基于matlab FPGA verilog的FIR滤波器设计

FIR滤波器说明









本例程实现8阶滤波器，9个系数，由于系数的对称性，h(0)=h(8)，h1(1)=h(7)，h(2)=h(6)，h(3)=h(5)，h(4)为中间单独一个系数。根据公式：





实现框图：









推导出当系数N为偶数时,例如N=4：y(n)=h(0)*{x(0)+x(n-3)}+h(1)*{x(n-1)+x(n-2)}

当系数N为奇数时，例如N=5：

y(n)=h(0)*{x(0)+x(n-1)}+h(1)*{x(n-1)+x(n-3)}+h(2)*x(n-2)

1、用matlab生成和量化滤波器系数

打开matlab，“start”—“toolboxes”—“Filter
Design”—“fadtool”，打开fdatool窗口，设置如下：





设置参数后，点击“Design Filter”按钮，“file”—“export”，把滤波器系数导出到workspace,如下图：





执行命令：Num=Num’ ,把滤波器系数拷贝到文件COFFICIENT.dat中。

量化系数：在matlab中运行quantization.m

2、说明

用matlab程序sin_1MHz_gen.m生成正弦波波形表，改变变量f0
= 1.5e6可以生成不同频率的波形。把第一个周期的波形数据存入signal_1m.dat文件中，存入的数据个数为Fs/Fo的最小正整数之比的分子，比如Fs=25MHz，Fo=0.3MHz,Fs/Fo=250/3(Fs=25/24MHz),则存入文件signal_1m.dat的波形数据个数为开头的250个数据。相应的signal_gen0.v中的语句if(i0<50)相应的改为if(i0<250)。仿真时signal_1m.dat放在仿真目录下

3、滤波器的multisim仿真

运行matlab，用sin_1MHz_gen.m产生5MHz（f0
=5e6）正弦波信号，Fs/Fo=5，把数据hex_sin_data的前5个数据存入signal_1m.dat文件，相应的signal_gen0.v中的语句if(i0<50)相应的改为if(i0<5)。

仿真的波形如下图（fir滤波器的输入输出信号）：





运行matlab，用sin_1MHz_gen.m产生1MHz（f0
=1e6）正弦波信号，Fs/Fo=25，把数据hex_sin_data的前5个数据存入signal_1m.dat文件，相应的signal_gen0.v中的语句if(i0<5)相应的改为if(i0<25)。

仿真的波形如下图（fir滤波器的输入输出信号）：





由此可见FIR对带外信号起到衰减的作用。

部分代码：

//Date :2012-5-27

//Description : 8 阶FIR滤波器 ，通带2MH，阻带8MHz ，带外衰减80dB,通带波动1dB

//Uesedfor

//Taobao :

//E-mail :2352517093@qq.com

//==========================================================================

`timescale 1 ns / 1 ns

module fir_filter

(

i_fpga_clk ,

i_rst_n ,

i_filter_in,

o_filter_out

);

input i_fpga_clk ; //25MHz

input i_rst_n ;

input signed [7:0] i_filter_in ; //数据速率25Mh

output reg signed [7:0] o_filter_out; //滤波输出

//==============================================================

//8阶滤波器系数，共9个系数，系数对称

//==============================================================

wire signed[15:0] coeff1 = 16'd239 ;

wire signed[15:0] coeff2 = 16'd1507;

wire signed[15:0] coeff3 = 16'd4397;

wire signed[15:0] coeff4 = 16'd7880;

wire signed[15:0] coeff5 = 16'd9493;

