| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 96 === In order to realize broadband GCPW to SIW transitions covering the S-band (2.6-3.95 GHz), transitions using multi-section transmission lines, which includes multiple quarter-wavelength transformers, single quarter-wavelength transformer with an extended 90-bent slot , and single quarter-wavelength transformer with an extended 90-bent tapered slot are adopted. Systematic design rules for transitions using these structures are investigated and back-to-back circuits are carried out to verify the simulation results. Transition using a single quarter-wavelength transformer could achieve a bandwidth of 25.86 % for which the return loss is larger than 15 dB. In order to widen the bandwidth, a 90-bent slot or a 900-bent tapered slot are added at the end of the quarter-wavelength transformer. It has been shown that the transition using a quarter-wavelength transformer with a 90-bent slot and that using a quarter-wavelength transformer with a 90-bent tapered slot could achieve a bandwidth of 38 % and 42 %, respectively. A transition using two sections quarter-wavelength Chebyshev transformers, which has a bandwidth of 40.53 % is designed for comparison. It can be seen that the transition using a quarter-wavelength transformer with a 90-bent slot and that using a quarter-wavelength transformer with a 90-bent tapered slot have similar bandwidth with that of the transition using two sections quarter-wavelength Chebyshev transformers, but the transition size is cut into half.
Besides, in order to further reduce the transition size, we take advantage of the quarter-wavelength SIR to replace the quarter-wavelength transformers in the previous designs. A GCPW to SIW transition using a quarter-wavelength SIR and a GCPW to SIW transition using a quarter-wavelength SIR with an extended 90-bent slot are proposed. As the total electrical length θT for the SIR is chosen as 60, the circuit size for the transition using a quarter-wavelength SIR is further reduced to two-third of that using a quarter-wavelength transformer, but the bandwidth is slightly reduced from 25.86 % to 23.77 %. Similarly, the circuit size for the transition using a quarter-wavelength SIR with an extended 90-bent slot is also reduced to two-third of that using a quarter-wavelength transformer with an extended 900-bent slot, but the bandwidth is slightly reduced from 38 % to 36.8 %. In a word, a compact transition could be achieved by slightly sacrificing the bandwidth as trade-off.
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