Second order distortion in CMOS direct conversion receivers for GSM

Direct conversion receivers are currently being considered for the future generations of GSM chipsets. It is shown that for the direct conversion receiver architecture second order distortion is a major problem. The GSM requirements on AM suppression are compared with base-band simulations to yield specifications for the second order linearity of the receiver. Three origins of second order distortion are analyzed and approximate equations for the second order nonlinearity are derived. The circuits considered are based on RF CMOS technology, a technology nearing a breakthrough.