M/N Phase Detector - HP 8340B Manual

A31
M/N PHASE DETECTOR
The M/N
phase detector assembly contains
a
phase detector, a
mixer, and two programmable
fre¬
quency dividers (refer to Figure B-1).
The
mixer down converts
the
355 to 395 MHz
M/N VCO output
to
5
to
45 MHz by mixing it
with the
400 MHz reference
signal
from
A30 100
MHz VCXO.
This 5
to
45 MHz IF signal
is
frequency divided by the M
divider, which
is
programmed to
divide by an
integer ranging from
8 to
27. The output of the
M
divider is phase/frequency compared
with the
output
of the
N
divider:
The
N
divider divides the
20 MHz reference loop signal by an integer ranging from 13 to
36.
The
N
and
M
divider outputs are phase/frequency compared and the resultant error signal tunes the A32
M/N
VCO.
This keeps the M/N
loop phase-locked to
the reference
loop.
HP 8340B/41B
M/N
Loop Theory of Operation B-5/B-6