Miniaturised integrated passive device balun design with balanced amplitude and phase for Wi-Fi applications

A miniaturised integrated passive device (IPD) balun design with low insertion loss and balanced amplitude and phase is proposed for Wi-Fi/Bluetooth applications. In this design, a novel topology based on the modified T-type filter structure is introduced to offset the parasitic and coupling effects that cause poor balance in IPD design. The proposed balun design is fabricated on a GaAs substrate. The measured insertion loss is lower than 0.9 dB and the measured return loss is >16 dB in the frequency range of 2.2-2.9 GHz. The measured results of amplitude and phase show rather minor imbalances, which are lower than +/- 0.67 dB and +/- 1.8 degrees respectively. The fabricated device size is 0.9 mm x 0.6 mm only.