Design of SET tolerant LC oscillators using distributed bias circuitry

In this paper, a distributed biasing technique is proposed to improve the single event transient (SET) tolerance in LC-tank voltage controlled oscillators. The charge generated by a radiation strike at the drain of the bias current transistor results in voltage change at the drain node, which causes change in the output impedance of the transistor. This effect is more pronounced in the case of distributed biasing, and is used for improving the SET tolerance in the oscillator. Circuit simulations show that the phase error introduced due to a radiation strike is reduced to one-third in a 14 GHz LC-VCO designed in a standard 90 nm CMOS technology when the distributed bias is used, as compared to the phase error in a conventional LC-VCO.