Two-port Equivalent Circuits Deduced from S-parameter Measurements of NaCl Solutions

Abstract

We deduced two-port equivalent circuits related to molar concentrations M (0–1 mol/L) of NaCl solutions by measuring S-parameters S₁₁ and S₂₁ at frequencies from 1 to 100 MHz, using a portable vector-network-analyzer (NanoVNA) and two-port coaxial probes. The deduced two-port equivalent circuits of the NaCl solutions consist of three sub-CR circuits. Resistances R_n and capacitances C_n comprising the sub-CR circuits were calculated using the molar concentrations M related to solute-ions of Na⁺ and Cl⁻ and relative dielectric constant of solvent H₂O. The electrical conductivity of the two-port equivalent circuits reflected drift mobility of the solute ions and rotation and vibration of polar molecules of the solvent H₂O. Input impedances Z_in and transmission coefficients S₂₁ calculated from the deduced two-port equivalent circuits of the NaCl solutions were consistent with the measured S-parameters.

KEYWORDS:

• EIS
• Equivalent circuit
• Impedance
• NaCl solution
• NanoVNA
• S-parameter
• VNA
• Transmission coefficient

Additional information

Notes on contributors

Koyu Chinen

Koyu Chinen received the MSc and PhD degrees in electronics engineering from Shizuoka University in 1978 and 1981, respectively. In 1981 he was with Toshiba corporation working on developing optical electronics devices for high-speed optical fiber communications from 1981 to 2004. In 2005, he joined the National Institute of Technology Okinawa College, as a professor of Information Communication System Eng. In 2017, he was an emeritus professor and representative of GLEX. His main research interests include RF design in optical wireless communication and bio-electronics. Corresponding author. Email: [email protected]

Shoko Nakamoto

Shoko Nakamoto received the BEng degree from the Information Communication System Eng Dept of National Institute of Technology, Okinawa College in 2014. Since then, she has technically supported the GLEX. Her main interests include RF design and bio-electronics. Email: [email protected]

Ichiko Kinjo

Ichiko Kinjo received her PhD degree from Hokkaido University in 2005. In 2005, she joined the Information Communication System Eng Dept of National Institute of Technology, Okinawa College, as an assistant professor and was a professor in 2020. Her main interests include OR and information communication technologies. Email: [email protected]