Novel high-impedance probe for multi-gigahertz signal measurement

摘要

This paper describes a high-impedance probe based on theelectro-optic sampling (EOS) for multi-GHz signal measurement ofon-board circuits. The probe head and detection optics are assembledinto a compact probe module. The probe head consists of a metal needletip and electro-optic material (EOM). The top of the shaft is bonded tothe EOM. When the tip makes contact with the signal line of a circuitunder test, the signals are measured by detecting the polarizationchange of laser pulses that propagate through the EOM. Experimentalresults show that the effective 3-dB down bandwidth of the EOShigh-impedance probe is 5.5 GHz, which is 2 times higher than that of aconventional active probe. The minimum detectable voltage is <1mV/√Hz. The input resistance and capacitance are >100 MΩand <0.2 pF, respectively. The probe system has been successfullyapplied to measure multi-GHz signals of a communication IC mounted on aboard