Research on Receiver Dynamic Range Extension with Adjustable Attenuator

In this paper, two dynamic range (DR) extension schemes based on adjustable attenuator (AA) are discussed. In scheme 1, AA is located after low noise amplifier (LNA), while in scheme 2, AA is placed before LNA. To reduce the noise figure (NF) in scheme 2, the method of reducing bias current of LNA was utilized. Through analyzing third-order intermodulation (IM3) when receiving strong signals, it demonstrates that scheme 2 can effectively improve DR upper bound and avoid receiver blocking. By comparing NF when receiving weak signals, it is shown that under certain conditions, the receiver sensitivity of scheme 2 is better than that of scheme 1. Furthermore, the advantages of scheme 2 are verified by circuit simulations and measurements.