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VP-7722P
3.4
lST,. 2ND NOTCH BOARDS AS,. A9
The notch circuit ( the fundamental wave rejection filter) consists of two
stages;
lst
and 2nd NOTCH board s .
obtain wide, but steep rejection of the fundamental wav e .
3 . 4 . 1
lst NOTCH board
The
lst
notch filter consists of the U12 (NE5534) and the
composed of the automatic tuning circuit U23 and automatic balancing
U21 .
Analog
multipliers
resistors so that the chopper of the field-effect transistor ,
circuit , can yield the minimum fundamental wave rejection factor .
shows the block diagram of the lst notch circuit.
inp
ut
ATT
20dB
40dB
Figure 3-4
Two-stage multiple feedback is used
are
installed in both circuits as
u12·
lST NOTCH
FILTER
U18,U23
AUTOMATIC
TUNING
CIRCUIT
U 1 8 , U 2 1
AUTOMATIC
BALANCING
CIRCUIT
Block diagram of lst notch circuit
!LC
the
sync detection
Figure 3-4
Ull
2ND NOTCH
FILTER
QlS
Q 1 4
BALANCE
CHOPPER
U16,U17
90° PHASE
SHIFTER
3-10
to
circuit
circuit
variable
out
put
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