IEEE Microwave and Wireless Components Letters · 2010 · 31 citations · 5 references
EngineeringElectrical EngineeringMicroelectronicsMicrowave EngineeringWireless CommunicationsHigh-frequency Semiconductor DevicesImpedance MatchingMicrowave AmplifiersMicrowave Integrated CircuitsMicrowave Transmission LinesRadio-frequency Integrated CircuitsBalanced AmplifiersBranch-line CouplersCompact Coupler DesignCoplanar WaveguidesCoupled Transmission LinesMicrowave Coupler DesignMillimeter-wave Integrated CircuitsReturn Loss
A 60 GHz reduced-size branch-line coupler has been developed using elevated-center coplanar waveguide (EC-CPW) transmission lines. The coupler is fabricated in a 90 nm CMOS technology and has a chip area of 0.102 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The measurements indicated an amplitude-imbalance of 0.7 dB and a phase difference of 88 degrees at 60 GHz, a return loss of greater than 15 dB at every port over the 60 GHz band (57-64 GHz), and an isolation better than 17 dB. A 73% size-reduction compared to a conventional CPW coupler design has been achieved using capacitively loaded high-impedance EC-CPW lines. The proposed coupler is well suited for the design of millimeter-wave (mmW) CMOS subsystems including: balanced amplifiers, vector modulators, and balanced mixers.
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