Design and broadband verification of RF amplifier for 4G/ 5G front-end modules

The RF amplifier for broadband front end module of 4G or 5G terminals should be capable of handling transmission rate over 100Mbps to over 1Gbps with low BER and low non-linearity spectrum products. This paper reports broadband verification of a front-end RF amplifier designed for broadband 4G and 5G transmission. The RF amplifier employs an Infineon SiGe Bipolar transistor matched to 50Ω load and source impedance through 3-section and 2-section L-C network, respectively. Broadband S-parameter characteristic was verified showing encircling S₂₁ behavior around |S₂₁| ≅ 7 over hundreds of MHz centering at 2.4GHz. The S₁₁ and S₂₂ show encircling curves centering the origin with relatively small radius. The broadband performance of LTE FDD 64QAM signal transmission thru the RF Amplifier was verified on the signal spectrum and modulation quality by utilizing Keysight M9381A Vector Signal Generator (VSG), M9391A Vector Signal Analyzer (VSA) and VSA 89600. Broadband signal of LTE FDD 64QAM was generated by Keysight M9381A Vector Signal Generator (VSG) by setting 64QAM modulation and LTE signaling parameters resulting broadband LTE FDD signal with bandwidth of 20MHz at frequency of 1.8GHz and 2.4GHz. The LTE FDD 64QAM signal spectrum and modulation constellation measured at the output of front-end RF Amplifier by Keysight M9391A VSA and VSA 89600 subsequently. Broadband modulation constellation, spectrum as well as EVM summary of the LTE FDD signal were observed by VSA 89600 at frequency 1.8 and 2.4GHz. Out-of band noise spectrum and non-linearity products of the 20MHz LTE FDD 64QAM signal increase at the output of front-end RF amplifier at frequency 1.8GHz, though less visible at 2.4GHz. The 64QAM vector-point constellation of the LTE FDD 64QAM signal in 2.4GHz is relatively still intact, eventhough the EVM slightly degrades to 11.478 % from 10.772% after amplified by front-end RF amplifier.