Transformer-based dual-mode VCO for multi-mode multi-standard receiver

Abstract

The proposed VCO in this paper is used in frequency synthesizer for multi-mode, multi-standard wireless transceiver. The overall scheme uses two VCOs, each VCO adopts transformer-based structure. On-chip transformer uses coplanar central tap structure and adopts the top metal winding, while primary and secondary inductances adopt octagon differential structure. Electromagnetic field (EM) simulation is carried out by using ADS Momentum. Negative conductance unit adopts the current reuse of cross coupled MOSFET. Oscillation mode can be chosen by switch. The primary and secondary inductances of the transformer connect 4 bit binary switch capacitor array and varactor under different oscillation mode to extend the range of frequency adjustment. Measurement results show that the frequency range is from 1.2GHz to 7.3GHz and the phase noise at 1MHz offset is less than -80dBc/Hz in the whole frequency range.