Finite-pole frequencies in monolithic crystal filters

The use of a capacitor in a monolithic crystal filter to obtain finite poles is well known. Several authors have illustrated the variation of the pole frequencies due to the magnitude of the capacitor. The empirical conclusion is that the larger the capacitor, the closer the pole frequencies to the passband or the steeper the skirt. A simple formula is presented for calculating the precise value of a capacitor required to produce prescribed pole frequencies.