A 16-44 GHz compact doubly balanced monolithic ring mixer

A novel and compact 16-44 GHz ultra-broadband doubly balanced monolithic ring mixer for Ku- to Ka-band applications implemented with a 0.15-μm pHEMT process is presented. The proposed mixer is composed of a C-band miniature spiral balun and a 180° hybrid formed with an interdigital coupler, a low-pass π-network, and a high-pass T-network. The 180° hybrid eliminates the use of a cross-over structure for application in the balanced mixer, as well as provides an output port for the RF extraction of up-converter application. This proposed configuration leads to a die size of less than 0.8 × 0.8 mm². From the measured results, the mixer exhibits an 11-14 dB conversion loss, a 27-50 dB high LO-to-IF isolation over 16-44 GHz RF/LO bandwidth, and a 1-dB compression power of 14 dBm for both down- and up-converter applications.