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When a PLL is locked on the input frequency the VCO frequency?
This means that the VCO frequency will change until it is equal to the input reference signal frequency. When this happens, the two signals are synchronized or “locked.” The phase difference causes the phase detector to produce the DC voltage at the VCO input to keep the PLL locked to the input signal.
What is lock time in PLL?
PLL lock time is the time a PLL needs to generate the target frequency with phase match (between the PLL reference clock and PLL feedback clock) after power is applied to the system. Figure 2 shows the lock signal is asserted high when the feedback clock’s frequency is same as that of the reference clock.
How do you determine the free running frequency lock range and capture range of a PLL?
The range of frequencies over which PLL will track the input frequency signal and remains locked is referred as PLL Lock range. The lock range is usually band of frequencies above and below the PLL free running frequency as described earlier.
How does phase locked loop PLL demodulate an FM signal?
Demodulation of frequency modulation (FM): If PLL is locked to an FM signal, the VCO tracks the instantaneous frequency of the input signal. The filtered error voltage which controls the VCO and maintains lock with the input signal is demodulated FM output.
What is the free running frequency?
The VCO is a special type of oscillator that has a frequency controlled by an applied voltage. The frequency of the VCO without any control signal applied is called the free- running frequency, f0.
What is the use of phase-locked loop?
A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator that constantly adjusts to match the frequency of an input signal. PLLs are used to generate, stabilize, modulate, demodulate, filter or recover a signal from a “noisy” communications channel where data has been interrupted.
In ideal case, this voltage is linearly proportional to the VCO frequency. Time interval needed for VCO tuning voltage to achieve a stable value after initiating the PLL frequency change, is equal to the PLL settling time.
How is settling time measured in PLL locking?
The simplest method for PLL settling time measurement is monitoring the VCO tuning voltage waveform during the PLL locking process. In ideal case, this voltage is linearly proportional to the VCO frequency.
What’s the difference between PLL frequency pushing and frequency pulling?
This page describes basic difference between PLL Frequency Pushing and PLL Frequency Pulling. It mentions how to measure VCO FREQUENCY PUSHING and PULLING. Both of these parameters are very useful in the design of RF frequency synthesizer using VCO, frequency divider and loop filter. VCO is the short form of Voltage Controlled Oscillator.
What does frequency pulling mean on a VCO?
Here term frequency pulling refers to a change in VCO frequency due to a change in the load on the VCO output. Typical value for one of the minicircuit VCO device is 0.80 (MHz) peak-to-peak at 12dBr.