Broadband Rf Receiver

High linearity wideband RF front end has excellent performance, which plays an important role in electronic countermeasure, software radio and other fields. In this thesis, analog RF front-end with high dynamic range is developed, in which standard hardware modules are used to transfer 2MHz-2000MHz wideband signal into 70MHz.The feature of superheterodyne structure is many combined interference, so the problem of this system is high harmonic and clutter wave rejection ratio in wideband as well as high dynamic range. The wideband local oscillator and RF electromagnetic compatibility is also important. The main work includes:1 Based on discussing wide-band RF front-end design methods in detail, overall scheme is given. By Matlab programming and ADS simulation, reasonable frequency configuration is finished. The whole spectrum is divided into three parts: 2-30MHz, 30-400MHz, 400-2000MHz, proper intermediate frequency (IF) is chosen. It is proved that strong combined interferences are moved outside IF band, which reduces spurious response and improve selectivity. Furthermore, the first IF with narrow bandwidth minimizes the combined interference in the next conversion.2 A C-band bandpass filter used in the first IF is fulfilled. The measured results show that it has bandwidth of 200MHz with return loss more than 18dB and insertion loss about 1dB, rejection of 60dB and the group delay fluctuation is 20ns.3 The LNA, switch and limiter in the system are simulated, while the IF AGC loop, electronically tunable filter are made and tested. And the reasons causing the difference between simulation and experiment results are described.By choosing proper devices, receiver module is made and tested, in which electromagnetic compatibility is considered. The RF front-end realizes combined interference rejection of more than 70dBc, IF and image frequency rejection of more than 85dBc with noise figure of 3.3dB and 90dB dynamic range.