Multi-objective optimization design of compact MIMO antennas with canonical structures (viz., transformation or combination by regular shapes) for wideband radiation and fragment structures (viz., combination by discrete fragment patches) for high isolation is proposed and demonstrated. In the design, MOEA/D-DE for optimization of canonical structures and MOEA/D-GO for optimization of fragment structures are combined and iterated. The design is demonstrated with compact bow-tie MIMO antennas sharing a small common ground plane. The four orthogonally deployed bow-tie antennas are optimized by using MOEA/D-DE to acquire dual polarization and wideband radiation. Fragment-type structures on the common ground plane are optimized by using MOEA/D-GO to acquire very high isolation. Both simulation and measurement show that the optimized MIMO bow-tie antennas provide isolation higher than 30dB in a relative bandwidth of 40% (from 2.6GHz to 3.9GHz). With the proposed design technique, dual-band high isolation MIMO antennas may also be designed.
SUMMARYScalable modeling with very simple topology for stacked millimeter-wave transformers is presented. Because of high-frequency effect and thick metal effect, the architecture is based on single-π and double-π network for transformers with turn ratio 1:1 and 1:2, respectively. The model parameters are extracted from two factors-the layout and process data. Simple and accurate expressions for the self-inductance, mutual coupling inductance, and oxide capacitance are provided for the model. The proposed model is verified by 65 nm technology transformers. A very close agreement is shown for S-parameter, self-inductances of each coil, and coupling coefficient up to 110 GHz.
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