Figure 1.

Schematics demonstrating the general ideas of constructing RID circuits using a “butterfly” (“figure eight”) coil (A) a regular surface coil (B). Two geometrically identical resonant coils #1 and #2 are coupled with their shared impedance Z₁₂ and characterized by the inductance L, and the resistance R, In the presence of the sample the mutual impedance Z₁₂ contains both reactive, jωM, and resistive component, R₁₂. RID circuits shown in A) and B) are characterized by the inductance L₀ and the resistance R₀.