Search

Radio frequency (RF) communications systems in space flight are subject to single-event upsets (SEUs) due to dropout of the local oscillator (LO) during a single-event transient (SET), named here as single-event dropout (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 dropout dynamics and recovery times of two types of RF $\boldsymbol {LC}$ 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\times $ faster recovery. This improved response was examined using a hybridized circuit/technology computer-aided design (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.

Standard digital modulation schemes are compared for receiver-level single-event upset (SEU) sensitivity. Single-event transients (SETs) on the wideband silicon–germanium (SiGe) low-noise amplifier (LNA) carrying on–off keying (OOK), binary phase-shift keying (BPSK), and frequency-shift keying (2-FSK) modulated data were induced using laser pulses. Both the modulation scheme and its detection method had a significant impact on the SEU sensitivity of the receiver. The SET sensitivity and noise sensitivity of the modulation schemes and demodulation techniques were correlated. Therefore, designing a receiver to be more robust to noise inherently makes it more robust to SETs. For space missions that anticipate a high flux of radiation, taking SETs into account when choosing the radio frequency (RF) modulation scheme and the demodulation method may be important to avoid underestimating the total bit-error rate (BER) when other system trade-offs are compared against the system BER.

A comparison of laser-induced single-event transients (SETs) in silicon-germanium heterojunction bipolar transistor (SiGe HBT) variants designed for high-speed (HS) applications and high-breakdown (HB) applications is presented. A significantly lower amplitude SET response at low laser pulse energies was observed in the HS device compared to the HB device. At high laser pulse energies, however, the transient amplitudes converged and produced a nearly identical response. A 3-D technology computer-aided design (TCAD) model of a SiGe HBT was used to understand the differences between the observed SET responses. During an SET produced by a low laser pulse energy, the mean electric field in the collector-base (CB) junction of a simulated HB device is shown to have a greater magnitude across the depletion region compared to that of its HS counterpart. Motivated by the proportional relationship between drift current and CB junction electric field, a greater breakdown voltage device produced a larger SET response. During an SET produced by a high laser pulse energy, the charge from the SET exceeded the collector doping in both the HS and HB SiGe HBT. This creates a conductive path to the output terminal, removing the dependence of collector doping on SET amplitude. The results of this study should help inform design choices of which device breakdown variant should be used in a given circuit if SETs are a major consideration for the application.

An accessible approach for estimating the laser-equivalent linear energy transfer (LET $_{\mathrm {L}}$ ) for any pulsed-laser single-event effect (PL SEE) testing condition is developed and validated. This approach satisfies one of the three criteria required for laser testing to serve as a predictive surrogate for heavy-ion testing. By using easily interpretable equations and identifying the relevant laser, materials, and device parameters, the LETL and its uncertainty ( $\Delta $ LET $_{\mathrm {L}}$ ) can be accurately estimated. The approach is validated by observing agreement between experimentally acquired and LETL-calculated collected charge (CC) across a variety of laser testing geometries and for multiple devices with different sensitive depths. Given the ubiquitous use of the 1064 nm wavelength for laser testing, additional analyses are devoted to understanding the contributions to the LETL. The sensitivity of the LETL to its input parameters and their error contributions to $\Delta $ LETL are also considered. By employing this calculational approach, multiple testing conditions are found to satisfy the three criteria for predictive testing. Software that can facilitate calculations of LETL and other laser-generated quantities would benefit the radiation effects community, and efforts are currently underway toward this goal.

A series of distance metrics to quantitatively assess the level agreement between laser- and ion-induced single-event effects are presented. Historically, this agreement has been assessed by visual inspection. While traditionally effective, this approach can lead to misleading comparisons and erroneous conclusions. To enable quantitative comparisons for response agreement, a more objective approach is required. The present work defines and demonstrates the use of five distinct distance metrics to quantitatively assess the level of single-event effect (SEE) response agreement. These metrics correspond to each of the five categories in which most of the published SEE work can be sorted. Various applications of these metrics are shown, including the objective correlation of laser pulse energy (PE) and ion linear energy transfer (LET). While demonstrated with laser and ion data, this approach can be applied to other surrogates for heavy-ion testing and may be used to validate results obtained from potential predictive surrogate testing techniques.