What is a Phase Locked Loop?

[gen123]

please what is it.

 

[Electronica]

What is PLL?

In PLL error signal is prop to phase difference

 

[A.Anand Srinivasan]

Re: What is PLL?

PLL is phase locked loop...
it is a circuit with a feedback equal to the difference in phase between the input and the reference signal produced by the voltage controlled oscillator(VCO) this feedback acts as the input to the VCO and it takes care that the output of the VCO is in phase with the input signal.... hence effectively locking and tracking the input signal.....

it is widely used in radar.....

 

[sunnyhere]

Re: What is PLL?

As Nanand Said, its the same, adding a little to it. its main application is in phase Modulation & Frequency Modulation. Its Mostly used in these applications.

Added after 3 hours 40 minutes:

PLP is a best example of feedback system. the error drives the output to reduce the error & come to a steady-state. in PLP error is difference in phase with the reference signal. best i can suggest you go through wikipedia.org

 

[Meridian]

Re: What is PLL?

please what is it.

hello gen123:

Try the link below for a short tutorial on Phase-Locked Loop.
**broken link removed**

Added after 3 minutes:

it is widely used in radar.....

It is widely used in practically anything, radar, TV, radio, transmitters/receivers, Radio Control, etc. But I guess you know that already. No pun intended...

 

[emadi]

Re: What is PLL?

phase lock loop=pll
It means a mechanism that can lock on a special phase

 

[forkschgrad]

Re: What is PLL?

PLL - Phase Lock Loop

Phase-locked loops are building blocks used extensively in
many analog and digital system.
Applications:
(1) Clock/data recovery
(2) Frequency synthesis/generation
(3) Frequency modulation/demodulation
The PLL does two jobs:
(1) if reference frequency differs from VCO in frequency, the PLL adjust its
frequency to equal the input frequency.
(2) Once the PLL adjusted in frequency, locked, it must hold
that frequency by developing a voltage, which is related to a
phase difference, to enable it to stay locked in frequency to
the input frequency.

 

[sundarmeenakshi]

Re: What is PLL?

please what is it.

hI
pll OPERATION IS FIRst it compare referance signal with input.
based on he difference between these two signal out signal frequency will change

 

[ultrabrains]

What is PLL?

is there any book available for phase locked loops that has both practical, theoretical and real life application on phase locked loops
?

like how it is used for FM transmiters

 

[ultrabrains]

What is PLL?

Thanks, i will have a look at this book, and will let you know if it helped.

cheers

 

[mosti]

What is PLL?

PLL in the past mostly analog PLLs are used, some of them used sigma-delta modulators to control the frequency divider part in the feedback of the loop (used e.g. in --> fractional n PLL topic). The mutli modulus divider in these fractional n-Plls is a digital circuit but treated as a analog design issue. (one part e.g. could deals with 4GHz or above, so it is no digital design issue at all. Current research is done in the field of full digital PLLs, so this is also an interesting point to look at.

Added after 3 minutes:

Lee's book at CMOS RF integrated circuits is also quite interested to look at, because you will gain a deeper understanding in how PLLs are used in e.g. Transceiver circuits. But don't forget to look at papers, because most of the real interesting material you will found in the IEEE journals and transactions an in conference proceedings.

 

[ehsanelahimirza]

Re: What is PLL?

It is a feedback loop system in which output signal (the
fed back signal) follows the input signal. When the two
signals have same frequency and their phase difference
is either zero are some fixed value, the PLL is said to be
locked. It consists of:
1. A Loop Filter ( Low pass filter)
2. A Phase Detector
3. A Voltage Controlled Oscillator (VCO)

 

[danube]

What is PLL?

PLL could have a phase detector or frequency detector
or a phase and frequency detector PD, FD or PFD

 

[ultrabrains]

What is PLL?

can i have more of a practical example (circuit) of its application in fm transmiters say frequency locked to 90.5Mhz

thanks

 

[tarun21]

Re: What is PLL?

PLL stands for PHASE LOCK LOOP. it is basically a feedback system which locks the phase of incoming signal with the phase of feedback signal generated by the VCO (voltage controlled oscillator) i.e the frequency of input signal and the feedback signals are the same and phase error between two signals is constant which is defined as static phase error.

 

[salem_eng1]

Re: What is PLL?

can i have more of a practical example (circuit) of its application in fm transmiters say frequency locked to 90.5Mhz

thanks

To use the PLL as a PLL transmitter / receiver system
at transmitter you need only a VCO
the input of the VCO is your signal and the output will be the FM signal you want then you can up convert your signal with a carrier = 90.5MHz using a mixer

At the receiver Using PLL , the input of the PD is your received signal , after locking the output of the VCO will be as the received signal so the input of the VCO will be the transmitted signal

I hope that help

If you want more about PLL you can read Best Book (Best is the Best)

 

[rajsrikanth]

Re: What is PLL?

pll is a phase locked loop. This is actually used in demodulation ckt. actually at the receiver side we have to detect the carrier and remove the carrier signal from original so this type of technique is useful in that case.

 

[johnchau123]

Re: What is PLL?

I think reading some datasheets on phase lock loop, such as 74HC4046 from Philips, is useful to understand more on PLL.

 

[ahmad_abdulghany]

What is PLL?

https://en.wikipedia.org/wiki/PLL

 

[kengloong]

Re: What is PLL?

In communications, a circuit technique by which a local oscillator is synchronized in phase and frequency with a signal being received.