Figure 5.
Amplitude and phase in the low-frequency region. Solid lines: amplitude (A) and phase (B) of the exact form (Eq. 13). Dashed lines: amplitude (A) and phase (B) of the approximated form (Eq. 19). Three lines correspond to values of 0 (blue), 1/2 (purple), and 1 (red). The unit of amplitude is .
