fft verilog代码

以下是一个基于蝶形运算的16点FFT（快速傅里叶变换）的Verilog代码示例：

module fft (
  input wire clk,
  input wire rst,
  input wire [15:0] in_real [0:15],
  input wire [15:0] in_imag [0:15],
  output reg [15:0] out_real [0:15],
  output reg [15:0] out_imag [0:15]
);

parameter N = 16;
parameter LOG2N = 4;

reg [15:0] twiddle_real [0:N/2-1];
reg [15:0] twiddle_imag [0:N/2-1];

integer stage, d, b, butterfly;

// 初始化蝶形运算所需的旋转因子
initial begin
  for (b = 0; b < N/2; b = b + 1) begin
    twiddle_real[b] = $signed(16384 * cos(2 * $itor(3.14159265358979) * b / N));
    twiddle_imag[b] = $signed(-16384 * sin(2 * $itor(3.14159265358979) * b / N));
  end
end

// FFT计算
always @(posedge clk or posedge rst) begin
  if (rst) begin
    for (b = 0; b < N; b = b + 1) begin
      out_real[b] <= 16'b0;
      out_imag[b] <= 16'b0;
    end
  end else begin
    for (stage = 0; stage < LOG2N; stage = stage + 1) begin
      for (b = 0; b < N/2; b = b + 1) begin
        for (butterfly = 0; butterfly < N/(2 << stage); butterfly = butterfly + 1) begin
          d = butterfly * (2 << stage) + b;
          out_real[d] <= in_real[d] + (twiddle_real[b] * in_real[d + N/(2 << stage)]) - (twiddle_imag[b] * in_imag[d + N/(2 << stage)]);
          out_imag[d] <= in_imag[d] + (twiddle_real[b] * in_imag[d + N/(2 << stage)]) + (twiddle_imag[b] * in_real[d + N/(2 << stage)]);
          out_real[d + N/(2 << stage)] <= in_real[d] - (twiddle_real[b] * in_real[d + N/(2 << stage)]) + (twiddle_imag[b] * in_imag[d + N/(2 << stage)]);
          out_imag[d + N/(2 << stage)] <= in_imag[d] - (twiddle_real[b] * in_imag[d + N/(2 << stage)]) - (twiddle_imag[b] * in_real[d + N/(2 << stage)]);
        end
      end
    end
  end
end

endmodule

该Verilog代码实现了一个16点FFT。通过输入`in_real`和`in_imag`数组，分别表示实部和虚部，通过输出`out_real`和`out_imag`数组，分别输出变换后的实部和虚部。

代码中使用了蝶形运算的方法进行FFT计算。在每个阶段中，对输入数据进行分组并进行旋转因子的乘法运算。通过迭代计算，最终得到变换后的结果。

请注意，此代码仅供参考，可能需要适应特定的设计需求进行修改和优化。