| 摘要 |
<p>Application for Patent of LLOYD F. HLAVKA for RF PICK-UP COIL CIRCUIT FOR A WIDE TUNING RANGE NUCLEAR MAGNETIC RESONANCE PROBE In a wide tuning range nuclear magnetic resonance spectrometer, the probe structure includes a series resonant pick-up coil circuit disposed in RF magnetic field exchanging relation with the sample under analysis for detecting nuclear magnetic resonance of the sample. A variable capacitor is series resonated with the inductance of the pick-up coil and the capacitor is arranged for tuning the series resonance of the pick-up coil over a wide tuning range, for example, from 6 to 32 megahertz. The low series resonant impedance of the pick-up coil, as of 1.5 to 5 .OMEGA., is matched to the relatively high input impedance, as of 50 ohms, of a low noise RF amplifier by means of a pair of series connected transmission line transformers for transforming the 50 ohm input impedance of the amplifier to the low series resonance impedance of the pick-up coil. The transmission line transformers are formed of two wire lines, one wire being connected in series with the pick-up coil and the other wire being arranged so that a current is induced to flow therein due to the distributed inductance and capacitance of the two wire line. The induced current is added, at the low impedance end of the transformer, to the current flowing in the first wire, whereby a broadband impedance transformer is obtained. Two such transformers are employed in series with the pick-up coil for transforming the low impedance of the coil to the relatively high input impedance of the preamplifier. The transformers are broadband so that the impedance is well matched over the entire tuning range of 6 to 32 megahertz.</p> |
