Analysis and Comparison of Ring and LC-Tank Oscillators for 65 nm Integration of Rad-Hard VCO for SpaceFibre Applications

The paper presents the comparison between two VCO (Voltage Controlled Oscillator) architectures designed in 65 nm CMOS for aerospace applications. In particular, the two VCOs have been designed targeting the 6.25 GHz frequency required in the SpaceFibre standard. The ring oscillator has been designed using three current mode logic stages connected in a loop. Although its performance in terms of low area occupation are attractive, the process variations simulations have demonstrated its inability to generate the target frequency in harsh operating conditions. Instead, the LC-Tank based oscillator, fixing the central frequency with the resonance of the L-C tank, has highlighted a lower influence through Process-Voltage-Temperature simulations on the oscillation frequency. Thanks to varactor-based voltage tuning control, it is able to cover the range from 5.18 to 6.41 GHz. Both architectures are biased with a supply voltage of 1.2 V. The complete layout of the last solution has been designed and its parasitic has been extracted for post-layout simulations. Achieved results are attractive to address the requirements of the new SpaceFibre aerospace standard.