Patent ID: 6990327

Claim:
A wideband tunable high Q image rejection notch filter comprising: a Q-enhancement circuit used in a notch filter by creating a negative resistance to compensate for resistive losses in inductive components of said Q-enhancement circuit, said Q-enhancement circuit comprising: a differential series LC resonator comprising a first and a second transistor, where the source and the drain of said first and said second transistor are paralleled by a first and a second capacitive means, respectively, where a first and a second inductive means is coupled across the gate and the drain of said first and said second transistor, respectively, where the drains of said first and said second transistor are the input terminals of said Q-enhancement circuit, where the sources of said first and said second transistor are coupled together via a first and a second terminal of a capacitance tunable varactor means, where a third terminal of said capacitance tunable varactor means is coupled to an input port providing an input signal, and where the drain of said first and said second transistor is coupled via capacitive means to the gate of said first and said second transistor, respectively, where said differential series LC resonator is a transconductor based negative resistance generator resonating at an image frequency to compensate for the resistance of said inductive means; and a differential Q compensation circuit providing extra negative impedance to further compensate for the resistance of said inductive means of said differential series LC resonator, said differential Q compensation circuit comprising a cross-coupled differential third and fourth transistor, the drain of said third and fourth transistor coupled to the source of said first and said second transistor, respectively.