Patent ID: 7196574

Claim:
A continuous-time active complex bandpass ladder filter with transmission zeros comprising: a ladder filter having a transfer function having poles and imaginary transmission zeros and generated using only a plurality of filter elements including transconductors, g m , capacitors, C, and inductors, L, L being implemented as g m —C gyrators, wherein the poles and transmission zeros of the filter are solely defined by all the g m and C filter elements in the ladder filter, and including: I input and 90-degree phase shifted Q input: I output and 90-degree phase shifted Q output: each input of the I input and the Q input coupled to an input g m -cell voltage-to-current converter: an input 1 /g m source resistor connected to the converter; and an input 1 /g m load resistor connected to one of the I output and the Q output the ladder filter output, such that the transfer function forms an unsymmetrical complex bandpass transfer function that transmits signals for positive frequencies and blocks signals for negative frequencies or transmits signals for negative frequencies and blocks signals for positive frequencies.