Patent ID: 7221924

Claim:
A wideband tunable high Q image rejection notch filter comprising: at least one cascoded LNA having inputs and outputs and coupled in series, where a first of said cascoded LNAs receives an RF input signal at its input and where a last of said cascoded LNAs provides at its output an amplified signal of said RF input signal; a Q-enhancement circuit for a wideband high-Q notch filter, said Q-enhancement circuit creating a negative resistance to compensate for resistive losses in inductive components of said Q-enhancement circuit, said Q-enhancement circuit comprising: a LC resonator comprising LC networks coupled to terminals of a pair of transistors, where a tuning capacitive means of said LC network is coupled across a source and a drain of each of said pair of transistors for adjusting the frequency distance between poles and zeros of said Q-enhancement circuit and low noise amplifiers, where a gate and said source of each transistor of said transistor pair are in communication with each other, where said sources of said transistor pair are in communication with each other, and where said drains of said transistor pair are coupled to said last of said cascoded LNAs, where said LC resonator, when resonant at the image frequency, produces said negative resistance; and a Q compensation circuit coupled to said LC resonator, said Q compensation circuit providing extra negative impedance to further compensate for the resistance of said LC networks, said Q compensation circuit comprising a pair of cross-coupled transistors.