Designs of True-Time-Delay Lines and Digital Phase Shifters Using Composite Right/Left-Handed Transmission Lines

This dissertation, "Designs of true-time-delay lines and digital phase shifters using composite right/left-handed transmission lines" by Jun, Zhang, 张君, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The studies of the designs on true-time-delay lines (TTDLs), n-bit digital phase shifters and wideband switched-line phase shifters using composite right/left-handed transmission-line (CRLH TL) unit cells are presented in this thesis. To simplify these designs, a symmetrical CRLH TL unit cell having equal input and output impedance is proposed. In the design of TDDLs, the symmetrical CRLH TL unit cell with higher time-delay efficiency helps achieve a size reduction of 67.9%, compared with the TTDL designed using right-handed transmission line (RH TL). The symmetrical CRLH TL unit cell is further modified to a compact CRLH TL unit cell to further reduce the size by 58%. For performances comparison, the TTDLs using the compact CRLH TL unit cells, symmetrical CRLH TL unit cells and RH TL are studied using computer simulation and measurement. Results show that the TTDLs using the compact CRLH TL unit cells can achieve much longer time delays. The TTDLs designed using CRLH TL unit cells have narrow bandwidths because CRLH TL unit cells have narrow bandwidths. In this thesis, a wideband unit cell obtained by rotating the CRLH TL unit cell by 900is proposed in the design of TTDLs. Simulation and measurement show that the TTDL using wideband unit cells can achieve a time delay about 3 times and 6 times longer than that of the periodic microstrip line (PML) and RH TL, respectively. A 2-bit, 3-bit and 6-bit phase shifters using symmetrical CRLH TL unit cells are designed using computer simulation. In these designs, positive-intrinsic-negative (PIN) diodes mounted on the fingers of the CRLH TL unit cells are used as switches to control the phase response at the output. Different phase shifts are achieved using different switching states determined by controlling bits. The phase shifters are fabricated and measured. Simulated and measured results agree very well. Power-handling capability is also analyzed using surface-current density on the CRLH TL unit cells. Results show that the phase shifters have much higher power-handling capabilities than that of the PIN diodes. A wideband 1800-switched-line phase shifter using symmetrical CRLH TL unit cell is proposed. The switched-line phase shifter employs a symmetrical CRLH TL unit cell as the reference arm and a RH TL as the delay arm to produce a constant phase shift across a wide frequency band. For comparison, a traditional 1800-switched-line phase shifter using RH TLs for both reference and delay arms is also designed. To reduce the size, the CRLH TL unit cell is realized using lump elements (LEs). Wideband 900-and 1800-switched-line phase shifters using LE-CRLH TL unit cells are studied and compared with the traditional 900-and 1800-switched-line phase shifters. Simulated and measured results show that the proposed designs using symmetrical CRLH TL unit cells and LE-CRLH TL unit cells have very constant phase shifts with smaller variations compared with the traditional designs. DOI: 10.5353/th_b4985880 Subjects: Delay lines Phase shifters Strip transmission lines