A Dual-Band Transformer-Coupled Notch Filter Mixer for 2.45-/5.2-GHz WLAN Application

This paper presents a dual-band down-conversion mixer with image rejection feature using transformer-coupled notch filter for 2.45-/5.2-GHz WLAN application. A single center-tapped transformer is integrated to form two differential series inductor–capacitor (LC) resonators as a filter circuit to create attenuation at the image frequencies in eliminating the signal distortion caused by the image signals. Furthermore, an NMOS cross-coupled pair was adopted in the notch filter to improve the image rejection capability due to the presence of negative resistance. Simulated on a standard 130nm CMOS process, the proposed transformer-coupled notch filter mixer achieves a conversion gain of 15.3/10.7 dB, input-referred third-order interception point (IIP3) of − 6.8/− 2.0 dBm and a noise figure of 8.8/14.8 dB for an input RF of 2.45/5.2 GHz with an IF of 500 MHz. The notch filter mixer consumes 5.5 mW of power from a supply voltage of 1.2 V.