Comparison of wideband LNA designs for SDR applications

This paper describes the design of two wideband LNA topologies for TIA-603 software defined radio (SDR) applications. The two LNA designs are the negative feedback and the balanced amplifier. The negative feedback employs the resistive drain to gate feedback whereas the balanced amplifier incorporates a compact 3dB branch line coupler. Both designs utilized the GaAs transistor, operated by a 5V DC supply and were implemented in a RO4003 PCB. Comparing the performance of the two designs, the balanced amplifier achieved the best RF performance with a stable gain of at least 17.5dB, noise figure lower than 1.03dB, input and output return loss of greater than 11dB and IIP3 of at least 14dBm, which makes it comparable to previously published works.