Analysis and Design of a CMOS LNA With Transformer-Based Integrated Notch Filter for Ku-Band Satellite Communications

摘要

A transformer-based notch filter is proposed in this article. The notch filter is integrated into a three-coil transformer in the matching network. While the primary coil and the secondary coil build a magnetically coupled resonator (MCR) and transfer the in-band signal to the next stage, the tertiary coil is coupled with the primary coil to absorb the interferers. Resonating with the switched capacitors, the notch frequency can be tuned digitally. A cross-coupled pair can further enhance the quality factor of the tank and, therefore, the rejection level. A low-noise amplifier (LNA) for Ku-band satellite communication with the proposed notch filter is implemented in 65-nm CMOS to verify the theory. The LNA achieves a measured power gain of 19.5 dB at 12.2 GHz with a -3-dB bandwidth of 9.2-12.7 GHz. The LNA can achieve 13.5-dB gain suppression at 13.9 GHz. The suppression level can be enhanced by tuning the quality factor of the active notch filter, which consumes up to 0.6 mW. The noise figure (NF) is 2.3 dB at 10.6 GHz and the NF is below 2.7 dB from 9.2 to 12.7 GHz. The input return loss is better than -15 dB from 8.8 to 18.5 GHz. The LNA consumes 5.9 mW from a 1-V supply. The whole chip occupies an area of 1000 x 800 mu m(2).