把有源低通滤波器放进锁相环电路中,可以提供附加的环路增益、便于控制、扩大跟踪和捕获范围。这一跟踪和捕获范围可比采用无源滤波器的电路增大10倍。图1是锁相环的线性模型。环路直流增益为K_dK_οF(0),它决定了跟踪范围Δf_t。F(0)是外接低通滤波器的直流电流增益,K_d和K_ο分别是鉴相器和电流控制振荡器的 Putting an active low-pass filter into the phase-locked loop can provide additional loop gain, ease of control, and increased tracking and capture range. This tracking and capture range can be up to 10 times greater than with passive filters. Figure 1 is a linear phase-locked loop model. The loop DC gain is K_dK_οF (0), which determines the tracking range Δf_t. F (0) is the DC current gain of the external low-pass filter, K_d and K_o are the phase detector and current-controlled oscillator