项目里面有用到插值滤波器的场合，用matlab做了前期的滤波器性能仿真，产生的滤波器系数保存下来输入到FPGA IP中使用即可。
下面是仿真的代码
1 % clear all 2 close all 4 Nx = 4096; 5 Tx = 16; 6 nx = 0:Nx-1; 7 x = sin(2*pi*2*nx/Tx); 8 L = 7; 9 % Ny = L * Nx;10 % ny = 0:Ny-1;11 % yi = zeros(1,Ny);12 % yi(1:L:Ny) = x;13 % figure;14 % stem(yi);16 Fst1 = 0.05;17 Fp1 = 0.09;18 Fp2 = 0.11;19 Fst2 = 0.15;20 Ast1 = 60;21 Ap = 0.01;22 Ast2 = 60;23 % bandpass filter works well, try lowpass to check whether DC signal affects pm24 % hband = fdesign.bandpass('Fst1,Fp1,Fp2,Fst2,Ast1,Ap,Ast2',Fst1,Fp1,Fp2,Fst2,Ast1,Ap,Ast2);25 hband = fdesign.lowpass('Fp,Fst,Ap,Ast',Fp2,Fst2,Ap,Ast2);26 Hband = design(hband);27 info(Hband); %show filter info29 Fp = 0.08 %pass band corner freq30 Fst = 0.24 %stop band corner freq31 Ap = 0.01; %pass band attenuation(dB)32 Ast = 80.0; %stop band attenuation(dB)33 h1 = fdesign.interpolator(L,'lowpass',Fp,Fst,Ap,Ast);34 Href = design(h1);35 info(Href); %show filter info36 fvtool(Hband,1,Href,1); %show freq response37 title('lowpass filter interpolator filter');38 legend('lowpass filter','interpolator filter');40 % import sample_dara41 a=dlmread('1.prn');%以字符形式打开文件 42 v1=a(:,38); %16进制转化为10进制数，存储进v1矩阵43 figure;44 subplot(3,1,1);45 plot(v1);46 v2 = filter(Hband,v1);47 subplot(3,1,2);48 plot(v2);49 y = filter(Href,v2);50 subplot(3,1,3);51 plot(y);52 % b=dlmread('2.prn');%以字符形式打开文件 53 % y=b(:,37); %16进制转化为10进制数，存储进v1矩阵56 fft_analysis_func(v2,455/14/16, 16);57 legend('lowpass filter');58 fft_analysis_func(y,455*L/14/16, 16);59 legend('interpolator filter');61 %axis([0 25 -120 5]) %zoom-in 0 to 25MHz62 %generating the coe file63 ref_filter = Hband.Numerator;64 gen_coe_rad10(Hband.Numerator,'lowpass_filter_rad10.coe');65 ref_filter = Href.Numerator;66 gen_coe_rad10(Href.Numerator,'inter_filter_rad10.coe');代码中用到了两个函数
function fft_analysis_func(x, fs, adc_width)%The following program code plots the FFT spectrum of a desired test tone. Test tone based on coherent sampling criteria, and%computes SNR, SINAD, THD and SFDR.%This program is believed to be accurate and reliable. This program may get altered without prior notification.;%fid=fopen('F:pelican_ADC_testvjtag_prjdata_analysissingle_tone.txt','r');%numpt=input('Number of Points in FFT? ');%fclk=input('Sampling Frequency (MHz)? ');%numbit=input('ADC Resolution (bits)? ');% numpt=length(x);numpt = 4096;fclk=fs;numbit=adc_width;
%Warning: ADC output may be clipping - reduce input amplitudeif (max(code)==2^numbit-1) | (min(code)==0) disp('WARNING: ADC OUTPUT MAYBE CLIPPING - CHECK INPUT AMPLITUDE!');Dout=code;Voltage=Dout./((2^numbit-1)/2)*(0.5);
Doutw=(Dout').*blackmanharris(numpt); %add Minimum 4-term Blackman-Harris windowDout_spect=fft(Doutw);Dout_dB=20*log10(abs(Dout_spect));figure;maxdB=max(Dout_dB(1:numpt/2)); %numpt points FFT result in numpt/2 points spectrum%计算距离满量程的幅度差max_voltage=max(Voltage);delta_amplitude=20*log10(max_voltage/0.5); %full scale voltage amplitude is 0.5vplot([0:numpt/2-1].*fclk/numpt,Dout_dB(1:numpt/2)-maxdB+delta_amplitude);% plot([0:numpt-1].*fclk/numpt,Dout_dB(1:numpt)-maxdB+delta_amplitude);grid on;title('SINGLE TONE FFT PLOT');xlabel('ANALOG INPUT FREQUENCY (MHz)');ylabel('AMPLITUDE (dBfs)');hold off;仿真出的结果如下：
产生了用于滤波器的系数：
1 radix = 10; 2 coefdata = 3 -0.001219138, 4 -0.002838337, 5 -0.005111633, 6 -0.007197151, 7 -0.007796326, 8 -0.005351278, 9 0.001364815,10 0.012476464,11 0.026308774,12 0.039101106,13 0.045443072,14 0.039549550,15 0.017241585,16 -0.021849408,17 -0.072532419,18 -0.123501332,19 -0.158497326,20 -0.159275461,21 -0.109905781,22 -0.001430991,23 0.164384860,24 0.373413481,25 0.600371089,26 0.812911647,27 0.977825248,28 1.067924092,29 1.067924092,30 0.977825248,31 0.812911647,32 0.600371089,33 0.373413481,34 0.164384860,35 -0.001430991,36 -0.109905781,37 -0.159275461,38 -0.158497326,39 -0.123501332,40 -0.072532419,41 -0.021849408,42 0.017241585,43 0.039549550,44 0.045443072,45 0.039101106,46 0.026308774,47 0.012476464,48 0.001364815,49 -0.005351278,50 -0.007796326,51 -0.007197151,52 -0.005111633,53 -0.002838337,54 -0.001219138;