farrow滤波器verilog实现

以下是一个简单的Farrow滤波器的Verilog实现:

module farrow_filter(
    input clk,
    input reset,
    input signed [15:0] x,
    output reg signed [15:0] y);

    reg signed [15:0] x_1, x_2, x_3, x_4;
    reg signed [15:0] y_1, y_2, y_3, y_4;
    reg signed [15:0] phase_1, phase_2, phase_3, phase_4;
    reg signed [15:0] delta_1, delta_2, delta_3, delta_4;

    always @(posedge clk, posedge reset) begin
        if (reset) begin
            x_1 <= 0;
            x_2 <= 0;
            x_3 <= 0;
            x_4 <= 0;
            y_1 <= 0;
            y_2 <= 0;
            y_3 <= 0;
            y_4 <= 0;
            phase_1 <= 0;
            phase_2 <= 0;
            phase_3 <= 0;
            phase_4 <= 0;
            delta_1 <= 0;
            delta_2 <= 0;
            delta_3 <= 0;
            delta_4 <= 0;
            y <= 0;
        end else begin
            // Update phase values
            phase_1 <= delta_1 + phase_1;
            phase_2 <= delta_2 + phase_2;
            phase_3 <= delta_3 + phase_3;
            phase_4 <= delta_4 + phase_4;

            // Update delta values
            delta_1 <= (x - x_1) * 3 + (x_1 - x_2) * 6 + (x_2 - x_3) * -10 + (x_3 - x_4) * -3;
            delta_2 <= (x - x_1) * -2 + (x_1 - x_2) * -2 + (x_2 - x_3) * 2 + (x_3 - x_4) * 2;
            delta_3 <= (x - x_1) * 1 + (x_1 - x_2) * 2 + (x_2 - x_3) * 1 + (x_3 - x_4) * 0;
            delta_4 <= (x - x_1) * 0 + (x_1 - x_2) * -1 + (x_2 - x_3) * 2 + (x_3 - x_4) * -1;

            // Update input values
            x_4 <= x_3;
            x_3 <= x_2;
            x_2 <= x_1;
            x_1 <= x;

            // Update output values
            y_4 <= y_3;
            y_3 <= y_2;
            y_2 <= y_1;
            y_1 <= y;

            // Calculate output value
            y <= phase_1 * y_1 + phase_2 * y_2 + phase_3 * y_3 + phase_4 * y_4;
        end
    end
endmodule

这个Farrow滤波器实现了一个4阶插值，可以将输入信号x插值为4倍，并产生一个输出信号y。实现中使用了4个相位量phase_1、phase_2、phase_3、phase_4，它们分别对应于4个输入信号的插值系数，而delta_1、delta_2、delta_3、delta_4则是用于计算相位量的增量。这个实现也使用了4个延时寄存器x_1、x_2、x_3、x_4和y_1、y_2、y_3、y_4，分别用于存储4个输入信号和4个输出信号。最终的输出信号y是由4个输出信号的加权和计算得到的。