verilog实现fft

实现FFT需要用到复数运算，Verilog中并没有直接支持复数的数据类型，因此需要自己定义复数类型和复数运算。以下是一个简单的Verilog实现FFT的代码，仅供参考：

module fft(
    input clk,
    input rst,
    input [7:0] in_real,
    input [7:0] in_imag,
    output [7:0] out_real,
    output [7:0] out_imag
);

parameter N = 8;  // FFT点数
parameter LOG2N = 3;  // FFT点数的对数

// 定义复数类型
typedef struct {
    logic signed [7:0] real;
    logic signed [7:0] imag;
} complex_t;

// 定义复数加法运算
function complex_t complex_add(complex_t a, complex_t b);
    complex_t c;
    c.real = a.real + b.real;
    c.imag = a.imag + b.imag;
    return c;
endfunction

// 定义复数乘法运算
function complex_t complex_mul(complex_t a, complex_t b);
    complex_t c;
    c.real = a.real * b.real - a.imag * b.imag;
    c.imag = a.real * b.imag + a.imag * b.real;
    return c;
endfunction

complex_t stage[N];  // FFT各级蝴蝶运算的输入和输出

// FFT主体
always @(posedge clk or posedge rst) begin
    if (rst) begin
        for (int i = 0; i < N; i++) begin
            stage[i].real <= 0;
            stage[i].imag <= 0;
        end
    end else begin
        // 第一级蝴蝶运算
        for (int i = 0; i < N; i++) begin
            complex_t tmp;
            tmp.real = in_real;
            tmp.imag = in_imag;
            stage[i] <= tmp;
        end
        // 其他级蝴蝶运算
        for (int s = 1; s <= LOG2N; s++) begin
            int m = 2 ** s;
            int n = m / 2;
            complex_t wn;
            wn.real = $cos(2 * $pi / m);
            wn.imag = -$sin(2 * $pi / m);
            for (int k = 0; k < n; k++) begin
                complex_t w;
                w.real = 1;
                w.imag = 0;
                for (int j = 0; j < N / m; j++) begin
                    int x = j * m + k;
                    int y = x + n;
                    complex_t u = stage[x];
                    complex_t v = complex_mul(stage[y], w);
                    stage[x] = complex_add(u, v);
                    stage[y] = complex_add(u, complex_mul(v, wn));
                end
                wn = complex_mul(wn, wn);
            end
        end
        out_real <= stage[0].real;
        out_imag <= stage[0].imag;
    end
end

endmodule

这个Verilog实现FFT的代码并不完整，还需要外部的控制逻辑来控制输入和输出数据，以及时序控制。此外，这个代码中使用了$cos$和$sin$函数，需要在代码中引入数学库，以及处理浮点数运算的问题。因此，在实际工程中，需要考虑这些问题，进行完整的设计和实现。