Wideband LNA design for SDR radio using balanced amplifier topology

This paper presents the design and development of a wideband low noise amplifier (LNA) suitable for Software Defined Radio (SDR) base station. The LNA design is based on the balanced amplifier topology, using the hybrid coupler and advanced GaAs E-PHEMPT transistor technology in order to produce a good wideband performance on all the critical parameters. By using the balanced amplifier design topology, the design yields excellent return loss, noise figure and linearity performance for the wideband application, and by utilizing the hybrid coupler in the balanced amplifier topology reduces the PCB size compared to normal balanced amplifier topology. The wideband LNA was designed on a PCB board with FR4 substrate and exhibits a small signal gain of 18 dB, noise figure of 1 dB, return loss (input and output) greater than 10 dB and IIP3 greater than 11 dBm across the wideband frequency range from 136-941 MHz (TIA-603C full frequency range), with a dual supply of 5V and total current consumptions of 120mA.