Noise Behavior and Implementation of Interferometer-Based Broadband VNA

Faisal Ali Mubarak*, Rafaelle Romano, Luca Galatro, Vincenzo Mascolo, Gert Rietveld, Marco Spirito

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)
117 Downloads (Pure)


This paper analyzes and accurately models the complex noise behavior of vector network analyzers (VNAs) when measuring large-mismatch devices and subsequently shows how the VNA measurement noise performance is enhanced through implementation of a high-speed, broadband, active RF interferometer module. The presented VNA noise model provides a solid framework, benchmarked by measurement data, to analyze existing RF interferometer approaches. The performance improvement of the proposed interferometer implementation is then benchmarked in terms of magnitude and phase stability of the renormalized impedance level. A test bench employing the novel add-on RF interferometer module is presented and demonstrated to achieve high-speed cancellation of the scattered wave over a broad frequency band. The first experiment shows ultralow noise in a 1-18 GHz broadband measurement of co-planar waveguide 0.5-Ω and 5-k Ω impedance standards. Employing the proposed hardware setup improves the noise uncertainty for the 5-k Ω impedance standard by a factor of 8 and 20 at 1 and 18 GHz, respectively. In the second experiment, a factor of 2 height-resolution enhancement is achieved in a scanning microwave microscope when the RF interferometer module is added to the instrument.

Original languageEnglish
Article number8566175
Pages (from-to)249-260
Number of pages12
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number1
Publication statusPublished - 2019


  • Extreme impedance measurement
  • impedance mismatch
  • microwave interferometry
  • nanoelectronics
  • nanostructures
  • noise
  • vector network analyzer (VNA)


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