9.2.1 Features of Adaptive Filters Unsupervised adaptation.When the desired response is unavailable In some applications,the input signal has some measurable property (i.e.,constant envelope)that is lost by the time it reaches the adaptive filter.The adaptive filter adjusts its parameters in such a way as to restore the lost property of the input signal. 例如：无线通信中接收机的AGCUnsupervised adaptation. When the desired response is unavailable. In some applications, the input signal has some measurable property (i.e., constant envelope) that is lost by the time it reaches the adaptive filter. The adaptive filter adjusts its parameters in such a way as to restore the lost property of the input signal. 例如：无线通信中接收机的AGC 9.2.1 Features of Adaptive Filters