Research On Anti-aliasing Receiving Algorithms Of Multi-band Signal And Its Hardware Implementation

Software Defined Radio is a kind of radio frequency communication technology which realizes the functions of different devices through software.It aims to realize the transition from analog to digital in wireless transmission systems.The core idea is to digitize the signal using a wideband analog-to-digital(A/D)converter as close to the antenna as possible,and then define the radio function as much as possible through software.In recent years,due to the development of A/D sampling technology and the improvement of sampling rate and accuracy,bandpass sampling is widely used in software defined radio receivers.However,in the process of sampling,the self-aliasing and the aliasing of useful signals of sampled signal are common,which affects the normal reception of multi-mode and multi-band signals on a same platform.Therefore,it is of great theoretical and practical value in wireless communication systems,especially multi-mode and multi-band software radio receivers.Based on the second-order bandpass sampling and multi-band signal sampling frequency priciples,the multi-band signal anti-aliasing reception is studied.First of all,this paper introduces the basic theory of software defined radio,which lays a theoretical foundation for the design of software defined radio anti-aliasing receiver.Based on the basic theory,the principle of the second-order bandpass sampling is introduced,and a phase adjustment filter algorithm is proposed based on the second-order bandpass sampling.The anti-aliasing filter is dedicated to extract original signals from the aliasing of the sampled signal.The effects of time delay,sampling signal position index difference,group delay and filter tap number on the performance of aliasing filters are analyzed in the simulation,which provide a optimized parameter design to the multi-band anti-aliasing hardware platform.Secondly,the sampling frequency selection method of multi-band signal is studied.Based on the existing multi-band signal minimum sampling frequency search algorithm,the sampling frequency constraint condition is improved,and a novel sampling frequency search algorithm dealing with aliasing signal at the same position after sampling is proposed.The correctness of the algorithm is verified by simulation results.The algorithm reduces the computational complexity greatly,which is more favorable to engineering and hardware realization.Finally,a software wireless hardware platform is designed to receive multi-band signal without aliasing effectively.Through the custom module,the connection of GNU Radio and platform is achieved.The platform verifies the correctness of the sampling frequency selection method and phase adjustment algorithm proposed in this paper,and finally separates the multi-channel aliasing signal.The GNU Radio-based bandpass sampling radio processing platform allows multiple signals to be received and eliminates aliasing without modifying the hardware,which provides a more convenient hardware platform for the development of wireless communication system based on software defined radio and the related experiments such as multi-band sampling.