Phase displacement study in ring VCOS and harmonic suppression techniques in RF mixers

Abstract

Harmonics of the LO and the interferes/blockers of the RF located at the harmonics of the LO gets down converted to base band frequency degrading the overall performance of the receiver. Harmonic rejection mixers are one of the potential solution to suppress the harmonics of the LO to the mixers. Similarly off-chip pre-mixer filters are used to suppress the harmonics of the RF input to the mixers. In this thesis we designed a 3P-8P Harmonic Rejection Mixer (HRM) with a modified transconductance stage as the mixer core. The double balanced mixer used in the HRM has a common source and a common gate configuration for the transconductance stage to improve the linearity of the mixer. The performance of the mixer is compared with the other HRM architectures. To suppress the RF blockers/interferers, inter-digitated hairpin resonating parallel coupled resonators are used as band pass filters to narrow down the RF signal to the mixers. The post-fabrication test results shows a very strong harmonic resonance for this proposed filter. The odd and even mode phase velocities of this filters are compensated by using triple CSRRs as Defective ground structures (DGS) specific to individual resonators without overlapping nearby resonators. newline