Abstract
The goal of this paper is to optimize a measurement methodology for the most accurate broadband modelling of characteristic impedance and other parameters for twisted pairs. Measured values and theirs comparison is presented in this article. Automated measurement facility was implemented at the Department of telecommunication of Faculty of electrical engineering of Czech technical university in Prague. Measurement facility contains RF switches allowing measurements up to 300 MHz or 1GHz. Measured twisted pair’s parameters can be obtained by measurement but for purposes of fundamental characteristics modelling is useful to define functions that model the properties of the twisted pair. Its primary and secondary parameters depend mostly on the frequency. For twisted pair deployment, we are interested in a frequency band range from 1 MHz to 100 MHz.
Highlights
The twisted pair was chosen in order of measurement methods comparison
The internal method is based on obtaining of return loss (RL, S11 parameter) at the input of Vector Network Analyzer ZVRE
The input impedance of the twisted pair is given by equations: Zc where Zref is reference 100 Ω impedance of the twisted pair and Γ is reflection coefficient of the twisted pair terminated by short, open or matched impedance
Summary
1. Introduction where r0 is the DC resistance, a is a parameter which characterizes the slope of the frequency response. 1 + ççèæ f fm öb ÷÷ ø where l0 is inductance at zero frequency limiting, l∞ is inductance at the highest frequencies of the band, fm and b are parameters that characterize the threshold between low and high frequencies. Where c0 is capacity at the highest frequencies in the band, c∞ is capacity at zero frequency limiting and cg is parameter characterizing the shape of frequencydependent waveform. Where g0 is conduction at low frequency and ge is coefficient increasing towards to high frequency. A certain problem at high frequencies the impedance inhomogeneity of transmission line that cause partial reflections and ripple on attenuation frequency dependence of twisted pair [5]
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