In pervious lablog, the reflected wave of the NMR pulse still is about half of the input pulse, that means, the power is reflected. And we had tuned the tuner to be “impedance matched”.

The problem is, when the tuner is not impedance matched but just frequency matched.

We tune the tuner by the help of network analyzer and tuning for a resonance depth at 12.8MHz.

The tuner contains a parallel capacitor and a series capacitor with the NMR coil. The resonance depth at 12.8MHz show that we matched the parallel capacitor with the insurance of the coil. The total impedance of the tuner and coil is :

i \left(1 - \frac{\omega^2}{\Omega^2} \left( \frac{C_s}{C_p}+1\right) \right) / \left( C_s \omega \left( 1 - \frac{\omega^2}{\Omega^2} \right) \right)

Thus the amplitude of the total impedance is determined by the series capacitor.

In conclusion, the total impedance is not matching with the coaxial cable. This gives the reflected wave.

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