写一个基于VHDL的34QPSK调制FPGA代码

下面是一个基于VHDL的3/4QPSK调制FPGA代码的示例：

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity QPSK_Modulator is
  generic (
    SYMBOL_RATE : integer := 1000000;  -- 符号率（Symbol Rate）
    CARRIER_FREQ : integer := 10000000;  -- 载波频率（Carrier Frequency）
    SAMPLING_FREQ : integer := 40000000  -- 采样频率（Sampling Frequency）
  );
  port (
    reset : in std_logic;
    clk : in std_logic;
    data_in : in std_logic_vector(1 downto 0);
    modulated_out : out std_logic_vector(3 downto 0)
  );
end QPSK_Modulator;

architecture Behavioral of QPSK_Modulator is
  constant SYMBOL_PERIOD : integer := SAMPLING_FREQ / SYMBOL_RATE;
  constant CARRIER_PERIOD : integer := SAMPLING_FREQ / CARRIER_FREQ;
  signal phase : unsigned(1 downto 0);
  signal modulated : unsigned(3 downto 0);
  signal count : integer range 0 to SYMBOL_PERIOD - 1 := 0;
  signal carrier_count : integer range 0 to CARRIER_PERIOD - 1 := 0;
begin
  process (clk, reset)
  begin
    if reset = '1' then
      count <= 0;
      carrier_count <= 0;
      phase <= (others => '0');
      modulated <= (others => '0');
    elsif rising_edge(clk) then
      if count = SYMBOL_PERIOD - 1 then
        count <= 0;
        case data_in is
          when "00" =>
            modulated <= "0011";
          when "01" =>
            modulated <= "0110";
          when "10" =>
            modulated <= "1100";
          when "11" =>
            modulated <= "1001";
        end case;
        phase <= (others => '0');
      else
        count <= count + 1;
        if carrier_count = CARRIER_PERIOD - 1 then
          case phase is
            when "00" =>
              modulated_out <= modulated(0) & '0' & modulated(1) & '0';
            when "01" =>
              modulated_out <= modulated(0) & '1' & modulated(1) & '0';
            when "10" =>
              modulated_out <= modulated(0) & '1' & modulated(1) & '1';
            when "11" =>
              modulated_out <= modulated(0) & '0' & modulated(1) & '1';
          end case;
          phase <= phase + 1;
          carrier_count <= 0;
        else
          carrier_count <= carrier_count + 1;
        end if;
      end if;
    end if;
  end process;
end Behavioral;

此代码实现了一个3/4QPSK调制器，将输入的2位数据流调制为4位的调制输出。SYMBOL_RATE表示符号率，CARRIER_FREQ表示载波频率，SAMPLING_FREQ表示采样频率。

设计中使用了一个计数器count来计算每个符号周期的位置，以及另一个计数器carrier_count来计算每个载波周期的位置。phase信号表示当前调制相位，modulated信号表示调制输出。

在每个符号周期的末尾，根据输入数据选择适当的调制输出。然后，在每个载波周期内，根据当前调制相位选择适当的调制输出位。

最后，将调制后的输出数据写入modulated_out端口