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A filtering technique to attenuate the receive-band noise enables a 65-nm CMOS WCDMA transmitter to achieve an output noise level of -160 dBc/Hz at 80-MHz offset, while dissipating 65 mW. Using a feedback filtering technique, the circuit introduces a null with an arbitrary width at the receive frequency and eliminates the need for an external SAW filter. A stability analysis is performed to choose the most suitable architecture for the feedback path, which ensures stability over a wide range of loop-gain. Nonideal effects such as quadrature phase and gain errors, LO feedthrough, harmonic downconversion and phase-noise are also analyzed.