Research And Implement RF Front-end Of UHF BNR Receiver

Now we place more and more demands on RF receiver front-end in Modern broadbandnetwork station system design, such as anti-interference performance, high linearity, highsensitivity, large dynamic range and other characteristics。As the major part of a research project，this dissertation is mainly concerned with the in-depth study of wideband RF receiver front-endcircuit and system。The main function of Receiver is receiving weak input signal from antenna and thenfiltering,amplification,frequency conversion and senting to the digital processing terminal fordigital-analog conversion and demodulation. This paper firstly analyzes the basic principle ofseveral common receivers and their structural features, and then introduces the main technicalindexes of RF receiver front-end detailedly,Such as sensitivity, dynamic range, linearity,signal-to-noise ratio, mirror rejection ratio, etc,and ultimately choose superheterodyne twofrequency structure form，the first intermediate frequency is1100MHz, the second intermediatefrequency is21.4MHz, in order to improve mirror frequency resistance ratio and choose mediumfrequency filter easily, complete extraction of useful channel and inhibition of adjacent-channelinterference. The RF receiver front-end is simulated in Advanced Design System2009and thesimulation results can achieve project expected design goal, According to the ADS simulationmodel, the final circuit is made. Rf front-end circuit is composed of High frequency amplifier unitand Intermediate frequency amplifier unit, mainly including primary filter, low noise amplifier,mixer, filters, amplifiers, automatic gain control circuit, digitally controlled attenuator circuit andother auxiliary circuit.In order to design a large dynamic range Intermediate frequency amplifierunit circuit, this scheme adopts the AGC amplifier AD8367and digitally controlled attenuatorHMC470, they are controlled by digital terminal system.According to the voltage value providedby detection circuit LT5534, Digital terminal system regulate the amplifier gain and attenuation,ensure the flatness and stability of output signal although different received signal go through thereceiving link. Finally, the design fully meet the system performance index after the systemdebugging and analysis the test result,so that it has good anti-interference performance and gaincontrolled function, apply to multiple carrier broadband network station.