verilog产生高斯白噪声，gwn_en信号产生使能，gdata是幅度服从高斯分布，功率谱密度为定值的高斯白噪声序列，共10位（现实中只能够做到带限，跟dac输出带宽有关，我的系统只能做到300kHz）-verilog Gaussian white noise, gwn_en signal enabled, gdata amplitude Gaussian distribution, power spectral density of white Gaussian noise sequence value, a total of 10 (in reality can only be band-limited, with dac output bandwidth related, My system can do 300kHz)