Integrated balun design for dual-band WLAN a/b/g applications

This paper presents an integrated balun design optimized for low insertion loss and minimal imbalance. The concept of an integrated dual-band balun is proposed to significantly improve the integration and reliability of WLAN a/b/g transceivers. The design has been implemented in standard 90nm CMOS technology. The measured minimum insertion loss (ILmin) is 1.6 dB in the 2.4 GHz band, and 1.2 dB at 5-6 GHz. The measured phase imbalance is less than 0.4*, and the amplitude imbalance is below 0.1 dB, in both frequency bands. Attributed to its symmetry, the balun yields more than 40 dB attenuation of undesired mode conversions. The balun core occupies 220 mu m x 220 mu m, and has the lowest measured insertion loss reported to date for integrated baluns in standard CMOS.