After that , it discusses the principle of the band - pass technology , illuminating the feasibility of the digital intermediate frequency system based on the sampling speed which is two times lager than the signal band but unsatisfying the nyquist theorem 随后讨论了带通采样技术的原理,说明可以使用不满足奈奎斯特低通采样定理但大于信号带宽两倍的采样速率进行中频数字化,减轻基带处理负担。