Research On Key Techniques Of RF Circuits In High Performance Receivers And Transmitters In Global Satellite Navigation Systems

The anti-jamming GNSS receiver and GNSS signal simulator are key equipment in GNSS.The linearity and out-band suppression of RF front-ends have great influence on anti-jamming performance of GNSS receivers,but there is no complete theory and method to design them so far.GNSS signal simulators provide an important test means for the research of receivers.To ensure accuracy of test,the simulator puts forward strict requirment for power control.But the power control implemented by traditional digital attenuators cannot satisfy the strict accuracy requirement.For above problems,the design and optimization of RF front-end linearity and out-band suppression,and the improvement of RF power control accuracy of the GNSS signal simulator are researched in this paper.The innovation and research fruits are listed below.?.Aiming at the design of RF front-end without AGC circuits in a GNSS receiver under interference environment,a design method of the linearity is proposed.Given A/D chips and mixers,according to the anti-jamming requirement,a method of solving 1dB compression point,third-order intercept point and noise figure of each circuit is proposed,which can direct the selection of components.According to this method,the RF front-end of a certain type of GNSS receivers is designed,which achieves the expected anti-jamming effect,proving that this method is effective.?.The requirement for out-band suppression is often too strict in GNSS receivers,causing high order of filters and degraded group delay.To solve this problem,a method to design the requirement reasonably is proposed.A method to select filter prototype functions and distribute out-band suppression requirement reasonably is proposed,which minimizes the maximal order of filters under the tolerance limit of group delay.Simulation results demonstrate that this method can reduce filters' order,improve performance of group delay and reduce the complexity and cost of filters obviously.?.Considering that digital attenuators cannot satisfy the strict requirement for accuracy of power control in a GNSS signal simulator,a method of improving the accuracy of voltage variable attenuators based on moving least squares curve fitting is proposed.The low boundary formula of radius of influenced domain is proved,which can direct the selection of radius,improve fitting accuracy and avoid singular matrix.Based on this method,the power control module of a record playback system is designed.Confirmed by test data,the maximum attenuation error of the module is 0.1dB,which decreases by 80% compared to use digital attenuators.