A Wideband IM3 Cancellation Technique for CMOS ${\bf \Pi}$- and T-Attenuators

A wideband IM3 cancellation technique for CMOS attenuators is presented. With proper transistor width ratios, the dominant distortion currents of transistor switches cancel each other. As a result, a high IIP3 robust to PVT variations can be achieved without using large transistors. Two prototypes in a 0.16 µm standard bulk CMOS process are presented: a
${\Pi}$
-attenuator with four discrete settings obtains +26 dBm IIP3 and +3 dBm 1 dB-compression point (CP) for 50 MHz to 5 GHz with only 0.0054 mm
$^2$
active area, and a similar T-attenuator system which obtains +27 dBm IIP3 and +13 dBm CP for 50 MHz to 5.6 GHz with only 0.0067 mm
$^2$
active area.