| Recently, phase array antennas are widely applied in both military and civilianfields due to its ability to flexibly control the beam direction by the phase shifter.Compared to traditional antennas which control the beam direction mechanically, thephase array antennas controlling the beam scanning electrically have the advantages offlexible control, fast speed and no inertia. As the key component in phased arraysystems, phase shifters can be realized in two different forms, digital phase shifters andanalog phase shifters. The analog phase shifters can adjust the phase shift continuously,but with a relatively narrow bandwidth. The composite right/left handed (CRLH)transmission line being proposed has provided a new idea to increase the bandwidth ofanalog phase shifters. The CRLH has the advantages of novel performance, simplestructures, adjusting parameters easily, being compatible with planar circuits andcompact size, thus has been widely used in microwave devices in recent years.This paper focuses on the phase-shift characteristic as well as the application ofCRLH. The relationship between the phase response of CRLH and frequency isanalyzed, and a novel wideband tunable phase shifter is designed and then applied inlinear microstrip phase array antennas. First, domestic and overseas research dynamic ofCRLH is introduced, then the transmission characteristic of electromagnetic wave inCRLH and the working principle of linear phased array antennas are analyzed. Afterthat, a new type of tunable CRLH unit cell is proposed, and a wideband tunable phaseshifter based on the relationship between the phase response of the CRLH unit cell andfrequency is designed and fabricated. Based on the above analysis, a new type ofresonance tunable CRLH unit cell is proposed and an electrically tunable filter with lowinsertion loss and high selectivity is fabricated. On the basis of tunable phase shifters, aphase modulation feed network for phase array antennas is designed, including powerdivider design, phase shifter design and feed network integration design. And then thedesign of a microstrip antenna element is completed based on the above feed network,followed with the design of4×1and4×3linear microstrip phase array antennas. Thephase shifter can be controlled by voltage, in this way, scanning continuously by the main lobe. All the above designs are fabricated and then verified through experiments.The simulation and measured results agree with each other quite well and the expectedgoals have been achieved.This paper also discusses the nonlinear effects of the varactor diodes used in theresearch, and puts forward the impact to measured results brought about by the parasiticparameters of the varactor diodes. Finally, the whole paper is summarized and furtherresearch work is expected. |
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