| 摘要 |
PURPOSE:To prevent the deterioration of the SN-ratio of a resonance signal due to a side-lobe, by finely dividing the measuring band of an NMR signal while sending out high frequency amplifier output to a 1st amplifier through a 2nd amplifier when the set frequency of a 1st intermediate frequency amplifier is coincided with a resonance frequency band. CONSTITUTION:A resonance frequency band is divided into five bands A1-A4, B and the frequency of an intermediate frequency amplifier 8 is set to the band A2. Output signals of a variable AC signal source (with frequency F1) 2 and an AC signal source of fixed frequency (F2) are mixed in a mixer 3 to obtain a resonance signal (F1-F2) which is, in turn, applied to a probe 5 through a band filter 12 and a power amplifier 4. The resonance signal (F1-F2) is passed through a mixer (F2) 7, the intermediate frequency amplifier (F2) 8, a phase detector 9 and an audible frequency amplifier 10 to obtain a free induction attenuated signal. When resonance frequency is coincided with the tuning frequency of the amplifier 8, the output of a band filter 13 receives frequency conversion in mixer 16 while the converted one is applied to the amplifier 8 through an intermediate frequency amplifier 17 and a change-over switch 19 to prevent the deterioration of a resonance signal due to a side-lobe. |
