An ultra-wideband low noise amplifier with cascaded flipped-active inductor for cognitive radio applications

Cognitive radio (CR) is an ultra-wideband communication system with a 50 MHz to 10 GHz frequency band that intelligently optimizes the use of the available frequency spectrum using dynamic spectrum monitoring. This paper proposes a differential ultra-wideband low-noise amplifier using two cascaded flipped-active inductors (CASFAI-LNA). The structure of each CASFAI consists of two transistors (gyrator-capacitor) and a common gate pMOS in its feedback path. The use of the capacitor cross-coupling method increases the transconductance of the circuit, which in addition to improving the gain and the noise figure, reduces the current consumption of the circuit. In addition, the biasing of active inductors from the feedback path reduces the power consumption of the circuit. This circuit is designed and validated in Cadence using a 0.18 mu m CMOS process. The post-layout simulation results show that in the whole desired bandwidth (CR frequency range), the input matching is better than -10 dB, the maximum power gain is higher than 10.6 dB, the minimum noise figure is 2.24 dB, the stability factor is higher than 2.8, and the maximum IIP3 is -2.3 dBm. The proposed LNA consumes 6.12 mW from a 1.8 V DC supply.