The effect of self resonance to the performance of low noise amplifier (LNA) designed for WLAN IEEE 802.11n transmission in 2.4GHz

Abstract

This paper will discuss the design and implementation of low noise amplifier (LNA)for 2.4GHz broadband transmission of WLAN iEeE 802.11n and the effect of self resonance in SMD lumped elements used for impedance matching. The design involves accurate measure of noise figure based on BER of broadband WLAN 802.11n transmission in addition to gain required to maintain sufficient SNR. Maximum noise figure of 2.63dB is required to sustain maximum BER of 3×10−5, while gain is maintained minimum at 19.3dB. The selfresonance effect of the element inductor and has degraded noise nnd gain performance of the LNA, due to lower resonance frequency than designed frequency at 2.4GHz. The inclusion into equivalent circuit model of SMD inductor and capacitor with equivalent parasitic elements showed correction of I S211, I S111 and I S22I to ones of matching elements with nominal ideal value. 1.19dB noise figure and 11.565dB gain at 2.4 GHz frequency meets the specification with some degradation of gain. This shows the self-resonance effect of matching elements deteriorating gain from 19.12dB. From measurement, gain has been found diminishing into to −1.8dB. This shows results of shifting of impedance matching in source-input network as a result of self-resonance effect of parasitic elements of matching elements of the SMD inductor/s and capacitor/s.