Precise RSSI with High Process Variation Tolerance

A receiving signal strength indicator (RSSI) built with transconductance amplifiers is presented. The RSSI achieves high tolerance to process variations by utilizing the unique nature of branch currents in a transconductance amplifier. These branch currents are used to implement a current-mode rectifier and amplitude clipping circuit that are tolerant of process variations. An on-chip offset control loop permits the entire RSSI to be realized with only one external component. In 0.18μm CMOS with a 1.8V supply, the RSSI draws 2.5mA and provides 80dB of offset suppression and more than 70dB of log-linear range with less than +/-2dB error due to process variation.