用VHDL实现DQPSK调制解调
时间: 2024-05-07 08:22:12 浏览: 48
DQPSK(Differential Quadrature Phase Shift Keying)调制解调器的实现可以使用VHDL语言来完成。下面给出一个简单的DQPSK调制解调器的VHDL代码示例。
首先,定义所需的输入、输出信号。例如,输入信号为in_data,输出信号为out_data和out_clk。
```vhdl
entity dqpsk_moddemod is
Port ( in_data : in STD_LOGIC_VECTOR (7 downto 0);
out_data : out STD_LOGIC_VECTOR (7 downto 0);
out_clk : out STD_LOGIC);
end dqpsk_moddemod;
```
接下来,定义内部信号变量,包括当前和前一个数据值、相位差等。
```vhdl
architecture Behavioral of dqpsk_moddemod is
signal cur_data, prev_data : std_logic_vector(7 downto 0);
signal phase_diff : std_logic_vector(1 downto 0);
signal cur_phase, prev_phase : std_logic_vector(1 downto 0);
signal out_data_int : std_logic_vector(7 downto 0);
begin
```
然后,实现DQPSK调制模块。这里采用了差分相位变换的方法,将相邻两个数据点之间的相位差作为差分相位,以实现DQPSK调制。最后输出调制后的数据和时钟信号。
```vhdl
dqpsk_mod : process(in_data)
begin
prev_phase <= "00"; -- 初始相位为0
out_data_int <= (others => '0'); -- 初始输出为0
for i in in_data'range loop
cur_data <= in_data(i);
phase_diff <= cur_data xor prev_data; -- 计算差分相位
prev_data <= cur_data;
case phase_diff is
when "00" => cur_phase <= prev_phase; -- 相位不变
when "01" => cur_phase <= prev_phase + "01"; -- 相位加π/2
when "10" => cur_phase <= prev_phase - "01"; -- 相位减π/2
when "11" => cur_phase <= prev_phase + "10"; -- 相位加π
end case;
prev_phase <= cur_phase;
case cur_phase is
when "00" => out_data_int(i) <= '0';
when "01" => out_data_int(i) <= '1';
when "10" => out_data_int(i) <= '0';
when "11" => out_data_int(i) <= '1';
end case;
end loop;
out_data <= out_data_int;
out_clk <= not out_clk; -- 时钟信号为数据信号的反相
end process dqpsk_mod;
```
最后,实现DQPSK解调模块。这里采用了相干解调的方法,对接收到的DQPSK调制信号进行解调,并输出解调后的数据。
```vhdl
dqpsk_demod : process(out_data, out_clk)
begin
prev_phase <= "00"; -- 初始相位为0
for i in out_data'range loop
if out_clk = '1' then -- 取样时钟信号
case out_data(i) is
when '0' => cur_phase <= prev_phase; -- 相位不变
when '1' => cur_phase <= prev_phase + "01"; -- 相位加π/2
end case;
prev_phase <= cur_phase;
end if;
end loop;
out_data_int <= (others => '0'); -- 初始输出为0
for i in out_data'range loop
if out_clk = '0' then -- 取样时钟信号的反相
case cur_phase is
when "00" => out_data_int(i) <= '0';
when "01" => out_data_int(i) <= '1';
when "10" => out_data_int(i) <= '0';
when "11" => out_data_int(i) <= '1';
end case;
end if;
end loop;
out_data <= out_data_int;
end process dqpsk_demod;
```
完整的VHDL代码实现了DQPSK调制解调器,可以在FPGA上进行验证和测试。
阅读全文