Magnetic-field probes can be used for electromagnetic interference measurement of high-speed circuits. The main magnetic probe performance includes sensitivity, spatial resolution, electric-field suppression ratio (EFSR), and measurement accuracy. In this article, a pair of differential magnetic-field probes is proposed to improve measurement accuracy without reducing sensitivity. The proposed differential probes consist of two asymmetric loop probes, which are designed in the same plane and separated by a row of periodic vias. The proposed differential probes are fabricated under PCB process. High accuracy can be achieved by measuring difference between outputs of the two probes. In addition, EFSR can be improved by size optimization of the differential magnetic-field probes. Simulation and measurement results show the operating bandwidth is from 100 MHz to 12 GHz, the measurement error is 3.4% and the EFSR is about 40 dB. The proposed probes have higher measurement accuracy and higher EFSR than the conventional single probe, and larger operation bandwidth than the stacked differential probes.
The realization of high‐performance thermosetting polymers with superior mechanical properties, flame retardancy and smoke suppression is very necessary but not yet implemented. Herein, a flame‐retardant curing agent (BICPD) combining cyclotriphosphazene and phosphaphenanthrene groups was synthesized, and used to prepare high‐performance, flame‐retardant epoxy (EP/BICPD) systems. Our results showed that the EP/BICPD systems began to cure at 110°C and solidify rapidly under heating. In comparison to the common epoxy system, the EP/BICPD thermosets exhibited improved glass transition temperature and mechanical properties. Most impressively, the EP/BICPD thermosets possessed outstanding flame retardancy and smoke suppression. The EP/BICPD‐20 thermoset achieved the LOI value of 37.7% and passed the UL94 V‐0 rating. Additionally, compared with the common epoxy thermoset, the peak of heat release rate (pHRR) and total smoke production (TSP) of EP/BICPD‐20 thermoset were reduced by ~70.0% and ~43.4%, respectively. The significant enhancements in flame retardancy and smoke suppression was mainly due to the collaboration of cyclotriphosphazene and phosphaphenanthrene in condensed and gaseous phases. Therefore, the high‐performance EP/BICPD systems with high glass transition temperature, satisfied mechanical properties, superior flame retardancy and smoke suppression showed profound scientific and industrial significance.
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