ACTIVE LOW-PASS FILTER WITH SWITCHED PASS BAND FOR SYNTHESIZER WITH PHASE-LOCKED LOOP Russian patent published in 2025 - IPC H03L7/107 

FIELD: radio engineering.

SUBSTANCE: result is achieved by changing the pass band of the PLL ring by switching RC circuits with different time constants in the feedback circuit of the operational amplifier of the active low-pass filter in combination with fast recharging of capacitors of the RC circuits and using voltage repeaters. For this purpose, the device includes third (Kl3), fourth (Kl4), fifth (Kl5) and sixth (Kl6) keys having control inputs, as well as first (10) and second (11) voltage repeaters.

EFFECT: reduced time of the transient process when changing the frequency of the output signal of the frequency synthesizer while maintaining a low level of phase noise in the spectrum of the output signal due to switching of RC-circuits with different time constants in circuit of active low-pass filter of PLL ring using voltage repeaters to equalize values of voltage level on elements of two switched circuits with minimization of time of undesirable parasitic transient process, characterized by sharp overshoot of output signal frequency at the moment of switching.

1 cl, 2 dwg