FIR基本型仿真_03

作者：桂。

时间：2018-02-05 20:50:54

链接：http://www.cnblogs.com/xingshansi/p/8419452.html 

---

一、仿真思路

　　设计低通滤波器（5阶，6个系数），滤波器特性：

 借助低通滤波器对信号进行滤波：

二、VIVADO仿真

　　首先利用MATLAB生成定点补码：

%=============设置系统参数==============%
f1=500;        %设置波形频率
f2=3600;
Fs=8000;        %设置采样频率
L=1024;         %数据长度
N=16;           %数据位宽
%=============产生输入信号==============%
t=0:1/Fs:(1/Fs)*(L-1);
y=sin(2*pi*f1*t)+sin(2*pi*t*f2);
y_n=round(y*(2^(N-3)-1));      %N比特量化;如果有n个信号相加，则设置（N-n）
%=================画图==================%
a=10;           %改变系数可以调整显示周期
stem(t,y_n);
axis([0 L/Fs/a -2^N 2^N]);      %显示
%=============写入外部文件==============%
fid=fopen('sin_data.txt','w');    %把数据写入sin_data.txt文件中，如果没有就创建该文件 
for k=1:length(y_n)
    B_s=dec2bin(y_n(k)+((y_n(k))<0)*2^N,N);
    for j=1:N
        if B_s(j)=='1'
            tb=1;
        else
            tb=0;
        end
        fprintf(fid,'%d',tb);
    end
    fprintf(fid,'\r\n');
end

fprintf(fid,';');
fclose(fid);

　　vivado的testbench：

`timescale 1ns / 1ps
module tb;
    // Inputs
    logic Clk;
    logic rst;
    // Outputs
    logic signed [23:0] Yout;
    //Generate a clock with 10 ns clock period.
initial  Clk <= 0;

always #5 Clk = ~Clk;

//Initialize and apply the inputs.
//-------------------------------------//
parameter data_num = 32'd1024;
integer   i = 0;
reg [15:0]  Xin[1:data_num];
reg  [15:0]  data_out;

initial begin
 rst = 1;
#20
  rst = 0;
#40
    $readmemb("D:/PRJ/vivado/simulation_ding/009_lpf6tap/matlab/sin_data.txt",Xin);
end


 always @(posedge Clk) begin
 if(rst)
 begin
    data_out <= 0;
 end
 else   
 begin
    data_out <= Xin[i];
    i <= i + 8'd1;
    end
end   

fir_6tap uut (
.Clk(Clk), 
.Xin(data_out), 
.Yout(Yout)
);
endmodule

　　子模块 fir_6tap：

`timescale 1ns / 1ps
module fir_6tap(
        input Clk,
        input signed [15:0] Xin,
        output reg signed [23:0] Yout
        );
    
    //Internal variables.
    wire signed   [7:0] H0,H1,H2,H3,H4,H5;
    wire signed   [23:0] MCM0,MCM1,MCM2,MCM3,MCM4,MCM5,add_out1,add_out2,add_out3,add_out4,add_out5;
    wire signed     [23:0] Q1,Q2,Q3,Q4,Q5;
    
//filter coefficient initializations.
//H = [-2 -1 3 4].
    assign H0 = -15;
    assign H1 = 19 ;
    assign H2 = 123;
    assign H3 = 123;
    assign H4 = 19;
    assign H5 = -15;

//Multiple constant multiplications.
    assign MCM5 = H5*Xin;
    assign MCM4 = H4*Xin;
    assign MCM3 = H3*Xin;
    assign MCM2 = H2*Xin;
    assign MCM1 = H1*Xin;
    assign MCM0 = H0*Xin;

//adders
    assign add_out1 = Q1 + MCM4;
    assign add_out2 = Q2 + MCM3;
    assign add_out3 = Q3 + MCM2;    
    assign add_out4 = Q4 + MCM1;   
    assign add_out5 = Q5 + MCM0;   
//flipflop instantiations (for introducing a delay).
    DFF dff1 (.Clk(Clk),.D(MCM5),.Q(Q1));
    DFF dff2 (.Clk(Clk),.D(add_out1),.Q(Q2));
    DFF dff3 (.Clk(Clk),.D(add_out2),.Q(Q3));
    DFF dff4 (.Clk(Clk),.D(add_out3),.Q(Q4));
    DFF dff5 (.Clk(Clk),.D(add_out4),.Q(Q5));
//Assign the last adder output to final output.
    always@ (posedge Clk)
        Yout <= add_out5;

endmodule

　　DFF：

`timescale 1ns / 1ps
module DFF
        (input Clk,
        input [23:0] D,
        output reg [23:0]   Q
        );
    
    always@ (posedge Clk)
        Q = D;
    
endmodule

　　主要电路图（4阶为例）：

　　仿真结果，与MATLAB测试一致：