DEVELOPMENT OF RECEIVER PROTECTOR FOR PULSED ESR

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 完成了35 GHz接收机保护开关大功率级的设计工作。我们正在将铁氧体开关与最近收购的快速、低功耗pin二极管开关集成在一起。我们成功地测试了一个基于铁氧体的锁存环行器，用于35 GHz的工作。它是由一个自制的，快速，脉冲电流驱动器控制。开关速度优于20 ns，满足FT-ESR的要求。该开关的重复频率为5 kHz，但由于缺少备用开关，我们没有尝试进一步提高重复频率。剩余的工作还包括最大限度地减少强电流脉冲在其正常操作模式下的电磁干扰，作为35 GHz光谱仪的一部分。 我们通常使用200 W限幅器来处理8-18 GHz频率范围内纳秒持续时间的1-1.5 kW脉冲。对于工作频率高达18 GHz，在更高的峰值功率，我们最近采购的被动接收器保护额定为1千瓦的1？的脉冲。 这对于更高强度的纳秒脉冲是足够的。 其50 ns的恢复时间对于低温DQC工作是足够的，但是对于死区时间应该在30 ns以下的2D-ELDOR可能是有问题的。 这将需要进一步努力采购20 ns铁氧体开关，并将其与低功耗二极管限幅器相结合，以实现小于25 ns的死区时间。 开关时间低于20 ns的X和Ku波段铁氧体开关不作为标准产品提供。 可以发现的是，指定为大于35 GHz开关的开关能量，因此我们计划获得样品并研究其开关性能。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The design work on the high-power stage of a receiver protector switch for 35 GHz is completed. We are integrating the ferrite switch with a fast, low-power, pin-diode switch that we recently acquired. We successfully tested a ferrite-based latching circulator intended for 35 GHz work. It is controlled by a home-built, fast, pulsed current driver. The switching speed is better than 20 ns, which is adequate for its use in FT-ESR. The repetition rate for this switch is 5 kHz, but we have not attempted to increase it further due to lack of a spare switch. The remaining work also includes minimizing electromagnetic interference from intense current pulses in its normal mode of operation as a part of the 35 GHz spectrometer. We routinely use 200 W limiters to handle 1-1.5 kW pulses of nanosecond duration for 8-18 GHz frequency range. For operating frequencies up to 18 GHz at higher peak power we recently procured passive receiver protectors rated to 1 kW for 1 ?s pulses. This would be adequate for nanosecond pulses of higher intensity. Their recovery time of 50 ns is adequate for low-temperature DQC work, but may be problematic for 2D-ELDOR for which dead-time should be under 30 ns. This would require a further effort to procure 20 ns ferrite switches and combine them with low-power diode limiters in order to achieve dead-time less than 25 ns. Ferrite switches for X and Ku bands with switching time under 20 ns are not available as standard products. What can be found is specified for larger switching energy than the 35 GHz switch, therefore we plan to obtain samples and study their switching performance.