Ultra-compact wideband Ka-band CMOS hybrid ring

A new microstrip ring hybrid has been developed in Ka-band (26.5-40 GHz) using multiple metal layers in a standard 0.25-mum RF/mixed signal CMOS process. The developed ring hybrid has -3.1 to -3.18 dB through, -5.1 to -5.7 dB coupling, and more than 17 dB isolation and 10 dB return loss across 25-35 GHz while occupying merely 282 times 314 mum.