High-Voltage Ultra Wideband Coaxial Load With Distributed Ceramic-Carbon-Rod Resistor

An ultra wideband coaxial termination load is developed using a distributed ceramic-carbon-rod resistor for high-voltage fast transient impulse measurements. The difficulty in the development of a high-voltage ultra wideband termination device is a compromise in the size of the internal resistive element for optimizing performance between high-voltage insulation and wideband frequency operation. A smaller resistor shows better high-frequency performance but worse high-voltage insulation characteristics. In this letter, we propose a logarithmically tapered coaxial load device having wideband and high-voltage properties simultaneously. For high-voltage operation exceeding tens of kilovolts, a ceramic-carbon-rod resistor with distributed parameters is used as the termination element. For wideband frequency operation, we constructed a linearly decreasing coaxial characteristic impedance along the solid rod resistor for compensating impedance mismatch and maintaining consistent synthetic impedance in the entire load device. The implemented coaxial load shows a return loss under -18 dB from dc to 10 GHz, peak impedance variation under 8% with converged value of 54 Ω, and insulation performance up to 20 kV with a rise time of 100 ps.