标签: 群延迟

物理意义：一段信号通过某一信号处理系统后，其中所包含的各种频率分量，将会获得各自的频率分量的加权（幅频特性）和相位上的偏移（相频特性）。其中相位上的偏移，将会导致最终输出信号，获得时间上的前后错位（相对于输入信号包络的延迟）对应关系为 delta t==e^j*w*t . 为保证原信号的各个频率分量在同一时间输出，需要保证对于各个w取值，具有相同的delta t.也就是说总的相移delta phase (=wt)对所有的w都得到同一个t取值。 From WiKI： http://en.wikipedia.org/wiki/Group_delay_and_phase_delay In  signal processing ,  group delay  is a measure of the time delay of the amplitude  envelopes  of the various  sinusoidal   components  of a signal through a  device under test , and is a function of frequency for each component. All frequency components of a signal are delayed when passed through a device such as an amplifier, a loudspeaker, or propagating through space or a medium, such as air. This signal delay will be different for the various frequencies unless the device has the property of being  linear phase . (Linear phase and  minimum phase  are often confused. They are quite different.) The delay variation means that signals consisting of multiple frequency components will suffer distortion because these components are not delayed by the same amount of time at the output of the device. This changes the shape of the signal in addition to any constant delay or scale change. A sufficiently large delay variation can cause problems such as poor  fidelity  in audio or  intersymbol interference  (ISI) in the demodulation  of  digital information  from an  analog   carrier signal . High speed  modems  use  adaptive equalizers  to compensate for non-constant group delay.