Apparatus for enhancing the dynamic range of shockline-based sampling receivers

Abstract

Shockline-based samplers of a vector-network analyzer (VNA) have enhanced dynamic range by using a dynamic bias network applied to the non-linear transmission lines (NLTLs) or shocklines. The bias voltage applied to the NLTL provides direct control over the falling-edge shockline compression, and thus the insertion loss and overall RF bandwidth of the sampler. Alternating between a forward bias voltage to turn off a shockline sampler when it is not needed and thereby reducing spurious generation and improving isolation can be alternatively applied with a reverse bias voltage to turn on the shockline sampler in a normal operation mode. By measuring the shockline output and providing feedback in the reverse-bias mode, the bias voltage can be dynamically adjusted to significantly increase the performance of the NLTL based sampler. In the presence of a strong positive bias voltage, the incoming LO and its harmonics experience large ohmic losses thus preventing gating pulses from forming in the shockline. The ohmic losses enable strong isolation between the LO sampling channels and will increase spectral purity at the VNA test ports.