A phase locked loop includes a controlled oscillator for delivering an
output signal at a determined output frequency, and a variable frequency
divider for converting the output signal into a signal at divided
frequency. The PLL is termed composite in that it includes at least one
first loop having a loop filter for generating a first control signal for
the oscillator on the basis of the signal at divided frequency, and a
second loop having a loop filter, different from the loop filter of the
first loop, for generating, on the basis of the signal at divided
frequency, a second signal for additional control of the oscillator. The
loop filter of the first loop and the loop filter of the second loop have
different respective cutoff frequencies. The passband of the first loop,
can be adapted to ensure the convergence and the stability of the PLL,
while the second loop can afford extra passband increasing the speed of
adaptation of the PLL in case of modification of the value of a preset
for the output frequency.