Back-gate coupled current-reused QVCO with modified STM technique

In order to achieve low power consumption, many improved VCO schematics were proposed. However, although the problem of power consumption has been improved, the amplitude imbalance of the output signals is relatively larger than the conventional cross-coupled VCO. Therefore, a new modified STM technique to improve the amplitude imbalance of VCO is presented. The measured amplitude imbalance ratio is less than 0.2%. It reduces from 1.7% of the VCO without modified STM technique. This back-gate coupled current-reused QVCO has been implemented using the TSMC 0.18um mixed-signal/RF CMOS 1P6M technology and the die area is 0.84×1.1mm2. The measured phase noise at 1MHz offset is -117.4dBc/ Hz at the oscillation frequency of 5.0 GHz. The figure of merit (FOM) of the proposed QVCO is -184.1 dBc/ Hz.