| 摘要 |
A reflectometer tuning unit for a magnetic resonance imaging (MRI) system, provided for the standing wave voltage adjustment of various MRI receive coil units, and which is also capable of detection of various open/short fault conditions in the MRI receive coil unit or the coaxial cable connected to the MRI receive coil unit. The reflectometer tuning unit comprises an oscillator, a directional coupler, and a measuring system. The oscillator produces an output signal having its frequency tuned to the Larmor frequency of the magnetic resonance imaging system. The directional coupler has OUT, IN and CPL ports. The output of the oscillator is connected to the OUT port, and selected impedances, and later the receive coil unit, are connected to the IN port. The directional coupler produces an output signal at the CPL port which is proportional to the port of energy reflected back from the IN port to the OUT port, which is also proportional to the impedance mismatch presented by the impedance at the IN port. The measuring system is connected to the CPL port of the directional coupler, and measures the magnitude of the output signal at the CPL port. The measuring system of the reflectometer tuning unit includes a rectifying detector connected to the CPL port of the directional coupler, which provides a DC voltage output. An amplifier is connected to the output of the rectifying detector, and an LED display is connected to the output of the amplifier.
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