1

Phase Locked-Loop

Rferences

• U. Tietze, Ch.Schenk, Electronics Circuits –

Handbook for Design and Applications,

Springer,2008

Phase-Locked Loop

Principle of the phase-locked loop (PLL)

2

PLL capture and hold frequency

Input Frequency

Ph.Det. signal

HOLD

CAPTURE

Phase-Locked Loop

ϕ

ϕαkkAc

ff

f

01−=−

m

f

m

f

f jf

kk

j

kk

V

VAs

ϕϕϕ

ωπ

===2

mjωωϕ 1=

∆

∆=−=t tt

tdtdtd0 0

1

0

2

~~~ ωωωϕ

ϕαϕ

α −==k

V

ttm

ωωω cos)( ∆=∆

tt m

m

ωω

ωϕ sin)(∆=

Phase-Locked LoopSample-and-Hold Circuit as a Phase Detector

A sample-and-hold circuit used

as a phase detector Voltage weveform in the phase detector

3

PLL – SH as Ph.Det. - dynamics

ϕϕ sinˆ1

VV = radVV /ˆ1ϕϕ ≈

radVd

dVk /ˆ

1==ϕ

ϕϕ

2221

/

1

ffjTjmm eVekk

πωϕϕ

−⋅− ==2/

1ˆ

ffj

m

f

m

f

mejf

Vk

jf

kkAs π

ϕ ==

2

1

2

ˆ

f

fand

f

Vk

V

VAs m

m

m

f

f

ππϕϕ −−===

PLL with a sample-and-hold circuit as phase detector

1;2

1;

2121

2 ==+

= II ARC

fRR

RAp

π

PLL – SH as Ph.Det. - parameters

Phase-Locked LoopSample-and-Hold Circuit as a Phase Detector

Mean absolute value of

the output voltage of a

multiplier for simusoidal

input voltages of

amplitude U

Application of a

synchronous demodulator

for the measurement of

noisy signalsOperation of a

synchronous demodulator

4

Phase-Locked LoopSynchronous Detector as a Phase Detector

PLL with a multiplier as

phase detector for

frequency demodulation

Transconductance multiplier as a switch

Transconductance multiplier as a switch

5

Transconductance multiplier as a switch

Transconductance multiplier as a switch

Multiplying circuit

φ

Gdy φ=0

VCC VCC

6

Synchronous AM detector

Gdy φ=0To nie jest detekcja szczytowa,

a średnia

VCC VCC

AM synchronous detector

Phase

det.

Low pass

filterVCO

fin

fout

VCC VCC

Phase-Locked LoopFrequency-Sensitive Phase Detector

Phase detector with

memory for sign of the

phase shift

Input and output signals

of the phase detector

Transfer characteristic of

the phase frequency

detector

7

Phase-Locked LoopPhase Detector with Extensive Range

Phase-Locked LoopPhase Detector with Extensive Range

Detection characteristic of

the phase detector

Frequency synthesis

n

f

k

f outin =

Phase Det.Low pass

filterVCO:k

:n

fin

foutfin/k

fout/n

inout fk

nf =

8

Phase-Locked LoopSample-and-Hold Circuit as a Phase Detector

Phase-Locked LoopSample-and-Hold Circuit as a Phase Detector

PLL applications

• AM Demodulation

• Synchronous detection (LockIn Amp)

• FM, PM demodulation

• Frequency synthesis

• Synchronous telekommunication

9

PLL IC - 4046

4046 phase detector I

4046 phase comparator II

10

4046 features

Feature Detector I (exor) Detector II

Lack of input signal fwyj=f0 fwyj=fmin

Phase shift on output90deg for f0

0 to 180 in the range of 2fT

0deg

Harmonic synchronization synchronize No synchronization

Immunity t noise high low

2fT (lock range) fmax - fmin

2fC (capture range) fC < fT (depends on filter) fC= fT

FM detector

ktuftf

ftmftf

ftmftf

out

out

in

⋅+=∆⋅+=

∆⋅+=

)()(

)()(

)()(

0

0

0

Phase det.Low pass

filterVCO

fin(t) fout(t)

)()( tmk

ftu

∆=

)()( tmk

ftu

∆=

4046 as FM demodulator

FM signal

10kHz

Follower

11

4046 as AM demodulator

multiplier

PLL IC LM565 (up to 500kHz)

LM565

12

NE564

NE564 (up to 50MHz)

NE567

13

NE567

ADF4360-7

(350-1800MHz)

ADF4360-7 (350-1800MHz)

14

ADF4360-7

generator 500MHz

Summary

• P, PI, PID controllers

– parameters adjustment

• PLL

– Principle of operation

– examples of VCO, filters, phase detectors

– Applications – frequency synthesis, detectors

test questions• What is the principle of operation of PLL ?

• What is the principle of operation of PLL as FM

detector ?

• What is the principle of operation of PLL as AM

synchronous detector ?

• What is the principle of operation of PLL as

frequency synthesizer ?