An optimized design of distributed active transformer

A novel structure distributed active transformer (DAT), which significantly reduces the coupling from the DAT to the feed line is demonstrated. A grounded guard line is implemented to isolate the feed line from the magnetic field of the DAT. The measured result of the DAT on a GaAs substrate shows a 10.5-dB reduction in the coupling. To reduce DAT loss, an air-bridge connected double primary DAT structure is implemented. The DAT at 2 GHz shows a 0.7-dB loss reduction in comparison to the conventional DAT. The improved DAT performance is related to the reduced metal resistance and closer coupling between the primary and secondary loops without any increase in the DAT area.