(s.c.e.t) appliction of pll fm demodulation fsk demodulation
DESCRIPTION
PLL APPLICATIONTRANSCRIPT
SARVAJANIK COLLEGE
OF
ENGINEEING & TECNOLOGY
TOPIC APPLICTIONS OF PLL
FM DEMODULATION
FSK DEMODULATOR
NAME ENROLLMENTNOJARIWALA SIDDHARTH R. 140423109005VASAVA CHIRAG M. 140423109014
SUB NAME :- ANALOG ELECTRONICS
Internal Block Diagram of IC 565
The LM565 is a general purpose
phase locked loop(PLL) containing a
stable, highly linear voltage controlled
oscillator(VCO) and a double balanced
phase detector with good carrier
suppression.
• PLL – Phase Locked Loops
• It is two type – linear and Nonlinear
• It is use in TV , FM Demodulation , FSK Demodulation Motor speed control
, etc.
• PLL ICS :- 560,561,562,564,565 & 567
INRODUCTION OF PLL
APPLICATION OF PLL
1. Frequency multiplication/division.
2. Frequency translation
3. AM detection
4. FM detection
5. FSK demodulation
FM DEMODULATION USING PLL
Circuit Diagram
of
FM Demodulation
The operation of FM demodulation using PLL
The FM signal is applied to PLL.
As the PLL is locked to the FM signal, the VCO start tracking instantaneous frequency in the input FM signal.
The error voltage produced at the output of the error amplifier is directly proportional to the frequency deviation.
Thus the ac component of the error voltage represents the modulating signal.
Demodulation FM output is obtained at the output of the error amplifier.
Advantage of using PLL for FM demodulation
PLL ensures a high degree of linearity between the instantaneous input frequency and VCO control voltage which is the output of error amplifier.
The bandwidth of the incoming FM signal can be much wider than that of the low-pass which is restricted to the baseband.
The control voltage signal of the VCO has bandwidth of the modulating signal.
FSK DEMODULATOR USING PLL
OPRATION OF FSK DEMODULATOR USING PLL
The capacitor coupling at the i/p is used for removing the dc level in the i/p FSK signal.
As we apply the FSK signal at the i/p, the loop gets locked to the i/p frequency and the VCO
tracks the i/p frequency between the two frequencies Fh and Fl. A corresponding dc shift will be
produced at the o/p.
The three stage RC low pass filter is used for removing the carrier component from the o/p.
R1 & C1 are decide the free running frequency of VCO .
VOC Control voltage is produced which is given by:
Vc1 = Fh – F0
K
Where, F0 = Free running VCO frequency &
K = V to f transfer coefficient of VCO.
When the i/p frequency is FL the control voltage is given by:
Vc2 = F0 – FL
K
Where, Vc2 is i/p side capacitor
These voltages are compared whit the reference voltage by the external comparator to produce a
digital signal.
ANY QUESTION
?
THE END
Thank..u