Hybrid Integrated Microfluidic Channels on Multilayer Organic Substrate and on Copper for Tuning and Cooling an RF Reconfigurable S-/C-Band GaN-Based Power Amplifier

In this paper, a gallium nitride (GaN)-based power amplifier (PA) is cooled and tuned thanks to multifunctional hybrid microfluidic channels integrated on a multilayer organic substrate composed of liquid crystal polymer and ceramic-filled polytetrafluoroethylene. The tuning microchannels are integrated in the organic materials, while the cooling microchannels are micromachined in a copper carrier. The tuning allows the PA to switch the frequency of operation from 2.4 to 5.8 GHz and vice versa. Heat removal is achieved by the motion of distilled water below the GaN die, while tuning is achieved by swapping air and acetone inside the source and load matching network microchannels. The novel idea behind the design of such tunable PAs relies on the design of microfluidically tunable matching networks. For the first time, tunability parameters are introduced and a generic methodology is described for the design of microfluidically tunable matching networks for any dies, frequencies, fluids, or stackups. The measured power added efficiency (PAE) and output power (P
_out
) are: 1) PAE = 33.9% and P
_out
= 37.1 dBm at 2.4 GHz with acetone and 2) PAE = 51.1% and P
_out
= 37.9 dBm at 5.8 GHz with air. The liquid cooling seems to have no effect on P
_out
for all measurements but shows a 1.5% increase in PAE for the 5.8-GHz measurements.