简介

FIR滤波器是非递归型滤波器的简称，又叫有限长单位冲激响应滤波器。带有常系数的FIR滤波器是一种LTI(线性时不变)数字滤波器。冲激响应是有限的意味着在滤波器中没有发反馈。长度为N的FIR输出对应于输入时间序列x(n)的关系由一种有限卷积和的形式给出，具体形式如下：
$$y(n)={\Sigma }_{k=0}^{N-1}h(k)\times x(n-k)$$
其运算过程可以采用如下图所示的流程：

代码

设计部分(采用移位寄存器+并行乘法阵列+加法树实现)

`timescale 1ns / 1ps
//
// Company: 
// Engineer: 
// 
// Create Date: 2022/07/12 14:23:22
// Design Name: 
// Module Name: my_fir
// Project Name: 
// Target Devices: 
// Tool Versions: 
// Description: 
// 
// Dependencies: 
// 
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
// 
//


module my_fir
#(parameter F=10)
(
input logic clk,
input logic rst,
input logic signed [15:0] filter_in,
output logic signed [31:0] filter_out
    );
//
logic signed [15:0] shift_regs [0:16];
logic signed [15:0] coes [0:16];
logic signed [31:0] mults [0:16];
logic signed [31:0] psum [0:4-1];
logic signed [31:0] sum;
//shift_regs
always@(posedge clk,posedge rst)
if(rst)
   for(int i=0;i<=16;i++)
     shift_regs[i]<=0;
else
begin
   shift_regs[0]<=filter_in;
   for(int i=0;i<16;i++)
      shift_regs[i+1]<=shift_regs[i];
end
//coes
assign coes[0]=-17;
assign coes[1]=62;
assign coes[2]=456;
assign coes[3]=1482;
assign coes[4]=3367;
assign coes[5]=6013;
assign coes[6]=8880;
assign coes[7]=11129;
assign coes[8]=11983;
assign coes[9]=11129;
assign coes[10]=8880;
assign coes[11]=6013;
assign coes[12]=3367;
assign coes[13]=1482;
assign coes[14]=456;
assign coes[15]=62;
assign coes[16]=-17;
//mults
always@(posedge clk,posedge rst)
if(rst)
   for(int i=0;i<=16;i++)
      mults[i]<=0;
else
begin
   for(int i=0;i<=16;i++)
      mults[i]<=coes[i]*shift_regs[i];
end
//psum
always@(posedge clk,posedge rst)
if(rst)
for(int i=0;i<4;i++)
   psum[i]<=0;
else
for(int i=0;i<4;i++)
   psum[i]<=mults[4*i]+mults[4*i+1]+mults[4*i+2]+mults[4*i+3];
//sum
always@(posedge clk,posedge rst)
if(rst)
   sum<=0;
else
   sum<=psum[0]+psum[1]+psum[2]+psum[3]+mults[16];
//
assign filter_out=(sum>>>F);
endmodule

测试平台

`timescale 1ns / 1ps


// Company:  
// Engineer: anxu chan
// 
// Create Date:    16:17:14 08/02/2017 
// Design Name:    FIR filter
// Module Name:    fir 
// Project Name:   FirDesign
// Target Devices: Xilinix V5
// Description: test bench
// Revision: 1.0
// Revision 0.01 - File Created
// Additional Comments: 
//


module fir_tb;

	// Inputs
	reg clk;
	reg rst;
	reg signed [15:0] filter_in;

	// Outputs
	wire signed [31:0] filter_out;

	// Instantiate the Unit Under Test (UUT)
	my_fir uut (
		.clk(clk), 
		.rst(rst), 
		.filter_in(filter_in), 
		.filter_out(filter_out)
	);

	// define reset time
	initial begin
		rst = 1;
		#15;
		rst = 0;
	end

	// define clock
	initial begin
		clk = 0;
		forever #10 clk = ~clk;	
	end

	// define a ram store input signal
	reg signed[15:0] mem[241:0];
	// read data from disk
	initial begin
		$readmemb("E:\\rtl_project\\fir\\src\\project\\databin.mem" , mem);
	end

	// send data to filter
	integer i=0;
	initial begin
		#15;
		for(i = 0 ; i < 242 ; i = i+1) begin
			filter_in = mem[i];
			#20;
		end	
	end

	// write data to txt File
	integer file;
	integer cnt=0;
	initial begin
		file = $fopen("dataout1.txt" , "w");
	end

	// write data was filtered by fir to txt file 
	always @(posedge clk) begin
		$fdisplay(file , filter_out);
	end

	always @(posedge clk) begin
		$display("data out (%d)------> : %d ," , cnt, filter_out);
		cnt = cnt + 1;
		if (cnt == 250) begin
			#20 $fclose(file);
			rst = 0;
			#20 $stop;
		end
	end
	
endmodule

结果

完整工程见链接