Counter-Intermodulation in the Context of CMOS Outphasing Transmitters

This work presents the design of a CMOS outphasing modulator based on an IQ-modulator topology with passive mixers. The implications from such an architecture on the phase-modulator performance are analysed. Particularly, the problem of counter-intermodulation in the context of outphasing modulation is studied. It is found that the generated distortion is a function of the outphasing angle. Based on the analysis, a 65-nm CMOS prototype is designed and fabricated. Measurements show an ACLR performance of -46.7 dB and -42.5 dB for a 64-QAM modulated signal with a 5MHz and 40MHz bandwidth, respectively.