A 5-GHz radio front-end with automatically Q-tuned notch filter and VCO

A low-voltage receiver front-end for 5-GHz radio applications is presented. The receiver consists of a low-noise amplifier (LNA) with notch filter, a voltage-controlled oscillator (VCO), and a mixer. The LNA/notch filter has an automatic Q-tuning circuit integrated with it to provide good image rejection. On-chip transformers are used extensively in the receiver to improve performance and facilitate low-voltage operation. The receiver has a gain of 19.8 dB, noise figure of 4.5 dB, a third-order input intercept point (IIP3) of -11.5 dBm, and an image rejection of 59 dB, and the VCO had a phase noise of -116 dBc/Hz at 1-MHz offset.