Flip-Chip Assembled GaAs pHEMT $Ka$-Band Oscillator

In this letter, we present a Ka-band oscillator with flip-chip assembled 0.15-mum-gate pHEMT. With a characterized 0.15-mum-gate GaAs pHEMT and consideration of the Au-Sn pillar bump transition, the GaAs pHEMT was flip-chip assembled on Al
₂
O
₃
substrate where the passive components and coplanar waveguide connection were designed and fabricated. The measured output signal was at 27.55 GHz with an output power of 1.87 dBm and a phase noise of -109 dBc/Hz at 1-MHz offset, respectively. To our knowledge, this is the first flip-chip assembled pHEMT oscillator in the Ka-band