First-Order Allpass Filter Section

Analog Transfer Function:

$$\hbox{AP}_{1}^{\,\omega_b} \mathrel{\stackrel{\mathrm{\Delta}}{=}}\frac{s-\omega_b}{s+\omega_b}. \protect$$

Digital Transfer Function:

$$\hbox{AP}_{1}^{\,g_i} \mathrel{\stackrel{\mathrm{\Delta}}{=}}\frac{g_i + z^{-1}}{1 + g_i z^{-1}}.$$