RF linearity study of SiGe HBTs for low power RFIC design. II. Analysis

For pt. 1 see ibid., p. 70-73 (2002). An analysis is introduced for the third-order-intermodulation (IM3) cancellation induced by the emitter-terminations, which has been observed in part I of this paper. The analysis shows that the IM3 can be perfectly cancelled if the emitter impedance at the second harmonic and the sub-harmonic frequencies are terminated properly and if the effect from q_bc is negligible. When the effect of q_bc cannot be neglected, optimized source and load harmonic terminations are proposed to minimize the q_bc effects. Increasing the source impedance at the fundamental frequency is found effective in minimizing the residual IM3 that is not cancelled from the proposed terminations.