Wideband low noise amplifier design for software defined radio at 136 to 941 MHz

The low noise amplifier (LNA) for mobile software defined radio (SDR) in this work is targeted to be applied in a two-way communication mobile system architecture. The operating frequencies of the design were based on the TIA-603C standard for Land Mobile FM Communication Equipment (136-941MHz), which is the preferred standard used by established two-way radio suppliers. The technical specification was also deduced from the TIA-603C standard receiver system sensitivity and intermodulation. The LNA adopts a negative feedback wideband amplifier topology where the negative feedback is to counter the long RF trace problem inherited at the targeted frequencies. This proposed topology can solve the problem of economically impractical PCB size rendered by other wideband amplifier methods. The measured results show the proposed LNA has a stable gain of 12dB, more than 13dBm of IIP3 and a noise figure of less than 1.5dB. The whole design consumes 80mA of current from a 5V supply.