Figure 1.

A circuit model for a band-pass birdcage coil design. The L_n and $L_n^{\text{ER}}$ are the effective inductances of the nth leg and ER segment, respectively; $C_n^{\mathit{\text{lp}}}$ and $C_n^{\mathit{\text{hp}}}$ are the capacitances on the nth leg and ER segment, respectively; and I_n is the current intensity in the nth loop. The voltage at the end point of the nth leg is $V_n^{\text{leg}}$. When $C_n^{\mathit{\text{lp}}}$ is given, the virtual ground is assumed at the middle of the legs (see the left box labeled HP); if $C_n^{\mathit{\text{hp}}}$ is known, a virtual ground is inserted at the middle of the (n − 1)th ER segments on both ER planes (see the right box labeled LP).