Direct Down-Conversion 38 GHz GaAs and SiGe Receivers

Direct down-conversion receivers at Ka band in GaAs and SiGe are measured and analysed with particular attention to linearity. The GaAs receiver is observed to have the superior overall linearity although SiGe has the better second-order behaviour. The linearity is discussed with respect to the requirements of point-to-point radio and for the first time, to the authors' knowledge, an explanation is established for the effect of third-order distortion in the LNA on the second-order distortion from the complete receiver.