SNR Analysis and Optimization in Near-Field Scanning and EMI Applications

Giorgi Maghlakelidze*, Xin Yan, Li Guan, Shubhankar Marathe, Qiaolei Huang, Bumhee Bae, Chulsoon Hwang, Victor Khilkevich, Jun Fan, David Pommerenke

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In a near-field scanning system, each element of the measurement chain contributes to the thermal noise power density: probe, cables, amplifiers, and the measuring instrument. The signal-to-noise ratio (SNR) is strongly affected by the source output impedance, source temperature, the lossy transmission lines between probe and amplifiers, amplifier noise, amplifier temperature, and amplifier gain. By minimizing the loss between the probe and by using ultralow-noise amplifiers (noise figure (NF) < 0.5 dB), SNR improves by >10 dB, compared to a setup using a 1-m cable and a 3-dB NF amplifier. A resonant probe that is cooled with liquid nitrogen improves measurement SNR by an additional 10-12 dB, as compared to a broadband probe of similar loop size. To combine the advantages of a resonant probe, without sacrificing the ability to measure broadband, a proof of concept is demonstrated that uses a tunable resonant probe which is synchronized to the frequency sweep of the spectrum analyzer.

Original languageEnglish
Pages (from-to)1087-1094
Number of pages8
JournalIEEE Transactions on Electromagnetic Compatibility
Issue number4
Publication statusPublished - 1 Aug 2018
Externally publishedYes


  • Electromagnetic interference (EMI)
  • field sensors and probes
  • GPS
  • GSM
  • liquid nitrogen
  • measurement uncertainty
  • near-field modeling and measurements
  • probe cooling
  • resonant probes
  • signal-to-noise ratio (SNR)
  • Wi-Fi

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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