Design Of Multi-band Digital Receiver Based On Software Define Radio

Software define radio is a kind of radio broadcasting communication technology,which can upgrade the communication function by reorganizing and redefining the software modules on the general hardware platform.At present,software define radio is widely used in the 5th-generation(5G)network architecture,providing network business convergence services for the mobile network reconstruction on demand.Radio frequency direct band-pass sampling structure is the receiver structure closest to the purpose of software radio,but its use is limited due to spectrum aliasing and ADC hardware limitation.Therefore,it is of great significance to design anti-aliasing digital receivers for multi-band bandpass signals.In this paper,the design of digital receiver is completed from two aspects: anti-aliasing filtering algorithm and sampling system error modeling and compensation method:Firstly,an anti-aliasing filtering algorithm based on the principle of band-pass sampling is designed to solve the problem of overlapping frequency spectra after multiple signal samples.The phase adjustment filter bank is designed to form a general model of high-order anti-aliasing filtering system,and the receiving simulation of multi-band band-pass signals is completed.Simulation results show that band-pass signals at any position in the 0.5-3GHz frequency spectrum can be received by the same receiver and when the four signals are simultaneously aliased,the aliasing suppression can exceed 25 d B.Then,aiming at the problem that the hardware error of the band-pass sampling system affects the system performance,the system hardware error is modeled and the compensation method is designed.Specifically,the relationship between amplitude error,angle error and signal-to-interference ratio of received signal is given,and the hardware error is compensated from amplitude and phase respectively.In the aspect of amplitude,according to the results of quadratic fitting,a function is designed to compensate the amplitude error;In terms of phase,the fixed part of the error and the part changing with frequency are compensated respectively,and an anti-aliasing filter based on phase error compensation is designed to compensate the phase error.Based on the measured values,the anti-aliasing performance of the digital receiver after error compensation is significantly improved.Finally,the hardware platform of multi-band digital receiver is built to verify the feasibility of the above two methods.The Field Programmable Gate Array(FPGA)is used for digital signal processing,and modules such as reconfigurable anti-aliasing filter,digital down conversion and Ethernet transmission are designed on Quartus II software to realize the separation and reception of multi-channel aliasing signals,and then the data is transmitted to MATLAB for baseband processing through Gigabit Ethernet interface.The receiving test shows that the hardware platform can suppress two mixed signals by more than 25 d B.There are 58 figures,8 tables and 80 references in this paper.