Patent ID: 7072617

Claim:
A radio frequency interference (RFI) suppression system, comprising: a first input for receiving a differential input signal V d ; a second input for receiving a signal V cm which varies with the common mode component of said differential input signal; a first amplifier PGA 1 having a programmable gain G 1 which varies in response to a first control signal and which receives V cm at an input and produces an output V A1 which varies with V cm *G 1 ; a subtractor circuit which receives V d at a first input and V A1 at a second input and produces an output V sub which varies with V d −V A1 ; a second amplifier PGA 2 having a programmable gain G 2 which varies in response to a second control signal and which receives V sub at an input and produces an output V A2 which varies with V sub *G 2 ; and a processor which receives a signal that varies with V A2 at an input and is arranged to: provide said second control signal to adjust programmable gain G 2 such that V A2 equals a predetermined value; provide said first control signal to adjust programmable gain G 1 to minimize V A2 ; and provide, after V A2 is minimized, said second control signal to adjust programmable gain G 2 to increase V A2 such that it equals said predetermined value.