| Summary: | 碩士 === 國立成功大學 === 電腦與通信工程研究所 === 101 === Two quasi-circulators and a active balun using TSMC 90 nm CMOS process for communication front-end system applications are proposed. First, a broadband and high isolation active quasi-circulator MMIC is introduced. The quasi-circulator cascaded two buffer stages to expand the bandwidth and improve the isolation from port 2 to port 1 and from port 3 to port 2. The leakage signal from port 1 to port 3 can be reduced effectively by the phase cancellation technique. As the measured results show, the proposed quasi-circulator possesses an insertion loss less than 8 dB and all isolations on 5-33 GHz are better than 20 dB.
Afterward, a Ka to W band CMOS quasi-circulator combined Lange coupler and transistors to achieve high isolation and broad bandwidth by phase cancellation technique. Based on the simulation, very wideband operation from 26 to 120 GHz can be obtained. The measured data shows that better than 40 dB isolation between the port 1 and port 3 with 94 GHz (26-120 GHz) operational bandwidth. While that for port 2 to port 1 and port 3 to port 2 is better than 30 and 35 dB, respectively. The insertion loss of port 1 to port 2 is 7-10 dB, and that of port 2 to port 3 is 6-10 dB. Due to the measurement system limitation, the overall measured bandwidth of the proposed quasi-circulator was implemented in the range of DC-67 GHz, therefore, the measured insertion losses is about 6-9 dB and isolations are better than 20 dB from 26-67 GHz.
Finally, a high gain and high P1dB active balun with low power consumption was proposed. The proposed circuit consisted of differential stage and current-reuse LNA to achieve high insertion gain and reduce the DC power consumption. Moreover, the proposed active balun used single differential stage can avoid to decreasing the P1dB, and cascaded a gate inductor with differential stage to enhance the operation bandwidth. Base on the simulated results, the proposed active balun exhibits good insertion gain of 12-15 dB and low gain/phase error are less than 1.5 dB/4 degree with high P1dB of 2.3 dBm in 6-25 GHz operation bandwidth.
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