An Image-Reject Low-Noise Amplifier with Passive Q-Enhanced Notch Filters

An image-reject low-noise amplifier with passive Q-enhanced notch filters in 0.18 mum CMOS is presented. Available IR-LNA designs employ a single notch filter to reject the precise image frequency and therefore require an additional automatic tuning circuit. This design achieves image-rejection over a bandwidth by using two series-connected passive notch filters, thereby relaxing the requirement of any additional tuning circuit. The proposed image-reject low noise amplifier has 16 dB gain at the signal frequency of 2.4 GHz and 58 dB rejection over a bandwidth of 100 MHz centered at the image frequency of 1.6 GHz. Noise Figure of 2.25 dB and P1dB of -13 dBm are obtained with bias current of 3.9 mA drawn from a 1.5 V power supply.