A 5.2 GHz image rejection CMOS low noise amplifier using notch filter

This paper represents a low noise, high gain image rejection low noise amplifier (IR-LNA) used in the superheterodyne architecture. The advantages and disadvantages of two different notch filters are analyzed and discussed. Based on that, the third order active notch filter is proposed. The IR-LNA is implemented by integrating the low noise, high gain LNA with the proposed third order active notch filter. The proposed IR-LNA is optimized for 5.25 GHz WLAN with IF frequency of 500 MHz applications. The measurement results show power gain of 20.5 dB, lower than 1.5 dB NF, and image rejection of 26 dB. Two-tone test results indicate -5 dBm and -8 dBm of IIP3 for the case of using and not using the notch filter, respectively. The circuit operates at supply voltage of 3 V, and dissipates 4 mA in 0.18 μm CMOS technology.