Abstract: Fast switching and fast settling is achieved in a phase locked loop (“PLL”) containing a bandwidth switched active loop filter (8) by feeding the phase error signal of the phase detector (1) of the PLL to the non-inverting input of the amplifier (7) within the loop filter and having the electronic switch (17) control the loop filter bandwidth through changing the resistance (9, 11) to ground at the inverting input of the amplifier between a high and low value associated respectively with broad bandwidth and narrow bandwidth to the loop filter. Switching is possible in as little as one microsecond, and is accompanied by fast settling of the loop with minimal generation of phase/frequency perturbation. The foregoing PLL is of particular benefit in fast switching frequency synthesizers, such as used in frequency hopping frequency synthesizers of frequency and time division multiplexing systems.

Abstract: Fast switching and fast settling is achieved in a phase locked loop (“PLL”) containing a bandwidth switched active loop filter (8) by feeding the phase error signal of the phase detector (1) of the PLL to the non-inverting input of the amplifier (7) within the loop filter and having the electronic switch (17) control the loop filter bandwidth through changing the resistance (9, 11) to ground at the inverting input of the amplifier between a high and low value associated respectively with broad bandwidth and narrow bandwidth to the loop filter. Switching is possible in as little as one microsecond, and is accompanied by fast settling of the loop with minimal generation of phase/frequency perturbation. The foregoing PLL is of particular benefit in fast switching frequency synthesizers, such as used in frequency hopping frequency synthesizers of frequency and time division multiplexing systems.