SET-Induced Drop-out and Recovery of Cross-Coupled and Differential-Colpitts Microwave Oscillators Using SiGe HBTs

RF communications systems in space flight are subject to single-event upsets (SEUs) due to drop-out of the local oscillator during a single-event transient (SET), named here as single-event drop-out (SEDO). If the duration of the SEDO is substantial, it inevitably compromises data. To help alleviate SEUs due to SEDO, the present work compares the drop-out dynamics and recovery times of two types of RF LC oscillators with matched performance: the cross-coupled and the differential-Colpitts. The SEDO responses of both oscillators were tested using a pulsed laser to deposit charge via a two-photon absorption (TPA) process. For matched electrical performance and laser excitation conditions, the Colpitts oscillator demonstrated 14× faster recovery. This improved response was examined using a hybridized circuit/TCAD simulation approach, and it was determined that a lower impedance at the bases of critical oscillating transistors naturally reduces the SEDO sensitivity for Colpitts oscillators. While cross-coupled oscillators are widely used, the present work demonstrates that Colpitts oscillators should instead be considered in frequency synthesizers to mitigate SEUs due to SEDO in oscillators.