High speed (30ps) Transmission line current sensor

A new high speed current sensing resistor measurement located anywhere along a coaxial transmission line is described. Minimal impedance discontinuity preserves the high voltage capabilities of the transmission line by inserting a short, low value (0.5 ohm or less) tubular film resistor into the outer conductor of a coaxial transmission line. Minimum resistor length and minimum skin effect along with high speed ferrites isolate the resistor from the shorting effects of the surrounding metal shield. Specially shaped high speed ferrites isolate both sides of the current sensing resistor from parasitic capacitance and external current paths. Additional low speed ferrites and tape wound cores can be added to extend the slow time response to milliseconds.