 1d B up to the working frequency of 15.5GHz. The obtained differential phase shift at 12.6GHz is 282°,which is 50% larger than the one shown in [57]. Based on the proposed tunable phase shifter, a 4-unit uniform linear array antenna is developed. While the effective dielectric constant changes from 2.5 to 3.3, the main lobe direction of the phased array antenna scans from-19° to 22° at 12.6GHz. The gain is around 10 d Bi and the side-lobe level is better than 10 dB.In chapter 4, the microwave network property of the 2-port T-type CRLH(composite right/left-handed) transmission line is analyzed. The adjustment method of the balanced CRLH transmission line in practical application is summarized and then applied to design a liquid crystal based CRLH tunable phase shifter. The impedance of the CRLH transmission line corresponding to the T-type network can be extracted. Then the CRLH transmission line can be adjust to balance state by tuning the series and shunt impedance, respectively. Employing the previously proposed sealing and feeding method, as the effective dielectric constant of liquid crystal varies from 2.5 to 3.3, the obtained differential phase shift at 12.6GHz is up to 474°,which is 80% higher than the miniaturized meandered-line phase shifter proposed in chapter 3 with the same circuit area. |
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