3. INTRODUCTION
the pll is one of the most
commonly used circuit
in electrical engineering
1
obtained either as the
voltage singal
corresponding to the
error voltage in the
loop
2
(or) as a frequency
singal at VCO output
terminal
3
4. TRACKING BAND –PASS FILTER
Because of their temperature dependence, narrowband band
pass filters cannot be implemented by conventional analog filter
1
The carrier frequency of angle –modulated signal to be
selected varies.2
If a PLL tracking the carrier is used as a band pass filter.
3
The relationship between the input and output phase
modulation is determined by the close-loop transfer function.4
5. CW CARRIER RECOVERY
In every coherent receiver , the
carrier has to be recovered from the
recovered from the noisy input
singal
1
2
It is assumed that the carrier is
present all the time in the
received spectrum
The recovery of a suppressed
carrier will be considered later
3
4 The aim of cw carrier recovery is
to retrieve the carrier and to
suppress as much noise ,
modulation.
7. FREQUENCY SYNTHESIS
4
If necessary ,to operate as an analog or
phase modulator
3
the PLL is widely used in frequency
synthesis to generate spectrally pure
signal
2
In many application ,the frequency of
generated signal must be varied
1
Signal with high frequency stability and
spectral purity are often