1.算法描述

整个数字下变频的基本结构如下所示

NCO使用CORDIC算法，CIC采用h结构的CIC滤波器，HBF采用复用结构的半带滤波器，而FIR则采用DA算法结构。

这里，我们首先假设不考虑中频信号输入的载波频偏问题，即发送的中频频率和本地的载波频率是一致的。

为了验证系统的正确性，我们首先需要设计一个发送源，由于你要求的信号带宽为20M，

所以整个系统我们设计的系统参数为，中频为80M，A/D采样为60M。本地接收端的载波频率为20M。

即发送端通过80M的中频调制之后，信号的频谱会搬移到80M附近，然后接收端通过AD60M采样后，会将频谱搬移到20M附近，且不会发生混叠现象。

那么系统测试方案可以简化为，一个中心频率在20M附近的中频输入测试信号进行测试。

首先设计一个发送测试信号。

信号的基本结构如下所示：

我们首先在FPGA中设计这么一个结构得到中频测试信号，然后使用这个测试信号进行下变频测试。

整个系统的原理框图如下所示：

RTL图：

综合资源占用：

2.仿真效果预览

quartusii10.0,ModelSim-Altera 6.6d Starter Edition

3.verilog核心程序

 
 
module tops2(
	reset,
	clk,
	clk0,
	rst0,
	clk1,
	rst1,
	I0,
	phase0,
	phase1,
	Q0,
	cosr,
	I_cic,
	I_d,
	I_hb,
	I_out,
	Q_d,
	Q_out,
	R,
	sinr
);
 
 
input wire	reset;
input wire	clk;
input wire	clk0;
input wire	rst0;
input wire	clk1;
input wire	rst1;
input wire	[7:0] I0;
input wire	[7:0] phase0;
input wire	[7:0] phase1;
input wire	[7:0] Q0;
output wire	[7:0] cosr;
output wire	[47:0] I_cic;
output wire	[13:0] I_d;
output wire	[31:0] I_hb;
output wire	[15:0] I_out;
output wire	[13:0] Q_d;
output wire	[15:0] Q_out;
output wire	[13:0] R;
output wire	[7:0] sinr;
 
wire	[47:0] I_cic_ALTERA_SYNTHESIZED;
wire	[31:0] I_hb_ALTERA_SYNTHESIZED;
wire	[47:0] Q_cic;
wire	[31:0] Q_hb;
wire	[13:0] SYNTHESIZED_WIRE_0;
wire	[13:0] SYNTHESIZED_WIRE_1;
wire	[13:0] SYNTHESIZED_WIRE_2;
wire	SYNTHESIZED_WIRE_3;
wire	SYNTHESIZED_WIRE_4;
wire	SYNTHESIZED_WIRE_5;
wire	SYNTHESIZED_WIRE_6;
 
assign	I_d = SYNTHESIZED_WIRE_0;
assign	Q_d = SYNTHESIZED_WIRE_1;
assign	R = SYNTHESIZED_WIRE_2;
 
 
 
 
cic_top	b2v_inst(
	.i_clk(clk),
	.i_rst(reset),
	.i_din(SYNTHESIZED_WIRE_0),
	.o_clk16(SYNTHESIZED_WIRE_3),
	.o_dout(I_cic_ALTERA_SYNTHESIZED));
	defparam	b2v_inst.WIDTH = 48;
 
 
cic_top	b2v_inst1(
	.i_clk(clk),
	.i_rst(reset),
	.i_din(SYNTHESIZED_WIRE_1),
	.o_clk16(SYNTHESIZED_WIRE_4),
	.o_dout(Q_cic));
	defparam	b2v_inst1.WIDTH = 48;
 
 
Rec	b2v_inst12(
	.clk(clk1),
	.rst(rst1),
	.phase(phase1),
	.recs(SYNTHESIZED_WIRE_2),
	.Iss(SYNTHESIZED_WIRE_0),
	.Qss(SYNTHESIZED_WIRE_1));
 
 
hb_filter_02	b2v_inst2(
	.i_clk(SYNTHESIZED_WIRE_3),
	.i_rst(reset),
	.i_din(I_cic_ALTERA_SYNTHESIZED[34:19]),
	.o_clk2(SYNTHESIZED_WIRE_5),
	.o_dout(I_hb_ALTERA_SYNTHESIZED));
	defparam	b2v_inst2.h0 = 27316;
	defparam	b2v_inst2.h1 = 20073;
	defparam	b2v_inst2.h11 = 1238;
	defparam	b2v_inst2.h13 = -1175;
	defparam	b2v_inst2.h15 = -624;
	defparam	b2v_inst2.h3 = -4745;
	defparam	b2v_inst2.h5 = 965;
	defparam	b2v_inst2.h7 = 667;
	defparam	b2v_inst2.h9 = -1238;
 
 
hb_filter_02	b2v_inst3(
	.i_clk(SYNTHESIZED_WIRE_4),
	.i_rst(reset),
	.i_din(Q_cic[34:19]),
	.o_clk2(SYNTHESIZED_WIRE_6),
	.o_dout(Q_hb));
	defparam	b2v_inst3.h0 = 27316;
	defparam	b2v_inst3.h1 = 20073;
	defparam	b2v_inst3.h11 = 1238;
	defparam	b2v_inst3.h13 = -1175;
	defparam	b2v_inst3.h15 = -624;
	defparam	b2v_inst3.h3 = -4745;
	defparam	b2v_inst3.h5 = 965;
	defparam	b2v_inst3.h7 = 667;
	defparam	b2v_inst3.h9 = -1238;
 
 
firfilter_da	b2v_inst4(
	.CLK(SYNTHESIZED_WIRE_5),
	.Reset(reset),
	.DIN(I_hb_ALTERA_SYNTHESIZED[30:23]),
	.Dout(I_out));
 
 
firfilter_da	b2v_inst5(
	.CLK(SYNTHESIZED_WIRE_6),
	.Reset(reset),
	.DIN(Q_hb[30:23]),
	.Dout(Q_out));
 
 
Trans	b2v_inst6(
	.clock(clk0),
	.reset(rst0),
	.I(I0),
	.phase(phase0),
	.Q(Q0),
	.cosr(cosr),
	.r(SYNTHESIZED_WIRE_2),
	.sinr(sinr));
 
assign	I_cic = I_cic_ALTERA_SYNTHESIZED;
assign	I_hb = I_hb_ALTERA_SYNTHESIZED;
 
endmodule
01-115m