A wideband beamformer for a phased-array 60GHz receiver in 40nm digital CMOS

For high-data-rate wireless communication in the 7GHz band around 60GHz, the IEEE 802.15.3c standard [1] provides channels with a 0.88GHz bandwidth for the AV-OFDM mode. For the single-carrier modes, the ECMA 387 standard [2] foresees the possibility of bonding together adjacent channels, yielding higher data-rates. Radios for these 60GHz standards often use phased antenna arrays to relax the link budget. A phased-array receiver needs a variable phase shift on each antenna path and a combiner that sums the signals from the individual paths after phase shifting. The beamforming circuitry presented here handles 4 paths. It can operate both with one 0.88GHz channel and with bonding of two such channels. Phase shifts are realized with a resolution better than 20°. Bandwidth is high thanks to the use of current amplifiers with very low input impedance.