| 摘要 |
In a magnetic resonance imager or other spectrometer, an interface (D) selectively connects quadrature probe coils (E) with a transmitter (C) and with a receiver (F). The interface includes a first RF switch (10), such as a first PIN diode (12) which has a low radio frequency impedance state for passing transmitted radio frequency signals to the probe coils and a high radio frequency impedance state for blocking the passage of radio frequency signals to the probe coils. A quarter wave length cable (20) or the equivalent is connected between the probe coils to shift the phase of the radio frequency signals 90 degrees. A second radio frequency switch (40) includes a second quarter wave length cable (42) and a second pin diode (44) which selectively pass and block radio frequency signals from passing between the probe coils and the receiver. A third pin diode (52) selectively connects a third quarter wave length cable (54) with ground to provide a band pass filter in the transmit mode and causes the third quarter wave length cable to be connected to ground through a fourth quarter wave length cable (60) in the receive mode to provide a band stop filter. A control (G) selectively biases the PIN diodes between their conductive and non-conductive states to establish the transmit and receive modes.
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