How can a PLL be used as a frequency multiplier?

A phase-locked loop (PLL) uses a reference frequency to generate a multiple of that frequency. A voltage controlled oscillator (VCO) is initially tuned roughly to the range of the desired frequency multiple. The signal from the VCO is divided down using frequency dividers by the multiplication factor.

What would happen if the input frequency of PLL is not within the capture range?

If the frequency of the input signal is outside the PLL lock range than PLL will not be able to lock. Under this condition, VCO frequency jumps to its fundamental free running frequency.

How does PLL reduce frequency?

The PLL compares the voltage-controlled oscillator signal with the input/reference signal. This difference is passed on to the low-pass filter that removes any high-frequency elements, and filters the error signal into a varying direct current (DC) level.

What is the purpose of frequency multiplier?

Frequency multipliers are often used in frequency synthesizers and communications circuits. It can be more economical to develop a lower frequency signal with lower power and less expensive devices, and then use a frequency multiplier chain to generate an output frequency in the microwave or millimeter wave range.

What is the output of PLL?

In a PLL, the two inputs of the phase detector are the reference input and the feedback from the VCO. The PD output voltage is used to control the VCO such that the phase difference between the two inputs is held constant, making it a negative feedback system.

What part of the PLL frequency synthesizer determines the frequency of the output?

Principle of PLL synthesizers The output frequency is fed through a frequency divider back to the input of the system, producing a negative feedback loop. If the output frequency drifts, the phase error signal will increase, driving the frequency in the opposite direction so as to reduce the error.

What is capture frequency in PLL?

The range of input frequencies over which PLL will capture the input signal is referred as PLL capture range. As shown in the fig-2, it is much narrower compare to the PLL lock range. Both PLL lock range and PLL capture range are centered around the VCO free running frequency.

How is the output frequency of a PLL synthesizer changed?

The digital PLL RF frequency synthesizer works by placing a digital frequency divider into PLL between the VCO & phase detector and by changing the division ratio of the divider, the output frequency changes.

How PLL is used as FSK demodulator?

PLL Application – FSK (Frequency Shift Keying) Demodulator Several standards are used to set the mark and space frequencies. As the signal appears at the input of 565 PLL, the PLL locks to the input frequency and tracks it between the two possible frequencies with a corresponding dc shift at the output.

Why frequency fogging is used in a carrier system?

Why frequency fogging is used in a carrier system? Explanation: The interchanging of the frequencies of carrier channels to accomplish specific purposes. It is used to prevent feedback and oscillation. It is also used to reduce cross-talk and also to correct for a high frequency response slope in the transmission line.