Design Of A Monolithic Passive Notch Filter

The fundamental role of a notch filter in communication systems is the attenuation, if not outright rejection, of signals whose frequencies lie within a specified passband. If the passband identified for rejection lies at very high frequencies, passive notch filters prove more effective than their active counterparts, but their design realization is necessarily less systematic. In this paper, open circuit impedance parameters comprise the foundation for a new approach to designing a passive RLC notch filter. The third order circuit model of the filter is thoroughly analyzed in the interest of achieving reliable performance prediction and meaningful design optimization. The mathematical analyses are complemented by HSPICE simulations, wherein requisite inductors are presumed to derive as planar on chip spiral metallization. These manual and computer-based investigations lead to a pole-zero cancellation method for controlling the symmetry between the low and high frequency transfer characteristics of the notch filter.