Broadband Rf Front-end System Simulation Study

The designing of RF front-end becomes one of the key technologies of Software-Defined Radio(SDR). But it is not feasible to realize the ideal SDR by directly placing the AD converter close to the antenna. Converting the broadband RF signal to the IF signal which can be digital is the key to realize the SDR. Firstly the principles for SDR are discussed in the paper. The key technologies and the primary structures to realize the SDR are recommended detailed.In this paper, for 2~2000MHz broadband RF front-end, using subsection processing fixed intermediate frequency superheterodyne architecture, and combining with the actual component's level, a broadband RF front-end system simulation platform is presented, which provided the universal, standardization, and modularization of transmitter and receiver. The RF front-end structure is predigested greatly due to using the electronically tunable filters.With the established RF front-end system simulation platform, adding the digital modulated baseband signal, this paper simulated the multifold digital modulated signal's transmission, such as 2ASK, QPSK, and 16QAM. Then researches of power compression and phase noise of local oscillation influence the bit error ratio for different modulated system. The designing is satisfied multifold functions request with the high-powered and integrated broadband RF front-end.As a key component of RF front-end, broadband low noise amplifier (LNA) becomes important in the SDR receiver. This paper studies the design methods and techniques of the broadband LNA. Using negative feedback techniques and lossy match method, a broadband LNA acceptable for SDR is presented. The measured results showed that over 30MHz~3000MHz, the LNA achieved a maximum noise figure of 2.0dB, a power gain of 22dB with gain flatness of less than±2.0dB.