2.45GHz/5.2GHz switched dual-band CMOS LNA with 4 gain control modes

Abstract

A switched dual-band low noise amplifier with four gain control modes operating at the 2.45-GHz/5.2GHz has been simulated based on a 0.18-um TSMC CMOS process. This dual-band LNA with two input channels and each tuned to 2.45GHz and 5.2GHz separately, by switching the output resonator inductor on/off, the input transistors are enabled/disabled for band selection. A novel gain control scheme is introduced, and this gain control scheme is low in circuit complexity. The four gain control modes are executed by turning on/off the four shunted NMOS at the output of this cascode topology, and the four gain modes can be controlled digitally to adapt to the received RF signals. Compared with the current literatures, this novel gain control scheme not only have high gain control range in both bands, but also have reasonable noise figure in the low gain mode even with 12-dB power gain lower than the high gain mode. The P1dB of the proposed LNA in the low gain mode is 13dB higher than the one in the high gain mode in both bands. The peak of the input and output return loss is locked in band in each gain mode which is an important feature of this proposed LNA. In the high gain mode, the LNA approaches 22-dB maximum power gain and 2.67 DSB noise figure at 2.45GHz. In the 5.2-GHz band, the maximum power gain is 15-dB and the DSB noise figure is 2.47-dB. The gain can be switched by 12-dB between the high gain and the low gain mode at 2.45-GHz and 5.2-GHz.