Design And Implementation Of Subband Adaptive Filter

Subband adaptive filter has a wide range of applications in communications,radar,etc.It has a special structure that can band-divide and extract input signals,reduce the correlation of input signals,improve convergence speed,and reduce the requirement of signal processing.Therefore,the research on subband adaptive filter has a certain practical significance.In order to solve the problem of the aliasing component at the output of the traditional subband adaptive filter and the contradiction between the convergence speed and the steady-state offset error of the subband adaptive algorithm,combined with the steepest descent algorithm and the minimum perturbation principle,an improved multi-band structure subband adaptive filtering(Mon-IMSAF)algorithm based on momentum gradient descent is proposed.By superimposing the update vector value of the previous time on the update vector at the current time,the acceleration in the same direction of the filter weight update vector iteration is promoted,and the oscillation problem is suppressed by reducing the speed in other iteration directions.The simulation results show that the Mon-IMSAF algorithm reduces the steady-state offset error of the modified multi-band structure subband adaptive filtering(VRM-IMSAF)algorithm with variable regularization matrix by 2dB when the autoregressive signal AR(10)is input,and has faster convergence speed.The subband adaptive filter based on the Mon-IMSAF algorithm is adapted to the multiple subband waveform of the F-OFDM system,and supports dynamic soft air interface parameter configuration of 5G according to service requirements,so the filter is applied to the F-OFDM waveform.The simulation results show that the designed subband adaptive filter improves the outband leakage suppression of the F-OFDM system by 20 dB compared with the conventional OFDM.When the signal-to-noise ratio is 10dB,the Mon-IMSAF algorithm is 3dB lower than the IMSAF algorithm,and has a fast convergence speed and good system tracking performance.As the signal-to-noise ratio increases,the general orientation of the Mon-IMSAF algorithm is not affected,indicating that Mon-IMSAF has obvious advantages as a sub-band filtering algorithm,and can optimize the F-OFDM sub-band transmission waveform,which is suitable for flexible transmission of 5G rich services and scenarios.Based on the above research,the design of sub-band adaptive filter based on Mon-IMSAF algorithm is implemented on FPGA.It mainly includes model design of subband filter banks,adaptive filter and model design of weight update subsystem.Finally,model simulation and functional simulation were implemented by Simulink and Model Sim respectively,which verified the correctness of the design.