Design and Verification of a 6.25 GHz LC-Tank VCO Integrated in 65 nm CMOS Technology Operating up to 1 Grad TID

TID Sensitivity Assessment of Quadrature LC-Tank VCOs Implemented in 65-nm CMOS Technology

“…Before irradiation, the frequency of the PQVCO ranges from 2.524 GHz to 2.786 GHz with a TR of 9.86% and the frequency of the SQVCO ranges from 2.635 GHz to 2.908 GHz with a TR of 9.88%. Similar to the TID experiments [28,29], the oscillation frequency of both the oscillators gradually increases with respect to TID and an increment of approximately 0.5% can be observed at the center frequency. The increase in the frequency can be accounted for primarily due to the decrease in the transconductances (g mP , g mN ) of the cross-coupled PMOS-NMOS pair with respect to TID [37].…”

“…The effects of oxidetrap charges and interface trap charges on the varactors with respect to bias voltage are analyzed in detail in [42]. During irradiation, the radiation induced negative charges (oxide-trap and interface trap) result into reduction of the width of the depletion region, which in turn increases the capacitance of the varactors [29,43]. This radiation-induced effect is counteracting previous g m induced increase in frequency.…”

“…In the case of the PQVCO, the change in phase error is much more rapid with respect to the mismatch for lower values of the coupling factor (K). During the radiation experiment, the capacitance of the NMOS varactor with respect to the tuning voltage increases with respect to the radiation dose [29,43]. The increasing capacitances eventually reduce the relative mismatch between the C tank .…”

“…Overall, the phase noise characteristic of the SQVCO is slightly better than for the PQVCO due to the tail-noise filter [40] in the form of the coupling inductor present in the SQVCO. Table 1 presents a performance comparison of the implemented QVCOs with respect to previously reported VCOs [28,29,46,47] and QVCOs [33] which are studied under radiation (TID) exposure. Similar to [28], the implemented QVCOs in this work are targeted to operate in the s-band.…”

“…As reported in the literature, the performance of LC-tank based single VCOs operating under ionizing radiation are extensively studied in [27,28]. The vulnerability of VCO architectures with respect to TID effects for space applications as well as in HEP experiments are explored in [29], whereas the effects of radiation-induced single-event-effects (SEEs) in VCOs are studied and a few possible remedies are suggested with some design improvements in [28,30,31]. In comparison, the knowledge about the effects of ionizing radiation on the performance of QVCOs are limited due to scarcity in the number of studies [32,33] done on QVCOs under radiation exposure.…”