C/A 码扩频与解扩fpga代码
时间: 2023-12-08 17:06:01 浏览: 38
以下是一个使用 Verilog HDL 编写的 C/A 码扩频与解扩的 FPGA 代码示例:
```verilog
module ca_spread(despread_signal, noisy_signal, CA_code, carrier, fs, fc, SNR);
parameter code_length = 1023;
parameter PRN = 1;
parameter Tc = 1/1.023e6;
parameter Ts = 1/10e6;
parameter fc_t = 1023;
parameter fs_t = 9765;
input [31:0] fs;
input [31:0] fc;
input [31:0] SNR;
output [31:0] despread_signal;
output [31:0] noisy_signal;
output [fc_t-1:0] CA_code;
output [fc_t-1:0] carrier;
reg [fc_t-1:0] CA_code_reg;
reg [fc_t-1:0] carrier_reg;
// 生成 C/A 码
generate_CA_code CA_code_inst(
.PRN(PRN),
.code(CA_code_reg)
);
// 生成载波信号
generate_carrier carrier_inst(
.fc(fc_reg),
.carrier(carrier_reg)
);
// 扩频
assign spread_code = {16{CA_code_reg}};
assign spread_signal = carrier_reg * spread_code;
// 添加噪声
assign noise = $random;
assign signal_power = $sqrt($pow(spread_signal)/fc_t);
assign noise_power = signal_power / $pow(10, SNR/10);
assign noise = noise * $sqrt(noise_power);
assign noisy_signal = spread_signal + noise;
// 解扩
assign despread_signal = noisy_signal * spread_code;
endmodule
module generate_CA_code(PRN, code);
parameter code_length = 1023;
input [31:0] PRN;
output [code_length-1:0] code;
reg [9:0] LFSR1;
reg [9:0] LFSR2;
reg [code_length-1:0] ca_code;
always @(negedge clk) begin
LFSR1[9:1] = LFSR1[8:0];
LFSR1[0] = LFSR1[2] ^ LFSR1[9];
LFSR2[9:1] = LFSR2[8:0];
LFSR2[0] = LFSR2[1] ^ LFSR2[2] ^ LFSR2[5] ^ LFSR2[7] ^ LFSR2[8] ^ LFSR2[9];
ca_code[0] = LFSR1[9] ^ LFSR2[9];
for (i = 1; i < code_length; i = i + 1) begin
LFSR1[9:1] = LFSR1[8:0];
LFSR1[0] = LFSR1[2] ^ LFSR1[9];
LFSR2[9:1] = LFSR2[8:0];
LFSR2[0] = LFSR2[1] ^ LFSR2[2] ^ LFSR2[5] ^ LFSR2[7] ^ LFSR2[8] ^ LFSR2[9];
ca_code[i] = LFSR1[9] ^ LFSR2[9];
end
end
assign code = (PRN + 1 <= code_length) ? ca_code[PRN + 1 : code_length];
endmodule
module generate_carrier(fc, carrier);
parameter Tc = 1/1.023e6;
parameter Ts = 1/10e6;
parameter fc_t = 1023;
parameter fs_t = 9765;
input [31:0] fc;
output [fc_t-1:0] carrier;
reg [31:0] t;
always @(negedge clk) begin
for (i = 0; i < fc_t; i = i + 1) begin
t = i * Tc + $random * Ts;
carrier[i] = $cos(2 * $pi * fc * t);
end
end
endmodule
```
上述代码中,首先生成了 C/A 码和载波信号,然后将载波信号与 C/A 码进行扩频,得到扩频信号。再添加噪声后,使用与发送端相同的 C/A 码进行解扩,得到解扩后的信号。最后将扩频信号、解扩后的信号、C/A 码和载波信号输出到 FPGA 的输出端口。其中,`generate_CA_code` 模块生成 C/A 码,`generate_carrier` 模块生成载波信号,`ca_spread` 模块进行扩频和解扩,并将结果输出到 FPGA 的输出端口。