Balanced Amplifier Technique for LNA in UHF Band

This paper describes the design and realization of a low noise amplifier (LNA) at 410MHz. A balanced amplifier structure which consists of hybrid coupler and amplifier has been used to realize this LNA. This approach gives the advantage of good voltage standing wave ratio, higher linearity and good stability. Noise figure of 1dB with a flatness of 0.5 dB and input-output return losses better than-15dB have been achieved over 100MHz bandwidth. The design is carried out with Advanced Design Systems software. LNA has been realized on FR4 substrate, using SiGe HBT (BFY640) and chip type passive components.