//===============================================================

//延时链

//===============================================================

reg signed [7:0] delay_pipeline1 ;

reg signed [7:0] delay_pipeline2 ;

reg signed [7:0] delay_pipeline3 ;

reg signed [7:0] delay_pipeline4 ;

reg signed [7:0] delay_pipeline5 ;

reg signed [7:0] delay_pipeline6 ;

reg signed [7:0] delay_pipeline7 ;

reg signed [7:0] delay_pipeline8 ;

always@(posedge i_fpga_clk or negedge i_rst_n)

if(!i_rst_n)

begin

delay_pipeline1 <= 8'b0 ;

delay_pipeline2 <= 8'b0 ;

delay_pipeline3 <= 8'b0 ;

delay_pipeline4 <= 8'b0 ;

delay_pipeline5 <= 8'b0 ;

delay_pipeline6 <= 8'b0 ;

delay_pipeline7 <= 8'b0 ;

delay_pipeline8 <= 8'b0 ;

end

else

begin

delay_pipeline1 <= i_filter_in ;

delay_pipeline2 <= delay_pipeline1 ;

delay_pipeline3 <= delay_pipeline2 ;

delay_pipeline4 <= delay_pipeline3 ;

delay_pipeline5 <= delay_pipeline4 ;

delay_pipeline6 <= delay_pipeline5 ;

delay_pipeline7 <= delay_pipeline6 ;

delay_pipeline8 <= delay_pipeline7 ;

end

//================================================================

//加法，对称结构，减少乘法器的数目

//================================================================

reg signed [8:0] add_data1 ;

reg signed [8:0] add_data2 ;

reg signed [8:0] add_data3 ;

reg signed [8:0] add_data4 ;

reg signed [8:0] add_data5 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(0)+x(8)

if(!i_rst_n)

add_data1 <= 9'b0 ;

else

add_data1 <= i_filter_in + delay_pipeline8 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(1)+x(7)

if(!i_rst_n)

add_data2 <= 9'b0 ;

else

add_data2 <= delay_pipeline1 + delay_pipeline7 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(2)+x(6)

if(!i_rst_n)

add_data3 <= 9'b0 ;

else

add_data3 <= delay_pipeline2 + delay_pipeline6 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(3)+x(5)

if(!i_rst_n)

add_data4 <= 9'b0 ;

else

add_data4 <= delay_pipeline3 + delay_pipeline5 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(4)

if(!i_rst_n)

add_data5 <= 9'b0 ;

else

add_data5 <= {delay_pipeline4[7],delay_pipeline4} ;

//===================================================================

//乘法器

//====================================================================

reg signed [24:0] multi_data1 ;

reg signed [24:0] multi_data2 ;

reg signed [24:0] multi_data3 ;

reg signed [24:0] multi_data4 ;

reg signed [24:0] multi_data5 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //（x(0)+x(8)）*h(0)

if(!i_rst_n)

multi_data1 <= 24'b0 ;

else

multi_data1 <= add_data1*coeff1 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //（x(1)+x(7)）*h(1)

if(!i_rst_n)

multi_data2 <= 24'b0 ;

else

multi_data2 <= add_data2*coeff2 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //（x(2)+x(6)）*h(2)

if(!i_rst_n)

multi_data3 <= 24'b0 ;

else

multi_data3 <= add_data3*coeff3 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //（x(0)+x(8)）*h(3)

if(!i_rst_n)

multi_data4 <= 24'b0 ;

else

multi_data4 <= add_data4*coeff4 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(4)*h(4)

if(!i_rst_n)

multi_data5 <= 24'b0 ;

else

multi_data5 <= add_data5*coeff5 ;

//========================================================================

//流水线累加

//========================================================================

reg signed[25:0] add_level1_1;//1级

reg signed[25:0] add_level1_2;//1级

reg signed[25:0] add_level1_3;//1级

always@(posedge i_fpga_clk or negedge i_rst_n) //（x(0)+x(8)）*h(0)+（x(1)+x(7)）*h(1)

if(!i_rst_n)

add_level1_1 <= 26'b0 ;

else

add_level1_1 <= multi_data1+multi_data2 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //（x(2)+x(6)）*h(2)+（x(3)+x(5)）*h(3)

if(!i_rst_n)

add_level1_2 <= 26'b0 ;

else

add_level1_2 <= multi_data3+multi_data4 ;

always@(posedge i_fpga_clk or negedge i_rst_n) //x(4)*h(4)

if(!i_rst_n)

add_level1_3 <= 26'b0 ;

else

add_level1_3 <= {multi_data5[24],multi_data5} ;

//==2级加法

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