A Phase-Locked Loop (PLL) is a control system that synchronizes the phase of an output signal with that of an input reference signal. By adjusting the output frequency to match the input, PLLs are essential in applications requiring precise frequency control and stability.
Key Components of a PLL:
- Phase Detector (PD): Compares the phases of the input and output signals, generating an error signal proportional to the phase difference.
- Low-Pass Filter (LPF): Smooths the error signal from the phase detector, filtering out high-frequency components to produce a control voltage.
- Voltage-Controlled Oscillator (VCO): Adjusts its output frequency based on the control voltage, aligning the output signal’s phase with the input.
- Feedback Path: Routes the output signal back to the phase detector, completing the feedback loop.
Applications of PLLs:
- Frequency Synthesis: Generating stable frequencies for communication systems.
- Clock Recovery: Extracting timing information from data streams in digital communications.
- Signal Demodulation: Recovering information from modulated signals in radio receivers.
- Motor Speed Control: Maintaining consistent rotational speed in motors.