Design Of RF Front-end For Broadband Receiver

In order to monitor the known and unknown radio frequency signals in space,this thesis developed a broadband fast scanning RF receiver front end.The main work of the thesis is:1.A front-end scheme for wideband fast scanning RF receiver is proposed.By comparing and analyzing the mainstream receiver front-end schemes and their performances,the overall implementation scheme of the receiver front-end is determined for the frequency range and image suppression of the broadband receiver.The signal frequency from 80 MHz to 1.8GHz is converted to zero frequency after being upconverted to 2.53 GHz.The signal frequency from 1.8GHz to 6.1GHz is directly converted to zero frequency.And signal frequency from 6.1GHz to 8.7GHz is mixed to zero with two mixers.At last,the baseband signal from the zero-IF mixer is filtered and amplified.The local oscillator can be reused.In terms of structure,the use of the RF connector and the stacked structure effectively reduces the area of the receiver.2.The solution to the near-end strong spur problem in the broadband local oscillator frequency source is studied.Many broadband receiver front-ends use a phase-locked loop chip with an integrated VCO to implement the local oscillator.Due to the mismatch of the phaselocked loop charge pump and the fractional division,most points of the local oscillator will have spurs around them.Spurious signals may fall into the baseband.Especially for the front end of the receiver,the received signal frequency range is up to 8 GHz,the intermediate frequency bandwidth is 80 MHz and variable.So that the spur of the local oscillator signal will have a more serious impact.In this design,a two-stage phase-locked loop cascading scheme is adopted,which is matched with the double-loop algorithm configuration on the software.Finally,reducing near-end spurs at any frequency of the local oscillator output,which improves the dynamic range of the receiver and reduces probability of error in signal detection.3.The schematic design,performance simulation,layout design and the physical testing of the wide frequency range and fast channel scanning RF receiver front end are completed.The power gain,mixing spur component and noise figure of the working frequency band are verified by ADS simulation.The phase noise and spurious distribution of the local oscillator are verified with the PLLatinum Sim.Finally the system architecture and key device selection are determined.The final test results of the front end meet the system requirements.The broadband fast-scanning RF receiver developed in this thesis receives a signal with a frequency range of 80MHz-8.7GHz and a sweep rate of 10 K times per second.It can be used as a wireless spectrum monitoring device or a frequency hopping receiver with different digital baseband systems,and has broad application prospects.