Design of a Low Noise Amplifier with integrated notch filter for interference rejection in ultra-wideband systems

A fully integrated 0.18um CMOS Low Noise Amplifier (LNA) with Notch Filter for interference rejection at 5-6 GHz in UWB systems is presented. The notch filter comprises a series LC resonance circuit, which with a resistance cancelation approach yields excellent attenuating characteristics. The post layout simulation of this circuit is able to achieve more than 25 dB of attenuation at 5.6 GHz. The LNA is composed of two stages-cascode and cascade stage, in addition to inter-stage LC components to achieve wider gain. The shunt resistive feedback is employed to obtain a good input matching and low noise figure. The proposed UWB LNA achieves a simulated (post layout) gain of 18 dB and has the input and output matching less than -7dB and -10dB respectively over the entire range. The NF in the region of interest is less than 5.1 dB.