A quad-band 0.9/1.8/2.45/3.5 GHz, multi-standard, concurrent LNA using a dual-band impedance transformer

In this paper, a quad-band, multi-standard, concurrent, low noise amplifier operating in the 0.9/1.8/2.45/3.5 GHz bands is presented. The amplifier design is based on an ultra low noise PHEMT transistor connected in the common source topology with inductive degeneration. The input matching network is based on a three-section, dual-band transformer. A feedback capacitor is inserted between the gate and source terminals allowing fractional bandwidths of 52% and 15% at the lower and higher bands, respectively. To enhance the fractional bandwidth and amplifier stability, small inductive source degeneration in the form of etched transmission lines on the substrate are implemented. Furthermore, a drain resistor is used to enhance the stability factor of the design without affecting the overall design noise figure. A triple notch filter is utilized at the output to implement the quad band operation. A small signal gain (S21) of 10.7, 9, 9.1, and 7.2 dB is obtained, and a corresponding noise figure of 0.9, 0.9, 1.1 and 1.2 dB is achieved in the four operation bands, respectively.