A vector network analyser sweeps to on a RG-58 run of unknown length (velocity )…

PHYSICS · Multi-part · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Electromagnetic waves and their propagation · Electromagnetic waves and their propagation

Inside the Instrument, Ch Transmission lines, grounding and the bench

Problem

A vector network analyser sweeps

1

100\,\mathrm{MHz}

on a

50\,\Omega

RG-58 run of unknown length (velocity

v_p = 2.0\times10^8\,\mathrm{m\,s^{-1}}

) after a one-port calibration. The line is otherwise matched and lossless, with a single fault somewhere beyond the near end. Across the sweep the magnitude

|S_{11}|

stays at

-6\,\mathrm{dB}

, while the unwrapped phase of

S_{11}

falls by one full turn every

\Delta f = 5\,\mathrm{MHz}

. ((a)) Find the distance from the analyser to the fault. ((b)) Find the fault's reflection coefficient magnitude and the VSWR it produces.

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